There Was No Global Warming 'Hiatus,' 40-Study Review Concludes

Another scientific analysis has debunked the theory that global warming stalled 15 years ago.  A similar finding by U.S. government scientists is at the center of a months-long probe led by Texas Republican Rep. Lamar Smith, chairman of the House science committee.

There is no evidence of a recent pause or hiatus in global warming, according to an analysis of 40 peer-reviewed studies on the subject published Tuesday in the Scientific Reports, a peer-reviewed journal of the Nature Publishing Group.  Researchers found that the studies positing a hiatus didn't examine a long enough period of time to support such a conclusion.

"There has never been a pause in global warming unless you try to create one by looking at an insufficiently large number of data points," said lead author Stephan Lewandowsky, a social scientist and professor of psychology at the University of Bristol in the U.K.  The study's co-authors are James S. Risby, a climate scientist with Australia's national science agency, and Naomi Oreskes, a science historian at Harvard University.

The most recent study is the sixth paper this year that reached similar conclusions, Lewandowsky said.  Smith, a prominent climate change denialist, for months has been investigating the National Oceanic and Atmospheric Administration focusing on a study NOAA scientists published in June debunking the hiatus theory.

Rep. Eddie Bernice Johnson, the House science committee's ranking Democrat, called the NOAA probe a "fishing expedition" and "a witch hunt designed to smear the reputations of eminent scientists for partisan gain."

The new findings cast additional doubt on studies that found a pause in climate change.  In their review of papers that found a hiatus in global warming and were published between 2009 and 2014, Lewandowsky and colleagues found no consistent definition of such a pause nor agreement on when it began or how long it lasted.

The average duration of a pause found by the studies was 13.5 years.  Using a duration that short to analyze fluctuations in global temperature would show that global warming paused more than a third of the time over the past 30 years, even as the planet's average temperature increased by 1.1 degrees Fahrenheit.

"If you want to see a pause and you don't understand statistics, and you want to mislead the public, then it is very easy to find a pause," Lewandowsky said.  "The problem is that it's meaningless, because those are short-term fluctuations that we always expect.  If you do it right, which is to look at enough data so you have a chance to observe a significant long-term trend, then you always detect a significant warming trend."

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