For far too long the climate science community has grappled with an inconvenient truth: the vast majority of the datasets used to constrain temperature trends of the recent past come from the Northern Hemisphere. Over a dozen reconstructions of Northern Hemisphere temperature spanning the past millennium exist and have played a critical role in distinguishing natural from anthropogenic climate change. However, the extent to which recent temperature variations in the Northern Hemisphere resemble those in the Southern Hemisphere remains unclear. Such information is critical to a complete understanding of the mechanisms of global, rather than hemispheric, climate change. Writing in
Nature Climate Change, Raphael Neukom and co-authors
1 present a new, millennium-long reconstruction of Southern Hemisphere temperature by combining information from a wide variety of palaeoclimate sources. Although the new reconstruction resembles the Northern Hemisphere reconstructions in some key aspects — the anomalous nature of twentieth century warming being one of them — it also suggests that
temperatures in the two hemispheres may have differed more than they have agreed over the past millennium.
The best-dated, highest-resolution records of past climate variability rarely extend beyond the past millennium, making this time period an important test bed for quantitative comparisons between climate field reconstructions and numerical climate model simulations of past climate
2, 3. Yearly temperature can be reconstructed from archives, such as corals, ice cores, tree rings, lake sediments and cave stalagmites, by calibrating their geochemical or physical signals against the instrumental record of climate, where they overlap over the past century. In this regard, extremely poor data coverage for Southern Hemisphere ocean temperature observations makes this calibration more difficult (
Fig. 1). Scientists use a variety of advanced statistical techniques to extract the shared signals across a given network of palaeoclimate records. The uncertainties associated with reconstructed temperature estimates inevitably increase further back in time, as the number of available records decreases, but can be quantified using a variety of approaches.
One of the first such reconstructions was the so-called hockey stick, published by Mann
et al. in 1999
4. As a reconstruction of Northern Hemisphere temperature spanning the past millennium, the hockey stick graph reflected a long-term cooling into the seventeenth century, the stick, followed by a sharp warming that began in the late nineteenth century, the blade. Multiple teams of scientists have subsequently generated dozens of alternative Northern Hemisphere temperature reconstructions, each using slightly different methods and data networks
5. Climate model simulations that include natural forcings from volcanic eruptions and solar variability, as well as anthropogenic forcings such as greenhouse gases, reproduce many of the key features seen in the collection of Northern Hemisphere temperature reconstructions, within the combined uncertainties of the forcings and the reconstructions
5. Such features include multi-year, hemispheric-scale cooling associated with large volcanic eruptions, as well as pronounced warming over the industrial era. The high level of data–model agreement suggests that scientists have a good grasp of the dominant mechanisms of climate change on decadal to centennial timescales, and that such mechanisms are fairly well represented in the current suite of climate models used to project future temperature.
[I beg to differ:]
However, the new reconstruction of Southern Hemisphere temperature
1 suggests that the climate model simulations of past climate
systematically underestimate the magnitude of natural climate variability in the Southern Hemisphere. At first glance, the reconstruction contains the same basic features of the Northern Hemisphere family of reconstructions — a centuries-long cooling into the seventeenth century, and a twentieth-century warming of unprecedented duration and magnitude. But a close comparison between the Northern and Southern Hemisphere reconstructions reveals many intervals when the two series diverge for decades at a time. Notably, some of these differences occur following large volcanic eruptions, when the Northern Hemisphere cools significantly but the Southern Hemisphere does not, at least according to the new reconstruction
1. The fact that many of these differences occur within the past 400 years, when the data networks from both hemispheres are most robust, makes it less likely that such temperature differences are artifacts of poor data coverage. That said, it is possible that small but cumulative age errors in single palaeoclimate records may smear out interannual variability in large-scale temperature reconstructions
6, 7 — currently the topic of vigorous debate
8, 9.
