While the media circulates the talking points pre-release “leaked draft” of IPCC’s AR5 amongst themselves, there are a few nuggets of interest coming out here and there we can write about. One such nugget is contained in a series of bullet points on the Washington Post Capital Weather Gang in an article by Jason Samenow:
7) The 30 years from 1983-2012 was very likely the warmest 30-year period of the last 800 years.
That is an interesting statement, not so much for what it says, but for what it doesn’t say. A caveat; that’s likely the reporter’s summary, not the exact text from the IPCC “leaked draft”. IPCC verbiage tends to be a bit more bloated. But, I think it is a fair summary.
Bishop Hill points out what was said in IPCC’s AR4 in 2007:
Average Northern Hemisphere temperatures during the second half of the 20th century were very likely higher than during any other 50-year period in the last 500 years and likely the highest in at least the past 1,300 years.
So, they’ve gone from saying warmest in the last 1300 years to the last 800 years. Where does that figure in on Mann’s hockey stick graph from AR3 in 2001?
![Hockey_stick_chart_ipcc_large[1]](http://wattsupwiththat.files.wordpress.com/2013/08/hockey_stick_chart_ipcc_large1.png?quality=75)
Figure 1. The hockey stick graph as it appeared in the IPCC Third Assessment Report WG1 (2001) summary, Figure 2.20, Northern Hemisphere temperature reconstruction.
So basically what they are saying is that at the year 1200 (2000AD minus 800 years), temperatures were warmer (or at least equal to) temperatures today.
This is curious, because it looks like we are back to what the IPCC said in the first report in 1990. Notice the bump, peaking at 1200AD:
![800px-IPCC_1990_FAR_chapter_7_fig_7.1%28c%29[1]](http://wattsupwiththat.files.wordpress.com/2013/08/800px-ipcc_1990_far_chapter_7_fig_7-128c291.png?quality=75)
Figure 2: IPCC 1990 FAR chapter 7 fig 7.1(c) from http://www.ipcc.ch/ipccreports/far/wg_I/ipcc_far_wg_I_chapter_07.pdf
Compared and overlaid with Mann’s work, which was highly criticized for turning all the proxy data from 1000AD to 1900AD into a nearly straight flat shaft with an upturned blade at the end, that 1200AD bump looks like the elephant in the proxy samples room.
Figure 3: IPCC 1990, Mann 1999 and Moberg 2005 data overlaid.
- (red) IPCC hand-digitised from IPCC 1990 figure 7.1c (note: it has been assumed that the tickmarks on the y axis are in units of °C and that the middle of the three represents zero).
- (blue) Mann from ftp://ftp.ncdc.noaa.gov/pub/data/paleo/contributions_by_author/jones2004/jonesmannrogfig5.txt
- (black) Moberg from http://www.nature.com/nature/journal/v433/n7026/suppinfo/nature03265.html
- (green dashed line) Central England temperatures to 2007 overlaid from Jones et al. 2009 page 34 fig. 7. http://pubs.giss.nasa.gov/docs/2009/2009_Jones_etal_2.pdf
Somewhere, Hubert Lamb must be pleased that his work from IPCC’s FAR in 1990 showing a warmer Medieval Warm Period than the present is getting attention again. Steve McIntyre must also be smiling at this.
The question now is: will this inconvenient bump be flattened and sanitized in the final version of IPCC AR5?
UPDATE: WaPo’s Jason Samenow adds in comments –
I’m the author of the blog post on the IPCC report. My post just featured a handful of findings… it’s not at all comprehensive…just a teaser.
As I note in my post, I’ll dig deeper into the report once it’s finalized. As for the MWP, the IPCC says a couple things:
“Analyses of paleoclimate archives indicate that in the Northern Hemisphere, the period 1983–2012 was very likely the warmest 30-year period of the last 800 years (high confidence) and likely the warmest 30-year period of the last 1400 years (medium confidence).”
“Continental-scale surface temperature reconstructions show, with high confidence, multi-decadal intervals during the Medieval Climate Anomaly (950−1250) that were in some regions as warm as in the late 20th century. These intervals did not occur as coherently across seasons and regions as the warming in the late 20th century (high confidence).”
The IPCC stresses these statements are draft and subject to change via the government review.
Thanks for reading…
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@Josh, in case you are reading this …
This is the kind of post that begs for a specific cartoon from you … Michelangelo … MichaelManngelo … chipping away the MWP and LIA and other periods to reveal the
David statuehockey stick that was there all along!Mann’s HOCKEY STICK is not worth the paper it is written on.
