There are a number of climate requirements that have emerged over the past several years that have specific relevance to National Polar-orbiting Operational Environmental Satellite System (NPOESS). Some of these are now codified; e.g., U.S. Climate Change Science Plan, Global Climate Observing System, National Academies, etc. The Intergovernmental Panel on Climate Change (IPCC) provides an assessment on how well we have been able to assess climate variability and change based on existing systems. NPOESS offers the opportunity to advance the state of knowledge about climate variations and changes in ways never before achieved. These will be reviewed as well as challenges related to the continuity of data and the maintenance of the climate record.