I am a skeptic about global warming here on earth. I'm easily convinced that temperatures are increasing historically and thus agree that it is occurring. What I don't so quickly agree with is the hubris involved with predicting that it is humanity's fault. One of the main items I had pointed at as evidence that we don't know what we're talking about is that science can't yet explain the Little Ice Age and the reasons for its end.

Now I read that Mars is experiencing global warming too. Since we aren't releasing CO2 - which is a crucial component of combustion - there, it stands to reason that solar activity is driving much of the warming of both planets.