A new program led by the U.S. seeks to limit amounts of soot, hydrofluorocarbons and methane released into the atmosphere. In this file photo from 2009, a researcher ignites trapped methane from under a pond's ice cap in Alaska. Todd Paris/AP hide caption
The new version of the map includes 13 zones, with the addition for the first time of zones 12 (50-60 degrees F) and 13 (60-70 degrees F). U.S. Department of Agriculture hide caption
Altering the upper atmosphere could block enough sunlight to offset the warming effects of climate change and protect food crops. But what are the risks? iStockphoto hide caption
Families displaced by drought line up for food this week in Mogadishu, Somalia. AFP/AFP/Getty Images hide caption
Prepare to see this more often, even in usually cooler climes, the experts say. Elaine Thompson/AP hide caption