Global warming is caused by uncontrollable temperature fluxuations in the Sun.
Many believe the global warming of the Earth being observed is directly a result of humans' introduction of carbon-dioxide into the atmosphere. Space exploration has revealed global warming on Mars, which puts the cause of global warming in doubt.
Comments
Global Warming is partially caused by the fluxuations in the sun, but that is one of the many causes of it. People play a part in it, UV Rays play a part in it, there's not really a specific one cause of Global Warming.