Do you believe global warming is manmade and a threat to our future?

I know this has been discussed, but it came up again in this question about the debunking of the ‘Climategate’ critics, so I decided to revisit it.

NOAA has a great FAQ online answering a number of important questions about GLobal Warming. The bulk of the world’s climatologists appear to be convinced that:
1—Earth is warming,
2—Human activity and fossil fuel burning is contributing to that warming in a way never before seen,
3—Unless we take steps to reverse the trend, it will pose serious threats to life as we currently live it.
In a study of the world’s climate scientists, 97% said they felt warming was happening and was influenced by human activity.

In the debate, there appear to be three positions.
1—Global Warming is happening and is man made.
2—Global Warming is happening, but is natural and will take care of itself.
3—Global temperatures haven’t increased, sea levels haven’t risen, and glacial retreat is a lie.

Which position do you favor, and why?