What do we know about Arctic sea ice trends?

A very significant post over at Dr. Curry’s blog ~ctm

From Climate Etc.

Posted on August 16, 2017 |

by Dr. Ronan Connolly & Dr. Michael Connolly

Satellite observations indicate that the average Arctic sea ice extent has generally decreased since the start of the satellite records in October 1978. Is this period long enough to assess whether the current sea level trend is unusual, and to what extent the decline is caused by humans?

This change in Arctic climate is often promoted as evidence that humans are causing drastic climate change. For instance, an April 29th 2017 article in the Economist (“Skating on thin ice”, pg 16) implied that the Arctic is melting unusually, dramatically and worryingly:

“The thaw is happening far faster than once expected. Over the past three decades the [Arctic sea ice extent] has fallen by more than half and its volume has plummeted by three-quarters… SWIPA estimates that the Arctic will be free of sea ice in the summer by 2040. Scientists previously suggested this would not occur until 2070.”

However, is the 1978-present satellite record really long enough to allow us to:

  1. a) Assess how unusual (or not) the recent trends are?
  2. b) Determine how much of the recent climate change is human-caused vs. natural?

Recently, we published a study in Hydrological Sciences Journal (HSJ) in which we extended the Arctic sea ice estimates back to 1901 using various pre-satellite era data sources (Abstract here).

HSJ have chosen this article as one of their “Featured Articles” which means that it is free to download for a limited time: here. But, if you’re reading this post after that offer has expired and you don’t have paywall access, you can download a pre-print here.

In our study, we found that the recent Arctic sea ice retreat during the satellite era actually followed a period of sea ice growth after the mid-1940s, which in turn followed a period of sea ice retreat after the 1910s. This suggests that the Arctic sea ice is a lot more dynamic than you might think from just considering the satellite records (as the Economist did above). So, in this post, we will review in more detail what we currently know about Arctic sea ice trends.

Sea ice trends during the satellite era

The Arctic and Antarctic sea ice extent satellite data can be downloaded from the US National Snow & Ice Data Center (NSIDC) here. In the graphs below, we’ve plotted the average annual sea ice extents from this satellite data for both the Arctic and the Antarctic. For comparison, we’ve also shown Arctic air temperature trends since 1900 (adapted from our HSJ article).

We can see that, yes, the average Arctic sea ice extent has generally decreased since the start of the satellite record. Although, interestingly the average Antarctic sea ice extent has generally increased over the same period. However, when we look at the much longer Arctic temperature record we can see that this is not surprising. The Arctic region has been warming since the late 1970s (when the satellite records began), but this followed a period of Arctic cooling from the 1940s to the early 1970s! In other words, if the satellite records had begun in the 1940s and if the Arctic sea ice extent is related to Arctic temperatures, we would probably have detected a period of Arctic sea ice growth.

Arctic sea ice changes during the pre-satellite era

One of the reasons there has been such interest in the satellite-based sea ice records is that the satellites are monitoring most of the planet and provide almost continuous coverage. But, people were also monitoring Arctic sea ice before the satellite era using various land, ship, submarine, buoy and aircraft measurements.

In the 1990s and early 2000s, Profs. Walsh and Chapman decided to try to combine together some of these pre-satellite measurements to extend the satellite record back to the early 20th century. You can see from the figure below, that their estimates implied that there was almost no variability in Arctic sea ice extent before the satellite era!

For many years, their “Walsh and Chapman dataset” was assumed to be fairly reliable and accurate, and it was widely used by the scientific community.

As can be seen from this clip, it even was shown in Al Gore’s 2006 An Inconvenient Truth film, although Gore seems to have been confused about what data he was showing and mistakenly claims that the Walsh & Chapman graph is based on “submarine measurements of ice thickness”.


By the way, we suspect the submarine measurements Gore refers to are probably the ones from Rothrock et al. 1999 (Open access), but those measurements are a lot more limited than Gore implies, and it had already been published in 1999, so it’s unclear why Gore felt he needed to “persuade them to release it”.

However, when we looked in detail at the available pre-satellite data, we realised that there were serious problems with the Walsh & Chapman estimates.

The main problem is that the pre-satellite data is unfortunately very limited. If a ship travelled through a particular region in a given season, then they could have reported how much ice was in that region, or whether it was ice-free. But, what do you do if there were no ships (or airplanes, buoys, etc. ) in that region?

It seems that in a lot of cases when Walsh & Chapman didn’t have measurements for a given region they effectively ended up assuming that those regions were ice-filled!

For example, in the figure below, the map on the left shows the main data source used by Walsh & Chapman for August 1952. It’s an estimate of the Arctic sea ice extent that was compiled by the Danish Meteorological Institute (DMI). On the map, the red lines indicate the ice boundaries where the DMI actually had taken measurements – in this case, mostly around Greenland and eastern Canada. The white regions on the rest of the map indicate regions where “ice supposed, but no information at hand”. In other words, the DMI was guessing that there might be ice there, but didn’t know!

This period was in the middle of the Cold War and unfortunately there was very little data-sharing between the Soviet Union and western countries like Denmark. So, the DMI had almost no information for the Russian Arctic. However, as it happens, the Russians were making their own observations of the Russian sea ice using aerial reconnaissance, ships, buoys, etc. In the 21st century, some Russian scientists began digitizing this data and publishing it. The map on the right hand side shows the Russian observations for the exact same month (August 1952). The blue regions were ice-free, the white regions were ice-filled and the grey regions were regions they weren’t measuring.

Notice how all of the Siberian Arctic regions that the Russians could see were ice-free were assumed to be ice-filled by the DMI?

The Walsh & Chapman estimates assumed that the DMI’s guesses were accurate, but they weren’t!

Now, we must point out that while we were carrying out our study which used both the Russian data and the DMI data, Walsh and Chapman also updated their estimates. And, the new 2017 Walsh et al. dataset (Open access) uses the Russian dataset too.

However, as we discuss in the paper, their approach still ends up effectively assuming that most of the regions without observations were “ice-filled”! To us, this is a very unwise assumption, particularly for the earlier years when there were very few observations.

So, we realised that the pre-satellite data needs to be re-calibrated to account for the limited observations and also the changes in different data sources (airplanes vs. ships vs. buoys, etc.) for different regions and times. For a detailed discussion of our re-calibration procedure, we’d recommend reading our paper (Abstract here). But, essentially, we used Arctic temperature records from weather stations on land to ensure that the sea ice measurements from each of the data sources show a similar response to Arctic temperatures to that observed in the satellite era.

After re-calibration, we obtained the following result including error bars:

There are several points to notice:

  • While Arctic sea ice has indeed been generally decreasing since the start of the satellite era, this coincidentally followed a period of Arctic sea ice growth from the 1940s to 1970s!
  • Indeed, the Arctic seems to routinely alternate between periods of sea ice growth and sea ice retreat. This is quite different from the previous Walsh & Chapman estimates which implied that Arctic sea ice was almost constant before the satellite era!
  • If we ignore the error bars, perhaps you could argue that sea ice extents since 2005 are lower than they have been since 1901. However, we shouldn’t ignore the error bars. We can see that the lower error bars for the pre-satellite era have been lower at several stages than the upper error bars for the entire satellite era. In other words, the recent low values are still consistent with our estimates for the pre-satellite era.

A useful test of the Global Climate Models used by the IPCC reports (called “CMIP5” models) is to see how good they are at “hindcasting” Arctic sea ice trends. A “hindcast” is a “forecast” that goes backwards in time.

Below, we compare our summer reconstruction with the average of the IPCC’s climate model hindcasts.

We can see that the IPCC climate models were completely unable to reproduce the different growth and retreat periods.

Arctic sea ice changes over the last 10,000 years

In recent years, several researchers have developed an interesting new “proxy” for Arctic sea ice cover, called “PIP-25”, which can be used for estimating long-term changes in Arctic sea ice extent. A “proxy” is a type of measurement which can be used to indirectly approximate some property – in this case, Arctic sea ice cover.

In 2007, Prof. Simon Belt and colleagues noticed that a type of algae which seems to only grow in sea ice produces a specific group of molecules called “IP-25” – see Belt et al., 2007 (link to abstract, link to Google Scholar). They found that if the sea ice in a region melts in the summer, some of this IP-25 will sink to the bottom of the ocean as part of the ocean sediment. However, if there is no sea ice, or if the sea ice remains frozen all year, then the ocean sediment for that year doesn’t contain any IP-25. They realised that if you drill an ocean sediment core for that region, you could use the presence of IP-25 as a proxy for “seasonal sea ice”, i.e., ice that only forms for part of the year.

Later, it was realised that if the IP-25 was absent you could also use the presence of certain species of phytoplankton to distinguish between periods with permanent ice cover (less phytoplankton growth because the sea ice reduces the amount of sunlight under the ice) and ice-free conditions (more phytoplankton growth). So, by combining the IP-25 and phytoplankton measurements in an ocean sediment core, you have a “PIP-25” proxy series (“P” for phytoplankton) which can distinguish between three types of sea ice cover:

  • Permanent ice cover (low IP-25 and low phytoplankton)
  • Seasonal ice cover (high IP-25)
  • Mostly ice-free (low IP-25, but high phytoplankton)

In Stein et al., 2017 (abstract here, although the paper is paywalled), Prof. Rüdiger Stein and colleagues presented the results from two new PIP-25 ocean sediment cores (from the Chukchi and East Siberian Seas) and compared them with another two cores from earlier studies in different parts of the Arctic (one from the Laptev Sea and the other from Fram Strait).

We have adapted the maps below from Figure 2 of Stein et al., 2017, with some editing to make the locations easier to see. The maps show the location of the four cores relative to the maximum and minimum Arctic sea ice extents in 2015. The four cores are quite well distributed throughout the Arctic and so should give us a reasonable estimate of how sea ice has varied throughout the Arctic over longer time scales.

Notice that all four locations were ice-free during the summer minimum (06 September 2015), but three of the locations (the Chukchi Sea, East Siberian Sea and Laptev Sea cores) were ice-covered during the winter maximum. In other words, these three locations currently experience “seasonal sea ice cover”. The remaining location (the Fram Strait core) was still outside the ice extent even during the winter maximum (17 March 2015). So, currently that location is “mostly ice-free”. However, as we will see, the PIP-25 sediment cores suggest that these conditions have changed over time.

For the four plots below, we have digitized the PIP-25 results for the four sediment cores from Figure 10 of Stein et al., 2017. Roughly speaking, PIP-25 values below about 0.5 indicate that the region was mostly ice-free at the time (Stein et al., 2017 use the term “reduced sea-ice cover”), while values above about 0.7 indicate that the region was permanently ice-covered, i.e., it remained ice-covered throughout the entire year (Stein et al., 2017 use the term “perennial sea-ice cover”). Values between 0.5 and 0.7 indicate that the region experienced “seasonal ice coverage”, i.e., it was usually ice-covered during the winter maximum, but ice-free during the summer minimum.

As we discussed above, three of the locations (the Chukchi Sea, East Siberian Sea and Laptev Sea sites) currently experience “seasonal ice coverage” and the Fram Strait site is currently “mostly ice-free”. However, according to the PIP-25 data, over the last 10,000 years, all four of these sites have gone through extensive periods with less ice coverage as well as extensive periods with more ice coverage. In particular, all four locations seem to have experienced much less ice coverage 6,000-8,000 years ago (i.e., well before the Bronze Age) than they do today.

This suggests two points particularly relevant to our discussion:

  1. Arctic sea ice extents have shown a lot of variability over the last 10,000 years (at least), so we shouldn’t be too surprised that the extents have substantially changed since the start of the satellite records in 1978.
  2. Despite the widespread belief that the current Arctic sea ice coverage is “unusually low” (based on a combination of the 1978-present satellite records and computer model results), it seems that the coverage was actually a lot lower 6,000-8,000 years ago.


  • After re-calibrating the pre-satellite data, it now transpires that Arctic sea ice has alternated between periods of sea ice retreat and growth. The satellite record coincidentally began at the end of one of the sea ice growth periods. This has led to people mistakenly thinking the post-1978 sea ice retreat is unusual.
  • The results from new sea ice proxies taken from ocean sediment cores suggest that Arctic sea ice extent has varied substantially over the last 10,000 years. They also suggest that Arctic sea ice extent was actually less before the Bronze Age than it is today.
  • The current Global Climate Models are unable to reproduce the observed Arctic sea ice changes since 1901, and they seem to drastically underestimate the natural sea ice variability

313 thoughts on “What do we know about Arctic sea ice trends?

  1. I would note to the authors of this paper that the Satellite record does NOT start in 1978. The National Snow and Ice Data Center has obtained satellite records back to nearly the beginning of the space era which provide a LOT more and accurate information on Arctic ice trends. Our team was involved in recovering the Infrared Radiometer data from the Nimbus I, II, and III satellites, that flew in 1964, 1966, and 1969 respectively.

