The science is in, and the basic facts are no longer disputable: Global warming is happening, and it's happening because of us. Human activities are transforming the Earth's atmosphere, and the result is a dangerous imbalance. In the course of the coming century, global warming threatens to drive so many species extinct that we will no longer recognize the world we remember from our childhoods.

The good news? If we act fast, we still have a chance. If we act fast, the polar bears whose sea ice is melting beneath them still have a chance; the great whales that sing deep beneath the swiftly warming oceans — who depend on a complex and delicately balanced food chain — still have a chance. Our coastal cities still have a chance, too.

More than any other single issue, the fight to stop global warming depends on swift and sure action: to avoid the worst effects of climate change, we need to get greenhouse gas emissions down by more than 80 percent by 2050. The Center is leading the charge to save species like polar bears and penguins that are already severely threatened by the effects of climate change, and to call for drastic changes in our nation's energy policies that contribute to greenhouse gas emissions. But what will help us win the fight, ultimately, is the conviction and political will of Americans from all walks of life to make changes at home and to demand them from our nation's leaders. Please, take action today.