We're apart of nature. We couldn't really do anything that wasn't technically natural. Even if it is caused by us it's apart of nature's way. We won't literally destroy the Earth, I believe the max damage we will do will be righted by it's becoming uninhabitable to us, but not for the less developed, more instinctual creatures. One of which may find the conditions ideal to become king of the food chain, and may even become the next 'humans' ready to leave their permanent natural mark on the planet.

All of this aside, I feel global warming could be caused by the sun.

Earth goes through cycles. But even if it's man made, it doesn't matter because there is nothing we will do to fix it. ;)

the world has been cooling and warming since the begenning of time so it is the only reson there is the possiblity of blobal warming its naturally cuased humans might help out a very small fraction

Uhhh...

Both! The climate has always changed, but referring to the greenhouse effect increasing, that's man made. We make a hell of a lot of greenhouse gasses with intensive farming and combustion, and destroy forests which help to convert them. Of course that's going to have an effect.