If the new reconstruction of Southern Hemisphere temperature is accurate, then
estimates of climate sensitivity — the response of global temperature change to a given amount of external radiative forcing — may be lower than those calculated based solely on Northern Hemisphere reconstructions10. Indeed, instrumental temperature data suggest that warming in the Northern Hemisphere has been greater than that observed in the Southern Hemisphere over the past two decades (
Fig. 1c) — a feature reproduced in the current suite of climate models
11. Therefore, this hemispheric asymmetry may be a fundamental feature of the climate system’s response to a change in radiative forcing
12, whereby
the ocean-dominated Southern Hemisphere acts as a buffer of sorts to global temperature change on decadal to centennial timescales. On the other hand,
Neukom et al. propose that divergent hemispheric temperatures arise from strong natural climate variability in the Southern Hemisphere, and have been a constant feature of the past millennium.Given the new information now available from the Southern Hemisphere, climate scientists must consider a larger role for natural climate variability in contributing to global temperature changes over the past millennium. While the new reconstruction brings strong additional support to the phrase ‘anthropogenic global warming’, it also highlights the limits of our current ability to understand, and predict, global temperature variations from decade to decade. In other words, global temperatures will warm appreciably by 2100, but the road may be bumpy and full of surprises.
I like it better without the selective highlighting.
is this a climate-changer? looking forward to informed comments.
There’s only one sentence that will make it to the mainstream media headlines:
–” In other words, global temperatures will warm appreciably by 2100, but the road may be bumpy and full of surprises.”
And I question that even the second half of the sentence will make it, though it does make for a great ‘weasel clause’.
Inter-tropical convergence zone is about 8 degrees north of the equator. This means that variations in variations in atmospheric climate over the tropics will be linked more strongly to the NH ocean gyres than SH.
Thus NH variability is probably more strongly linked to variations in cloud cover and other variability.
There is also the ‘polar see-saw’, quite possibly also linked to the position of the ITCZ
The usual sop to AGW.
“In other words, global temperatures will warm appreciably by 2100, but the road may be bumpy and full of surprises.”
BS all of it.
It’s amazing that no matter how much contradictory evidence they get, they can always find a nugget of AGW in there somewhere.
Eventually they will have to admit:
CS ≤ 0.0K
News: Climate scientists fail to find UHI in southern hemisphere…
…film at 11
There is much more variability in NH than SH, which seems to show a fairly abrupt change in direction around 1910 with almost linear down then up either side of it.
The variability in NH looks more like a folded cosine ( rectified to an E. Eng mind ) than a straight harmonic ‘oscillation’.
http://www.woodfortrees.org/plot/hadsst3nh/detrend:0.8
It is good to see someone looking at regional variation separately, even if it is just N/S divide. Bundling everything into global averages has been one of the major reasons for lack of progress in understanding climate in the last 30 years.
Natural variability has been admitted, but seemingly forgotten again
Here is my comment quoting Phil jones that the 1730′s was the warmest decade until the 1990′s and that natural variability might be underestimated.
http://wattsupwiththat.com/2014/01/17/phil-jones-2012-video-talks-about-adjusting-sst-data-up-3-5c-after-wwii/#comment-1539164
‘UNUSUAL CLIMATE IN NORTHWEST EUROPE DURING THE PERIOD 1730 TO 1745 BASED ON INSTRUMENTAL AND DOCUMENTARY DATA’. Jones and Biffa. Revised version published 2006.
http://rd.springer.com/article/10.1007%2Fs10584-006-9078-6
tonyb
Retreat! Perhaps all we need to wring our hands over is Anthropogenic Hemispheric Warming.
“In other words, global temperatures will warm appreciably by 2100, but the road may be bumpy and full of surprises.”
Including no overall warming at all.
The southern hemisphere is:
‘south’,
upside down,
unadjusted,
not checked by peer review,
not published in peer reviewed journals,
a well known denialist,
not contributing to the current debate,
not important to readers of the journal,
not made the cut off date in time,
not in the right amount of words to fit into journal,
redefined as to what the peer reviewed literature is,
a rogue journal editor who needs to be replaced,
written before the summary for policymakers was finished,
only looking to find something wrong we have worked on for 25 years, etc etc
So what they’re saying is … we’ve really no idea, having two hemispheres is cool but really confusing, so we’ll insert a few get out clauses and summarise with ‘keep the funding rolling’ or it will be a bumpy road ahead.
