Climate change is the climate of Earth changing. The Earth's climate has been much hotter and colder than it is today. Climate change this century and last century is sometimes called global warming, because the average temperature on the surface has risen. The last decade (2011–2020) was the warmest on record, and each of the last four decades has been warmer than any previous decade since 1850. The climate is now changing much faster than it has in the recent past. This is because people are putting more greenhouse gases in Earth's atmosphere, and they block some heat from escaping from the Earth into space.