| 摘要 | Contrary to President Clinton, the science underlying the Kyoto Protocol is not "compelling" or "settled." Highly accurate satellite observations show no global warming over the past two decades. What is more, history and scientific analyses suggest that warming on balance would be beneficial, producing longer growing seasons, diminishing the frequency and intensity of severe storms, and even slowing down sea level rise.
Nonetheless, since atmospheric levels of carbon dioxide (CO2) and other "greenhouse" (heat-trapping) gases are increasing, policy makers need to know what can be done to mitigate any climate warming and/or reduce the growth of greenhouse gases, should that prove desirable. There are three basic approaches: cooling the climate, reducing emissions, and sequestering CO2. Another alternative is to improve mankind’s capacity to adapt to climate change.
Cooling the climate would require increasing the reflecting power (albedo) of the Earth’s surface or atmosphere, reducing the solar energy reaching the Earth’s surface, or modifying the circulation of the atmosphere or ocean. All sorts of speculative schemes have been suggested, including pumping sun-reflecting aerosols into the atmosphere, launching light-blocking platforms into space, building dams or canals to change oceanic circulation. However, none currently is economically feasible and some may have undesirable environmental side effects.
Emissions reduction – the goal of an international climate treaty – can be accomplished by taxing or rationing energy use, by tightening fuel economy and energy efficiency standards, and by increasing the use of non-carbon energy technologies (hydropower, nuclear, solar). All these options have problems. Efficiency mandates can actually waste energy when they result in premature replacement of capital equipment. Hydropower may harm fisheries; nuclear energy carries political baggage; and solar power is uneconomic. Energy taxes destroy jobs. Energy rationing schemes (even with emissions trading) are costly, difficult to monitor, and practically impossible to enforce.
Sequestering CO2 by setting up giant tree farms would require planting an area 4,500 by 4,500 miles just to absorb current emissions. A more promising technique is to stimulate the growth of CO2-absorbing phytoplankton by adding minute amounts of inorganic iron to seawater. Preliminary experiments indicate that iron fertilization of the oceans could reduce atmospheric carbon dioxide at a cost of $2.50 per ton of CO2 versus $25 per ton for reforestation and $100-200 per ton for energy rationing. More research is needed to assess the economics and environmental impacts of this approach. While it may never be necessary to reduce atmospheric CO2, it will be reassuring to know that we have the technical capability to do so.
The best climate change insurance policy, however, is the wealth and resilience of a dynamic market economy. It is difficult to justify major expenditures to address climate change in the presence of more urgent social needs, such as better health care, adequate nutrition, sanitary drinking water, education, and personal and public safety. Wealthier societies are not only better at meeting those fundamental needs, they provide more of the infrastructure and assets – safe and sturdy housing, local climate control, modern communication and transportation systems, high-tech agriculture, emergency relief services, and so on – that will allow people to adapt to climate change. |