I am now even more of the opinion that “climate science” has only scratched the surface of actually understanding the climate mechanism. An analogous state of actual knowledge would be an understanding of human anatomy at about 1200 to 1400 AD. This paper is interesting although I was aware of the hemispheric anomaly difference from my ongoing plot of the HADCRUT3 & 4 series ( GL, NH, SH, NH-SH,). The difference averages about 0.1˚ ( SH cooler) over the past 150 years but a few years ago got to 0.3˚, a record of some note. And blow me down, I’m not a climate scientist.
A list of questions about climate models.
Why are all the climate models made in 1978?
They hardly had computers back then.
Back then they still believed in global cooling.
Wouldn’t a climate model that was made in say 2005 use the actual temperature data collected up until that date? Shouldn’t it only start deviating from the actual temperature record after the day of it’s creation? Why is it already 2º higher than the actual temperature on it’s first day? Does it then go back in time to be wrong over previous 30 years?
Or, back to my earlier question, are all the climate models listed on the above chart created in 1978? If so wouldn’t they adjust their model at least once a decade back to the actual temps? How can they be wrong for 35 years and still get funding? I seriously don’t get it.
Bollocks!
[There! I’ve wondered what it would be like to use that ancient Anglo-Saxonism.]
If [incremental] ECS exists at all, it is below 1°C and probably below 0.2°C.
And [incremental] ECS may not exist at all in the practical sense, since atmospheric CO2 LAGS temperature at all measured time scales, and the future cannot cause the past.
Alternatively, as Richard Courtney said some years ago, “Show me your time machine.”
Regards to all, Allan
I like this statement:
“At first glance, the reconstruction contains the same basic features of the Northern Hemisphere family of reconstructions — a centuries-long cooling into the seventeenth century, and a twentieth-century warming of unprecedented duration and magnitude.”
Always “unprecedented.” They love that word.
I have a solution which will allow them to reconcile the data for both hemispheres: add more thermometers in the past, especially at higher elevations. Possibly 3 or 4 at Machu Picchu, to get some good 15th century temp data.
“The high level of data–model agreement suggests that scientists have a good grasp of the dominant mechanisms of climate change on decadal to centennial timescales, and that such mechanisms are fairly well represented in the current suite of climate models used to project future temperature.”
So, in a nutshell: the models and proxy data climate reconstructions are going to broadly agree because the analysis of historical proxy data produces hockey sticks and the models assume a relationship between co2 and temperature that produces hockey sticks.
The instrumental and satellite temperature records don’t (so far as we can see) produce hockey sticks. This means that the instrumental and satellite temperature records don’t broadly agree with the models.
So there is something wrong with either the proxy reconstructions or the instrumental and satellite records. Either the methods used to reconstruct historical temperature through statistical analysis are unreliable or there is something (take your pick) suppressing the CAGW signal in the instrumental and satellite temperature records.
I know where I’ll place my bet.
It always amazes me how these kind of papers get past peer review! They make a number of unsupported statements – like climate models do a good job of simulating the past. How can that possibly be true when the modellers themselves admit, and this paper shows, that they have very poor knowledge of what drives natural ‘variability’. That poor knowledge stems from a denialist attitude to solar variability (other than in the visible spectrum) and the nature of the dreaded ‘cycles’ and oscillations. All the models do is fit the parameters until they get the answer they know from the past record is about right – in this case, since the LIA in their book cannot be caused (i.e. modelled) by solar processes that they have limited knowledge of – then it must be down to lots of volcanoes depressing temperatures.
The reason the southern hemisphere has not warmed as much as the northern is obviously an oceanic phenomenon – but there are TWO possibilities, one that the oceans absorbed the extra heat, the other that the oceans did a better job of DISSIPATING the heat to space. The southern ocean has an unimpeded circumpolar current – unlike the north. Thus surface heat is continually channeled into the zone of permanent heat loss. In the north, the sub-polar gyres caused by the land constrictions, allow heat to build up at depth. During global warming periods the oceans are in accumulation mode and the heat is slowly transferred to land by prevailing westerlies. Climate shifts are caused by changes in northern cloud patterns – when these heat stores are no longer insulated from the polar night, they cool – but first the heat migrates to the surface. Then suddenly, its gone, and the westerlies cool. Its a cycle.
