greenhouse gases

Scientists said the concentration of carbon dioxide, which contributes to climate change, is the highest in data going back 800,000 years, based on ice core records.

Scientists who warned of heat waves and rising seas this week also say that it's possible to avoid the worst effects of the warming climate. They're relying on computer models of the world economy.

Cutting carbon emissions to zero in the next 30 years would save about 74 million lives this century, a new analysis estimates.