Kyoto Protocol effective today. But not in the U.S.

141 countries constituting 55% of global carbon dioxide and other greenhouse gas emissions have agreed to a 5.2% collective reduction by 2012 - starting today. But the world's top polluter (responsible for nearly 25%) is not among them.

President Clinton signed the Kyoto Protocol treaty in 1997, but it was never ratified by Congress, and has since been renounced by President Bush as too costly and flawed (due to developing countries like China and India being outside its framework, for example).

Yet treaty proponents such as British PM Tony Blair warn of an impending environmental catastrophe within a generation - and assert that U.S. participation is "the only solution". Thankfully, there is also mounting domestic political pressure; Senators John McCain and Joe Lieberman are preparing to reintroduce their Climate Stewardship Bill.

(For a look at the effects of global warming, check out this photo gallery, and more of Gary Braasch's environmental documentary photography here.)