Global climate change: turning the tide.

In the cauldron of questions surrounding global climate change, public policy issues are heating up. At this time next year in Berlin, the developed countries that signed the United Nations Framework Convention on Climate Change in Rio de Janeiro in 1992 will bring to the table their national plans for limiting greenhouse gas emissions. In preparation for this meeting, the treaty's Intergovernmental Negotiating Committee is hammering out details in a series of preliminary sessions; the most recent one was held in February in Geneva. In the spotlight was the United States Climate Change Action Plan, a $1.9-billion pledge by the Clinton administration to cut greenhouse gas emissions by voluntary measures. In an abrupt change from the past, the United States is now is leading the way. It is time for the framework to be fleshed out. The public policy questions seem seductively simple: what should be done, who should do it, how much will it cost, and who goes first? But complicating these questions are scientific uncertainties and other wild cards such as not-yet-discovered technologies, local impacts, and a host of human dimensions that broaden the issue beyond merely climate to global change. Global change encompasses not only climate change, but also ozone depletion, biodiversity, and the interactions of human development with the environment. The one certainty is that responding to global change will require unprecedented international cooperation. At the framework convention, 36 developed nations pledged to aim at reducing their greenhouse gas emissions to 1990 levels by the year 2000. They also promised to help developing nations reduce their emissions. But are those James Bruc commitments enough? The teen develop(United States, among others, ing countries is thinks not. "Our convention takes us to the end of the decade-we have not yet begun to look beyond that date," the U.S. statement to the Intergovernmental Negotiating Committee said. Emissions aren't the only debatable point. Because greenhouses gases (carbon dioxide, nitrous oxide, and chlorofluoro-carbons) are so persistent in the environment , their concentrations in the atmos-e-ed a sarm phere adjust slowly to changes in emissions. "There's also a general objective stated in the convention that the countries of the world agree they will try to limit concentrations not emissions-of greenhouse gases at a level that will not cause dangerous interference with the Q climate system," explains Jim Bruce of the Intergovernmental Panel on Climate Change (IPCC). "That means the countries are going …