Global warming is caused by greenhouse gases like carbon dioxide trapping heat in the atmosphere. When sunlight reaches Earth, some is absorbed and warms the surface while the rest radiates back out. Greenhouse gases in the atmosphere absorb some of this outgoing radiation and reflect it back to Earth, warming the atmosphere in a process known as the greenhouse effect. Major causes of increased greenhouse gases are burning fossil fuels for electricity and transportation, methane from agriculture and livestock, deforestation, fertilizer usage, and increased chemical usage on farms. Effects of global warming include rising sea levels worldwide, more extreme storms, crop failures, species extinction, and destruction of coral reefs.