This paper also states that the 20th century rise – both rate and magnitude, is unprecedented! No supporting material other than reference to the Medieval Warming Period and as far as this excerpt goes, no indication of the uncertainty level on their 0.25 C ‘warmer than’. Let them show similar analyses for all of the Holocene warming episodes recorded in ice-data – plenty of time when it warmed at a higher rate and to a higher level. Unprecedented in the last 1000 years, maybe – though the rate from 1920-1940 is the same as 1980-2000, if not the magnitude. The current magnitude is NOT without the bounds of natural variability and can be at least partly explained thus far by long-term cyclic recovery for the LIA trough. The 0.25 C may be anthropogenic – but that is hardly proven – it is assumed by radiative forcing theory. The parameters of that theoretical function are now under closer scrutiny – IPCC started (1990) out by backing a factor of 0.88 times the computed RF in watts. They were advised by their own experts in 2007, that this perhaps ought to be reduced to 0.44. Other experts suggested 0.3 as a lower bound, and one or two would go lower still. The lower it goes, the more must be attributed to natural forces.
These factors are built into model predictions of the future. Thus UKMO did a recent study of the impact on global warming of a solar shut-down – a new LIA. They put in many ‘good’ parameters for the solar power, but chose the old 0.88 instead of 0.44 (and those IPCC experts who advocated the lower figure were also chief advisors to UKMO – so they ignored their own experts). Of course, the resultant prediction is that CO2 warming is only slightly affected – but the full Monty returns with renewed vengeance. Gerry Meehl at NCAR has a more honest model – at least with regard to the RF factor – and temperatures flat-line to 2060. Both models cannot bring themselves to use parameters that would show a cooling – Meehl’s model unaccountable starts from a baseline 1.5 degrees warmer than 1950 – the same place that ‘standard’ models arrive at by 2015! I have yet to work through the logic of that.
I did write a critical commentary for Journal of Geophysical Research – it went through the review process, which did pick up a couple of ways in which I had not fully understood the methodology – and got a first rejection, which I then rejected, met the criticisms, but the final rejection was simple – why don’t you go away and run your own model! This despite one of the reviewers indicating that critical comments were rather rare and should be welcomed. I will return to the fray – because the UKMO paper still stands with most people, including many atmospheric scientists unaware of how ‘political’ considerations (what I would call prior commitment) affect the parameterisation of models. I did point this out – hoping that ‘the community’ would accept that kind of feedback – but the reviewers were unanimous – such comments have no place in a ‘scientific’ journal. How else do we get through???
Jones, G.S., M. Lockwood, & P. Stott. (2012) What influence will future solar activity changes over the 21st century have on projected global near-surface temperature changes?
Journal of Geophysical Research, 117, D05103, doi:10.1029/2011JD017013, 2012
Meehl, G.A., J.M. Arblaster, and D.R. Marsh (2013), Could a future “Grand Solar Minimum” like the Maunder Minimum stop global warming? Geophys. Res. Lett., doi:10.1002/grl.50361.
I don’t know we keep feeding the warmist trolls with this drivel from a trashy journal that publishes work from Mann et al.. The surface datasets are totally compromised, RSS AMSU are showing nothing. Please refer to Steven Goddard’ site for accurate information concerning the never ending fraudulent adjustments to Global temperatures
the ocean-dominated Southern Hemisphere acts as a buffer of sorts merely ‘a buffer of sorts’, not a real buffer…
Given the new information now available from the Southern Hemisphere good thing we found that SH, but wait what about the global ‘One Tree of Yamal’? Mikey won’t like this.
Maybe this has something to do with why Antarctic sea ice has been setting daily maximum record levels for ice area and looks like it will continue doing it for a while.
http://arctic.atmos.uiuc.edu/cryosphere/antarctic.sea.ice.interactive.html
There is nothing new here. Actually even Mann agrees see
http://pubs.giss.nasa.gov/docs/2001/2001_Shindell_etal_1.pdf
In earlier posts on this site
http://wattsupwiththat.com/2014/04/07/climate-forecasting-for-the-21st-century/
I have made the case that the IPCC modelling method is useless for climate forecasting and that a different forecasting methodology is required. Here is a quote from an earlier post at
http://climatesense-norpag.blogspot.com/2013/10/commonsense-climate-science-and.html
showing different forecasts for the NH and Global temperatures.
