Pollution cuts: Industrialized countries of Europe, North America and Asia agreed to slash emissions collectively to levels 5.2 percent below where they were in 1990. Because emissions have been steadily increasing since 1990, the actual cuts will be much larger.
Deadlines: Countries must show "demonstrable progress" by 2005 and achieve their target between 2008 and 2012.
Poorer countries: Developing nations refused to accept binding limits for now, arguing that rich Western nations historically bear responsibility for global warming. The Climate Change Convention commits all countries to take voluntary action on climate change.
Flexibility: The Kyoto agreement gives countries flexibility in how they make and measure emissions reductions. For example, industrialized nations can set up "emissions trading" regimes that allow buying and selling of pollution credits on the open market. Wealthy countries can also receive credit for investing in clean-air projects overseas. Such programs could greatly reduce the cost of compliance.
International law: Nations have until next March to sign the agreement, but it doesn't become law until it is ratified by parliaments in 55 countries, including developed countries representing 55 percent of the world's emissions.

Unfinished Business
In two weeks of talks, government ministers meeting in Buenos Aires will begin to decide how to achieve the goals set in Kyoto. Here are some of their tasks:

Enforcement: Diplomats may decide how to monitor compliance with the Kyoto treaty and what to do about chronic violators. Options could range from a simple suspension of voting rights at future meetings to some form of economic sanctions.

Emissions trading: Countries will begin to decide ground rules for international trading programs that allow the buying and selling of pollution "credits." European countries favor strict limits on trading to force each country to achieve most of its cuts at home; the United States is pushing for maximum flexibility to reduce costs.

Investing abroad: Negotiators hope to begin drawing up guidelines for a "Clean Development Mechanism" that promotes investment in clean-air technology in poorer countries. The country making the investment would receive credit for cutting emissions, while the host country would benefit from new technology and a cleaner environment.

Sinks: Work is just beginning on the question of whether countries should be able to claim credit for creating carbon "sinks." Sinks are natural systems, such as forests, that remove carbon dioxide from the air. If the idea is approved, countries could offset their pollution-cutting obligations by planting trees or carbon-absorbing crops.