Warming in the solar system has become a hot topic these days, and I’ve been getting lots of questions that go something like this: I’ve read that other planets have global warming. There are no SUVs on other planets, so the warming must be due to increased energy from the sun. Doesn’t that mean that Earth’s warming is also due to increased solar energy?

The short answer is, whatever warming there may be on other planets is not due to changes in the Sun. Scientists have thoroughly investigated this possibility, and in nearly 30 years of satellite observations, we’ve seen no increase in overall solar output. (For more on this, see our article on global warming and solar activity [PDF].)

Solar variation cannot explain global warming on any planet, including Earth. So what’s up with our neighbors?

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The second installment of the IPCC’s 4th Assessment on Climate Change, titled “Impacts, Adaptation and Vulnerability”, was released on April 6, 2007. In recognition of this report, I’m doing a weekly series called “Climate Dangers You May Not Know About“.

1. More Acidic Oceans
2. Drinking Water and Disease
3. Shifts in Lifecycle Timing
4. Drought and Violence
5. Melting of the North Pole

What happens when there isn’t enough food and water for the people who need it? Fighting can ensue. And when drought and famine extend over a wide area, the fighting can escalate to civil war. This is what’s happening today in Darfur, a country in the sub-Saharan (or "Sahel") region of Africa.

We can’t say for sure that the Darfur droughts were caused by global warming, but there’s evidence it was a significant factor (for example, see this recent study of the Sahel drought [PDF] by NOAA’s Geophysical Fluid Dynamics Laboratory). But whether those past droughts were caused by global warming is not the main issue. We know that global warming will cause more and more severe droughts in the future, especially in the Sahel region of Africa.

The story of Darfur cautions that events triggered by global warming can lead to a human tragedy of global proportions.

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Erica Rowell, today’s guest blogger, is a Web Editor and Producer at Environmental Defense, and our resident expert on compact fluorescents.

Last year, in converting my apartment to energy-saving compact fluorescent lights (CFLs), I broke two. I opened the window, swept up the fragments, wiped the floor with a damp paper towel, put the towel and the broken CFLs in a plastic bag and tied it. My super disposed of the bag. I’m not worried about mercury exposure – they broke a couple of months ago, and my cats and I are fine. A similar incident in Maine was a different story.

When Brandy Bridges shattered a CFL spiral in her daughter’s bedroom, aware that it contained trace amounts of mercury, the concerned mother looked into proper disposal. After a mishmash of good and bad advice, she ended up with a $2,000 clean-up bill and a lot of fear (read full story).

What can we learn from Ms. Bridges? Know some basic facts.

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