Mars is inhabited by humanoids now. What we are mistaking for global warming is actually the first stage in Martiaforming - the removal of most of the atmosphere. The Martians are doing this in response to our probes, before we do it to them.

And there's an international government conspiracy to hide the true facts.

And the UFO's keep track of progress on the Martiaforming.

And if you don't believe this, then why was the Weekly World News driven out of business?

Aha, proof positive!

(I don't think I'll sign this. They might be watching.)