by John Timmer - Nov 20, 2012 - arstechnica
Many governments have set a goal for limiting climate change: two degrees by the end of the century, and no more. However, most projections show we're lagging badly. Unless we accelerate a transition to renewables and nuclear, we're going to shoot right past that 2°C limit. But even as the hand-wringing about missed targets and bad trajectories has increased, it's been relatively rare to see a detailed analysis of the potential consequence. The World Bank has now stepped into that breach.
In a report released today, the World Bank analyzed the consequences of allowing temperatures to reach 4°C above preindustrial levels by the end of the century.
Even the well understood problems—up to a meter of sea level rise, winter months that are warmer than our current summers—sound pretty ugly. The report also notes the possibility of tipping points and synergies make some of the impacts much harder to predict.
The report itself is a collaboration between the Bank's Global Expert Team for Climate Change Adaptation and the Potsdam Institute for Climate Impact Research and Climate Analytics. In addition to taking a different perspective on the problem of climate change, the report comes at a valuable time. It's been five years since the release of the fourth Assessment Report from the Intergovernmental Panel on Climate Change; the fifth isn't due until late next year.
So, what are the chances of adding an extra 4°C by the end of the century? The report estimates that, even if all countries are able to meet their current emissions pledges, there's still a 20 percent chance we'll hit 4°C by the end of the century. The longer we wait to meet those pledges, the harder it will be in part because it means we've already built fossil fuel infrastructure that has a life span of decades.
What does a world that much warmer look like? To give a sense of how hard it is to imagine, the report notes some points in the last glacial period were only 4.5°colder than present temperatures—and there were ice sheets covering a lot of the Northern Hemisphere. We've already hit levels of CO2 in the atmosphere that haven't been seen in over 15 million years. To reach 4°C, they'd have to roughly double again. And these changes would take place at a pace that probably has few geological precedents.
So, even the report's authors admit that predications are a challenge. Still, they do their best to try to paint a picture, and boy, is it grim.
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Please, let's not do this.
Amen to that!!
