I agree with Becker that the
And desperately required; for I believe that the threat of global warming is very serious, and that it is not merely a long-term threat. (If it were, there would be no urgency about taking measures to slow it, for normal technological progress will eventually solve the problem at low cost.) The particular danger which concerns me, and which I emphasized in my book Catastrophe: Risk and Response (2004), is that of abrupt global warming. The climate equilibrium (like the economic equilibrium, as we have discovered) is unstable, in part because of feedback effects. For example, as the Alaskan and Siberian permafrost melts, methane, a potent greenhouse gas, is released into the atmosphere, causing surface temperatures to rise, which in turn accelerates the release of methane. And also as surface temperatures rise, the amount of water vapor in the atmosphere increases—and water vapor is a potent greenhouse gas, and so increasing it accelerates the warming trend. The ocean’s capacity to absorb atmospheric carbon dioxide is limited, so that as emissions increase, more remain in the atmosphere longer. Similarly, the destruction of forests to make way for agriculture increases net carbon emissions because trees absorb more carbon dioxide (during the day, in photosynthesis) than they emit (at night, when they are breathing oxygen and exhaling carbon dioxide).
The effects of rapidly rising concentrations of greenhouse gases in the atmosphere in heating the earth’s surface could produce such catastrophes as the melting of the Greenland and Antarctic ice caps, which would raise the level of the oceans by several feet, and the melting of the Arctic ice cap, which by diluting the salt in the North Atlantic could shift the Gulf Stream from northeast to north, which would give Europe, because of its northern latitude, a Siberian climate. These are catastrophes that could occur within the next one or two decades.
No probabilities can be attached to abupt global warming, so no expected cost can be calculated that would enable a cost-benefit analysis of preventive measures. But when the likelihood of an immense disaster cannot be estimated, yet does not seem negligible, there is an argument for taking preventive measures, at least if they are not prohibitively costly.
The free-rider problem is defeating efforts to limit carbon emissions. Emissions limitations even by a major emitter (the two biggest emitters are
The free-rider problem would not be serious if the cost of reducing emissions by significant amounts were low; but it is high. Given existing technology, it requires a substantial reduction (whether brought about by emissions taxes or by quotas) in the use of motor vehicles, in the generation of electricity (other than in nuclear reactors), and in the clearing of forests for agrcultural and other uses. What is needed to make a solution to global warming feasible is cheap technological fixes. One is actually at hand, though strongly resisted by environmentalists (I am tempted to put “short-sighted” in front of “environmentalists”), and that is to inject sulphur dioxide, a potent sun-screen gas, into the atmosphere. This solution (called “geoengineering”) is resisted because sulphur dioxide in the atmosphere causes acid rain; but acid rain is a far less serious problem than global warming.
Other possible technological solutions include injecting carbon emissions from electrical power generation underground, cheap battery-driven motor vehicles, and artificial “bacteria” that would devour carbon dioxide in the atmosphere. All of these solutions would require large investments in research and development to achieve feasibility at low cost. The benefits, however, would include not only reduced carbon emissions but also reduced dependence by the