Global warming means that the Earth's surface and the air around it are getting warmer all over the world. Recently, there have been many scary reports saying that the world's climate is changing a lot. These reports show strong proof that the Earth's temperature is going up every day. The reason for this temperature increase is the growing amounts of gases that trap heat, called greenhouse gases, in the air around the Earth. There are also different kinds of dirty stuff that make the air warmer. People using things like oil and gas and cutting down lots of trees are making more of these heat-trapping gases, and that's causing the air to warm up.
Most scientists who study the climate think that this warming air could lead to serious problems. They think that the warming air might make the Earth's temperature go up a lot by the middle of this century – maybe as much as 4 degrees Celsius. If this happens, it could be really bad. It might make it very hard for people to grow enough food, and it could hurt or even destroy many living things and places. It could also make the sea levels rise, flooding areas where people live and where they grow crops. That's why people are so worried about global warming.