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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This is great, The IPCC graph from 1990 is what was presented as the accepted norm for the 30+ years prior when I was stumbling across paleo-climate when reading up on paleo-anthropology. Mann’s version was and is pure fabrication, created for political purposes, by a tool.
Since the IPCC spearheads this war of propaganda for the warmist side, I would not get my hopes up that it will come clean any time soon in the near future. The rewriting of climate history is a necessary component for the IPCC.
Oh, and regarding that inconvenient hump on the left that is so incongruous with Mann’s plot, it was proceeded by an even larger one.
http://i39.tinypic.com/dcxzwh.jpg
Excerpt from a Breitbart article today:
http://www.breitbart.com/Big-Peace/2013/08/20/UN-Struggles-with-Data-Suggesting-No-Global-Warming
But just as the report stated that 95% of scientists believe that man’s actions cause global warming, climate change advocates quickly reasserted their belief in their omniscience; climate scientist Michael Mann wrote, “The report is simply an exclamation mark on what we already knew: Climate change is real and it continues unabated, the primary cause is fossil fuel burning, and if we don’t do something to reduce carbon emissions we can expect far more dangerous and potentially irreversible impacts on us.”
Probably more accurately stated as “…..“The report is simply an excremation mark on what we already knew….”
MtK
No, not likely – there will be another statement about the longer period, just with slightly less certainty, like there was in the draft leaked in December, that said
“There is medium confidence that in the Northern Hemisphere 1981–2010 was the warmest 30-year period of the last 1300 years.”
Reports of the resurrection of the MWP have been exaggerated.
And as Tony Brown at Climate reason has shown and recently posted here, a 50 year smoothing and a 30 year smoothing eliminate the decadal variability which according to CET records suggests there were multiple warmer decades more recently than the MWP.
Still a bit of possible climb down given all the post AR4 hockey stick controversy.
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…
Here is Lamb in 1965 on the Medieval Warm Period and the Arctic.
http://themigrantmind.blogspot.com/2010/03/why-climatologists-are-not-to-be.html
I believe this is one of those “the science has moved on, why haven’t you?” moments.
They don’t mention the bit about obviously bad science being ignored for a long time before being quietly swept under a rug.
Even Michael Mann says it was a bit toasty in the Northern Hemisphere during the Medieval Warm Period.
Now, where are those German olive groves?
DavidA:
Your post at August 21, 2013 at 8:50 am says in total
OK, but we are trying to minimise the damage to science from climastrology and, therefore, we need to make the climastrologists walk over the rug so they trip up over the bump caused by what is under it.
Richard
Clever move to keep dragging the old hockey stick out of the cupboard, Tony. It keeps the image clear in our minds – after all, it is around 15 years old.
Before you work yourself up into too much of a lather, though, isn’t it best to wait for publication?
(Ah, yes, Hubert Lamb, one of the first ‘alarmists’: “In 1973 and 1975 he arranged for two international conferences which were hosted in Norwich. At first his view was that global cooling would lead within 10,000 years to a future ice age and he was known as “the ice man”, but over a period including the UK’s exceptional drought and heat wave of 1975–76 he changed to predicting that global warming could have serious effects within a century. His warnings of damage to agriculture, ice caps melting, and cities being flooded caught widespread attention and helped to shape public opinion”)
The 30-year period 1983-2012 was the warmest of the last 750 years, except for the period 1923-52. A number of 30-year periods between 923 and 1252 were warmer, as too during 77 BC to AD 252, 1077 to 748 BC and 6077 to 3252 BC.
There, fixed it.
Amazing caveat, it says everything about climate science you ever wanted to know.
“The IPCC stresses these statements are draft and subject to change via the government review.”
Those who pay for the research will insist on having the results they were promised.
This 800 year statement on its own kill’s off the AGW hypothesis as it seems the modern warm period lies within the probably natural temperature range for this interglacial. You cannot say the modern warm period is both natural and anthropogenic. So where in the AR5 report is the apology for Mann’s erroneous work? I guess that is to be discovered. I mean they are now saying they got it wrong are they not?
I guess the word ‘likely’ means 97% consensus.
This raises the question as to how the IPCC gravy train is to be fuelled in future or more likely what new jobs will be available to people who have helped rob the people blind for years and years. Something in the UN, or maybe banking?
Village Idiot:
re your post at August 21, 2013 at 9:02 am.
Please go to the WUWT thread on Trenberth’s recent egregious comment.
There have been no trolls on that thread and it would benefit from having troll comments to laugh at.
This is a link to it.
http://wattsupwiththat.com/2013/08/21/stalking-the-rogue-hotspot/
Richard
they barely snuck in that 800 year mark…
…went back as far as they could to claim it
When the whole picture looks like this…..short and regular peaks in temps, and the overall trend is down
http://www.foresight.org/nanodot/wp-content/uploads/2009/12/histo4.png
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.
Non-sequitur I’m afraid. The statement only says that ‘ The 30 years from 1983-2012 was very likely the warmest 30-year period of the last 800 years.’ It says nothing about what went before.
Then there was that warm period coinciding with the Roman Empire, and a warm period around 1500 BC which lasted for quite a while. The whole point is, the greenhouse gas paradigm precluded the incommensurate theories and data from the start. The relations between solar activity, volcanic activity, and temperatures affecting civilization and crops are still being ignored. Powerful infrastructure, agricultural and mass manufacturing will carry people through a period of low solar activity and further temp drops from large volcanic eruptions.
So the last half of the 20th century was warmer than any other period since the start of the Little Ice Age. Isn’t that about what we’ve said all along? It was that whole “get rid of the MWP” BS that was the issue. This seems to me they are in a roundabout sort of way without saying it that the MWP existed and was as hot or hotter than we are today. Which is exactly what we’ve said for 10+ years.
“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)”
so basically the hockey stick graph’s gray confidence region needs to be a LOT bigger.
Quote by Clive Crook: “Which comes first — the science of climate or the art of persuasion?”
I don’t argue with that claim at all. Of course, the numbers they come up with are a result of weather stations placed next to asphalt and air conditioning vents within urban heat islands as well as magically turning older averages colder to make the present seem warmer. I’m sure the IPCC will remember that in their conclusions. (/sarc)
Yeah but, anyone with half a brain knows the Minoan, the Roman, the MWP all were warmer – in all cases much warmer than the present day but in having said that……………………. what does it matter?
http://notrickszone.com/2012/10/09/new-paper-confirms-co2-lagged-global-temperature-models-get-it-all-wrong-again/
>T’s always precede >CO2.
Just one iteration from
IPCC throws Mann under bus