Contents: Clouds, Radiation, Water Vapor, and Precipitation. Oceans: Circulation, Productivity, and Air-sea Exchange. Greenhouse Gases and Tropospheric Chemistry. Land Surface: Ecosystems and Hydrology. Ice Sheets, Polar and Alpine Glaciers, and Seasonal Snow. Ozone and Stratospheric Chemistry. Volcanoes, Dust Storms, and Climate Change. An Overview of International Earth-observing Capabilities--Planned and Present. Assessing the Impact of Climate Change.