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ne of the most vigorously debated topics on Earth is the issue of climate change, and the National Environmental Satellite, Data, and Information Service (NESDIS) data centers are central to answering some of the most pressing global change questions that remain unresolved. The National Climatic Data Center contains the instrumental and paleoclimatic records that can precisely define the nature of climatic fluctuations at time scales of a century and longer. Among the diverse kinds of data platforms whose data contribute to NCDC's resources are: Ships, buoys, weather stations, weather balloons, satellites, radar and many climate proxy records such as tree rings and ice cores. The National Oceanographic Data Center contains the subsurface ocean 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. And, for climate information that extends from hundreds to thousands of years, paleoclimatology data, also available from the National Climatic Data Center, helps to provide longer term perspectives.

This section offers scientific information and data on climate change in the past and projections for the future. Specific information about the U.S. government's role in conducting and evaluating science as well as EPA's role in these efforts can be found on the U.S. Global Change Research Program and EPA Research and Assessment pages in the Policy section.

Climate change refers to any significant change in measures of climate (such as temperature, precipitation or wind) lasting for an extended period (decades or longer). For full definitions of "climate change" and "global warming," see the Basic Information page.

Energy from the Sun drives the Earth's weather and climate. The Earth absorbs energy from the Sun, and also radiates energy back into space. However, much of this energy going back to space is absorbed by “greenhouse” gases in the atmosphere (see Figure 1 of Greenhouse Effect). Because the atmosphere then radiates most of this energy back to the Earth’s surface, our planet is warmer than it would be if the atmosphere did not contain these gases. Without this natural "greenhouse effect," temperatures would be about 60ºF lower than they are now, and life as we know it today would not be possible.

much of this in recent decades, according to NASA's Goddard Institute for Space Studies.

The rate of warming is increasing. The 20th century's last two decades were the hottest in 400 years and possibly the warmest for several millennia, according to a number of climate studies. And the United Nations' Intergovernmental Panel on Climate Change (IPCC) reports that

years are among the dozen warmest since 1850.