Wednesday, April 30, 2008
Global warming may 'stop', scientists predict
Researchers studying long-term changes in sea temperatures said they now expect a "lull" for up to a decade while natural variations in climate cancel out the increases caused by man-made greenhouse gas emissions.
Melting icebergs: The study predicts the IPCC's 0.3ºC temperature rise for the next decade may not happen
The average temperature of the sea around Europe and North America is expected to cool slightly over the decade while the tropical Pacific remains unchanged.
This would mean that the 0.3°C global average temperature rise which has been predicted for the next decade by the UN's Intergovernmental Panel on Climate Change may not happen, according to the paper published in the scientific journal Nature.
However, the effect of rising fossil fuel emissions will mean that warming will accelerate again after 2015 when natural trends in the oceans veer back towards warming, according to the computer model.
Noel Keenlyside of the Leibniz Institute of Marine Sciences, Kiel, Germany, said: "The IPCC would predict a 0.3°C warming over the next decade. Our prediction is that there will be no warming until 2015 but it will pick up after that."
advertisementHe stressed that the results were just the initial findings from a new computer model of how the oceans behave over decades and it would be wholly misleading to infer that global warming, in the sense of the enhanced greenhouse effect from increased carbon emissions, had gone away.
The IPCC currently does not include in its models actual records of such events as the strength of the Gulf Stream and the El Nino cyclical warming event in the Pacific, which are known to have been behind the warmest year ever recorded in 1998.
Today's paper in Nature tries to simulate the variability of these events and longer cycles, such as the giant ocean "conveyor belt" known as the meridional overturning circulation (MOC), which brings warm water north into the North East Atlantic.
This has a 70 to 80-year cycle and when the circulation is strong, it creates warmer temperatures in Europe. When it is weak, as it will be over the next decade, temperatures fall. Scientists think that variations of this kind could partly explain the cooling of global average temperatures between the 1940s and 1970s after which temperatures rose again.