Den stora tråden om global uppvärmning/växthuseffekten

Arctic ice is melting faster than computer models of climate calculate, according to a group of US researchers.
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The scientists suggest forecasts from the Intergovernmental Panel on Climate Change (IPCC) may be too cautious.
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They also calculate that about half, if not more, of the warming observed since 1979 originates in humanity's emissions of greenhouse gases.
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This is the third time in the last few months that studies have suggested the IPCC's latest major global climate analysis, the Fourth Assessment Report, is too conservative.

Air temperatures are rising with respect to the 1961-1990 average
In December, a German team published research suggesting that sea levels could rise by 50-140cm over the coming century. The IPCC, in February, gave a range of 28-43cm.

Then, also in February, came an analysis showing that temperature and sea level rises had been rising at or above the top end of IPCC projections since the panel's previous major assessment in 2001.

This is the opposite view from that put forward by many "climate sceptics", who view the whole field of computer modelling as deeply flawed, and the IPCC as an alarmist organisation.

Because of the way it works, the IPCC is bound to be conservative, as it assesses in considerable depth research already in the public domain. This process takes time, and means the panel's conclusions will always lag behind the latest publications.

Nevertheless, Marika Holland believes there is agreement on the major questions regarding Arctic ice; it is receding, and greenhouse gases of human origin are largely responsible.