Spot the difference. Anthony Watts can't!

UPDATE: See below for more information and clarification by Jason Samenow of Capital Weather Gang.  I got some bits right and one wrong.  On balance more right than wrong :)  Anthony got it all wrong!


Things amuse.  Anthony Watts published a false accusation about the IPCC and wrote: Spot the difference. The IPCC can't.  Well it turned out the IPCC could and did.  And it was staring everyone in the face but Anthony Watts didn't see it.

Now let's play spot the difference with two quotes on WUWT.

First of all, Anthony Watts writes a wishful thinking headline with the word "Mann" and "Hockey Stick" - which are powerful words on WUWT.  It's a signal to WUWT readers that Anthony is giving them very wide latitude in the comments section.  They can make whatever accusations they like and be as irrelevant to the topic at hand as they wish, as long as they are taking pot shots at Michael Mann.  The headline reads:

IPCC throws Mann’s Hockey Stick under the bus?

Anthony then compares these two statements, the first from Capital Weather Gang reporting what is said to be in the current nearly final draft of the AR5 IPCC report, and the second from WG1 of the IPCC AR4 report.  This is the part where you can play "spot the difference" if you want to.  Anthony can't!

CWG: 7) The 30 years from 1983-2012 was very likely the warmest 30-year period of the last 800 years.

IPCC AR4: 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.

As HotWhopper readers know, Anthony has some major difficulties when it comes to tackling logic.  From the above two statements this is what he deduces:

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.

Anthony has committed another of his logical fallacies.  That's not what "they" are saying at all.  They are simply stating that there's a 90 to 100% likelihood that the past thirty years are hotter than any 30 year period of the last 800 years.  They are not saying that it was hotter 801 years ago.  The CWG/AR5 statement says nothing at all about the period prior to 800 years ago.

Not only that, but Anthony seems to have missed seeing a number of important differences between the CWG (AR5) statement and the AR4 statement:

• The CWG(AR5) statement is probably about global surface temperatures, the AR4 statement is more conservative and specific to the Northern Hemisphere only.  (See update below - the CWG statement was about Northern Hemisphere too, not global temperature.)
• The AR5 statement is a comparison of a thirty year stretch, the AR4 a comparison of a less conservative fifty year stretch.
• The AR5 statement is "very likely" (ie 90-100% probable) global surface temperatures are the warmest 30-year period in the last 800 years; the AR4 statement's "very likely" (ie 90-100% likelihood) relates only to the past 500 years
• The AR5 statement does not include a "likely" estimate; the AR4 statement says it is "likely" (ie 66-100% likelihood) that the past 50 years were the warmest of the past 1300 years in the Northern Hemisphere.

The bottom line is that the AR5 statement, if anything, signals more confidence now than at the time of AR4, that the current warming is unusual at the global level.

Bring back the MWP sez Anthony Watts

Anthony is wishing that scientists would decide that it was warmer several hundred years ago than it is today - not just in some parts of the northern hemisphere, or at different places at different times.  He wants scientists to find that it was warmer everywhere at the same time. 

Why?  Good question.  There is no logical answer.  The illogical answer is that Anthony wants to be able to deny the greenhouse effect that he says he accepts.  

Some deniers think that if there was warming in the past and it wasn't caused by a higher CO2 then the current warming can't be caused by the high levels of CO2.  Logical? No.  But deniers aren't strong on logic.  If it were warmer all around the world at the same time in medieval times, compared to now, something would have caused that to happen.  And if it was something little, like a bit of a brighter sun, then that would mean that climate sensitivity is high and we're in for a heap more warming than we currently expect. 

Globally, the average surface temperature wasn't higher in medieval times than it is today

All that speculation on the illogic of science deniers is irrelevant though.  As more studies like PAGES 2k and Marcott et al are added to the pile of knowledge, it's becoming more and more apparent that there wasn't a synchronous warming all around the world a few hundred years ago.  Some regions were hotter, such as Greenland and parts of northern Europe while others were cooler.  Some warmed later, after other parts cooled.

I've written about the medieval warming denier meme here, with a few charts and some discussion.  Science deniers keep claiming that scientists try to "hide" the warming.  They are wrong. If it weren't for scientists we wouldn't know much at all about where the world was warm or cold in the past.

My educated guess is Anthony is going to be disappointed.  What is more likely is that in AR5 there will be an expansion of what was written in CWG, along the lines of:

Globally, the 30 year period from 1983-2012 was very likely the warmest 30-year period of the last 800 years and likely the warmest 30-year period of the last xxx years. (See update below.)

...where xxx could be anything from 1000 to 2000 - based on the length of the PAGES 2K analysis, Mann et al (2009) and other temperature reconstructions that are at a sufficiently fine resolution to make such a statement.  For example, one of the charts I show in this article is based on PAGES 2K with HadCRUT and Mann et al, courtesy ClimateProgress:

Green dots show the 30-year average of the new PAGES 2k reconstruction. The red curve shows the global mean temperature, according HadCRUT4 data from 1850 onwards. In blue is the original hockey stick of Mann, Bradley and Hughes (1999 ) with its uncertainty range (light blue). Graph by Klaus Bitterman. 
Source: ClimateProgress

Poor Anthony has been having a bad run and it's showing in his increasingly erratic and silly posts.  I think he's not getting enough people writing articles for him.  Willis had a shot but I couldn't get past the first couple of paragraphs it was so dreadful.  Anthony needs something new and original.  How many more times can he publish the same old "ice age cometh" articles and magical leaping ENSO articles without boring everyone into a stupor?

Update

Jason Samenow of Capital Weather Gang has written a comment at WUWT.  Looks as if I got some bits right (eg there is an additional "likely" statement) and one bit wrong - his original statement was northern hemisphere only, not global.  Here is his comment:

Jason says:

August 21, 2013 at 8:48 am

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…

Correction: I originally attributed the AR5 statement to Grist.  It was published by Capital Weather Gang of the Washington Post.