    • I would also strongly suggest looking at the Nimbus Advanced Video Camera System (AVCS) that has also been recovered. It has almost daily Arctic ice data. I would also suggest the book NASA SP-489, Arctic Sea Ice, 1973-1976: Satellite Passive Microwave Observations. This book shows a lot of variability in Arctic ice just over a four year period in the 1970’s.

      • Yes, and IPCC decided after 1990 to ignore pre 1979 because there was an inconvenient truth there.
        In addtion, I believe i read somewhere that Chapman cautioned against using that graph as gospel.

      • Does anyone know if polar ocean currents were taken into account? Just because a certain algae produces IP-25 and drops to the seabed, doesn’t necessarily mean that the algae was produced directly above where it was found in the core samples. Ocean currents could have transported it hundreds of miles away from its original surface location.

      • The paper is a good reminder that the pre-satelite data is nothing more than an arbitrary assumption that nothing changed before humans affected the Arctic. However, it is already clear from the detailed consistent satelite data that we are not seeing the “run-away” decline that everyone has been screaming about. It seems quite likely that there will be in increase in Arctic sea ice over the next 5 years.

      • and this article makes no mention of post Chapman research collating all possible record sources, which is summarised in this article by the NSIDC’s Florence Fletterer
        From the conclusions of the article, summarising the research:
        “Most fundamentally of all, the new dataset allows us to answer the three questions we posed at the beginning of this article.
        First, there is no point in the past 150 years where sea ice extent is as small as it has been in recent years. Second, the rate of sea ice retreat in recent years is also unprecedented in the historical record. And, third, the natural fluctuations in sea ice over multiple decades are generally smaller than the year-to-year variability”
        Curry’s blog also contained this statement in one of its pieces on historical ice conditions (referencing the above and then yet to be completed NSIDC research)
        “The 1920-1940’s arctic sea ice melt can therefore be seen as remarkable, albeit the caveats about apples and oranges need to be applied. Looking at the evidence available from each of the arctic oceans means the ice extent probably lies somewhere within that experienced during the first half of the 2000’s, but was probably not as low as 2007 and 2012.
        It is anticipated that the ‘Back to 1870’ project will objectively look at the available information from all sources and put the period to 1870-and especially 1920-1940/50- into its proper context to today.”
        finally we have to acknowledge a particular change in sea ice conditions, not seen in the period of the historical record – the opening of the NW passage yearly, to all forms of shipping without icebreaker support, for the past decade.

      • Griff, what is alarming about this in your post….
        “Looking at the evidence available from each of the arctic oceans means the ice extent probably lies somewhere within that experienced during the first half of the 2000’s, but was probably not as low as 2007 and 2012.”

      • Sheri
        Open for business – as in a regular commercial shipping route – the NW passage may not be – but it is open for navigation – which it clearly was not in the 19th and 20th centuries.
        and Russia’s Northern Sea route?
        that IS open for business, for longer each year without any need for ice breaker assistance…

      • Again, the giffiepoo slime crawls from beneath the red algae to spew false information. Proving again that giffiepoo is not here to learn, but to spread false propaganda.

        “giffiepoo August 18, 2017 at 1:15 am
        and this article makes no mention of post Chapman research collating all possible record sources, which is summarised in this article by the NSIDC’s Florence Fletterer”

        You have been unable to defend that useless piece of trash alleged science each of the previous times you felt the need to throw it up.
        That trash science approach to the Arctic ignored all inconvenient evidence while accepting every bit of frozen Arctic nonsense they could find.
        e.g. one of the sources your fake science buddies conveniently overlooked:

        Arctic Warming” During 1920-40:
        A Brief Review of Old Russian Publications
        Sergey V. Pisarev
        P.P. Shirshov Institute of Oceanology
        Russian Academy of Science
        Moscow, Russia
        1. The idea of Arctic Warming during 1920–40 is supported in Russian publications by the following facts:
        * retreating of glaciers, melting of sea islands, and retreat of permafrost
        * decrease of sea ice amounts
        * acceleration of ice drift
        * change of cyclone paths
        * increase of air temperature
        * biological indications of Arctic warming
        * ease of navigation
        * increase in temperature and heat content of Atlantic Waters, entering Arctic Basin.
        2. The reasons of Arctic Warming (according to old Russian publications).
        3. Cooling in 1950–1960.
        Retreating of glaciers, melting of islands, and retreat of permafrost
        During the Persey cruise in 1934 Zubov noticed that the glaciers of Jan-Mayen and Spitsbergen were considerably reduced, relative to their sizes adduced in British sailing directions of 1911. Retreat of glaciers was observed also at Spitsbergen, Franz-Joseph Land, and Novaya Zemlya. The ice bridges between some of Franz-Joseph islands melted.
        Alman explored the glaciers of Spitsbergen in 1934 and came to the conclusion that they were melting. The observations of 1935–1938 showed that Iceland glaciers were melting too.
        According to Sumgin, the south boundary of permafrost shifted to the north by 40 km during 1905–1933.
        The disappearance of Vasilievsky Island in the Laptev Sea and washing away of the Lyakhovsky islands were phenomena of the same type.
        The decrease of sea ice amounts in 1920–1940
        The area of ice in the Greenland Sea in April–August of 1921–1939 was 15–20% less than in 1898–1920 (data of Karelin).
        In the Barents Sea the area of ice was 12% less in 1920–1933 than in 1898–1920 (data of Zubov).
        Vise pointed out that since 1929 the south part of the Kara Sea in September was free of ice, while in 1869– 1928 the possibility of meeting ice there in September was about 30%.
        The polar ice very often came close to the coast of Iceland in the last century and in the beginning of this century. During 1915–1940 the situation changed: no ice was observed in that region; negligible amounts of polar ice were noticed there only in 1929.
        The thickness of ice determined during the Fram cruise was 655 cm; during the Sedov cruise it decreased to 220 cm (the reason for this was more intensive summer melting of ice).
        Before Arctic warming, the strait of Jugorsky Shar froze near the 24th of November, but in 1920–1937 it became frozen two months later—in January.
        According to Vise, near Dicson and Franz-Joseph Land the amplitudes of tides increased by 20–30% as a result of a decreasing amount of ice.
        The acceleration of ice drift
        In spite of the fact that the amount of Arctic ice transported to the Greenland sea increased (established by Soviet expeditions in 1920–1940), the amounts of ice in that sea decreased because of the influence of factors promoting destruction and melting of ice:
        * an increase in the velocity and temperature of the Norway and Spitsbergen currents
        * an increase in the velocity of winds, connected with common intensification of atmospheric and hydrospheric circulation.
        The velocity of the drift of North Pole station in 1937 was 2.4 times greater than the velocity of Fram’s drift.”

        Meanwhile: Multiple satellite MIRS (Microwave Integrated Retrieval System) sea ice concentration images.
        There is not the massive sea ice melt giffiepoo endlessly bleated since last winter. Without a massive polar storm to disrupt sea ice in the next three weeks, this year’s sea ice minimum looks to gain substantial sea ice.
        Satellite NOAA 19:
        Satellite NOAA 18:
        Satellite Metop A:
        Satellite Metop B:
        Satellite DMSP F17:
        Satellite DMSP F18:
        Trollop giffiepoo’s voice of nonsense, falsehood and sheer absurdity, debunked again!

      • Mod, please check the trash, black hole, bad word and spam dumps.
        Two posts in this comment section, that I submitted, have vanished into the WordPress ethers without any indication of a successful or even moderated post.
        Perhaps WordPress’s is trashing posts for obscure reasons again?
        [Yes, rescuing Trashed posts has become almost a full time job here. Not sure why. Found your post and rescued it. -mod]

      • “[Yes, rescuing Trashed posts has become almost a full time job here. Not sure why. Found your post and rescued it. -mod]”

        Thank you!

    • There is also the declassified reconaissance satellite photos (CORONA, LANYARD, ARGON and HEXAGON) from 1960-1984. For example the first satellite photograph ever retrieved, taken on August 18 1960 shows that the sea around Mys Shmidta in Chukotka was ice-free at that time.
      Not to mention older USAF (and USAAF) photos. For example USAAF photographed all of Greenland in 1943 and 1946.

      • Many people have seen the graph of pre 1979 ice in the IPCC-FAR report
        Figure 7.20: (a) Northern Hemisphere, and (b) Southern
        Hemisphere sea-ice extent anomalies. Data from NOAA (USA).
        Did you know it came with a discussion?
        7.8.2 Sea-ice Extent and Thickness
        Especially importantly, satellite observations have been used to map sea-ice extent routinely since the early 1970s. The American Navy Joint Ice Center has produced weekly charts which have been digitised by NOAA. These data are summarized in Figure 7.20 which is based on analyses carried out on a 1° latitude x 2.5° longitude grid. Sea-ice is defined to be present when its concentration exceeds 10% (Ropelewski, 1983). Since about 1976 the areal extent of sea-ice in the Northern Hemisphere has varied about a constant climatological level but in 1972-1975 sea-ice extent was significantly less.

        So from IPCC, starting at a high point on the left side of the chart falsifies the slope.
        Then there is March 2, 1975 & the Trib is confirming that:
        The current start of Arctic Sea ice is a high point. In the last decade, the Arctic ice and snow cap has expanded 12 per cent,
        There was a ‘Little Ice Age’. No scientist is forecasting a full-scale Ice Age soon, but some predict that in a few decades there might be little ice ages like the ones which plagued Europe with severe winters from 1430 to 1850.
        “Wilson Smith, you missed another one.”

  2. This is consistent with the common theme in the 1970’s that the Earth was heading into a new ice age. What should be done is a search of Cold War era spy satellite views of the Arctic, which the US and Russians probably still have, but have never released.

      • This chart is not the actual data that the original satellite data produced (I don’t know what the IPCC was doing).
        It original satellite data goes from 1972 to 2002 for the Arctic and starts in 1973 for Antarctica.. This was done on the same basis, the same algorithm that is used today).
        The data is here (although there needs to be a tiny bit of matching up with the 1979-on data so they are consistent but there is little difference actually).
        The University of Bremen maintains a chart of the data here:

      • richard, how about links to your source material?

        How about you providing it since you appear to have an opinion of it anyway?
        I’m quite bored to the usual SkS suspects that come up here and basically just troll when had the opportunity to table their best and well-written credible science. Instead, we see some advocacy with keywords like ‘unprecedented’ which totally suck with no credibility what so ever. If you are here to turn a head of a skeptic, then ffs, please table your knowledge. If you have some.
        And no, the fact something got through the peer review with totally alarmist language is not gonna convince anyone. I agree with the conclusions of the above paper, that we do NOT have outstanding, accelerating, and dangerous sea ice loss, but rather fluctuating decadal changes that do not much differ what has happened before, and which do not concern me a bit as such.

      • crackers345 August 17, 2017 at 6:24 pm
        The source is in plain sight on the document, ie USDOE, December 1985.

      • @science of fiction and crackers 345
        You are both regular commentators on this blog, so I would have envisaged that you would have seen these plots before, because they have been posted before (by myself, and no doubt by others). If indeed you are genuinely interested in this topic, I would have thought that you would have come across them independently in the course of your own investigation/reading into the topic, for example had you actually read the IPCC reports and the historic papers published in leading journals prior to the mid 1980s (ie., at a time before the science became hijacked by activists).
        The source info is actually set out if one looks at the plot one can see the source material.
        The Latitude plot comes from the IPCC First Assessment Report, ie., claimed to be the gold standard. It is a plot direct from the horse’s mouth. It is ditched in the later reports and you may know that it is now difficult to get one’s hand on the First Assessment Report. It used to be linked on the IPCC website, but since the First Assessment Report contains inconvenient historic data (eg. plots showing the great variation in Northern Hemisphere temperatures with both a MWP and a LIA very different to the Mann Hockey Stick), this has been expunged.
        The plot I set out came from the US Department of Energy Report of 1985, as I noted before setting out the plot. The source can be seen from the plot itself since it is a scanned copy. As can be seen, it actually comes from their Carbon Dioxide Research Division and is based upon a 1980 study paper by Vinnikov (I used to have a copy of the Vinnikov paper on a different computer which has since died. I recall that this paper was published in a Peer reviewed journal.) Don’t forget that Vinnikov was one of the lead authors of Chapter 7 of the IPCC First Assessment Report so his credentials are solid.
        The fig 5.2 from the USDOE 1985 Report is not at all surprising since it fits well alongside what we know about the 20th century Northern Hemisphere temperature profile, namely that there was significant warming between 1920 to 1940 when a high was reached, and there was cooling through to the early 1970s, and there there was some modest warming such that by about 1980 the Northern Hemisphere temps were about 0.3 to 0.4 degC cooler than they were back in 1940.
        This profile of Northern Hemisphere temps is seen in the 1980 Phil Jones et al paper, and in the 1981 James Hansen et all paper, and it is consistent with the Vinnikov reconstruction of Arctic ice.
        When looking at a reconstruction, one needs to bear in mind that it is only a reconstruction and with any reconstruction (eg., the land based thermometer record is a reconstruction), there are always wide error bounds.
        Further, when looking at reconstructions published before around 1983/85 these can be considered to be based upon our best estimation using available data, whereas after the mid 1980s the science has become hijacked and promoted by those with an agenda/activists and reconstructions made after the mid q980s need to be considered with even more circumspect because of that. One can see this in the Climategate emails where they openly discuss that the tree ring data shows no 1970s warming, the fact that Southern Hemisphere temperatures are largely made up, that there is a need to get rid of the 1940s warming/blip etc. etc. This attitude has made later stuff (they are not objective scientific reports) very unreliable.
        PS. Don’t forget to look at the comment above made by DD More August 18, 2017 at 1:17 pm. The text quoted comes from Chapter 7 of the the IPCC First Assessment Report of which Vinnikov was one of 3 lead authors (C K Folland, and T R Karl being the other two).

