IN WASHINGTON DC they are starting to believe. A report commissioned by Congress from the National Academy of Sciences has concluded that the controversial 鈥渉ockey stick鈥� graph of global warming is real, and that the spike in temperatures has probably been caused by human activity.
鈥淭he report concludes that the 鈥榟ockey stick鈥� graph of global warming is real鈥�
The NAS report says that the past few decades have been the warmest in the past 400 years and that it is 鈥減robable鈥� that the last 25 years have been the warmest since AD 900. Sherwood Boehlert, chairman of the House science committee, requested the report in November 2005 in response to the political debate around the work of palaeoclimatologist Michael Mann of Penn State University at University Park. Mann鈥檚 work examined average temperatures over the past 1000 years. When he plotted the results they showed that for the first 900 years there was little variation 鈥� like the shaft of a hockey stick 鈥� but that there has since been a spike of massive warming 鈥� the blade of the stick.
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The NAS report finds that conclusions drawn from Mann鈥檚 reconstructions of warming bear weight, but it says that there is too little evidence to be statistically certain that a given year or single decade stands out as unusually warm.
Some people try to promote the idea that the recent warming is unconnected with human activity, says Martin Rees, president of the Royal Society in London. 鈥淭his report renders that notion much less plausible.鈥�
