For hundreds of millions of years, Earth's climate has remained on a fairly even keel, with some dramatic exceptions: Around 80 million years ago, the planet's temperature plummeted, along with carbon dioxide levels in the atmosphere. The Earth eventually recovered, only to swing back into the present-day ice age 50 million years ago. Now geologists at…

After dropping more than 20 spots this year in one ranking that measures how well countries are working to protect the environment, the United States is taking steps to improve its environmental impact. The 2010 Environmental Performance Index (EPI) ranks 163 countries based on 10 indicators of environmental protection, such as levels of air pollution,…