One 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.