warming is happening largely due to us, but it snows in Indiana in early April and you're ready to disbelieve it?!
Go to Glacier NP and try to shoot the glaciers that were there 70 years ago but are gone now. Heck, just wait till summer in Indiana and see how you feel.
Someone suggested it's solar activity. Could be that's partly to blame but even if it is shouldn't we be doing what we can to cool the place off? All the greenhouse gasses we're putting into the air don't shut shorter wavelength radiation from the sun out (lucky for us photographers), but make it tougher for the longer wavelength radiation the earth tries to radiate back out to get out. So it gets warmer.
We've got more CO2 in the air than any time in the last 20 million years and it's increasing fast, as well as methane and chemicals that were never there before that have a big effect.
Look it up, say in Wikipedia.