Global Climate Change: Preparing for Kyoto

Article excerpt

Global climate change issues will be making headlines and leading newscasts again late this year. Politicians, environmentalists, corporation reteleucrats and test spokesmen all have climate change messages. Each of those sources' versions is tied to an agenda. Anticipating a world summit meeting on the issue, Harvard's Jim Hammitt updates his NewsBackgrounder offering journalists analytical tools for looking at the science and the policy of global climate change.

The nations of the world are expected to sign a new agreement in Kyoto, Japan this December to add teeth to the Framework Convention on Climate Change (FCCC). Signed at the 1992 Earth Summit in Rio de Janiero, the FCCC calls for "stabilization of greenhouse-gas concentrations ... at a level that would prevent dangerous anthropogenic interference with the climate system."

Although recent research on climate change and policy have led to substantial improvements in understanding the issues, neither the appropriate level of greenhouse concentrations nor a suitable policy to obtain it has been identified. Primary areas of disagreement include:

The likely magnitude and consequences of global climate change if no significant mitigation is undertaken.

The relative benefits and costs of preventing or slowing climate change.

The allocation of responsibility and mitigation costs across countries.

The chance that human actions will alter global climate is one of the most serious environmental risks. The probability of significant change is difficult to assess, but most scientists who have studied the issue believe that continued emissions of carbon dioxide, methane, and other "greenhouse gases" into the atmosphere will increase the average air temperature at the Earth's surface and modify other aspects of climate. Changes in temperature, precipitation, and storm patterns are likely to differ between regions, seasons, and even between daytime and nighttime. The consequences for humans and wildlife are equally uncertain, although it is likely that some changes will be harmful and others beneficial. As both humans and ecosystems might, to some extent, adapt to otherwise harmful changes, the rate of change could be as important as its ultimate magnitude. In this NewsBackgrounder; I briefly describe the risk and suggest a way to frame the policy issue.

The Enhanced Greenhouse Effect

In addition to its primary constituents, nitrogen and oxygen, the atmosphere contains a number of gases that ee present in only tiny proportions. Among these minor and trace gases, water vapor, carbon dioxide (CO2), and ozone are important in shaping the Earth's climate. These gases allow the sun's visible, ultraviolet, and near-infrared radiant energy to penetrate to the Earth's surface, but trap the outgoing infrared radiation emitted by land and ocean, thus containing this energy within the Earth system. Without an atmosphere, the temperature at the Earth's surface would average 320 C lower than its current 150 C (590 F, about the annual average at Santa Barbara, CA and Charlotte, NC). At this temperature, water would freeze and life as we know it could not exist.

There is no doubt that C02, water vapor, and other trace gases keep the Earth's surface warmer than it would otherwise be. That is not at issue. The debate concerns the enhancement of this "greenhouse" effect by increasing atmospheric concentrations of greenhouse gases (GHGs) released through human activities. The major enhanced GHG is C02, which is released primarily through combustion of fossil fuels, with additional amounts from deforestation and cement production. Significant additional contributions to the greenhouse effect are due to methane, produced by sheep, cattle, and other ruminant (cud-chewing) animals, termites, rice paddies, landfills, leaking natural-gas pipelines, coal mining, and other sources; nitrous oxide (from agriculture and combustion); and various chlorofluorocarbons (CFCs) and related industrial compounds. …