New and Improved CRUTEM4 Global Land Surface Temperature Data vs IPCC AR4 (CMIP3) Climate Models

Guest post by Bob Tisdale

INTRODUCTION

Chapter 4-7 of If the IPCC was Selling Manmade Global Warming as a Product, Would the FTC Stop their deceptive Ads? included comparisons of the CRUTEM3 Land Surface Temperature anomalies to the multi-model mean of the CMIP3 climate models. For those who have purchased the book, see page 99. As you will recall, CMIP3 stands for Phase 3 of the Coupled Model Intercomparison Project, and CMIP3 served as the source of the climate models used by the Intergovernmental Panel on Climate Change (IPCC) for their 4^th Assessment Report (AR4). CRUTEM3 is the land surface temperature data available from the Met Office Hadley Centre and the Climatic Research Unit at the University of East Anglia.

This post compares the new and improved CRUTEM4 land surface temperature anomaly data to the same CMIP3 multi-model mean. CRUTEM4 data was documented by the 2012 Jones et al paper Hemispheric and large-scale land surface air temperature variations: An extensive revision and an update to 2010. I’ve used the annual time-series data, specifically the data in the second column here, changing the base years for anomalies to 1901 to 1950 to be consistent with Figure 9.5 of the IPCC’s AR4.

And, as I had with the other 20^th Century Model-Observations comparisons, the two datasets are broken down into the 4 periods that are acknowledged by the IPCC in AR4. These include the early “flat temperature” period from 1901 to 1917, the early warming period from 1917 to 1938, the mid-20^th Century ‘flat temperature” period from 1938 to 1976, and the late warming period. The late warming period in the chapter 4-7 comparisons in If the IPCC was Selling Manmade Global Warming as a Product, Would the FTC Stop their deceptive Ads? ended in 2000. For the late warming period comparisons in this post, I’ve extended the model and CRUTEM4 data to 2010.

COMPARISONS

As shown in Figure 1, and as one would expect, the models do a good job of simulating the rate at which the CRUTEM4-based global land surface temperatures rose during the late warming period of 1976 to 2010.

Figure 1

But like CRUTEM3 data, that’s the only period when the IPCC’s climate models came close to matching the CRUTEM4-based observed linear trends.

According to the CMIP3 multi-model mean, land surface temperatures should have warmed at a rate of 0.043 deg C per decade from 1938 to 1976, but according to the CRUTEM4 data, global land surface temperature anomalies cooled at a rate of -0.05 deg C per decade, as shown in Figure 2.

Figure 2

Figure 3 compares the models to the global CRUTEM4 data during the early warming period of 1917 to 1938. The observed rate at which global land surface temperatures warmed is almost 5 times faster than simulated by the IPCC’s climate models. 5 times faster.

Figure 3

And in Figure 4, the models are shown to be unable to simulate the very slow rate at which land surface temperatures warmed during the early “flat temperature” period.

Figure 4

According to the models, the linear trend of the global land surface temperatures during the late warming period should be 6.6 times higher than during the early warming period. See Figure 5.

Figure 5

Yet according to the new and improved CRUTEM4 land surface temperature data, Figure 6, the land surface temperatures warmed during the late warming period at a rate that was only 40% higher than during the early warming period.

Figure 6

CLOSING

The models show no skill at being able to simulate the rates at which global land surface temperatures warmed and cooled over the period of 1901 to 2010. Why should we have any confidence in their being able to project global land surface temperatures into the future?

ABOUT: Bob Tisdale – Climate Observations

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SOURCES

The CMIP3 multi-model mean data is available through the KNMI Climate Explorer

http://climexp.knmi.nl/selectfield_co2.cgi?id=someone@somewhere

And as noted in the post, the annual CRUTEM4 data is available through the Met Office website:

http://www.metoffice.gov.uk/hadobs/crutem4/data/diagnostics/global/nh+sh/index.html

Specifically:

http://www.metoffice.gov.uk/hadobs/crutem4/data/diagnostics/global/nh+sh/global_n+s