This year's Nobel Peace Prize went to people fighting global climate change. What does fighting climate change have to do with world peace? Here's the answer that Michael Oppenheimer, Ph.D., one of the team of authors of the IPCC's 2007 reports and science advisor to Environmental Defense, gave in an interview with PBS:

A stable climate helps keep the peace. We see situations all around the world where shortages of the sorts of resources that will shrivel under a changing climate, like water for food, water for agriculture, are contributory factors in places like Darfur, the Horn of Africa, where instability is rife, and governments just can't hold it together, and people die. That's ultimately why this is justifiably a prize for peace.

Today Al Gore and the IPCC received the Nobel Peace Prize in recognition of their efforts to raise public awareness and understanding of the global climate change crisis. We applaud them, and also the Nobel committee for recognizing the threats global warming poses to security and stability around the world.

Congress now has the opportunity to make the U.S. a leader on climate change by harnessing the unprecedented momentum for strong policies to cap and cut greenhouse gas emissions.

"It would be great to see the U.S. Congress nominated next year for taking on the problem and passing comprehensive climate legislation." said Environmental Defense President Fred Krupp. "After Al Gore stands on the stage in Oslo to receive his award, I think the American public will turn to the leaders of both parties in the U.S. Congress to see where they stand. The scientific evidence that the former vice president and the IPCC have helped drive home tells us there’s no consolation prize for Congress if it fails to act."

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.

How did the drought lead to civil war? Darfur is a region characterized by disparity. The south is fertile and temperate, while the north is dominated by desert and scrubland. The southerners, who call themselves Africans, rely on farming to meet their needs. The Arabs in the north live a nomadic lifestyle based on herd grazing.

The Arabs and Africans in Darfur have always competed for water, but until the 1980s, these disputes were resolved by tribal councils. Then the government replaced the tribal councils with ineffective government programs and – simultaneously – Darfur was hit by a severe drought. In the ethnic conflict that ensued, hundreds of thousands of Darfurians have been murdered, and even more left starving and homeless, fearing for their lives in dangerous refugee camps.

And the problem is not just in Darfur. In 2004, the peer-reviewed Journal of Political Economy published a study called "Economic Shocks and Civil Conflict [PDF]". It found lack of rainfall was strongly associated with civil war in African countries whose economies depend largely on rain-fed agriculture. Industrial economies like our own may not depend on rainfall for survival, but that doesn't mean we have nothing to worry about.

We live in a global community. When there's an environmental catastrophe half-way around the world, it can affect us, too. And even here at home, conflicts can arise as a result of environmental crises. Just look at what happened after Hurricane Katrina.

The crisis in Darfur is a warning – climate change can destabilize an entire region in just a few years.