Global warming is caused by greenhouse gases like carbon dioxide and methane trapping heat in the atmosphere. This is called the greenhouse effect. (1) Svante Arrhenius first proposed in 1896 that fossil fuel use could lead to global warming. (2) Effects of global warming include melting ice, rising sea levels, stronger storms, and shifting climate patterns. (3) People are trying to reduce global warming through actions like recycling, using less electricity, and transportation alternatives that emit fewer greenhouse gases.