The Impact of Climate ChangeDer Spiegel
got its greasy mitts on an unpublished draft
of the second
part of the IPCC's fourth assessment report--the section dealing with the effects of manmade climate change, due out in April. Some of the language will still need to be hammered into shape, but the findings are worth going through. Spiegel
's headline, "Climate Change Impact More Extensive Than Thought," seems apt. Let's roll with the bullet points:
Scientists are observing a lot of changes--an increase in glacial lakes, warming permafrost, rivers and lakes that are heating, early springs, weird animal migrations--that are very likely due to manmade climate change.
Some 20 to 30 percent of all species face a "high risk of extinction" if global temperatures rise another 1.5 to 2.5 degrees C above 1990 levels.
Coral reefs are "likely to undergo strong declines," salt marshes and mangrove forests could disappear as sea levels rise, and tropical rainforests could be replaced by savanna.
As far as humans are concerned, the panel expects "increasing deaths, injuries and illness from heat waves, floods, storms, forest fires, and droughts."
Most of these forecasts are backed with either "strong certainty" (which, I assume, means 67-90 percent likely) or "very strong certainty" (over 90 percent likely). For the most part, global warming will have negative effects for both humans and the environment, outweighing the positive effects. The regions that will suffer most include Africa south of the Sahel, due to droughts, and densely populated river delta regions in Asia, due to flooding.
Interestingly, parts of Northern Europe and the United States may benefit thanks to better agriculture and forestry yields. But those yields will sink once temperatures rise more than 3 degrees (which, according to the first part of the AR4, would likely happen if carbon concentrations in the atmosphere doubled). Moreover, if temperatures keep rising unabated, oceans will eventually begin releasing greenhouse gases rather than absorbing them, accelerating the change. Eventually, no one will escape.
I'll add one note. The scientists working on the IPCC report are very good. But they tend to concentrate largely on the first- and second-order effects of climate change. There are also potential third
-order effects--famines, refugee crises, changes in disease vectors--that are less certain, and so don't get as much play in the IPCC report. Even fewer people really speculate on how political and social systems may be affected by global warming. So in that vein, I found this report
, linked to by David Ignatius
, extremely interesting.
The report's author, Peter Schwartz, tries to look at social and political dynamics that are already under stress and could be one day be altered dramatically by climate change. An example: Say the Yucatan peninsula is devastated by alternating floods and droughts, the Mexican government fails to respond adequately, and so Zapatistas start causing havoc and destabilize the central government, creating a massive rush of refugees to the United States. That's not the sort of thing the IPCC is in the business of predicting, but it's not overly far-fetched, either. So Schwartz wants to find a way to measure what parts of the world are at risk of being destabilized by global warming. My guess is we'll need it.