      • TTY,
        Do you know if there has ever been a release of weather data collected to aid ICBM launch targeting? I have a mental picture that is probably wrong, of a dedicated weather recording station at each silo/site that might be able to give, for example, surface temperatures relatively unaffected by site moves and TOBS type complications. Geoff

    • Once upon a time back in the early 1970s, I worked as a janitor at a major missile manufacturing company.
      Several times as I cleaned one office, there would be this large magnificent coffee table book sitting on a table.
      Yes, it was marked “Restricted”, “eyes only”, “Do not display”, “Do not remove from office”.
      Hey, the janitor got to see and handle all of the room and trash.
      Sitting at the table during dinner hour, I occasionally browsed through the book. The satellite pictures from around the world and both poles were phenomenal.
      Large area shots and zoomed detail shots throughout the book; though there was near zero detail on exactly what each picture displayed.
      There are records prior to the known satellite climate imagery that should be released and used.

  3. Ignorance and uncertainty are such wonderful things — they allow you to shape them in whatever manner your pet idea allows.
    Just say, “We really don’t know”, and stop with the readjustment game to fit either a pro or anti alarmist perspective.
    It’s nice to know, though, that two can play this game. (^_^)

    • Yes you can pick one of these
      1) We don’t know => so there is no reason to be alarmed without evidence
      2) We don’t know => so there is a reason to be alarmed without evidence
      Anyway, all I know about the Arctic suggests there is no reason to be afraid of summer sea ice extent loss, if there is loss to be expected. Rather the other way around. The belief on catastrophic Arctic summer sea ice loss is just a scare story used by activists. The lack of non-activists believing it proves its credibility requires a confirmation bias.

  4. The temperature north of 80 usually tracks the average very closely when it is above zero C. Presumably the melting ice moderates the temperature. This year it has been low all season. That’s pretty remarkable. I have no clue what it means. link

    • CB-The daily temperature readings as graphed on the sea ice page show above past mean temperature for most of the year recently, rising just above 0C to match the mean only in summer. The non-summer temps are quite erratic. I believe this pattern is indicative of the mainly marine climate which is prevailing in the Arctic at this time. If there was less ice area the temps would track the longer term mean.
      I believe there is an important clue in this. The loss of ice is due to rising water temps, not air temps . The open water creates the higher air temps.
      So, the cycle is thus:
      Open water is self-sustaining as winds disturb the surface of the relatively warm water.
      This is indicative of a period of high-heat loss.
      Heat loss leads to colder Arctic water.
      Eventually, water temps are reduced to the point where the surface undergoes massive ice expansion.
      The ice covering reduces wind disturbance and so is self-sustaining.
      The ice covering greatly reduces heat loss.
      The ocean once again begins to accumulate heat.
      The ocean eventually warms to the point where the ice thins and winds are able to break up large areas again.
      The temp change in water across this cycle may be less than 1C as it is really about the balance between ice thickness and wind. The cycle will have a large effect on N.H. temperatures as it is an important mechanism whereby Earth loses massive amounts of heat on a cycle of 30 years or more. We appear now to have nearly completed the heat dumping portion of the cycle so ice has stabilized. If we had good information on Arctic water temps (by depths and location) we could track the temp decline and get an understanding of the total amount of heat involved. But NASA, NOAA, etc. look for what they want to find, not what matters.

    • Griff is in the UK and so likely asleep and we get a short break from the nonsense until it stirs from it’s nest and resumes the daily GLO-BULL warming rants.

      • Well, if you think someone’s comments are a waste of time why do you feel the need keep mentioning his name in his absence? Thus assuring his presence for him even while he sleeps !!
        If you have nothing of value to add to comments, stay silent.

      • Bob and Stewart,
        While you may find Griff’s contrary viewpoint to be annoying, the fact is that he is cheeful, he is friendly, and he has NEVER uttered an ad hominen against anyone on this site. That makes him, despite his contrary viewpoint, a much more valuable participant than those that lack these exemplary qualities.
        Make no mistake, I seldom, if ever, agree with Griff’s views but I do find his friendly and cheerful attitude to be refreshing compared to some.

      • Ray
        You are right he’s a great guy that only Slanders every scientist that he disagrees with, posting information and attacks on their character and credentials that are absolute fabrications. I suggest you go back and research good Griffy a little.
        If he was what you say I wouldn’t have an issue with him at all I would just ignore his BS or get whatever amusement I could from reading him, but you are wrong about his character.

      • Ray in SC August 18, 2017 at 5:56 am
        Griff’s disparaging real scientists as not being scientists because the consensus attacks them is not an ad hominem?

  5. Only one month in June, but there was virtually no difference in Arctic ice between June 2000 and June 1977. (fig.1) The Satellite and Arctic grid methods are different, but can easily be estimated to show similar coverage.
    Why should this matter?
    The trend of June’s (fig.2) shows June 2000 around the middle of the duration shown below. While June 1977 also represents the middle of the duration, indicates the trend after 1980 is nothing unusual to what happened before and confirms cyclic behaviour. The period during the 1970’s also had an increasing trend with 1979 around it’s maximum extent.

      • Johnny: In spite of your great play on words, Santa cannot live at the South Pole. The researchers and dog sled teams might stumble upon his lair—I mean workshop. He needs a place where no one goes. Which probably explains the lack of data on the Arctic ice….

    • Once the ice is gone there would be no reason for bored wannabes to be warning you that the ice will soon be gone.
      Those bored wannabes would need to find a new boogerman.

      • Completely wrong, Griff! The open water in the Arctic allows for much greater heat loss from the ocean waters. When ice conditions are higher, the ice prevents this heat loss and the Arctic ocean accumulates heat. Presently, we are losing that heat. Probably about 30 years of gaining, 30 years of losing.

    • Alarmist’s think it would cause the world to heat up and cause all sort of problems, but they wrong.
      It actually causes the world to cool faster because virtually all the energy at the North pole has been transferred there from the much warmer Southern locations. Water with no ice insulating it, releases energy into the atmosphere there much faster. Prevent the energy reaching the North pole and we have a situation similar to Antarctica, where little energy reaches there from the North even in Summer.
      Solar energy is not concentrated enough to warm the poles, so they rely on energy from elsewhere and the biggest difference between the poles currently.
      It is just one of the planets many natural negative feedbacks.
      There seems to be some advantages for example in shipping, but why have 100,000 year periods cooled every time it reaches it’s peak?
      It seems energy increasing in the north pole and melting sea ice was the trigger for an ice age with the right conditions. An ice age requites lot’s of precipitation to occur and fall as snow, preventing complete melting during the Summer time. What’s better on the planet then the Arctic ocean warmed up considerably, preventing formation of ice with extremely cold air around it?

      • Solar irradiance is important in the polar regions within a couple months of the summer solstices, even though heat also gets advected to them from parts of the wortld that get sun year-round. Note that insolation at the top of the atmosphere over one of the poles over the 24 hours centered on the summer solstice is 19% more (north) 27% more (south) than over the equator over 24 hours on one of the days of the equinox. The Arctic and Antarctic circles also get more on the summer solstice than the equator gets on an equinox. Even at the surface and year-round, the Antarctic gets anywhere from 80-100 to 120-140 W/m^2, the Arctic gets 60-80 to 100-120 with a couple little spots of 120-plus W/m^2, in comparison to the most insolated parts of the Sahara and the tropical Pacific getting 260-280 W/m^2.
        And insolation at the poles averaged over the 6 month period centered on the summer solstice is almost twice the annual value, which means a little less than 160-200 W/m^2 at the North Pole and a little less than 200-240 W/m^2 at the South Pole. A little less still at the Arctic and Antarctic circles for the 6 month period centered on the relevant summer solstice. Much more for 4, 3 or 2 months centered on the summer solstice.
        Notably, the Milankovitch cycles are often expressed in terms of solar irradiance at the top of the atmosphere at 65 degrees north latitude over the 24 hours centered on the summer solstice. The surface albedo feedback is highly positive (to an extent that is unsteady) in the Arctic and near-Arctic, although thankfully it gets less positive when the Arctic and near-Arctic loses sunlit seasonal snow/ice cover.

      • Matt there is another factor, well two actually. Convection. When the wind blows, as it does in those parts, with open water the latent heat of vaporisation will be transferred to the air from the water depending on the dew point of the air. This effect increases with water temperature but will occur even when the water is colder than the air. Then there is conduction, although I would expect this effect to be minor by comparison as air is not a good conductor.
        With regards to your suggestion that lack of sea ice could be a trigger for a new ice age I think the point of perihelion on our calendar has relevance here. This moves along at about 40 minutes a year and has passed Northern summer solstice so now Northern summers get shorter and the distance between the Earth and the sun during summer increases. This suggests that the probability of an ice free Arctic triggering the next ice age is increasing as time goes by but might perhaps require a grand solar minimum at the same time to nudge things over the edge. It seems the best days are behind us and that warming should be the least of our concerns.
        Donald given the low angle of incidence of Sunlight up North do your figures for insolation take reflection off water into account?

      • I found the difference between polar locations warming and cooling around 200 W/m^2. For example Iceland reaches these values in late October and cools significantly especially regarding SST’s. Regions cool as this threshold is reached further South in the NH and further North in the SH. This happens at the same time every year with no random variety. Solar irradiance although contributes a little energy below 200 W/m^2 isn’t enough to warm on the whole despite 24 hour daylight. Convection, conduction and ocean currents mainly warm locations under 200 W/m^2 from locations above 200 W/m^2. This is the main reason why Antarctica in Summer is around 20c-30c colder than the Arctic during Summer.
        The energy in the ocean keeps the polar regions in the Arctic much warmer than what solar irradiance could ever contribute. If the Arctic was land-locked it would be colder than Antarctica due to lower insolation.

    • Imagine the massive benefits from lower sea ice levels like in the MWP.
      Travel, commerce, fishing.. all without the need for ever present ice-breakers.
      The huge commercial gain just from having an Arctic that was actually open to “over the top” shipping for more than a couple of months (with ice-breaker availability, would be enormous !!
      Unfortunately, the RECOVERY from the extreme extent of the late 1970’s seems to have stopped, and with the AMO turning and the sleepy sun, the local inhabitants are going to have to put up with increasing sea ice again.

      • Well a short-cut through arctic would save lots of “carbon” transporting to chinese goods to consumers in the west.

      • Greg then we shouldn’t use it we need more CO2 in the atmosphere. CO2 is good for the environment.

    • Owen, this is a discussion worth having. Let us please accept the obvious evidence that Arctic sea ice is declining. If you want to argue “so what”, then fine, lets have it. This discussion is nt ossible if so many people are going to ignore the evidence in front of their face.
      Look at the graph from paper. we know this is not evidence from alarmists – it is the interpretation that is most charitable for the skeptics. Yet it still shows a rapid decline since 1979 to levels lower than in the previous century. There is just about room to argue that if the error bars overlap, but to have the recent lows not different from the previous lows we need the error to be in the very bottom of the previous and the very highest of the recent. This is very unlikely. We can say that the recent drop – even in this evidence – is very likely to be real and only has a tiny probability of being due to error.
      If we look at other reconstructions (as this is a reconstruction) we see an even greater difference. So if we look at all the evidence it is an act of supreme bias to conclude that sea ice is not at its lowest (over the last decade) over the last 150 years.

