Climate 411

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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I was in Ohio last week visiting with folks in Cincinnati and Columbus. Most of the discussion focused on business opportunities for Ohio in the new low-carbon economy, but I also got interesting questions about global warming science.

I was especially impressed to learn what the city of Columbus is doing to go "green" (details are on the Columbus city site). We heard from Andy Darrell last week on Mayor Bloomberg’s vision for New York City, and it’s great to see that New York isn’t the only city thinking of a greener future.

But I most wanted to share with you a science question from the visit.

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