Climate Change: A long-term change in the Earth's climate, especially a change due to an increase in the average atmospheric temperature. Greenhouse Gases: Gases that trap heat in the Earth's atmosphere, contributing to the greenhouse effect. Carbon Cycle: The series of processes by which carbon compounds are interconverted in the environment, chiefly involving the incorporation of carbon dioxide into living tissue by photosynthesis and its return to the atmosphere through respiration, the decay of dead organisms, and the burning of fossil fuels. Global Warming: An increase in the Earth's average surface temperature due to rising levels of greenhouse gases.