      • I do not consider anyone disputes that Arctic Ice (sea ice) is declining since 1979, but that does not mean that Arctic Ice is declining since it depends upon the start date.
        There are multiple lines of evidence that suggest that Arctic Ice today is no less than it was back in around 1940, and may well be higher. Therein lies an issue, since if one goes back further in time there may be no decline.
        No one knows what Arctic Ice will do in the near future (eg., the next 60, or so, years). Some claim that the decline from 1979 will continue unabated. Others claim that that decline is simply part of a cycle and the cycle will reverse and Arctic Ice will stop declining and will start growing.
        Only the future will establish which of these two outcomes comes to pass, but when discussing matters one should not deny the past and one should not limit discussions to what has happened as from 1979 (although of course, the best data sourced from satellites comes from the 1970s onwards).
        I agree the so what? debate is quite a separate debate and one which is worthy in itself

      • Richard
        The “so what” argument is fine. Accept the evidence of decline then argue so what. However, the decline on the evidence presented here is not since 1979 but over the last 150 years. Just look at the plots. It is far more likely than not that the levels today are lower than at any time in the last 150 years. This is from a paper co-authored by Willie Soon, so it cannot be classified as from an alarmist source. All other reconstructions show the same. There is no recently published reliable evidence that says the current levels are not lower than at any time in the last 150 years. So can you accept this and then make your “so what ” argument?
        “There are multiple lines of evidence that suggest that Arctic Ice today is no less than it was back in around 1940, and may well be higher. ”
        No there is not. Show me one recent piece of evidence that says this. Old graphs from last century will not cut it.

      • richard – sea ice will decline in the
        future. the science says
        it will.
        i wonder what u would have
        said about SIE in 1979. probably
        the same

  6. A couple notes on this. First, Dennis Wingo is correct that there is some early satellite data from the 1960s.
    The main point though is that there is an updated Walsh climatology that reanalyzed many of the ice charts and added a lot of new data from the pre-satellite era. The data are at NSIDC:https://nsidc.org/data/g10010. Info on the trends from the data were published in a paper here: http://onlinelibrary.wiley.com/doi/10.1111/j.1931-0846.2016.12195.x/full; Figure 9 from the paper is particularly relevant here. Hopefully people can access the paper.
    Finally, a note on the submarine ice thickness data. The Rothrock paper published in 1999 was based on data that was classified a few years earlier as part of a joint U.S.-Russia Environmental Working Group. Al Gore, Vice President at the time, was a major force in that project and pushed to declassify the U.S. submarine data.
    Walt Meier
    Senior Research Scientist
    National Snow and Ice Data Center

    • Walt Meier
      Senior Research Scientist
      National Snow and Ice Data Center

      “A couple notes on this. First, Dennis Wingo is correct that there is some early satellite data from the 1960s”.

      The main point though is that this data was never considered and never used.
      Why not?

      Instead Chapman et al used other historical data with infilling of all unknown areas, hence increasing the amount of ice present in the past.

      Correct ?

      “The main point though is that there is an updated Walsh climatology that reanalyzed many of the ice charts and added a lot of new data from the pre-satellite era.”

      again to reiterate not including the pre1970 data.

    • Thanks for the link to the recent Walsh paper. Sadly it stops around 2012 at the low point of the summer extents and does not show the following increase.
      An unfortunate choice for a paper published in 2016. Clearly they would have had access to and been aware of more recent data before finalising their paper, so why did they chose not to include it ?

  7. “4 March 2003
    Polaris has been melting for 150 years
    WWF reconstructs climate change in the Arctic
    Düsseldorf (rpo). The ice of the Arctic has been on the retreat for at least 150 years. This is the result of the WWF and the Norwegian Polar Institute (NPI) in a new study.”
    German source from 2003
    Back to 1550, the data are available here
    Follow the documentation.

  8. It is anecdotal but I remember during the cold war both US and Russian subs surfaced at the North Pole (in 1959). Now, I was just a child at that time, but I would think that there had to be fairly sever melting, but not necessarily ice free, to allow that to occur.

  9. The satellite ice data has always bothered me, whether it is the recent data from 1979 or earlier data from early satellites in the 1960s. Just like the hole in the ozone above the Antarctica we cannot know something until we can measure it or in the case of both polar regions until we actually go there directly or through remote imagery. We don’t know there were not holes in the ozone prior to humans going permanently to the Antarctica nor can we have exact estimate of sea ice at either polls until synoptic data from satellites. The CAGW crowed make such a huge deal over relatively little change or short term trends that it is vital to help the general public keep this all in perspective. Something impossible to do with the present state of the mainstream media. I cannot imagine that telling the public and having them accept it that going from an average earth temperature of 57.2 to 59.0 F is a really bad thing.

    • We don’t know there were not holes in the ozone prior to humans going permanently to the Antarctica nor can we have exact estimate of sea ice at either polls until synoptic data from satellites.

      Funny you say that Edwin. In fact we have had some fairly good data since the 1950s. Dobson managed to get one of his measuring contraptions down to Hadley Bay in time for the International Geophysical Year. Reading from three years (1956-8) led him to proposed the Antarctic winter ozone anomaly, where the persistent southern vortex blocked the Brewer-Dobson ozone transportation. Ozone banks up on the outside of the vortex, while on the inside the stratospheric air becomes substantially ozone depleted (this is the dramatic phenomenon you can see in those NASA satellite animations).
      Farman’s discovery of the ‘hole’ in the early 1980s was not this, but a further depletion (increasing from the late 1970s) in the spring. This is in October, after the sun returns, just before the vortex breaks up and the ozone floods back in. It was proposed that this October ‘hole’ was caused by extra stratospheric chlorine from photo-chemical destruction of CFCs. The proposed series of chemical reactions requires stratospheric polar clouds but also sunlight.
      So much of the discussion since 1985 conflates the winter anomaly with the spring ‘hole’. And the size (surface area) of the anomoly/hole has often been given as indicator of the CFC destructive effect — whereas this is more to do with the size of the vortex. So we do know there was a decline of spring time ozone from the 1970s, the cause of which seems to be increased chlorine, possibly from CFCs. But this effect only occurs in the last blink of the anomaly. That the CFC-caused ‘hole’ is only final dip in the vortex depletion anomaly is rarely explained. Indeed, I have seen NASA images supposedly depicting the hole that are dated August and September. Animations often cut off before the supposed CFC effect can begin. When scientists and scientific institutions (eg NASA) show a big (i.e., large surface area) depletion in winter (August or September) and explain it as a sign of the CFC depletion effect, then I can only conclude that they are either ignorant or knowingly deceiving the public in support of a noble cause.

    • There is good data prior to 1979 from multiple sources and nations…
      The NSIDC has collated this.
      We can be sure that sea ice extent lower now than at any time to earliest point they looked abck to – 1850

      • Griff – “extent lower now than at any time”
        Not according to your “current ice concentration – swiss cheese up there:” chart and this report
        The Arctic ocean is warming up, icebergs are growing scarcer and in some places the seals are finding the water too hot, according to a report to the Commerce Department yesterday from Consul Ifft, at Bergen, Norway.
        Reports from fishermen, seal hunters and explorers, he declared, all point to a radical change in climate conditions and hitherto unheard-of temperatures in the Arctic zone. Exploration expeditions report that scarcely any ice has been met with as far north as 81 degrees 29 minutes. Soundings to a depth of 3,100 meters showed the gulf stream still very warm. Great masses of ice have been replaced by moraines of earth and stones, the report continued, while at many points well known glaciers have entirely disappeared. Very few seals and no white fish are found in the eastern Arctic, while vast shoals of herring and smelts, which have never before ventured so far north, are being encountered in the old seal fishing grounds.
        Reports “that formerly the waters about Spitzbergen held an even summer teperature of about 3 Celsius; this year recorded temperatures up to 15, and last winter the ocean did not freeze over even on the north coast of Spitzbergen.

        Taken from Nov. 2, 1922 edition of The Washington Post: Arctic Ocean Getting Warm; Seals Vanish and Icebergs Melt. and George Nicolas Ifft [Under date of October 10, 1922] Monthly Weather Review – November, 1922.
        Unless the ice melts another 7 to 8 degrees latitude by November, it will be more than 1922.

      • “We can be sure that sea ice extent lower now than at any time to earliest point they looked abck to – 1850”
        Another porky pie, Skanky.

  10. If you want to draw any conclusions about Arctic sea ice trends, keep in mind:
    1. The satellite data begins in 1979, which happens to coincide with the end of the 1950 to 1978 cool period when sea was presumable at its maximum.
    2. Decline in sea ice from 1979 to 2000 is not surprising since it coincides with the 1979 to 2000 warming.
    3. Arctic temperatures over the past century have followed global temperatures and sea ice extent shows the same trends. Arctic temperatures were higher in the 1930s than at present (ie. during the 1915-1950 warm period), cooled during the 1950-1980 cool period, and warmed during the 1980-2000 warm period.
    4. Comparing extent of sea ice now (at the end of a warm period) with sea ice extent in 1979 at the end of a cool period) makes no sense at all. What should be compared is extent of sea ice now with the extent of sea ice at the end of the 1915 to 1950 warm period. Unfortunately, we don’t have good data for the earlier time period. We would also like to compare the sea ice extent in 1979 at the end of the 1950 cool period with the extent in 1915, the end of the 1880 to 1915 cool period. But again, we don’t have the data.
    Until we can make these kinds of comparisons, conclusions about trends since 1979 don’t mean much.

  11. In the 1950s it was widely believed that the Arctic sea ice was retreating naturally and that it would soon disappear. This was not considered a bad thing except when in 1956 the then president of the AGU argued that this would trigger a series of changes including greater snowfall on northern lands and eventually the next ice age.
    In the 1960s there were proposals to remove the bothersome sea ice in various ways, including by damming the Bering Straits and even by atomic explosions. They thought that once removed, negative feedback would keep the sea open. But attitudes were changing in the West. At this time the Soviets proposed reversing the flow of their Arctic rivers. The predicted consequence of the deprivation of fresh surface water would cause an end to sea ice. The Soviets seem to have always seen this as a good thing for their marginal agriculture regions, but in the West scientists worried that it might trigger NH climate change.
    By the early 1970s there was lots of evidence (and it was widely agreed) that sea ice was expanding, which was often seen as a sign of the creeping return of an ice age little or big. Attitudes were changing in the late 1970s as many NH locations were starting to show a warming trend, and a secular north north Atlantic oscillation seemed to have turned. However, the arctic seemed to remain cool, and 1979 was considered to be particularly cold (‘coldest on record’). This was widely put to counter the AGW proponents because it was the opposite to the expected polar amplification of the CO2 warming effect.
    Before the popular global warming scare took off in the late 1980s, there was concern that ice cap melt would cause sea level rise. However, already by the early 1980s the land ice melt threat was widely discounted (except West Antarctic ice cap sliding into the sea) by accepting the long-held view that (slightly) warmer temperatures could mean more snow falling on land, the growth of existing ice caps and sea level decline. However, the threat of sea level rise switched smoothly to the previously neglected thermal expansion. This moved the emphasis away from ice caps and towards sea temperature, which of course makes floating ice something of an indicator. Thus, although where land ice melt has been found it has been used to promote the scare, otherwise, and from the beginning, Arctic sea ice decline has been seen as an omen of coming diluvian catastrophe.

    • Arctic ice conditions are cyclical. They are a balance between ocean temps and wind. Please have a look at my post higher up. We are near the end of the high heat loss phase of the cycle.
      A tip of the hat to Matt G above. I believe we are close to being on the same page on this.
      He must be a smart guy ; )

    • “crackers345 August 17, 2017 at 4:38 pm
      …CO2’s forcing…”
      Can you explain this process of forcing?

  12. If global warming be the alleged cause of Arctic sea ice decline since 1979, then explain please why the highest Antarctic sea ice year in the satellite record was 2014, after steady increases since 1979.
    If air temperature be the cause, then why the stark difference, 180 degrees out of synch, between the two poles?

    • Because temperatures have risen more in the NH than in the SH. I.e., the warming isn’t global. Apparently, despite being well mixed in the atmosphere, CO2 bestows its warmth preferentially.

      • Because there is more land area in the NH than in the SH, temperatures have risen more in the NH than in the SH. Seriously Bart, you should know better than post such a stupid comment.

      • Not eggsactly (gloat your spelling’s atrocious… ☺), if agw brings about more warming over land than sea, then that would explain the difference. Which may well ultimately BE a falsification of agw theory. If all the excess heat eventually winds up in the oceans, then that lowers the value of ECS. This is probably what happens during the ice ages. Does anyone seriously believe that a half way to doubling of CO2 (from glacial to interglacial) outpaces the massive growth in water vapor? (that observation alone should be enough to put agw out to pasture)…

      • Mark, i don’t think bart is being stupid here. For reasons that i can’t quite understand yet, he doesn’t seem to see the oceans as a heat sink. It’s a point of view. (dr svalgaard pretty much thinks the same way)…

      • afonz, it’s pretty stupid to ignore the land/water differences between the NH and the SH when it comes to the measurement of temperatures. Ask anyone that lives adjacent to a large body of water how it affects air temps.

