Climate Scenarios
I was in the midst of writing a post on climate change, when The Economist went and dedicated a whole frickin' issue to it. The leader article sums up the state of debate and the immense difficulty in formulating policy around climate change very well, while a more focused piece gives the history of climate science. Unfortunately other sections of the report are subscriber only.
The key point is that the IPCC's prediction that temperatures will rise between 1.4 and 5.8 degrees Celsius is awfully broad. In short, 1.4C would be tolerable, 5.8C would be catastrophic, so how do we decide what to spend insuring the planet against the consequences?
There are various possible climate scenarios but each still contains a lot of uncertainty, because as The Economist says, the economics of climate change are at least as uncertain as the science. For instance capping carbon emissions could reduce global productivity for the century by 5%, or by less than 1%.
The following sum up what might happen:
1) Low-end climate change: Either we get the IPCC's minimal 1.4C or somehow the scientists were wrong and carbon dioxode and methane continue to build up in the atmosphere but temperatures fail to rise.
Expensive programmes to cut emissions would seem very foolish in this scenario. While it would be nice not to have to spend the money, the probability of this is very low.
2) Ultra climate change: energy policies continue as at present or change but with little effect and carbon continues to build up in the atmosphere. Temperatures rise by 5.8C by the end of the century and the following century is spent trying to recover from the effects. Moreover, tipping points such as melting of perma-frost would be reached meaning that the effects would be irreversible and the climate would be massively unstable for the foreseeable future.
This could mean rebuilding London in the Peak District, and finding a home for the surviving population of Bangladesh; the people of Africa migrating North en masse... etc. While the scenario is only as likely as the minimal climate change discussed above, the probability is non-zero and the costs are unimaginably high.
3) Moderate climate change. Some efforts are made to reduce emissions, atmospheric carbon stabilises and we see a temperature rise of about 3C. There would be major effects including coastal flooding in some seriously populated and built-up areas. I suppose it would be similar to the effects of Hurricane Katrina, but in many cities around the world, most of which aren't rich.
This scenario is the most likely given present policies, which is why there needs to be government action on two fronts: reducing emissions and preparing to adapt to a new climate. It will be interesting to see the results of the UK government's Stern Review of the economics of climate change, which are due to be published this Autumn. This should give a better idea of the type of preparation that's needed.
The key point is that the IPCC's prediction that temperatures will rise between 1.4 and 5.8 degrees Celsius is awfully broad. In short, 1.4C would be tolerable, 5.8C would be catastrophic, so how do we decide what to spend insuring the planet against the consequences?
There are various possible climate scenarios but each still contains a lot of uncertainty, because as The Economist says, the economics of climate change are at least as uncertain as the science. For instance capping carbon emissions could reduce global productivity for the century by 5%, or by less than 1%.
The following sum up what might happen:
1) Low-end climate change: Either we get the IPCC's minimal 1.4C or somehow the scientists were wrong and carbon dioxode and methane continue to build up in the atmosphere but temperatures fail to rise.
Expensive programmes to cut emissions would seem very foolish in this scenario. While it would be nice not to have to spend the money, the probability of this is very low.
2) Ultra climate change: energy policies continue as at present or change but with little effect and carbon continues to build up in the atmosphere. Temperatures rise by 5.8C by the end of the century and the following century is spent trying to recover from the effects. Moreover, tipping points such as melting of perma-frost would be reached meaning that the effects would be irreversible and the climate would be massively unstable for the foreseeable future.
This could mean rebuilding London in the Peak District, and finding a home for the surviving population of Bangladesh; the people of Africa migrating North en masse... etc. While the scenario is only as likely as the minimal climate change discussed above, the probability is non-zero and the costs are unimaginably high.
3) Moderate climate change. Some efforts are made to reduce emissions, atmospheric carbon stabilises and we see a temperature rise of about 3C. There would be major effects including coastal flooding in some seriously populated and built-up areas. I suppose it would be similar to the effects of Hurricane Katrina, but in many cities around the world, most of which aren't rich.
This scenario is the most likely given present policies, which is why there needs to be government action on two fronts: reducing emissions and preparing to adapt to a new climate. It will be interesting to see the results of the UK government's Stern Review of the economics of climate change, which are due to be published this Autumn. This should give a better idea of the type of preparation that's needed.
posted by Peter at 10:40
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