Berkley report disappoints climate-change skeptics

University of California-Berkley physicist Richard Muller has expressed doubts about the accuracy of climate-change data in the past. So when oil-industry executives helped fund a major study and asked him to lead it, they probably expected his results to refute the collection of studies showing global temperatures have been rising for the past 100 years.

But as sportscasters are fond of saying when an underdog team unexpectedly wins, that's why they play the game. To the disappointment of those hoping to discredit the previous studies, Muller unexpectedly told a congressional hearing last week, based on preliminary results of the study: "We see a global warming trend that is very similar to that previously reported by the other groups."

According to a Los Angeles Times article this week, Muller and a team of scientists launched the Berkeley Earth Surface Temperature project to address what he called "the legitimate concerns" of skeptics who believe that global warming is exaggerated.

According to the article, three groups – the National Oceanographic and Atmospheric Administration, NASA and a British research group -- have conducted studies of temperature data collected from tens of thousands of weather stations around the globe. While the studies used different data and different statistical methods, they each concluded the planet land surface has, on average, warmed about 1.2 degrees Celsius over the last 100 years. In his report to Congress, Muller notes that the portion of global warming attributed to human causes is smaller, becoming apparent after 1957. Global temperatures since then have increased by 0.7 degrees Celsius, according to the Intergovernmental Panel on Climate Change, with human causes accounting for about 0.6 degrees.

Critics have attacked those results as biased, skewed and based on incomplete or unreliable data, but Muller's results so far have mirrored the previous data and shown that statistical analysis can account for potential biases caused by differences in quality of weather stations or length of time they have been in service.

Muller's results are preliminary and have not yet been published in a peer-reviewed journal. The project Web site notes that the team analyzed a small subset of data representing 2 percent of the total, which includes 1.6 billion temperature measurements to check programs and statistical methods.  "The Berkeley Earth team," the Web site reads, "would be more comfortable sharing them after they had been published in a peer-reviewed journal. However, Dr. Richard Muller was called to testify before congress on 31 March 2011. We did not solicit this presentation, but understand that congress needs our best testimony. For this reason we have shared some preliminary results."

While the Berkley team works to complete their analysis of the full data set, climate-change believers and skeptics already are praising or condemning the results accordingly.  So stay tuned – the group plans to make their data available during the first half of 2011.  Surface-temperature measurements are just one factor in the debate over whether climate change is occurring and whether human activities play a role. Studies such as this will have influence though, as the United States and other world governments formulate policy related to global warming and greenhouse gas emissions.

Go to the Berkley Earth Website for more information on the study and the text of Muller's presentation to Congress.

Read more from the LA times.