White House report says people cause global warming

13:10 27 August 04

NewScientist.com news service

People are responsible for the spike in global warming in the last 30 years, says a new US government report. The verdict, long accepted by most scientists, has encountered resistance from the Bush administration in the past, prompting experts to question if the president will now enact policies to curb greenhouse gas emissions.

The report, titled Our Changing Planet, is part of a regular series that summarises recent and planned climate change research by 13 government agencies. It was released on Wednesday with a covering letter to Congress signed by the president's secretaries of commerce and energy, along with his science adviser.

The document reports that global warming in the first half of the 20th century, estimated at 0.2°C above pre-industrial temperatures, "was likely due to natural climate variation", including increased solar activity.

But the approximate 0.5°C rise over the second half of the century, most pronounced in the last 30 years, can only be explained when factors related to human activity, such as carbon dioxide and other greenhouse gas emissions, are taken into account.

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