A new climate study shows that since the mid-1950s, global average temperatures over land have risen by 0.9 degrees Celsius (1.6 degrees Fahrenheit), confirming previous studies that have found a climate that has been warming – in fits and starts – since around 1900. Most climate scientists attribute warming since the mid-1950, at least to some degree, to carbon dioxide emissions from human activities – burning coal, oil, and to a lesser extent gas, and from land-use changes.
The latest results mirror those from earlier, independent studies by scientists at NASA's Goddard Institute for Space Studies in New York, the Hadley Center for Climate Prediction and Research in Britain, and the National Oceanic and Atmospheric Administration (NOAA).
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These previous efforts, however, came under fire from some climate-change skeptics who said they had detected serious flaws in the analytical methods and temperature records the three groups used.
The new research, which has yet to be formally published but which appears in four papers posted on BerkeleyEarth.org, uses new analytical techniques and a much larger set of records than the previous studies did.
Indeed, the new approach to analyzing temperatures records allowed the team to make use of partial and older records previous studies had rejected as unusable, explains Richard Muller, a physicist at the Lawrence Berkeley National Laboratory who coordinated the effort.
In the end, the team's result shows that the earlier studies "were done carefully and that potential biases identified by climate-change skeptics did not seriously affect" the conclusions these studies reached, said Dr. Muller, who some climate activists have labeled a global-warming skeptic.
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