It fell to scientists to draw international attention to the threats posed by global warming. Evidence in the 1960s and '70s that concentrations of carbon dioxide in the atmosphere were increasing first led climatologists and others to press for action. It took years before the international community responded.

In 1988, an Intergovernmental Panel on Climate Change was created by the World Meteorological Organization and the United Nations Environment Programme (UNEP). This group issued a first assessment report in 1990 which reflected the views of 400 scientists. The report stated that global warming was real and urged that something be done about it.

The Panel's findings spurred governments to create the United Nations Framework Convention on Climate Change (UNFCCC). By standards for international agreements, negotiation of the Convention was rapid. It was ready for signature at the 1992 United Nations Conference on Environment and Development -- more popularly known as the "Earth Summit" -- in Rio de Janeiro.

The Intergovernmental Panel, or IPCC, now has a well-established role. It does not conduct its own scientific inquiries, but reviews worldwide research, issues regular assessment reports (there have now been three), and compiles special reports and technical papers.

The IPCC's findings, because they reflect global scientific consensus and are apolitical in character, form a useful counterbalance to the often highly charged political debate over what to do about climate change.

IPCC reports are frequently used as the basis for decisions made under the Framework Convention, and they played a major role in the negotiations leading to the Kyoto Protocol, a second, more far-reaching international treaty on climate change that is expected to take effect soon.

The United Nations Framework Convention on Climate Change (UNFCCC) and its Kyoto Protocol provide the only international framework for combating climate change.