Sunday, September 20, 2015

There Is No Pause In Global Warming

Global warming deniers have for some time been touting a "hiatus" or "pause" in global warming.  Here is the most upfront version of this claim.  I've presented my own analysis using loess regression to relax the linear assumption which shows a slight slowdown in the underlying trend in the middle 2000's, but reveals a renewal of the climbing trend in temperatures since 2009.  My analysis shows

So far we have an increase in .8 degrees Celsius from 1880.   Fitting a linear trend from the middle of 2009 to April 2015 the RSS data projects a decadal increase of .2726 degrees, and the UAH data .6347 degrees.  Thus by 2035, the RSS data suggests 1.34 Celsius global temperature, and the UAH a 2.07 Celsius. 

Two degrees Celsius is the threshold beyond which the circumstances are dire.  If nothing is done about the carbon dioxide (and methane) that we're pouring into the atmosphere, our planet will be in truly dire circumstances by 2050.

The claim of a pause in global warming however has a grip on the deniers and further work has been done to establish the facts.  A group of economists with expertise in evaluating trends in data have looked at this issue.  Their approach was to do a blind test of the finding for or against an increasing trend.
The authors asked a group of economists (each with a Masters or PhD degree in economics or an allied discipline) to evaluate the trend in global temperatures without awareness of the source of the data. 
The experts were told that the data referred to agricultural output and were asked questions about whether the agricultural output had “stopped”. In fact, the authors took exact statements from a climate contrarian, except they replaced words associated with global warming with statements associated with agricultural productivity.
And the result was
In this blind test, the experts strongly rejected the agricultural “pause” conclusion. In fact, they found mention of a pause “to be misleading and ill-informed”. The experts were divided about whether the “pause” statement was also fraudulent. What is particularly convincing is that a blind test like this, which removes the effects of personal biases or preconceived opinions, is the gold standard for many research areas.
These resulsts were published in Bulletin of the American Meteorological Society.

As described here, more nails have been driven into the coffin of the claim of a pause,
Another related paper has just been published; the fourth refutation of the “pause” myth, covered here in the Washington Post.