      • i hear you, mark (i hear you)… i went back and forth with svalgaard on this very topic for about two weeks to no avail. (felt like i was busting up a block of concrete with a hammer) So, yeah, i don’t get it. Vertical mixing constantly cools the surface so we should expect heat to sink into the ocean as a result. Vast implications for AGW theory that i don’t know have been very well thought out…

      • Mark S Johnson @ August 17, 2017 at 5:40 pm
        “Because there is more land area in the NH than in the SH, temperatures have risen more in the NH than in the SH.”
        And…? This is like an underpant’s gnome explanation:
        1) More land in the NH
        2) ???
        3) higher rate of temperature increase
        It’s obvious! No explanation needed!
        Land/ocean diff doesn’t explain it, folks. The series are not divergent until about the turn of the century. So, your hypothesis founders on the agreement pre-2000.
        Remember, these are anomalies we are talking about. Not absolute temperatures. At the very least, the series should be similar in form if not magnitude, if the global forcing is the same. They aren’t.

      • Chris, i added sea surface temps to your land + sea (above)… One has to wonder if temperatures will equalize once again as they had for most all of the twentieth century. Perhaps this is a testament to the heat sinking capacities of the oceans. (ultimately temperatures of the land and northern ocean may “sink” down once again to that of the southern ocean)…

      • Bart, if the warming around the turn of the millenium is exceptional, then perhaps we could see a divergence. Look at my graph at the four data sets. Implied is that nh land warms first, then nh sea, then sh land, and then sh sea. If the warming is not that exceptional, then they all stay together. Also, think for a minute that ocean temps have gotten further above equilibrium state temp (as exemplified in by derivative plot of CO2) and are thus sinking heat at a faster rate. This should also cause the divergence that we see. i’m telling you, bart, i really think this deep ocean warming thing is a disaster for agw theory. Ocean cooling acts like a negative feedback and only gets stronger the further we get above equilibrium state temps. (there may be such a thing as ‘peak’ warming)…

      • Cracker, i agree (i think you and i have been here before… ☺). What i’m getting at is that if the heat is showing up in the ocean, then it’s not showing up at the surface. This could mean YUGE implications for the calculation of ECS which i don’t know has been accounted for. (ocean cooling acting as a strong negative feedback)…

      • crackers345 @ August 17, 2017 at 7:25 pm
        Which is hotter: a bucket of water at 26 degC, or a bucket of soil at 26 degC?

      • Bill Illis August 17, 2017 at 7:31 pm
        Thanks for the imagery.
        Antarctic sea ice is more important among other reasons because it extends so much farther toward the equator, hence has around five times the albedo effect of Arctic sea ice.

      • Bartemis
        “Which is hotter: a bucket of water at 26 degC, or a bucket of soil at 26 degC?”
        When I see comments like this I wonder if they are actually serious questions or if the author thinks they are demonstrating something clever.
        The answer is that neither is hotter as they are at the same temperature.
        If Bartemis thinks there is some clever point about energy that scientists have missed it would be helpful if this was made clear. As it is, it appears that Bartemis is ignorant about temperatures and is seeking information – a laudable activity, or is ignorant about temperatures and is trying to make a point based on his or her ignorance – not so laudable.

  13. Then explain please why Arctic sea ice extent was so much less than now during the Holocene Climatic Optimum, c. 5000 years ago; the Minoan Warm Period, c. 3 Ka; the Roman WP, c. 2 Ka, and the Medieval WP, c. 2 Ka.

    • We don’t know the Arctic sea ice extent at previous warm periods. We do know Arctic sea ice extent was very reduced at the Holocene Climate Optimum, and the most likely cause was the much higher polar insolation.

      • yes, due to orbital tilt -an effect not in play now, yet we see declining ice trends below what was observed in the 20th century

      • The world has been warming for the past 400 years, Griff. It is only logical that Arctic sea ice has been decreasing. What is more puzzling is that Antarctic sea ice has been increasing.

      • Simon,
        It’s obvious that a single event in Sept 2016 is responsible for this year’s lower Antarctic sea ice. That event was associated with the Super El Nino of 2015-16.
        You manage to ignore (inGore) the inconvenient truth that from 1979 to the satellite era record high year of 2014, Antarctic sea ice grew while Arctic sea ice fell from 1979 to the record low year of 2012.

      • Javier,
        There indeed are estimates of Arctic sea ice extent during the Medieval WP. And we know that there was less ice than now for, among other reasons, the Greenland Norse expeditions to North America.

        • Gloateous, two things:
          1. Past observations of local ice conditions are not good enough to confidently estimate past Arctic sea ice extent. This is the equivalent of taking temperature measurements at one station in Southern Greenland and saying that it represents the whole Arctic.
          2. If I remember correctly, Stein et al., 2017 use three cores for their work. Inferring whole Arctic ice extent from that is not warranted in my opinion. To complicate matters, Stein et al., graph that is shown at the link ends in the year 0 BP, which is 1950. I remind you that since 1979 we have lost one third of Arctic summer sea ice cover, that is not accounted for in that graph. Where is the huge drop?
          Saying that there was less Arctic sea ice in medieval times amounts to nothing but wishful thinking.

      • Hi Javier,
        When I first read the Stein et al. (2017) paper, I thought the exact same as you, i.e., “B.P.” usually refers to before 1950, and inferring trends for the entire Arctic from just three cores taken from two regions (Chukchi Sea and the Eastern Siberian Sea) is unwise – especially since both of those regions are relatively close to each other.
        However, when we re-read the paper (and the other literature on PIP-25 proxies) a bit more carefully, we realised the study is actually a lot more interesting for several reasons. That’s why we included a summary of it in the final section of this post.
        1.) In their analysis, because the start of their proxies correspond to the upper part of the sediment cores, their “Present” actually refers to nowadays, rather than the standard “Before Present = Before 1950” nomenclature.
        2.) In Figure 10, they compare their two new regions (Chukchi Sea and the Eastern Siberian Sea) with two other cores from earlier studies. Here are the locations of all four cores:
        As you can see, the four cores collectively cover a large portion of the Arctic.
        For our post on Judith Curry’s blog (reproduced here), we digitized the data from Stein et al. (2017)’s Figure 10, and re-plotted the data in a less cluttered format for clarity:
        3.) Their PIP-25 combined proxy is designed to distinguish between three types of ice conditions: i) ice-free, ii) seasonal sea ice, iii) perennial (“permanent”) sea ice cover. When we compare the current conditions for the four regions (see maps above) to the proxy estimates for now (see plots above), they match quite well, i.e., the proxies correctly estimate the three of the regions (Chukchi Sea, Eastern Siberian Sea and Laptev Sea) currently experience seasonal sea ice, while the fourth region (Fram Strait) is currently “ice-free”.
        4.) Unlike a lot of proxies, e.g., tree ring widths, the general trends are quite similar for all four regions. So, the PIP-25 proxies do seem to a relatively consistent proxy. Of course, that doesn’t in itself mean that they are accurately describing the proposed characteristic, i.e., ice coverage. But, compared to many of the previous equivalent proxies, the theory and analysis seems quite promising.
        Have you read the paper itself yet? Unfortunately it’s paywalled, but if you haven’t a copy and you give me an e-mail address, I could send you a pdf…

        • Hi Ronan,
          Yes, I have access to the article, and I disagree with your interpretation. As figure 10 shows, only two of the four cores reach the 0 date, and of those two one doesn’t show any kind of decrease at the end, while we know that Arctic sea ice extent has been reduced by 34% since 1979.
          There is only one possible conclusion: That the proxy obtained doesn’t accurately reproduce the present, and therefore any comparison between present and past conditions based on this study is unfounded in evidence.
          Relying too much in one proxy and/or one study is a quite common mistake when discussing about paleoclimatology over the internet. We cannot say with any degree of confidence if there was more or less ice in the Arctic during the Medieval optimum. We don’t even know with confidence the Arctic sea ice state during the first half of the 20th century.

  14. I don’t think I have ever heard of the Walsh and Chapman study. If I had, I would have dismissed it outright. You simply cannot assume a value for the majority of your area of study simply because you do not have any data! In the late 1990’s, when the Walsh and Chapman study was done, there was a lot of pressure to get rid of any indications of natural climate variability in the past, because there wasn’t any variability in the CO2 concentration in the past. You can’t sell CO2 as the main controller of global temperatures if CO2 stays the same and the temperatures goes through lots of fluctuations.
    If Walsh and Chapman had submitted their work to a 5th grade science fair, they probably would have received a ‘D’ or an ‘F’ for their methodology. (If their parents stayed up the night before and put together a kick-butt display, they might have salvaged a ‘C-‘.) Fortunately for them, they weren’t doing a grade school science fair. They were submitting their work to a scientific community with an agenda, so their ridiculous paper was accepted with open arms.
    Connolly & Connolly have done a much better job and have discovered much more variability, but it is probably just the tip of the iceberg. Even with just 4 samples and a proxi that can only paint a fuzzy picture at best, the variability clearly shows up. It is highly probable that the actual variability is larger than this small sample can capture.
    Despite the best efforts of the scientific establishment, science marches on!

  15. The whole thing is silly. Why wouldn’t we expect less ice cover in warmer times, and more in colder times?
    All decreasing sea ice means is the temperature has risen. We already knew that. It’s not new information.
    The question is, why have the temperatures risen? The AGW hypothesis is presented as an answer, but there is no evidence supporting it except models which have done a poor job forecasting trends. The null hypothesis, that it is simply a natural warming spell like others that have come and gone before, cannot be rejected.

    • Any warming spell is warm for a reason… there is, in short, a climate driver.
      for example, at the start of the Eeemian period the arctic got more insolation in summer due to the orbital tilt of the earth, so arctic summers were ice free.
      What climate driver other than human produced CO2 is there to account for the observed warming and ice melt? No orbital tilt; the sun has been in a period of declining activity…

      • Why did the temperatures rise in the 1930s and then fall?
        This was before there was enough anthropogenic CO2 to cause the increase.

      • Why did the temperatures rise in the 1930s and then fall?
        a very interesting question. climate science has no answer. so they call it “natural variability”, which is very much like religious belief in miracles. An effect without a cause.

      • “What climate driver other than human produced CO2 is there to account for the observed warming and ice melt? No orbital tilt;”
        The same climate driver that produced the observed warming from 1910 to 1940, which was equal to the magnitude of the warming from 1979 to the present. No CO2 needed back then in 1940, so why claim CO2 is needed as a driver now, when the temperature changes we are talking about are the same?

    • Nope! Reduced sea ice causes higher air temps. Not the other way round. Especially in the Arctic, as temps shift to a marine mode. The higher air temps are due to high heat loss from open water. We will soon be missing this mode.

  16. got as far as the first paragraph where sea level is tied to the extent of arctic sea ice. As Archimedes showed, as long as the arctic ice floats, its existence (or not) can have NO effect on sea level.

  17. Slightly off topic but the Arctic sailing stunt seems to have been motionless for at least today.
    Significantly the site tracking the sailboat claims the voyage is *around* the north pole, not *to* the north pole.
    Bug difference.

  18. I posted the below data to supplement the comment by Latitude August 17, 2017 at 4:09 pm in which he provides a plot of Arctic Ice going back to 1975.
    The plot below goes back to 1925 and should be seen in conjunction with the plot set out by Latitude. One can see that in around 1940 there was less than 5 million sq km of ice, ie., even less ice than today.
    The warmists like to cherry pick the 1979 date since it best suits their meme.

    • richard verney August 17, 2017 at 5:36 pm
      I posted the below data to supplement the comment by Latitude August 17, 2017 at 4:09 pm in which he provides a plot of Arctic Ice going back to 1975.
      The plot below goes back to 1925 and should be seen in conjunction with the plot set out by Latitude. One can see that in around 1940 there was less than 5 million sq km of ice, ie., even less ice than today.
      The warmists like to cherry pick the 1979 date since it best suits their meme.

      And you and a few others like to cherry pick Vinnikov’s graph even though it certainly doesn’t cover the same area as the satellite data. Of course you don’t know what area is covered either and certainly won’t make any effort to find out (it was published in a Russian journal). If it were covering the same area as the current measurements do, Vinnikov’s data say that the yearly average in 1960 was about the same as the current extent!. You also like to line it up with the early NOAA satellite data, which equates the 0 anomaly of that data to the Vinnikov data, which certainly wasn’t 6.7×10^6 km^2.

