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Center for Economics and the Environment: Policy Series


Global warming is the quintessential environmental scare. While the local effects of litter, chemical contamination, and aerosol pollution had dominated our environmental concerns in the 1970’s and 1980’s, we are now faced with a threat that is global in extent and predicted to be long-lasting1. The culprit is humanity’s use of fossil fuels, which release carbon dioxide into the atmosphere when burned. Since carbon dioxide is a ‘greenhouse gas’, it affects the radiative energy budget of the Earth. While carbon dioxide is a relatively minor atmospheric constituent, with a concentration now approaching 400 parts per million (pre-industrial levels were about 280 parts per million), it acts like a ‘blanket’ for infrared (heat) radiation, warming the lower atmosphere, and cooling the upper atmosphere.

The direct warming effect of a doubling of carbon dioxide concentrations (doubling is predicted to occur late in this century) has been estimated to be only about 1 deg. C. While this is not a very worrisome level of warming, many computer climate models suggest warming levels of three or four times this magnitude. This extra warming is due to ‘positive feedback’ in the models. Positive feedbacks occur when the direct warming tendency of the carbon dioxide is amplified by changes in clouds, water vapor, snow cover, and sea ice in the models. The existence and magnitude of these positive feedbacks are at the heart of scientific arguments over how much of the current global warmth is due to mankind’s activities, and therefore how much global warming we can expect in the future.

But even if predictions of strong warming, say 10 deg. F by the end of this century, are correct it is not at all clear what the best policy reaction to that threat should be. Because of the necessity of inexpensive energy sources for the health and well being of humans, it will be impossible to achieve substantial reductions in energy use through conservation. Instead, massive reductions in greenhouse gas emissions will require new energy technologies. Those technologies will likely be developed in the countries that can afford massive energy R&D efforts. Therefore, draconian, government-mandated punishment of fossil fuel use through taxes or carbon caps could very well hurt rather than help efforts to develop those new technologies.

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