Analysis by former climate skeptic confirms Earth is warming

“Let me explain why you should not be a skeptic, at least not any longer,” said University of California physicist Richard Muller in October 2011.

In recent days, a story has emerged about new research on Earth’s temperature change over time – conducted by a physicist and former climate skeptic. The new research shows that global warming is real.

A “hockey stick” graph showing recent temperature rise. From IPCC TAR WG1 (2001). Image Credit: Wikimedia Commons

Richard Muller, a physicist at the University of California at Berkeley, led this new research, known as the Berkeley Earth Surface Temperature study.

For his outspokenness, in years past Richard Muller has been embraced by the community of disbelievers in global warming. Yet the results of the Berkeley Earth Surface Temperature study suggest that previously published studies, such as those of the IPCC, are correct in asserting that global temperature is on the rise. The team officially released its results in October 2011 in a non-peer-reviewed form. The results are now being submitted to a peer-reviewed journal.

Muller once called Al Gore’s 2006 movie An Inconvenient Truth a pack of half-truths. In 2004, he joined other climate skeptics in criticizing the climate research that produced the so-called “hockey stick graph” showing a distinct rise in global temperature since the Industrial Revolution began and particularly in the last century.

However, the new Berkeley study shows an average global land temperature rise of roughly 0.9 degrees Celsius since the 1950’s.

Richard Muller is a professor of physics at the University of California at Berkeley and also a faculty senior scientist at the Lawrence Berkeley National Laboratory. Image via American Association of Physics Teachers

Writing in the Wall Street Journal on October 21, 2011, Muller said:

… let me explain why you should not be a skeptic, at least not any longer.

Over the last two years, the Berkeley Earth Surface Temperature Project has looked deeply at all the issues [raised by climate skeptics]. I chaired our group, which just submitted four detailed papers on our results to peer-reviewed journals. We have now posted these papers online at www.BerkeleyEarth.org to solicit even more scrutiny.

Our work covers only land temperature – not the oceans – but that’s where warming appears to be the greatest. Robert Rohde, our chief scientist, obtained more than 1.6 billion measurements from more than 39,000 temperature stations around the world. Many of the records were short in duration, and to use them Mr. Rohde and a team of esteemed scientists and statisticians developed a new analytical approach that let us incorporate fragments of records …

We discovered that about one-third of the world’s temperature stations have recorded cooling temperatures, and about two-thirds have recorded warming. The two-to-one ratio reflects global warming. The changes at the locations that showed warming were typically between 1-2ºC, much greater than the IPCC’s average of 0.64ºC.

Via the Nature Conservancy

The science journal Nature has a great short post examining how Muller’s new study differs from its predecessors. Until now, instrumental temperature records dating back to the middle of the 19th century have been compiled by three main research groups: NASA’s Goddard Institute for Space Studies in Greenbelt, Maryland; the U.S. National Oceanic and Atmospheric Administration (NOAA) in Washington, D.C.; and a collaboration between Britain’s Met Office and the Climatic Research Unit at the University of East Anglia in Norwich, UK. Writing in Nature, Jeff Tollefson says:

All three records were developed in different ways, using separate, but overlapping, sets of data. By and large, all three studies line up fairly well as they document rising temperatures, particularly the sharp spike in recent decades, but that hasn’t halted criticism from climate skeptics regarding the quality of the data and the rigor of the analysis.

The Berkeley researchers developed their own statistical methods so that they could use data from virtually all of the temperature stations on land – some 39,000 in all – whereas the other research groups relied on subsets of data from several thousand sites to build their records. This meant that they [Muller’s team] also had to figure out ways to handle shorter temperature records from instruments or stations where the record was interrupted.

Muller and his team also used a different approach to analyzing the data. Scientists working on the earlier studies adjusted raw data to account for differences in the time of day when readings were made, for example, or for higher temperatures caused by the urban heat island effect, in which cities tend to be warmer than natural landscapes. Muller says his team included the raw data in its analysis and then applied standard statistical techniques to remove outliers.

Muller’s study has not yet been peer reviewed, but the Berkeley team is submitting four papers to the Journal of Geophysical Research for peer review. Will climate skeptics change their minds because Muller has changed his? It’s too early to tell. We can only hope so. In the meantime, hats off to scientist Richard Muller for doing what science is supposed to do and often does quite well: that is, keeping an open mind.

Berkeley Earth Surface Temperature study

Profile of Richard Muller at BEST site

Richard Muller on October 21 in Wall Street Journal: The Case Against Global-Warming Skepticism

Nature on October 21: Different method, same result: global warming is real

Opinion piece on October 24 in Washington Post: The scientific finding that settles the climate-change debate

Deborah Byrd

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