      • I take it that most people commenting on this site are scientifically literate which means that one should not need to spell out the basics, such as any raw data that has undergone adjustment is no longer data, and a reconstruction should be seen as a reconstruction and nothing more than that and any reconstruction comes with very wide error bounds, and it is important to compare like with like. But sometimes we simply do not have like for like data and in which case, the reader needs to be circumspect of any comparison.
        For example the time series land based thermometer record is a reconstruction and should be viewed with great caution because of the wide error bounds that come with reconstructions. It also never compares like for like data since the data sample set in say 1900 is not the same data sample set 1920 which is not the same data sample set in 1940 which is not the same data sample set in 1960 which is not the same data sample set in 1980 which is not the same data sample set in 2000 which is not the same data sample set in 2016. I do not consider it necessary to set out these caveats whenever information is posted.
        Vinnikov sought to make an estimation of the area of Arctic Ice over time. The satellite, via a different process, is attempting to do something similar. Everyone knows that Vinnikov did not use satellite data for his reconstruction of 1920s to 1940s, and this ought not need to be spelt out since I would expect everyone to know that this was before the first rocket was fired into space. Also there is no accepted definition of sea ice as the recent change to the DMI plots establishes.
        There may well be differences in methodology, but even if this is questioned, Vinnikov shows (within the limitation of his data and methodology) the profile of Arctic Ice from which one can see that it has varied substantially between 1920 and 1975. There have been large ups and downs, and there was a lot less Arctic Ice in 1975 than there was in the late 1920s.
        Even though the IPCC accepts that manmade CO2 emissions prior to the early 1950 cannot account for change, one can see from the Vinnikav reconstruction the dramatic loss in area of Arctic Ice between the late 1920s and 1954. This change is dramatic and natural, and confirms that the recent loss (1979 onwards) is not unprecedented. Don’t overlook that Vinnikov is one of the lead authors of Chapter 7 of the IPCC First Assessment Report.
        Finally, I will briefly comment upon the criticism you levy at me personally. If you had read my comments, you would have noted that I often state that sceptism is a two way street and that I am equally sceptical of all evidence in support of AGW as I am of evidence that goes against AGW, and I frequently state that the data is not fit for purpose (it cannot withstand the rigours of ordinary scientific scrutiny). the reason why there is a debate on AGW (particularly cAGW) is because of unfit data. If the data was good and sound, we would not be having this debate at all. Anyone who regularly reads this site should know that the data is not fit for purpose, and once again it ought not be necessary to set out that caveat every time one sets out evidence, reconstructions or data etc.

      • the satellite group at uah
        adjusts data all the time — huge changes
        going from v5.6 to v6!
        in fact, their “data” comes
        from a model!
        adjusting raw data is standard in
        all fields of science.

  19. When the sun has a lot of sunspot activity there are a lot more coronal mass ejections. These depending on their severity can involve the sun ejecting billions of tons of plasma into space with if they occur on the Earth facing disk, some of it penetrating Earth’s magnetic shield and giving us great auroras.
    To get an idea of what is possible the X class flares on March 10-12 2012 caused Earth’s thermosphere to absorb some 26 Billion kilowatts of energy (enough to power New York for two years). Fortunately 95% of this was reradiated back into space within a couple of days.
    A more interesting CME came from sunspot 1692 on March 17, 2013. It was a long duration (36 minute) M1 flare aimed at Earth’s northern hemisphere. Although again much of the energy got reradiated back into space enough of the protons were directed by Earth’s magnetic field to the North Pole where their energy (according to NASA) increased the temperature of the stratosphere by 60 deg C, which in turn was sufficient to reverse the polar vortex for a time and cause the arctic oscillation index to go below -5 for several days.
    This also caused an enormous high pressure cell (1074 mb) over Greenland. This, of course, messed up the jet streams and caused an unusually cold spring in much of the Northern Hemisphere.
    So the point I am making is that when the sun is very active there will be increased CME’s hitting Earth and some of their energy will affect the atmosphere above the arctic circle. When it is very inactive the atmosphere above the arctic circle will be less influenced

    • http://www.waclimate.net/climate-history.html has a convenient collection of about 70 linked newspaper stories dating back to the 1870s that report the latest climate crisis claims, many dealing with Arctic ice estimates. I chuckle that the most recent from 1974 is a research paper titled A Study of Climatological Research as it Pertains to Intelligence Problems.
      Forty three years later, I don’t think the problem has been solved.

    • I note that the period from the 1920’s to 1940’s shows spikes of high anomalies. This is consistent with the marine environment mode being in effect. Lots of open water. So approximately 80 years later (2000) we were at the same point of this heat rejection cycle. The ice will grow over the next 40 years to a maximum similar to 1979.

    • Humlums graf has been tempered with, read the fine print under the graf an look up the original paper, Gillet et al.(2008) It’s much warmer in the artic, now than back in 1940.

  20. And most of all, no one has said to me how can Ice melt if the air temperature goes from -38 to -8°C (30 degree of “warming”). Doesn’t ice melt at 0°C?
    There is some study about microwaves (ice melt without air warming) and/or sea waves, or tide, that can stress the ice border?

  21. For those that are interested, Ron Clutz has performed a useful study of Arctic temperatures and concludes that there is no alarming warming. See: https://rclutz.wordpress.com/2016/05/06/arctic-warming-unalarming/
    Ron looked at the temperature record of stations around the Arctic circle. Here is the details of the whereabouts of the stations studied.
    This is the result of his analysis of the reported data from those stations:

    • You apparently don’t know that trends reverse, hence extrapolation is unjustified.
      The trend since 2012 has been for growing ice. The trend was slowed by the 2015-16 Super El Nino, but should continue next year.
      Arctic sea ice, like all climatic phenomena, is cyclic. It’s decline for some 30 years was natural, having nothing at all to do with CO2. If manmade GHGs were the cause, then what caused the increase in Antarctic sea ice from 1979 to 2014?

      • If manmade GHGs were the cause, then what caused the increase in Antarctic sea ice from 1979 to 2014?

        And what caused the decline in Arctic Sea Ice between 1928 and 1945 (See the 1980 Vinnikov study paper referred to in posts above). The IPCC confirm that CO2 (manmade or otherwise) did not cause pre- 1945 changes.

    • Move along? Now? Right before it all disappears next month? Evidently your chart is not “peer reviewed”, your peers would have adjusted the chart to remove that embarrassing box in the upper right.

    • And only the most mathematically and scientifically illiterate would think that any natural cycle could be linked to a quadratic trend.
      Must be one of the really high up in the AGW hierarchy.

    • next time you post that chart you can compress it a further 50% and hey presto even greater rate of acceleration . alarmist visual manipulation of that sort was old hat a long time ago on here tony.

  22. During World War Two, in 1940, the Germans passed a warship disguised as a merchant ship called Komet into the Pacific Ocean through the North East Passage and the Bearing Strait. They had an Russian Ice breaker escort part of the way, but it was never needed. The Germans had plans to do like wise with other warships into 1943. The Russians routinely used the North East Passage during the 1930s. This indicates that there was probably less overall sea ice then than there is now, and that there was certainly less sea ice along the passage route than there is now.

    • KT66 August 17, 2017 at 6:36 pm
      During World War Two, in 1940, the Germans passed a warship disguised as a merchant ship called Komet into the Pacific Ocean through the North East Passage and the Bearing Strait. They had an Russian Ice breaker escort part of the way, but it was never needed.

      According to the captain, Robert Eyssen, he could not have achieved it without the assistance of the icebreakers.

      • According to some narratives the ice breakers lead him through intricate channels, but not needing to break ice. At one time the ice breakers would not continue fearing the passage blocked by icebergs, but the Komet was radar equipped and the Germans pressed on anyway. The Soviets suspected that the Komet was really a warship and reported that it apparently had advanced “radio intercept equipment.” The Russians withdrew their ice breakers prior to the final legs, figuring it could not complete the passage, and told them return to Murmansk. However, the Komet pushed on without escort and found the passages open.

    • Well look at the Russian northern sea route this year and in the last decade.
      Travel without icebreaker assistance possible – and even when part of the route blocked early in the season, longer and longer ice free stretches, earlier in the year.

      • I see your point, Griff. 1940 wasn’t identical to today. Just very, very similar. Now, how is that a problem? Is Hitler back?

      • About time, hey. Back some small way towards the lesser sea ice levels of before the LIA.
        The benefits of not needing an ice-breaker escort would be ENORMOUS, wouldn’t you agree, griff. !
        The benefits of open sea for more than a few weeks would also be ENORMOUS, wouldn’t you agree, griff.

    • Point of history: In 1906 Amundsen successfully completed sailing the Northwest Passage, sans icebreaker, in the sloop Gjøa. Someone earlier (at 4:42 a.m.) made the statement that the Northwest Passage was “… not open for navigation in the 19th and 20th centuries.”

  23. The fact that the arctic is melting, but the Antarctic is growing, and that CO2 is a well mixed gas, couples with the fact that solar input is next to nothing due to the angle incidence, it becomes obvious the CO2 is NOT the cause.
    Winds, and warm ocean currents are the more likely culprit.

      • The antarctic sea ice is now giving it’s response to the El nino of 2016.
        if you know your stuff you would know that the antarctic waters lag in response on each big el nino for about a year or two, to return normal afterwards..
        if you would have followed the SST anomalies you would have noticed that the big difference between a “typical el nino” and the one of 2015 is that most of the warm waters veered…. south instead of north The antarctic sea ice is responding very naturally to that displacement. As did the record low tropical cyclone season in the southern hemisphere. That’s where the cold waters got displaced to. In a good yera or two the arctic has recovered from that. it’s already doing that.

      • Crackers …… seriously? I guess if you hold the Antarctica edge ways, just right against the light, you might could see some “global warming” in it, but that would be a real stretch. According to the study in GRL …. the rapid melt of the latter part of 2016 was the result of some anomalous storm activity pushing massive amounts of warmer water and air to the Antarctic. They said that southern ice being so thin, it is extremely succeptable to wind and wave. The melt was all in a 6-8 mo period with the majority happening in just a few weeks around. Look at the NIDC graph. This is all Reminiscent of the cyclonic activity in the arctic that turned the north to slush in 2012.
        You are free to “believe” anything you want, but the fact remains …. the temp trend for Antarctic was down between 1979-july2016. Ice trend was up over the same period. A one time event that will recover the next 10 years is a case for alarm. …. nor does it support CAGW.

      • Antarctic sea ice grew from 1979 to a record high in 2014, all the while Arctic sea ice was supposedly falling. Hence, CO2 cannot possibly be the cause of Arctic decline. Don’t know where it will end up, but at the moment is not at a record low for this date.
        That both Arctic and Antarctic sea ice are lower than average right after the biggest El Nino of this century (at least) should surprise no one.

      • gloateus – you make one
        of the 3 or 4 basic mistakes:
        thinking that
        co2 is responsible for
        it isn’t. natural variability
        still exists.
        ps: global sea ice extent
        at a record low.

      • That’s right, and I think it will stay low for a while, but Antarctic Sea Ice has not been affected much of AGW, the switch we have seen in the last couple of years is du to a switch in the Pacific (PDO/IPO etc.)
        The extent the last decades har been about the same as in the days of Amundsen and Scott a hundred years ago. But not so in the Arctic that is unprecedented for several hundred of years.

      • Valaker commented – >> The extent the last decades har been about the same as in the days of Amundsen and Scott a hundred years ago. <<
        where's that evidence?
        you should have provided it
        without anyone having
        to ask.

  24. More than a decade ago John [Walsh] would be giving a talk to fellow academics and show his plot with the right most point diving to Hades. “Ah Ha! The Walsh Plot!” an academic in the audience would shout! All would laugh!
    Today the Main Stream Media types revel in “Walsh Plots”. Perhaps in their minds the plots show that indeed humanity along with the main stream media must be exterminated.
    Just the main stream media’s cup of tea!
    Ha ha

  25. Arctic temperatures are dropping in the summer. I wouldn’t be surprised if 2017 is in the top 3 for temperature staying below for the most consecutive days.
    Co2, directly, can not explain only a winter time increase in temperatures. Therefore attention should go elsewhere.
    Looking at temperature constructs from 1958 to present, we can see that it wasn’t unusual for arctic temperstures to be above average in winter. The duration was short though, before going to average or below average.
    I think most of this is a change in weather patterns and then, ironically, the resulting lower of sea ice, year on year, helping push temperatures higher. Maybe I’m wrong.
    Maybe that is co2 driven, but that should be shown. In the mean time, putting ones faith in co2 driven models for sea ice is a fools errand.

  26. I don’t rremember where I could read that whales skeletons carbondated thousands years ago were found in remote high latitudes places where these animals cannot go in our times due to permanent sea ice.

    • Did Mann clearly label his instrumental data? I don’t recall seing that on the graph, though I have not seen all versions of the graph. Marcott did label his, though all sources did not show that.

      • Sheri, what are you talking about?
        Go and read Climateaudit by Steve McIntyre. It will tell you all you need to know about Mann.

    • Isn’t Mann accused of doing similar?
      outside of climate science, splicing one proxy onto another is forbidden, because it generates mathematical nonsense.
      in climate science however, proxy splicing is seen as a positive boon, because it can be used to prove anything you want to prove.

