How is earths climate warming?

Answer 1

It isn't, really. Yes, the Earth has been warming, since the 1820's. Before that it was cooling, from the late 1600's, and before that it was warming. The world's climate goes in cycles; not only the annual cycles of winter and summer, but cycles hundreds, perhaps a thousand years long.

A thousand years ago, the world was warmer than it is now! There were dairy farms on Greenland, and the Vikings called it "Greenland" because it was green. Lief Erikson discovered a land with grape vines which he called "Vinland" (Not big on innovative names, those Vikings). We've discovered Vinland; it's in Labrador, Canada. No grape vines.