NASA's top climate scientist, James Hansen, has posted a new draft paper that makes a bold and deeply disturbing prediction.
[Business-as-usual] scenarios result in global warming of the order of 3-6°C. It is this scenario for which we assert that multi-meter sea level rise on the century time scale are not only possible, but almost dead certain. Such a huge rapidly increasing climate forcing dwarfs anything in the paleoclimate record. Antarctic ice shelves would disappear and the lower reaches of the Antarctic ice sheets would experience summer melt comparable to that on Greenland today.
If you've read the last IPCC report (2007), you might have noticed a major caveat in their prediction of sea level rise during the 21st century: they left out any and all ice-melting from their predictions. The only rise they considered was stearic rise, that is, the sea level rise that happens because water expands as it heats.
Some climate scientists were annoyed by this, as the resulting prediction, of merely a foot or so of sea level rise, was (they felt) far too reassuring given the reality of the situation.
Now James Hansen and Makiko Sato have pointed out that past records of sea level rise have including episodes when rise rates were many meters per century. These kinds of rapid rates imply that ice loss is a non-linear process: it might well be exponential. In that case, the critical factor is not the raw rate of sea level rise, but the time it takes for the rate to double.
In looking at the current rate of ice loss in both Greenland and Antarctica, the current data -- while still incomplete -- seems to point to doubling times of between 5 and 10 years. Even a more modest 12 year doubling time yields a 5 meter sea level rise by the end of this century. If the doubling time is 10 years or less, it could be double that.
So that's the cost of doing nothing on climate change: global coastal catastrophe.
You want more?
The Stern report (UK) estimates that the cost of doing nothing will be 5% to 20% of global GDP by 2100. That compares to 2-3% of GDP for early mitigation -- a bargain.
Watkiss et. al. (EU) estimate that the cost of doing nothing will be $26 trillion per year by 2100, rising to $76 trillion per year by 2200.
Kemfert (Germany) estimates the cost of doing nothing to be $20 trillion per year by 2100.
And those are the rosy estimates.
Last year I diaried the sobering paper of physicist Tim Garrett, who applied the basic equations of thermodynamics to civilization as a whole. His conclusion: our entire civilization faces collapse unless we do something, and now, about the energy/warming problem.
Okay. Now you can worry.