Global warming risk 'much higher' than IPCC forecast

Global temperatures will rise more than previous studies have indicated, according to new research to be published in the journal Geophysical Research Letters by two teams from the US and Europe. They used historical records to calculate the likely amplification of warming as higher temperatures induce release of carbon dioxide (CO2) from ecosystems and both conclude that current estimates of warming are too low, by anything up to 75%.

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 repeating, with higher temperatures again causing the biological world to release CO2 into the atmosphere, adding to emissions from homes, factories and vehicles.

The US study examined a period of about 400,000 years using data from the Vostok ice core of Antarctica and expressed its results as a climate sensitivity of between 1.6 and 6.0C. The European group looked back to the ‘Little Ice Age’, a period in the middle of the last millennium when the northern hemisphere experienced relatively low temperatures and calculated that temperature rises in the future have been underestimated by between 15% and 78%.

The results are similar and challenge the consensus view of the Intergovernmental Panel on Climate Change (IPCC) , the global body charged with collating and analysing climate science, which predicts that the global average temperature would rise by between 1.5C and 4.5C if human activities were to double the amount of CO2 in the atmosphere.

From a BBC report. See the full version here.