  27. The proxy data show a significant correlation between PDO/AMO 30-year warm/cool cycles and decreasing/increasing Arctic Sea Ice Extents.
    Arctic Sea Ice satellite data started at the end of the 1945~1978 PDO Cool cycle when Arctic Ice Extents peaked in size. When the 30-yr PDO warm cycle started in 1978, Arctic sea ice extents started to fall, and the when the AMO entered its 30-year warm cycle in the early 1990’s, the pace of declining Arctic Sea Ice Extents increased.
    The new PDO 30-yr cool cycle officially started in 2008, but its cooling effects have so far been masked by two El Nino events (2009/10 and especially the strong 2015/16 El Nino event), and the weird North Pacific “The BLOB” event (2013~15). Since both of these phenomena are over, a possible La Nina event starting at the end of 2017, the 30-year AMO cool cycle starting from around 2019, and with weakening solar cycles, It’s highly probable that we’ll start seeing a recovery of Arctic Ice Extent extent from this year and perhaps generally increasing for the next 50~100 years, depending on what effects a Grand Solar Minimum event has on our climate.
    An important aspect many CAGW advocates seem to miss is that low Arctic Sea Ice extents allow more ocean heat to be blown out to space as it’s not covered by ice, although, conversely, exposed open Arctic water also allows solar radiation to be absorbed and earth’s albedo is slightly decreased from less white ice/snow in Arctic regions.
    Both polar caps greatly assist the earth to maintain a relatively stable global temperature with warm tropical ocean gyres moving massive quantities of water to the poles, where the energy is eventually blasted out to space or used to melt sea ice under the 2nd Law of Thermodynamics.
    The next 4~5 years should be interesting and should indicate what effects PDO/AMO 30-year cool cycles and weak solar cycles have on polar ice extents, and land-ice growth in Greenland and Antarctica…
    It should be fun to watch. If this hypothesis is correct, the CAGW advocates will have an extremely hard time explaining why Arctic Ice Extents showed recovery over the next 5 years, in spite of 1/3rd of all manmade CO2 emissions since 1750 have been made over just the last 25 years…
    Let the games begin.

    • arctic sea ice is not recovering in 2017 – currently extent is below that for 2016.
      So let the games begin next year?

      • Griff-san:
        2017’s Arctic Minimum Ice Extent will be around the 3rd or 4th lowest since 1978 and close to 700 KM^2 larger than 2012, while Arctic Ice Area will be the 5th lowest, s0, yeah, even this year’s minimums will show recovery….
        A far cry from an Ice-free Arctic summer Minimum predicted by 2012 by silly Leftista….

      • Are you clairvoyant?
        three weeks to go and the ice is in bad shape.
        but at least 3rd lowest looks likely – and in a year which has seen a cold central arctic and poor melt conditions.
        Third lowest is a ‘recovery’? in such a poor melt year?

      • Hehe Griff, well, erm, it’s August, why would it be recovering now?
        Considering its starting point, ending up either 3rd or 4th lowest is quite remarkable.

      • If it was ‘recovering’ John, then we’d expect it not to be lower than last year/all previous years but 2 at this (late season) date.

      • Griff,
        Arctic sea ice, contrary to your prediction that it was sure to make a new low this year, will continue the recovery trend since 2012.
        Until there is indeed a new record low, Arctic sea ice is in recovery mode. Not that that is a good thing. An ice-free Arctic Ocean in summer would be way better.

      • Nope, the RECOVERY from the extremes of the late 1970’s has levelled out.
        Pity, because a lesser amount of sea ice would have been a great benefit t those people living up there.

      • “Griff August 18, 2017 at 4:48 am
        Are you clairvoyant?”
        You claim to be as you stated the sea ice in the Arctic would be the lowest on record. So far, it isn’t, not by a long shot.

      • Griffikins,
        You’re uncanny. On the very day you crow that Arctic sea ice extent is below 2016 for August 18, it crosses over it.
        Arctic sea ice is now more extensive than for 2007, 2012 and 2016, headed for 2011 and 2015. Unless there are cyclones this month or next, you’re sure to lose your “sure thing” bet, as your betters told you would be the case back in March.

      • Griffypoo,
        Your hopes are being cruelly dashed yet again by reality during this eclipse week.
        The turn that Arctic sea ice extent made the same day you crowed about how low it was has continued.
        As your betters foretold, it has now crossed over not only 2012, 2007, 2011 and 2016, but is headed for 2015.
        This trend is liable to hold until or unless there is a cyclone, again as your betters told you would be the case. As August wears on, the likelihood of a storm this month lessens.
        Instead of the new low which you so confidently predicted, 2017 is liable to end up as fifth, sixth or even higher low year, unless there be a freak late summer cyclone. All that open water which so excited you only served to cool the Arctic Ocean, again just as your betters told you would be the case.

      • Calling all Griffters!
        Hope you’re enjoying the games you said could now begin. And that you’re OK, since you have mysteriously disappeared as Arctic sea ice melt has slowed so dramatically.
        Looks as if this year will cross over 2015 tomorrow or Saturday.
        A lot could still happen over the next month, but right now, it looks as if 2017 Arctic sea ice extent will finish in the middle of the past decade, higher than 2012, 2016, 2015, 2011 and 2007, but lower than 2009, 2013 and 2014, while 2008 and 2010 are still up for grabs. Depends upon how long the current melt rate trend lasts and whether there are storms.

      • Griff is still missing, nowhere to be found. I wonder why?
        Yesterday, 2017 did indeed cross over 2015 extent for that date. So now this year is right in the middle of the past eleven years. From the record low of 2012 up, we have 2016, 2007, 2011, 2015 and 2017, with 2014, 2013, 2010, 2009 and 2008 higher than now.
        Thus, despite steadily rising CO2 for the past decade, Arctic sea ice extent is higher now than in 2007. It was also higher in every other year since then except 2012 and 2016, which was essentially tied with 2007.
        It’s increasingly likely that there will be no new record low this year, as so confidently predicted by Griff as a “sure” thing. As the loser’s betters told him was liable to be the case. As noted above, this will be the longest period in the dedicated satellite record without a new lower low.

    • it’s because they (=the CAGW meme groups) know nothing about the arctic.
      real researchers do say this: the problem with the arctic is that it is water surrounded by land and that the main drivers are the currents. the arctic is also not the coldest place during winters, it are the surrounding landmasses (Siberia, northen canada and greenland) that gather the cold, and release it over the arctic ocean. Ocean currents there are able to counteract this cooling and then they didn’t speak about the complex variability of these currents and the weather patterns
      in short it has a dynamic that is yet not fully understood. I would not be surprised to see it recover anytime in the future.

      • 1944 ice breaker. roflmao
        You really have to stretch reality to keep up your chicken-little Arctic sea ice farce, don’t you griff.
        Even though you must know by now that it is currently above what it has been for some 90-95% of the last 10,000 years.
        Its rather pathetic, wouldn’t you say. !!

      • And thanks for the link showing just how BENEFICIAL having a lesser sea ice extent would be.
        doing well, griff. !

      • I have been involved in shipping for some 30 or so years, and the idea that a vessel of the design of St Roch can be compared to a modern ice classed vessel is absurd. One of the commentators on the scepticalscience blog even suggested that St Roch was akin to an ice breaker and the moderator did not point out how absurd that comment was but instead appears to have endorsed it. Talk about being objective.
        If a vessel was constructed to today with the same design and specification as St Roch, it would be regarded as unseaworthy for plying an ice bound route.
        Griff, I do not expect you to be a naval architect and to be familiar with vessel design, ice strengthening, propeller design, changes in material used for propellers for ice classed vessels etc, but I would expect that common sense alone would tell you that an iron clad timber vessel is nothing like a vessel of 1980s on wards design. Quite simply there can be no comparison.
        But of even more significance, and this is a point completely overlooked in the scepticalscience article, is the change in navigational equipment. Modern vessels ere equipped with a vast array of modern technology providing them with almost real time ice data, satellite imaginary, extremely accurate GPS positioning (showing accurate position of the of the vessel in relation to ice), and the like. They are equipped with modern technology such as drones, or helicop[ters and/or snow scooters and can quickly see how ice conditions are changing and where ice is most broken up/open water exists. This makes navigational route planning and execution radically different to the early 20th century (for that matter prior to 1970). When a vessel like St Roch encountered ice and got stuck, they would have to either grin and bear it, or sent out a party on foot (if very lucky with a dog sleigh) to go on a 20 or 30 mile hike. Now they can get an aerial view from a drone or sent out a snow scooter to do reconnaissance. A vessel such as St Roch either had no charts of ice, or out of date charts of ice.
        It is so much easier to progress through ice conditions today than it was in the past, and this point alone strongly suggests that when vessels made a successful passage long ago, it was only because the ice conditions were far less severe compared to those of today.

    • AndyG55 August 18, 2017 at 3:35 am
      In 1944, Larsen in the St Roch negotiated the NWP passed Banks Island , without the aid of modern navigation and satellite sea ice maps.
      In 1969, The SS Manhattan followed the same route through the NWP..

      In late September, 2014 so did the MV Nunavik, carrying 23,000 tons of nickel ore to China.

  28. The Arctic ice is showing an upturn in the last couple of days (WUWT Polar ice page).
    Air temperatures up there are well below zero, ahead of schedule.
    So the death spiral is probably going to have to wait another year…

      • @Griff…which just shows that the current sea ice melt is caused by warm ocean currents moving into the Arctic, and wind patterns. The wind patterns have just recently made a change that is certainly part of or the main cause for the cooling in the Arctic. You miss so much with your preconceived outlook. Look out the window, so to speak.

      • very little arctic sea ice melt is due to water temperature. the majority of “heat” in atlantic water entering the arctic is lost to the atmosphere on its way there. the low salinity ,low density cold “lid” of water over the arctic ocean means little exchange of energy upwards from the denser water below.

    • Griff,
      Your oft-repeated prediction that Arctic sea ice was “sure” to make a new record low this year is looking bad, as you were warned by your betters would be the case.
      According to NOAA, Arctic sea ice extent for this date is well above 2012 and higher than 2007, although nearly tied at the moment. It’s close to 2016 and 2011.
      As your betters told you, what happens to the weather this month and early next will determine the final extent. If, as in 2007, 2012 and 2016, there are cyclones, then September minimum will be lower. If not, then higher. But in any case, the odds of a new record low are exceedingly low.
      That means that the now-trend remains increasing Arctic sea ice for the fifth year running.

  29. Greg
    First, off I wouldn’t care about Griff one way or the other except that he takes such pains to slander every scientist that he disagrees with I.E. Dr Soon, Dr Crockford and others. he doesn’t just counter their points he attacks them both personally and professionally, posting information about them that he knows is false and I have proven it multiply times.
    Second, value is in the eye of the beholder and you are not the determiner of what holds value. Griff can post here for ever and spew what ever none-sense he wants that’s his right, however i have every intention of pointing out as often as I can that he is both a Slanderer and a BSer. that is my right until Anthony tells me it isn’t (it’s his site after all).
    Third, i have challenged Griff to not just tell everyone else what they don’t know but to actually state what he does know and what he believes will happen, he obfuscates at every turn never making a stand or a statement to be held to, so why in gods name should anyone listen to him. It amazes me how many people post here that are just armchair quarterbacks, really great at attacking every attempt that others make to describe how the system may work but never actually making a stand and putting their name to an idea. This is what is wrong with our world today, people that want to tear down everyone and everything because they can find fault in it. Well guess what, every idea, everything and everybody has faults, it’s not those that can attack those faults but those that can generate the ideas that are contributing, like Dr Soon, Dr Crockford and all the people that post here like Willis, Middleton and Montock that Griff attacks. so forgive me if I waste a little bit of everyone’s time pointing out that Griff is a fraud.

    • I am merely repeating what scientists in their fields say about Soon and Crockford – and that only because if they are to be cited here, all need to understand what the wider scientific community think of those researchers. If your argument, which you intend to be convincing relies on their evidence, well, you cannot expect some sections of the wider community to accept it. Just as some people here might not be swayed by something Michael Mann publishes…
      but I would rather not be arguing about individuals, but the science.
      What do I know?
      I know what the published science is and I repeat it here. I would be pleased to debate you on the points of the science. If I am ‘BS’ ing, up to you to put the science which proves I am on the table.

      • the wider scientific community think of those researchers.
        there is nothing the scientific community hates more than researchers that show the scientific community to be wrong.
        in the history of science, there is almost no new idea that was not first ridiculed by the established scientific community. and the researchers that proposed the new ideas were almost universally called quacks and charlatans.
        and today’s science is almost 100% composed of once ridiculed ideas. I would be more suspicious of ideas that were not first ridiculed, because they are most certainly wrong.
        For example, the notion that heavy and light objects fall at the same speed. That heretical idea would probably have gotten you burned at the stake many times over the past 2000 years.

      • Griff,
        The consensus is always wrong. Always.
        Then, when a more correct consensus finally emerges after millennia, centuries or decades, which subsequently needs modification.

