The Economist has an excellent editorial summarizing the latest summary report (PDF) from the Intergovernmental Panel on Climate Change, on how much humanity ought to reduce its greenhouse-gas emissions and by when, and what various measures to do so might cost. (Although the IPCC’s “summaries for policymakers” are supposed to distill a lot of technical stuff out, they’re still replete with numbers and jargony abbreviations. The policymakers the IPCC has in mind, presumably, are environment ministers and their staffs, not voters.)
The report says that to stabilise greenhouse-gas concentrations at 550 parts per million (a level most scientists think safeish) would require a price of $20-50 per tonne of carbon by 2020-30. That is along the lines of the carbon price established the European Emissions-Trading Scheme, which varied between $6 and $40 in 2005-06. It has not bankrupted the European economy so far. The IPCC’s economic models reckon, on average, that if the world adopted such a price the global economy would be 1.3% smaller than it otherwise would have been by 2050; or, put another way, global economic growth would be 0.1% a year lower than it otherwise would have been.
The world would barely notice such figures; so one might think that climate change can be easily sorted. The problem, of course, is that the numbers work only if they are applied globally. If a few countries—even a few big countries—adopt a carbon price, it will make little difference. All the world’s big emitters need to do it. Which brings the world straight back to the problem that sank Kyoto. No country alone can make a difference, and it is in every country’s interest to ensure that everybody else bears the burden. As the IPCC report convincingly argues, the technology and the economics of this problem are easily soluble. It is the politics that is so difficult.
This conclusion strikes me as just very slightly off. “All the world’s emitters” now includes China and India, which were reportedly arguing for language in this this report that would put more of a burden on so-called developed countries (although how countries that include cities like Shanghai and Mumbai can be entirely exempted from this category, I don’t entirely understand). China is now, or soon will be, the world’s top greenhouse-gas emitter — though its giant population means its per-capita emissions are still comparatively low — and its heavily populated coastal districts are among the world’s most vulnerable to the effects of climate change. The stronger those “developing” economies get, the weaker their case for exemptions becomes and the more they have at risk. You’d think they’d want to get out in front of the problem and lay down green infrastructure now, rather than following us in having to replace so much once it’s already built.