The levels of carbon dioxide and methane in the atmosphere are increasing. These gases contribute to global warming, a rise in the average temperature of the Earth.
Global warming has biological consequences. Rising temperatures and melting ice cause sea levels to rise and can flood low-lying habitats. Changes in temperature and rainfall change where species can live, so the distribution of species changes and some species may move or die out. Changes in the migration patterns and the breeding seasons of some animals have also been seen. This can reduce biodiversity.
Evidence for global warming is not always complete, because climate is a very complex system. Even so, the scientific consensus on global warming and climate change is based on systematic reviews of thousands of peer reviewed publications.