Global warming is a trend of increasing average temperatures on Earth. This climate change is theorized to include more floods, draughts, heat waves, and cold snaps, as well as extreme events like tornadoes and hurricanes. Global warming also causes melting of glaciers and the polar ice caps, which raises sea levels and floods low-lying areas.
Global warming can be caused by natural changes over time, as the earth's climate is never exactly the same year-to-year. It is also believed by some scientists that human activities are causing global warming. This is thought to be through the burning of fossil fuels and release of carbon dioxide and other greenhouse gasses into the atmosphere.