The Earth's surface is warming, after all, says a team of researchers who sought to investigate claims that flawed data and methods had skewed existing analyses of global temperature trends.
The work by the Berkeley Earth Project shows that, on average, global land surface temperatures have risen about 1 degree Celsius since the mid-1950s -- on par with the warming trend described by research groups at the National Oceanic and Atmospheric Administration, NASA and the U.K. Meteorological Office.
The Berkeley effort's leader, astrophysicist Richard Muller, said his team had taken climate skeptics' criticisms of existing research into account when they began to examine global temperature data going back to 1800.
But in the end, the factors singled out by skeptics -- including some poorly sited temperature-monitoring stations -- did not have much bearing on his group's results.
"When we began this, I didn't know whether we would see more warming than people had previously seen, or less. I knew that some skeptics had raised legitimate issues that needed further study," said Muller, a professor at the University of California, Berkeley. "We've done that study now, and I think I'm surprised that the results agree with previous groups."
The Berkeley group published four papers describing its work, its data and the programs it used to analyze those data yesterday on its website, berkeleyearth.org. The papers have not been peer-reviewed, but Muller's team has submitted them for publication in scientific journals.
Several climate scientists said they weren't surprised that the Berkeley group's findings confirmed that the Earth is warming, something they said is supported by multiple lines of evidence -- not just the instrumental temperature records examined by Muller.
Skeptics' complaints don't check out
Asked whether the Berkeley Earth findings were newsworthy, NASA climatologist Gavin Schmidt had a simple answer: "No." But Schmidt said he thought the method Muller's team devised for analyzing temperature data "does seem to be interesting," though he cautioned that it had not been peer-reviewed.
Similarly, Kevin Trenberth, a senior scientist at the National Center for Atmospheric Research, said the Berkeley findings "need some good reviews."
"It is interesting in many respects," he said. "A good aspect is the sophisticated use of statistics. A bad aspect is the overuse of statistics and not enough common sense and basic physics."
Peter Thorne, a climate scientist at the North Carolina-based Cooperative Institute for Climate and Satellites, called the Berkeley Earth analysis "certainly useful, though ... not particularly novel."
Having multiple research groups examine temperature records, each with its own method, helps reduce uncertainty in scientists' estimate of ongoing warming, Thorne said. "I wish there were another 10 groups looking at the problem independently," he added.
Meanwhile, Muller said he hopes his results will convince people who doubt whether the Earth is warming that it is indeed happening.
"We can't win over the deniers," he said. "There are people on both sides who grossly exaggerate. But in between, there are a substantial number of properly skeptical people. I believe that work we're doing is the sort of work they're looking for."
It's a case Muller makes today in a Wall Street Journal op-ed. "Global warming is real. Perhaps our results will help cool this portion of the climate debate," he writes.
But reaction to the Berkeley Earth project has been mixed.
Before the group released its first set of findings last spring, liberal blogger Joe Romm of the Center for American Progress questioned the Berkeley group's motives, noting that it had received funding from the Charles G. Koch Charitable Foundation, which has supported efforts opposing mainstream climate change science.
And when Muller testified in March before a House committee that his group's preliminary analyses supported the overall warming trend reported by mainstream climate scientists, some skeptics were enraged.
Deniers remain in denial
Anthony Watts, a former TV meteorologist who runs the blog "Watts Up With That?" and who had initially consulted with Muller on the Berkeley effort, took the unusual step of submitting a letter decrying its findings to lawmakers before the House hearing where Muller spoke had ended (ClimateWire, April 1).
In a blog post yesterday, Watts said the Berkeley group's decision to publish its findings on the Web before they had been peer-reviewed was "troubling."
"Is their work so important, so earth shattering, that they can't be bothered to run the gauntlet like other scientists? This is post normal science at its absolute worst."
Meanwhile, the skeptic blog "Climate Depot" carried this headline yesterday afternoon: "Oh no, not Richard Muller's confused world again!"
Muller remains unbowed.
"Watts continues to jump back and forth between loving us and hating us," he said. "He has criticized one of our papers in a way that I have looked at. I believe his criticism is not valid, but I have not resolved that yet."
The Berkeley Earth team's focus now is publishing the results of its land surface temperature analysis and raising the money to examine records of ocean surface temperatures, Muller said.