Global warming is real and land temperatures have risen by 0.911 of a degree Celsius (1.64 degrees Fahrenheit) on average since the 1950s, a team of researchers including Nobel prize-winner Saul Perlmutter have found.
An analysis of 1.6 billion temperature records dating as far back as 1800 gave results that are similar to data series by the British Met Office, the US National Oceanic and Atmospheric Administration and the National Aeronautics and Space Administration, the Berkeley Earth Surface Temperature said in a report published today.
"Our biggest surprise was that the new results agreed so closely with the warming values published previously," the project's founder, Richard Muller, said in a statement. "This confirms that these studies were done carefully and that potential biases identified by climate change sceptics did not seriously affect their conclusions."
The project was established to try to produce a definitive temperature series after climate sceptics - including US senator James Inhofe - said leaked e-mails from the University of East Anglia showed data were manipulated. The British school helps compile the Met Office temperature series.
Three inquiries into the contents of the leaked e-mails found scientists hadn't manipulated data, though they had tried to avoid disclosing data.
Last year was the second-warmest on record, according to the Met Office series. The two US data sets put 2010 in a statistical tie with 2005. The latest study, which has yet to be peer-reviewed, uses data from five times as many weather stations as other groups, and has reduced uncertainty, according to the statement.
The team did not try to assess whether warming was caused by humans. They analysed only land temperatures and established that there is a "locally large and real" urban heat island effect surrounding cities, though that doesn't add significantly to the overall trend, according to the statement.
They found temperatures rose in about two thirds of sites analysed, and fell in the remaining third.
The team is composed of researchers from the University of California at Berkeley, the Georgia Institute of Technology, the Lawrence Berkeley National Laboratory and Oregon State University.
Mr Perlmutter, who has affiliations with the laboratory and the University of California, was awarded the Nobel Prize in Physics for his work in astrophysics on October 4th.
Bloomberg