Climate change is a long-term change in the average weather patterns that have come to define Earth's local, regional and global climates. These changes have a broad range of observed effects that are synonymous with the term. Climate change is a serious threat to the planet and its inhabitants. The main cause of climate change is human activity, particularly the burning of fossil fuels such as coal, oil, and natural gas. When fossil fuels are burned, they release greenhouse gases into the atmosphere. Greenhouse gases trap heat from the sun, causing the planet to warm.