Climate scientists have long held that the global temperature would rise by about 3 °C if atmospheric concentrations of CO2 doubled from pre-industrial levels. But new research suggests that the Earth's temperature might be as much as 30–50 per cent more sensitive to atmospheric greenhouse gases than previously thought.
While conventional estimates of climate sensitivity have focused on factors that influence temperature in the short term, such as cloud and snow cover, a team of scientists led by Daniel Lunt at the University of Bristol, UK, have devised a new estimate — termed 'Earth system sensitivity' — that also accounts for factors that affect temperature in the long term, such as land ice and vegetation. They used a state-of-the-art climate model to analyse the events that gave rise to a warm period about 3 million years ago, and they then compared these to actual temperature reconstructions derived from 3-million-year-old sediments on the ocean floor. Their analysis suggests that fast- and slow-adjusting components of the climate system will have an important influence on the extent of warming.2 °C mark.
The findings should send a strong message to policymakers, as they show that deeper emissions cuts will be needed to avoid dangerous climate change in the long term.
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Heffernan, O. The long and the short. Nature Clim Change 1, 3 (2010). https://doi.org/10.1038/climate.2010.133
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DOI: https://doi.org/10.1038/climate.2010.133
