Christopher Monckton of Brenchley has a must-read post today on Watts Up With That. “The long and model-unpredicted Great Pause of 18 years 8 months in global mean lower-troposphere temperature as recorded in the RSS satellite monthly dataset is inexorably driving down the longer-run warming rate, when the IPCC’s predictions would have led us to expect an acceleration,” he reports.
The bright blue line shows the 440-month lower-troposphere temperature trend in the Remote Sensing Systems (RSS) record. The green line shows the zero degree warming trend during the 224-month “pause” since December 1997, which, as Monckton notes, is “more than half the entire 440-month record.”
Here’s the cool thing (literally). Thanks to the pause, the trend during the full satellite record works out to just 1.21ºC per century. That is substantially below the IPCC’s central estimate in 1990, which (along with NASA scientist Jim Hansen’s overheated prediction in 1988), put global warming on the political map.
In 1990, the IPCC had predicted near-straight-line warming of 1 K to 2025, equivalent to almost 2.8 K/century. Of this warming, more than 0.7 K should have happened by now, but only 0.26 K has actually occurred. The IPCC’s central estimate in 1990, though made on the basis of “substantial confidence” that the models on which it relied had captured all the essential features of the climate system, has proven – thus far, at any rate – to be a near-threefold exaggeration.
The IPCC knows its models are predicting too much warming. In the graph below, Monckton enlarges the right-hand corner of Figure 10.1(a) from the IPCC’s 2013 Fifth Assessment Report (AR5). CMIP3 is the ensemble of models used in the 2007 Fourth Assessment Report (AR4), CMIP5 is the ensemble used in AR5. Although CMIP5 predicts less warming than CMIP3, it still increasingly diverges from reality.
Note also that a 21st century warming of 1.21ºC is well within the bounds (0.3ºC-1.7ºC) of the IPCC’s lowest projection (RCP2.6), which assumes a 70% reduction in cumulative greenhouse gas emissions from 2010 to 2100 compared to baseline projections. In short, the RSS data show about the same warming rate that climate campaigners urge policymakers to achieve via draconian restrictions on carbon-based energy.
What is to be done?