Global warming is a serious environmental problem. Scientists say that the average temperature of the planet is rising every year. As a result, glaciers are melting and sea levels are increasing. Some islands may disappear completely. In fact, the situation is already dangerous for polar bears, which need ice to hunt. Global warming is caused by human activity. Fossil fuels are burned, forests are cut down, and too much pollution is produced. However, people can change the situation. Modern technologies allow us to use renewable resources such as wind and solar power. If more countries follow this idea, future generations will have a chance to live on a healthy planet.