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New research suggests that global warming by the end of this century could be greater than predicted by the Intergovernmental Panel on Climate Change (IPCC), the international body that assesses scientific data on global climate change.

In a study published in the 18 April issue of Nature, Reto Knutti and colleagues from the University of Bern, Switzerland, conclude that there is a 40 per cent probability that global temperatures will exceed the range predicted by the IPCC, and only a 5 per cent probability that warming will fall below that range.

The researchers also carried out climate projections for the next 20 or 30 years, and estimated that mean global temperatures would be 0.5-1.1°C warmer than in 1990-2000.

In a separate study, also published in this week’s Nature, Peter Stott of the Met Office in Bracknell and Jamie Kettleborough of Rutherford Appleton Laboratory in Didcot, United Kingdom, came up with similar estimates of warming of 0.3-1.3 °C in the same period.

Both results — obtained using very different methods — are consistent with the IPCC’s estimates for that period.

Stott and Kettleborough find that climate response is the main source of uncertainty in climate predictions to the year 2040, with uncertainty over emissions increasing significance after that date.

Both groups place a 5-95 per cent probability on their prediction of medium-term temperature changes. This makes the figures more useful to policymakers attempting to assess the expected costs and benefits of their actions, says Francis Zwiers of the University of Victoria in Canada, in an accompanying article in Nature.

Reference: Nature, 18 April 2002

Link to news and views article by Francis Zwiers
Link to paper by Knutti et al
Link to paper by Stott and Kettleborough

Photo credit: NASA
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