The National Oceanographic Data Center contains the subsurface data which reveal the ways that heat is distributed and redistributed over the planet. Knowing how these systems are changing and how they have changed in the past is crucial to understanding how they will change in the future. The IPCC met in full session in 1990 and 1995, and is meeting now in 2000 and 2001. This list will be periodically updated, as new scientific evidence comes to light. The greenhouse effect is unquestionably real, and is essential for life on Earth.
Water vapor is the most important greenhouse gas, followed by carbon dioxide and other trace gases.
However, the concern is not with the fact that we have a greenhouse effect, but it is with the question regarding whether human activities are leading to an enhancement of the greenhouse effect. There is no scientific debate on this point. The warming has not been globally uniform. The recent warmth has been greatest over N. America and Eurasia between 40 and 70 N. Warming, assisted by the record El Ni o of 1997-1998, has continued right up to the present. Linear trends can vary greatly depending on the period over which they are computed.