Rising sea levels, sweltering temperatures, deeper droughts, and heavier downpours -- global warming's serious effects are already here and getting worse, the Obama administration warned on Tuesday in the grimmest, most urgent language on climate change ever to come out of any White House.
But amid the warnings, scientists and government officials seemed to go out of their way to soften the message. It is still not too late to prevent some of the worst consequences, they said, by acting aggressively to reduce world emissions of heat-trapping gases, primarily carbon dioxide from the burning of fossil fuels.
The new report differs from a similar draft issued with little fanfare or context by George W. Bush's administration last year. It is paradoxically more dire about what's happening and more optimistic about what can be done.
The Obama administration is backing a bill in Congress that would limit heat-trapping pollution from power plants, refineries and factories. A key player on a climate bill in the Senate, California Democrat Barbara Boxer, said the report adds "urgency to the growing momentum in Congress" for passing a law.
"It's not too late to act," said Jane Lubchenco, one of several agency officials at a White House briefing. "Decisions made now will determine whether we get big changes or small ones." But what has happened already is not good, she said: "It's happening in our own backyards and it affects the kind of things people care about."
Lubchenco, a marine biologist, heads the National Oceanic and Atmospheric Administration.
In one of its key findings, the report warned: "Thresholds will be crossed, leading to large changes in climate and ecosystems." The survival of some species could be affected, it said.
The document, a climate status report required periodically by Congress, was a collaboration by about three dozen academic, government and institute scientists. It contains no new research, but it paints a fuller and darker picture of global warming in the United States than previous studies.