I would go so far to say that the climate from 1850-present has featured one of the most stable climate intervals over the last 20,000 years. In addition their were many many periods when not only were the temperatures warmer then at present but the temperature rise into these warmer past periods was much more rapid.
The 1850-2005 interval of climate was a period when the sun emerged out of the Dalton Solar Minimum and displayed a steady 11 year sunspot rhythmic active cycles with peaks and lulls which brought the climate out of the Dalton, to what we have had since.
The good news is this active period of solar activty came to an end in earnest during year 2005, and we have now entered a prolonged solar minimum , which is going to result in a temperature decline going forward, and end the AGW theory.
The solar parameters necessary to accomplish this should be present for the balance of this decade and beyond.
solar flux sub 90
solar wind sub 350 km/sec
ap index sub 5.0
solar irradaince off .015%+
UV light 0ff upwards of 50%
The catch with solar /climate relationships is the degree of magnitude change and duration of time of solar variations must reach certain LEVELS, in order to overcome the inherent negative feedbacks in the earth climatic system,along with natural earth bound random climate events.(examples would be enso, volcanic activity)
Secondary effects from solar variations can become the main driver of random earthly climate events if the degree of magnitude change and duration of time of the solar variations reach certain sustainable levels.
This decade will give us a chance to see how this works out, and should bring about the downfall of the IPCC, and their useless climate models.
The 800 year period goes back to the beginning of the LIA. In that respects, it appears the IPCC is hedging their bets. As Dr Wegeman and McIntyre have previously pointed out, tree-ring proxies are not reliable beyond 400 or so years. To say that the latter half of the 20th Century was as warm as the final decades of the MWP is really not saying anything new. And the confidence of such a statement is 50% at best. Yet, the 800 year meme sounds impressive to the layman. It’s all about PR. Which is what the MBH9x proxies turned out to be alll along.
The problem is, many unengaged people (and thanks mostly to this invaluable site and others, that number will continue to decrease) will swallow that having the warmest 30-year period in 800 years is somehow significant. Will they look any further back?
Until they do, another winning alarmist headline…
“The IPCC stresses these statements are draft and subject to change via the government review”
That’s a great statement.
If the people who paid for this don’t like it, then it’ll be changed!
“The IPCC stresses these statements are draft and subject to change via the government review.”
LOL. The stance might change after government review? Uh, this is supposed to be science I thought?
Unless things really heat up fast, which doesnt appear likely looking at the sun, I think this might be our last IPCC report to laugh at. Sad part is much of the first world will likely be under the carbon tax by then. (the obvious clear goal much more so then truth or understanding of climate or mankinds impact on it)
======================================================================
Extreme Climate theory Change?
No AGW , No IPCC its that simple . Now does anyone think this turkey is about to vote for Christmas?
So the IPCC’s story will be: The last decade has been the hottest ever (for the past 800 years). They’d better scratch that last point, otherwise the current temps are not unusual. Also, do not look at that Mann behind the curtain, the Mr. No Temperature Rise this decade?
“MCA….These intervals did not occur as coherently across seasons and regions as the warming in the late 20th century”.
Once again, they are confusing data availability with reality.
I wonder of how many 30-year periods this could be said? For example: “The 30 years from 1810-1839 was very likely the warmest 30-year period of the last xxx years.” (Counting back from 1840, of course.) Or perhaps : “The 30 years from 1770-1799 was very likely the warmest 30-year period etc. etc. etc…”
Since the planet has pretty much been steadily warming for the past 15,000 years or so, surely — with some prominent exceptions — almost every most-recent-30-year-period would have been warmer than anything before.
Anyone seeking to disabuse Green Gang catastrophists on matters of fact will soon discover that, as indecent Watermelon types [Delingpole] rational debate is the very last concern of raging One World statist ideologues.
The 30 years from 1983-2012 was very likely the warmest 30-year period of the last 800 years.
Is this the beginning of the end for man made global warming?
Anthony, I find curious that you wrote that update quite quickly, but you haven’t amended your story in any other way. The update contradicts your starting point and your headline.
Even without the update, the argument was weak: the IPCC changed its “highly likely” time period from 500 years to 800 years — rather the reverse of dropping the hockey stick, it finds reduced uncertainty compared to six years ago.
