“Global warming” is a NATURAL event!! The Earth has been warming OR cooling since it began. The Earths climate, now get this, HAS NEVER BEEN STATIC!!! ANY object is either warming or cooling. There is nothing mere homo-sapiens can do about it.
It occurs naturally, but that still does not rule out it being impacted by increased levels of greenhouse gases (which are part man-made and part naturally produced). Climate change just does not happen, there are things like sun, volcanoes, meteors, changes in the earth's axises, etc, that causes change.