Who or What is Heating up the Earth?

From the Telegraph, November 12:

Mankind has had less effect on global warming than previously supposed, a United Nations report on climate change will claim next year.

The UN Intergovernmental Panel on Climate Change says there can be little doubt that humans are responsible for warming the planet, but the organisation has reduced its overall estimate of this effect by 25 per cent.

In a final draft of its fourth assessment report, to be published in February, the panel reports that the level of carbon dioxide in the atmosphere has accelerated in the past five years. It also predicts that temperatures will rise by up to 4.5 C during the next 100 years, bringing more frequent heat waves and storms.

The panel, however, has lowered predictions of how much sea levels will rise in comparison with its last report in 2001.

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