National Geographic is running an article that points to NASA data showing that it's not just the Earth that is experiencing global warming.
Data from the Mars Global Surveyor and Odyssey missions apparently show that the carbon dioxide ice caps at the South pole have been getting smaller for three summers in a row.
Habibullo Abdussamatov, a scientist from the St. Petersburg's Pulkovo Astronomical Observatory, suggests that this provides evidence that the amount of heat being generated by the sun has increased and this, rather than what we humans have been doing, is the cause of global warming.
Later in the article, other scientists point to "wobbles" in Mars's orbit as the underlying reason for the changes.
Just another example of the complexity of these issues.