IPCC Adjusts Model-Predicted Near-Term Warming Downwards

This is another post that illustrates and discusses just how poorly climate models simulate one of the most important climate variables: global surface temperatures.  I’ve included a copy of this post in pdf format, linked at the end, for readers who would like to treat this post as a supplement to my ebook Climate Models Fail.

My blog post No Matter How the CMIP5 (IPCC AR5) Models Are Presented They Still Look Bad was cross posted at WattsUpWithThat here.  Scrolling down through that WUWT thread, you’ll find a comment by Bill Illis:

Bill Illis says:

October 5, 2013 at 6:10 am (Edit)

Comment from Jochem Marotzke of the Max Planck Institute in a presentation at the Royal Society about the IPCC report.

“As a result of the hiatus, explained Marotzke, the IPCC report’s chapter 11 revised the assessment of near-term warming downwards from the “raw” CMIP5 model range. It also included an additional 10% reduction because some models have a climate sensitivity that’s slightly too high.”

http://environmentalresearchweb.org/cws/article/news/54904

Sure enough, if we look at the IPCC’s Figure 11.9 (my Figure 1) and Figure 11.25 (my Figure 2) we can see how the IPCC has lowered the near-term predictions—without changing their long-term prognostications.

Figure 1 (Full-sized with caption is here.)

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Figure 2 (Full-sized with caption is here.)

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The IPCC discussed Figures 11.9 and 11.25 in Chapter 11 of the IPCC’s 5^th Assessment Report (6MB .pdf).  For the discussion of Figure 11.9, see page 24/123 (Adobe Acrobat page numbering), under the heading of “11.3.2 Near-Term Projected Changes in the Atmosphere and Land Surface”, and with a further subheading of “11.3.2.1.1 Global mean surface air temperature.”

Figure 11.9 can be found on page 102/123.

For Figure 11.25, see the discussions under the heading of “11.3.6.3 Synthesis of Near-Term Projections of Global Mean Surface Air Temperature” starting on page 53/123.

Figure 11.25 can be found on page 120/123.

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The October 3, 2013 article Bill Illis linked at EnvironmentalResearchWeb Royal Society meeting discusses IPCC fifth assessment report was written Liz Kalaugher.  Jochem Marotzke was described in the article as:

…Jochem Marotzke of the Max Planck Institute for Meteorology, who was part of the IPCC team assembling scientific evidence on trends in temperature over the last ten to fifteen years.

In the article, Jochem Marotzke tried to downplay the significance of the hiatus:

“Such hiatus periods are common in the record and yet this last one has sparked enormous debate,” Marotzke told delegates at the Royal Society. “Does the surface warming hiatus mean global warming has stopped? No. Warming of the climate system continues. Sea ice continues to melt, the ocean continues to take up heat, sea level continues to rise.”

But if “hiatus periods are common in the record” why must the IPCC revise “the assessment of near-term warming downwards from the ‘raw’ CMIP5 model range” and include “an additional 10% reduction because some models have a climate sensitivity that’s slightly too high”?  And if they’re so common, why did the IPCC have to create a team to assemble “scientific evidence on trends in temperature over the last ten to fifteen years”?

The answer to both questions is, the CLIMATE MODELS CANNOT SIMULATE the multidecadal variations that exist in the surface temperature record.  These multidecadal variations are seen as warming periods that last for approximately 3 decades followed by periods of about 3 decades without warming.  We’ve recently discussed this in the posts IPCC Still Delusional about Carbon Dioxide and in Will their Failure to Properly Simulate Multidecadal Variations In Surface Temperatures Be the Downfall of the IPCC?  (Also see the cross posts at WUWT here and here.)  These multidecadal variations are well-known to the public, and that’s why I presented (in the “Downfall” post) the difference between the IPCC’s projection of Northern Hemisphere surface temperature anomalies and the public’s vision on how the warming will occur based on the past variations…assuming surface temperatures continue to warm in the future. (See Figure 3.)

Figure 3

And it’s well known by the public that the models used by the IPCC are tuned to the upswing that started in the mid-1970s (see Mauritsen, et al. (2012) Tuning the Climate of a Global Model [paywalled].  A preprint edition is here.), while failing to consider the impacts of naturally occurring multidecadal periods of no warming on their long-term (to 2100) prognostications.

Last, as far as I know, the IPCC did not lower their long-term prognostications based on their lower short-term predictions.

SUPPLEMENT 3 TO CLIMATE MODELS FAIL

For those who are collecting the blogs posts in pdf form as supplements to my book Climate Models Fail, the copy of this post is here.

Supplement 1 is here.  It’s a reprint of the post Models Fail: Land versus Sea Surface Warming Rates.

Supplement 2 is here.  It’s a reprint of the post IPCC Still Delusional about Carbon Dioxide.