by Nora Schultz (14:48 23 December 2008)
Despite the global economic downturn, spending money now to keep climate change in check makes sense as it will save us money in the long run. A new analysis has found that boosting spending is worth it because the chances of preventing catastrophic warming increases linearly with the amount invested.
Michiel Schaeffer at the University of Wageningen in the Netherlands and colleagues used data from climate models to look at how the cost of cutting emissions is linked to the probability of preventing extreme warming.
A crucial parameter in climate models is climate sensitivity, expressed as the number of degrees by which the mean global temperature will rise following a doubling in atmospheric CO2 levels. For example, the Intergovernmental Panel on Climate Change’s best guess for climate sensitivity is 3 ºC.
Using this, Schaeffer’s team found that reducing the target CO2 concentration from 550 to 500 parts per million (ppm) increases the chance of keeping the temperature rise within 2 ºC from less than 10% to 20%. This probability rises to 40% at 450 ppm and 80% at 400 ppm.
Schaeffer says further analysis shows that for every extra dollar spent, the probability of achieving the temperature target rises linearly. In other words, every extra dollar spent increases the chance of success by the same amount.
This linear relationship only holds true for big emissions cuts, though. For relatively lenient emissions targets, costs go up for every small increase in the chances of keeping warming under control. Committing to a realistic climate protection level, however, takes us beyond this regime and into the linear zone.
“To do more is relatively cheaper once you are past the threshold,” says Schaeffer. “And doing a bit is hardly going to be effective.”
Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0802416106
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