By the way, the image of figure 3 and its caption are under a CCA license. Surely you should give attribution? Right now it looks like you made the plot and write the caption.
http://commons.wikimedia.org/wiki/File:Ipcc7.1-mann-moberg-manley.png
30 year periods for temperature measurement are an oddity to me!, Why not 50 year or 100 year periods? Is this because 30 year periods can be shown to display what appear to be unusual/unexplained temperature spikes? Anyway from what I have seen, we are cooler today than we were at the end of the last Ice-Age 11,500 years ago, & the last 4 Inter-Glacial periods going back 500,000 years, were warmer than today by between 3-5°C!
If you study the Greenland Vikings at all you know it wasn’t “as warm” during the MWP. It was a LOT warmer. That quote of Lamb’s that “Jimbo” shared with us at August 21, 2013 at 8:48 am needs to be repeated over and over:
“The Arctic pack ice was so much less extensive than in recent times that appearances of drift ice near Iceland and Greenland south of 70[deg] N, were apparently rare in the 10th century and unknown between 1020 and 1194, when a rapid increase of frequency caused a permanent change of shipping routes. Brooks suggested that the Arctic Ocean became ice-free in the summers of this epoch, as in the Climatic Optimum; but it seems more probable that there was some ‘permanent’ ice, limited to areas north of 80[deg] N….”
The Vikings were able to do things, (such as grow barley for their beer,) during their first century in Greenland that are completely impossible now. I discussed this over at another post concerning Sea Ice:
“I feel I’ve seen plenty of evidence (of an ice-free arctic,) including pictures in geologist’s studies showing beaches formed by ice-free waves on arctic shores. I’m sure other’s will point out other evidence, but one thing that fascinates me is the phenomenon of cross-polar-flow, which gives us our cruelest and most bitter blasts of arctic air, even as far south as here in New Hampshire.
During the long arctic night air gets colder due to radiating away heat into the starry sky. The longer the air sits up there the colder it gets, however usually it is nudged out as a high pressure area. If it moves south it reaches sunlight and starts to warm and moderate, however if it moves the other way, from the Siberian arctic over the pole to Canada (or vice versa) it has far longer to radiate away heat, and can get colder than cold. That is how temperatures can plunge to the extreme levels of fifty to eighty below zero.
However, if the Arctic Sea is unfrozen, rather than that air getting colder it gets warmer as it crosses, (at least at the start of winter, until “baby ice” forms.) A warmer, ice-free Arctic Ocean would create a new source of maritime air.
I think this was the case when the Vikings settled Greenland and raised over 2000 cows and over 100,000 sheep and goats. Why? Because, during a cold winter here in New Hampshire one of the biggest battles is making sure my goats get enough water. It always freezes and you have to bash through the ice in buckets (or buy electronic gadgets to keep the water thawed.) The sheer amount of ice-bashing involved, to allow 100,000 sheep and goats to drink, would dull the toughest Viking’s ax and leave him exhausted. Therefore winters must have been considerably warmer, and the only way for it to be that much warmer would be to have an utterly transformed north wind, from a relatively ice-free Arctic ocean.”
This is not to say the Greenland Vikings ever had an easy time of it, or that their final hundred years wasn’t miserable. However they were there for longer than the United States has existed, and when they first arrived they experienced an utterly different climate than we know now. It wouldn’t be a bad thing at all to have such a climate return.
The fact politicians and their paid pseudoscientists are making such a spectacle of the issue of warming will someday be seen as an amazing example of greed-driven madness.
Greenland is not the globe. It was warmer in Greenland. It was also warmer in central England. It was cooler in certain other parts. Average those together and you get something akin to the Mann 1999 curve (though there’s lots more recent work you could go for instead).
The figure Anthony cites indicates that even in central England, current temperatures exceed the peak of the MWP. But that’s a mediocre figure: it’s got no error bars and is using long-obsolete data for the MWP.
“So basically what they are saying is that at the year 1200 (2000AD minus 800 years), temperatures were warmer (or at least equal to) temperatures today.”
The above is an odd interpretation. If the leak is the final word on the IPCC assessment of past temperatures then a more plausible interpretation is that the IPCC considers that data aren’t sufficiently precise to determine if temperatures in the year 1200 were warmer, colder or much the same as today.
Aren’t some of you are missing something here? … The 500 has become 800 meaning this is more certainly anomalous than before by going back further. The warmists will claim to be less cautious and more certain than before. The 50 has become 30, meaning that this is a spike that is sharper and therefore less explainable than previously thought. Like the blade of a hockey stick! Contrary to what you think, these words and numbers have been most carefully crafted to allow for the sloppiest possible interpretation that will be the opposite of what you think it will be.
And here’s the proof …
http://www.richarddawkins.net/news_articles/2013/8/22/ipcc-surer-than-ever-about-human-caused-climate-change#