      • Griff
        The wider community here knows what you are! though it is good to see you at least acknowledge that Dr Crockford is a scientist since you tried to convince everyone that she had no credentials only to have it shoved up your ***.

      • Griff
        OK man up and take my bet, you keep saying that arctic ice is melting at an unprecedented rate and that we will soon have an ice free North Pole in the summer (per your great knowledge of the science), well give us a date when this will happen, any date you want and I will bet you it won’t. The loser never posts anything here again. Tony M took me up this year and he’s going to be gone in three weeks, but at least he had the nuts to do it, i am betting you don’t.

      • ferdberple August 18, 2017 at 9:12 am
        Yup. Consider the history of the theory of gravity.
        Aristotle’s view was the consensus for about 2000 years, ie that heavy bodies fall because they seek their proper place at the center of the earth.
        Around AD 1600, Galileo showed this conclusion false, by demonstrating that objects of different mass fall at the same rate. Based upon this discovery, Hooker later in the 17th century suggested that gravity is a force acting on all masses at a distance in the inverse square law. Newton then used this relationship to derive the orbits of the moon and planets.
        The Newtonian consensus reigned supreme and unchallenged until 1905, when Einstein showed it false. For Newton, space and time were absolute and gravity acted instantaneously. Einstein stood this consensus on its head, demonstrating that space and time are relative and curved, that gravity acts at around the speed of light and is in effect acceleration.
        Now some are not so sure about Einstein’s conception of gravity. Some of his predictions have been confirmed, but others not so much. Science still doesn’t know what gravity is, after all these millennia.
        But “climate science” is settled. It is to laugh.

      • Bob boder August 18, 2017 at 9:56 am
        Tony M took me up this year and he’s going to be gone in three weeks, but at least he had the nuts to do it, i am betting you don’t.

        What exactly was the bet?

      • Just because it’s published and even peer reviewed does not make it science. Mann’s hockey stick is not science for example because it was not created by the scientific method. A corner stone of that method is the ability to replicate results by others doing the same experiment or using the same data and methods to reach identical or nearly identical results. That requires total transparency. Mann has not, and will not, even under a court order, release that fundamental information needed for such replication. Thus it is not science. In fact until proven otherwise it is fiction.

      • Bob boder August 18, 2017 at 3:42 pm
        An ice free geographic north pole

        By what measure? It was within a few feet of that last year. The Odeon sailed to 89°N 59.995 on 8/22/2016.

      • Look Griff you dud
        **I know what the published science is and I repeat it here. I would be pleased to debate you on the points of the science. If I am ‘BS’ ing, up to you to put the science which proves I am on the table.**
        How can you debate on science when you have no knowledge of it. I asked you to answer two questions and you refuse. Show us how you measure heating by CO2 and where is the paper which shows 2 deg C is critical to runaway warming. You are BS ing. Arctic ice is not decreasing in the last 10 years – there.
        ***I am merely repeating what scientists in their fields say about Soon and Crockford – and that only because if they are to be cited here, all need to understand what the wider scientific community think of those researchers.***.
        Only idiots and BS ers repeat lies that others said. Show me a credible scientist who has slandered Dr. Soon and Dr. Crockford like you have. They should sue you but you are not worth it.

      • Griff
        ” I would be pleased to debate you on the points of the science. ”
        Indeed, so would we all, but little chance as we will be cited some out of date graph from the 1980’s as best evidence.

  30. It would be fascinating to be able to give this data to a scientist who had never heard of global warming and see the results. Without an agenda, would the person note the lack of data, use error bars and include the whole record, not just parts? I don’t think we could find such a person, unfortunately.
    In the absence of that, maybe a double-blind experiment giving the same data to skeptics and advocates. I suspect the results would be very enlightening. Now that science is so tied up in politics and the apocalypse, actual objective results are harder and harder to find. I’m sure some researchers are very good. No doubt. However, confirmation bias is so engrained in both sides now, unbiased results are virtually impossible to find.

  31. – why are the error bars as large in the recent satellite era as they are in the early 1900s where data comes from estimating and combining multiple days sets? The smallest error bars are in the early satellite period, which doesn’t appear reasonable – surely these century-old estimates are less certain than our modern satellite observations. Same with the early 80s observations.
    – “proxy” means a stand-in, and is derived from procuracy (power of attorney), rather than “approximation”
    – “it now transpires” is just wrong – our changed observations change our understanding and conclusions, but not what “transpires”

    • – comparing the variation new estimate of variability against the mean and median of CMIP5 model runs is not useful. Taking the mean and the median automatically smooths out variability.

  32. “All of the research in this collaborative paper was carried
    out during the authors’ free time and at their own expense.”
    Thank you.

  33. No, lads, you have it all wrong!
    As i explained some time back, you have completely ignored basic scientific principles, which I shall lay out below.
    The Arctic ice melts, slowly; and the very cold water enters the oceans. Everyone knows that cold things fall down, so all that cold water drops down, through gravity, towards the Antarctic, where it freezes up again. Simples!

      • griff, i believe you missed bob boders post above regarding your conviction on disappearing arctic sea ice . your lack of response is typical of the majority of the vocal alarmist community. i may not agree with jim hunt on many things climate related, i do however respect the man as he had no problem in accepting a £1000 charity bet on arctic sea ice .

  34. “SWIPA estimates that the Arctic will be free of sea ice in the summer by 2040. Scientists previously suggested this would not occur until 2070.”
    I seem to recall a great deal of consensus predicting Sea ice demise by 2020 or so.

    • getitright – given your moniker it is incumbent on you to actually get it right. There was in fact no such consensus, so perhaps you should change your moniker to “getitwrong”.
      Prove me wrong if you can.
      Bear in mind that consensus is not one or two quotes. A good place to start for looking for the consensus position would be the IPCC reports.

  35. Has anyone correlated the amount of particulate matter in the atmosphere to the loss of Arctic ice? Are we chasing the wrong cause by laying the blame on greenhouse gasses alone? China’s rapid industrialization has seen massive releases of particulate matter into the northern hemisphere. They lag the west in the use of scrubbers for coal fired generation plants. Major cities are almost unlivable because of particulate pollution. In the 1960s and 70s the Soviets ran tests in Siberia to see whether powdered coal spread by bombers could be used to accelerate the natural spring thaw. You can see this effect yourself by spreading sand on ice in daytime. It would explain the difference between Arctic and Antarctic ice loss.

  36. I’m intrigued that Griff’s comments on this thread seem more substantial than those I’ve encountered in the past. He must have acquired a new set of ghost writers.
    Anyway, keep up the good work. I think it will be of real use for posterity.

  37. Hi everyone, first of all, apologies for not being available either here or on the original post at Judith Curry’s for the last week! Unfortunately, both Michael and I have been unexpectedly busy the last week and we’ve had almost no time for checking the blogs/replying to comments, etc.
    However, I am glad that our post (and our recent HSJ article) has created such interest. And thanks to Charles the moderator for reposting our article here on WUWT.
    I’m not sure how long this comment thread will stay open, but I will try to briefly address some of the main questions & comments now. Sorry if I don’t get to everyone’s comments, but I will also try to set aside some time tomorrow:
    Bryan A at August 17, 2017 at 7:50pm asks whether the PIP-25 studies took polar ocean currents into account. It’s a good question, which we asked ourselves when we first saw the data. Yes, they include a discussion of it in their paper, and they conclude it is not a major problem for their analysis. To me, the fact that all four of the sediment cores taken from very different regions within the Arctic show similar trends is another argument in favour of their reliability.

  38. Several commenters have pointed out that there were some satellites that monitored the sea ice before 1978 and wondered why these were not included in the standard satellite era datasets.
    We provide a discussion of these pre-1978 satellites in Section 3.2 of the paper. But, essentially, the reason why people focus on the 1978-present satellites is that these had multi-channel passive microwave detectors while the 1972-1977 NIMBUS-5 satellite only had a single-channel passive microwave detectors and the early satellites used different detectors such as visible light. If the NIMBUS-5 satellite had lasted a bit longer than 1977 or the NIMBUS-7 satellite had launched a bit earlier than October 1978 then it might have been possible to directly compare them. Walt Meier actually made an attempt at this in a 2014 paper.
    However, because of the nearly two year gap between NIMBUS-5 and NIMBUS-7 as well as the change in detector type, there are considerable challenges in combining the two datasets. So, this is the reason the satellite-era dataset begins with NIMBUS-7 in late 1978. At any rate, several of the so-called “pre-satellite era” datasets actually incorporate information from these earlier satellites. So, this earlier satellite data is included in our 1901-2015 reconstruction. And our re-calibration process should be equally applicable for making the pre-1978 and post-1978 satellite records more comparable.

  39. seaice1 said at August 18, 2017 at 4:13 pm:
    “Look at the graph from paper. we know this is not evidence from alarmists – it is the interpretation that is most charitable for the skeptics. Yet it still shows a rapid decline since 1979 to levels lower than in the previous century. There is just about room to argue that if the error bars overlap, but to have the recent lows not different from the previous lows we need the error to be in the very bottom of the previous and the very highest of the recent. This is very unlikely. We can say that the recent drop – even in this evidence – is very likely to be real and only has a tiny probability of being due to error.
    If we look at other reconstructions (as this is a reconstruction) we see an even greater difference. So if we look at all the evidence it is an act of supreme bias to conclude that sea ice is not at its lowest (over the last decade) over the last 150 years.”

    Unfortunately, the pre-satellite era data is very limited and so we really cannot ignore the error bars. This is why in Section 5, we point out that our reconstruction is unable to rule out the possibility that post-2004 sea ice extent is the lowest since 1901 or the possibility that it was just as low in the 1940s as it is today.
    At any rate, the Stein et al. (2017) PIP-25 sea ice proxies suggest that the recent decline is not unusual compared with the variability of the last 10,000 years.
    Everyone of us is prone to confirmation bias, and ironically a good test for whether you might be affected by it is if you believe you are unaffected and the people who disagree with you are! So, when you say “…it is an act of supreme bias to conclude [the opposite of what you happen to believe]”, I’d recommend a bit of self-reflection!

  40. Both Griff and Walt Meier have pointed out that as well as finally introducing the Russian dataset, the new 2017 version of the Walsh dataset also incorporates several sub-Arctic datasets for some of the sub-Arctic seasonal sea ice regions, such as the Bering Sea and Nova Scotia.
    As we discussed in Section 2 of the paper, we also looked at the same sub-Arctic datasets. However, aside from the Russian dataset, all of these datasets were taken from sub-Arctic regions, and because our reconstruction was confined to the Arctic Ocean and Seas, none of the other extra datasets were suitable for our analysis.
    In the figure below, the yellow, pink and blue regions correspond to the three sectors of the Arctic Ocean and Seas, while the white regions are sub-Arctic (according to the IHO’s “Names and Limits of Oceans and Seas”). The map on the left corresponds to the average winter maximum, while the map on the right corresponds to the average summer minimum
    As can be seen from the figure, the sub-Arctic regions do indeed contribute to some of the Northern Hemisphere sea ice during the winter, however they mostly just contain seasonal sea ice. The extra datasets Griff and Walt Meier are referring to provide some extra data for a few of these sub-Arctic regions. But, the Arctic regions comprise the vast majority of the sea ice extent during the winter (~80-82% during March) and almost all of the summer sea ice extent (~98-99% during September).
    By the way, thanks Walt, for clarifying that Al Gore was indeed referring to the Rothrock et al. 1999 paper and not the graph he actually showed in the film, and for providing that extra information on his role.

  41. Don Easterbrook said at <a href=” https://wattsupwiththat.com/2017/08/17/what-do-we-know-about-arctic-sea-ice-trends/#comment-2584152”August 17, 2017 at 4:28pm,
    “Comparing extent of sea ice now (at the end of a warm period) with sea ice extent in 1979 at the end of a cool period) makes no sense at all. What should be compared is extent of sea ice now with the extent of sea ice at the end of the 1915 to 1950 warm period. Unfortunately, we don’t have good data for the earlier time period. We would also like to compare the sea ice extent in 1979 at the end of the 1950 cool period with the extent in 1915, the end of the 1880 to 1915 cool period. But again, we don’t have the data.
    Until we can make these kinds of comparisons, conclusions about trends since 1979 don’t mean much.”

    I agree. This was one of the main motivations for our study.

  42. Gloateus said at August 17, 2017 at 4:41 pm:
    ” If global warming be the alleged cause of Arctic sea ice decline since 1979, then explain please why the highest Antarctic sea ice year in the satellite record was 2014, after steady increases since 1979.
    If air temperature be the cause, then why the stark difference, 180 degrees out of synch, between the two poles?”

    This is indeed a bit of a head-scratcher as we alluded to in our post. There have been some post-hoc attempts to explain the general increase in Antarctic sea ice extent over the satellite era, but it was certainly not predicted by the climate models in the 1980s, 1990s and 2000s.

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