“I have combined the PDO, ,Millennial cycle and neutron trends to estimate the timing and extent of the coming cooling in both the Northern Hemisphere and Globally.
Here are the conclusions of those posts.
1/22/13 (NH)
1) The millennial peak is sharp – perhaps 18 years +/-. We have now had 16 years since 1997 with no net warming – and so might expect a sharp drop in a year or two – 2014/16 -with a net cooling by 2035 of about 0.35.Within that time frame however there could well be some exceptional years with NH temperatures +/- 0.25 degrees colder than that.
2) The cooling gradient might be fairly steep down to the Oort minimum equivalent which would occur about 2100. (about 1100 on Fig 5) ( Fig 3 here) with a total cooling in 2100 from the present estimated at about 1.2 +/-
3) From 2100 on through the Wolf and Sporer minima equivalents with intervening highs to the Maunder Minimum equivalent which could occur from about 2600 – 2700 a further net cooling of about 0.7 degrees could occur for a total drop of 1.9 +/- degrees
4)The time frame for the significant cooling in 2014 – 16 is strengthened by recent developments already seen in solar activity. With a time lag of about 12 years between the solar driver proxy and climate we should see the effects of the sharp drop in the Ap Index which took place in 2004/5 in 2016-17.
4/02/13 ( Global)
1 Significant temperature drop at about 2016-17
2 Possible unusual cold snap 2021-22
3 Built in cooling trend until at least 2024
4 Temperature Hadsst3 moving average anomaly 2035 – 0.15
5 Temperature Hadsst3 moving average anomaly 2100 – 0.5
6 General Conclusion – by 2100 all the 20th century temperature rise will have been reversed,
7 By 2650 earth could possibly be back to the depths of the little ice age.
8 The effect of increasing CO2 emissions will be minor but beneficial – they may slightly ameliorate the forecast cooling and help maintain crop yields .
9 Warning !! There are some signs in the Livingston and Penn Solar data that a sudden drop to the Maunder Minimum Little Ice Age temperatures could be imminent – with a much more rapid and economically disruptive cooling than that forecast above which may turn out to be a best case scenario.
How confident should one be in these above predictions? The pattern method doesn’t lend itself easily to statistical measures. However statistical calculations only provide an apparent rigor for the uninitiated and in relation to the IPCC climate models are entirely misleading because they make no allowance for the structural uncertainties in the model set up. This is where scientific judgment comes in – some people are better at pattern recognition and meaningful correlation than others. A past record of successful forecasting such as indicated above is a useful but not infallible measure. In this case I am reasonably sure – say 65/35 for about 20 years ahead. Beyond that certainty drops rapidly. I am sure, however, that it will prove closer to reality than anything put out by the IPCC, Met Office or the NASA group. In any case this is a Bayesian type forecast- in that it can easily be amended on an ongoing basis as the Temperature and Solar data accumulate. If there is not a 0.15 – 0.20. drop in Global SSTs by 2018 -20 I would need to re-evaluate”
“elmer says:
April 30, 2014 at 6:03 am
A list of questions about climate models.
Why are all the climate models made in 1978?
They hardly had computers back then.
Back then they still believed in global cooling.”
Elmer,
The answer to “why 1978?” Is surprisingly simple. That marks the date of the launching of the third weather observation satellite by NASA, thus giving scientists (and psuedo-scientist) a uniform data set from which to make projections. Since prior data is in different formats it is not easily assimilated into computer models without a lot of annoying work. I often wonder what the forecasts would be if the satellites had been available,say, 10 years sooner.
http://science.nasa.gov/missions/goes/
This is a good quotation to cite in response to the warmist jibe, “Why don’t you publish your critique in the peer-reviewed scientific literature?”–implying that journals are open to being forums for debate and that peer reviewers in this rogue science aren’t mere gatekeepers.
Scientific journals seem only to want “findings”–they are not, contrary what naive science groupies imagine, places where issues get thrashed out and error confronted and defeated. But they ought to be–or there should be online neutral forums where this can take place
The riposte to the warmist claim that “the debate is over” should be, “We have not yet begun to debate.”