Date published: 2006/05/23
The BBC says:
Global temperatures will rise further in the future than previous studies have indicated, according to new research from two scientific teams.
They both used historical records to calculate the likely amplification of warming as higher temperatures induce release of CO2 from ecosystems.
They both conclude that current estimates of warming are too low, by anything up to 75%.
That figure, known as the climate sensitivity, results from a combination of two factors:
- the direct impact of rising CO2 on the greenhouse effect
- various "feedback" mechanisms which amplify the rate of warming, such as changes in the Earth's reflection of sunlight as ice melts
The new research adds a third component, by calculating the likely contribution of carbon dioxide released from natural ecosystems such as soil as temperatures rise.
This would add to the CO2 produced through human activities, raising temperatures still further.
To calculate this extra warming, both research groups have looked back into the Earth's history.
Regularly, spells of relatively high temperatures have produced rises in atmospheric carbon dioxide concentrations, which have fallen again as colder conditions took over.
The theory is that in warm spells, ecosystems such as soils, forests and oceans retain less carbon.
As the Earth's surface is now warming again, the process might be expected to repeat itself, with higher temperatures again causing the biological world to release CO2 into the atmosphere, complementing the gas coming from homes, factories and vehicles.
To calculate the relationship between temperature rise and carbon release, the US study examined a period of about 400,000 years using data from the Vostok ice core of Antarctica.
Well cute, and it could be correct, but the evidence sounds rather tenuous.
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