by Seth Borenstein

WASHINGTON  - When Bill Clinton took office in 1993, global warming was a slow-moving environmental problem that was easy to ignore. Now it is a ticking time bomb that President-elect Barack Obama can't avoid.

Since Clinton's inauguration, summer Arctic sea ice has lost the equivalent of Alaska, California and Texas. The 10 hottest years on record have occurred since Clinton's second inauguration. Global warming is accelerating. Time is close to running out, and Obama knows it.

"The time for delay is over; the time for denial is over," he said on Tuesday after meeting with former Vice President Al Gore, who won a Nobel Peace Prize for his work on global warming. "We all believe what the scientists have been telling us for years now that this is a matter of urgency and national security and it has to be dealt with in a serious way."

But there are powerful political and economic realities that must be quickly overcome for Obama to succeed. Despite the urgency he expresses, it's not at all clear that he and Congress will agree on an approach during a worldwide financial crisis in time to meet some of the more crucial deadlines.

Obama is pushing changes in the way Americans use energy, and produce greenhouse gases, as part of what will be a massive economic stimulus. He called it an opportunity "to re-power America."

After years of inaction on global warming, 2009 might be different. Obama replaces a president who opposed mandatory cuts of greenhouse gas pollution and it appears he will have a willing Congress. Also, next year, diplomats will try to agree on a major new international treaty to curb the gases that promote global warming.

"We need to start in January making significant changes," Gore said in a recent telephone interview with The Associated Press. "This year coming up is the most important opportunity the world has ever had to make progress in really solving the climate crisis."

Scientists are increasingly anxious, talking more often and more urgently about exceeding "tipping points."

"We're out of time," Stanford University biologist Terry Root said. "Things are going extinct."

U.S. emissions have increased by 20 percent since 1992. China has more than doubled its carbon dioxide pollution in that time. World carbon dioxide emissions have grown faster than scientists' worst-case scenarios. Methane, the next most potent greenhouse gas, suddenly is on the rise again and scientists fear that vast amounts of the trapped gas will escape from thawing Arctic permafrost.

The amount of carbon dioxide in Earth's atmosphere has already pushed past what some scientists say is the safe level.

In the early 1990s, many scientists figured that the world was about a century away from a truly dangerous amount of carbon dioxide in the atmosphere, said Mike MacCracken, who was a top climate scientist in the Clinton administration. But as they studied the greenhouse effect further, scientists realized that harmful changes kick in at far lower levels of carbon dioxide than they thought. Now some scientists, but not all, say the safe carbon dioxide level for Earth is about 10 percent below what it is now.

Gore called the situation "the equivalent of a five-alarm fire that has to be addressed immediately."

Scientists fear that what's happening with Arctic ice melt will be amplified so that ominous sea level rise will occur sooner than they expected. They predict Arctic waters could be ice-free in summers, perhaps by 2013, decades earlier than they thought only a few years ago.

In December 2009, diplomats are charged with forging a new treaty replacing the 1997 Kyoto Protocol, which set limits on greenhouse gases, and which the United States didn'tratify. This time European officials have high expectations for the U.S. to take the lead. But many experts don't see Congress passing a climate bill in time because of pressing economic and war issues.

"The reality is, it may take more than the first year to get it all done," Senate Energy Committee Chairman Jeff Bingaman, D-N.M., said recently.

Complicating everything is the worldwide financial meltdown. Frank Maisano, a Washington energy specialist and spokesman who represents coal-fired utilities and refineries, sees the poor economy as "a huge factor" that could stop everything. That's because global warming efforts are aimed at restricting coal power, which is cheap. That would likely mean higher utility bills and more damage to ailing economies that depend on coal production, he said.

Obama is stacking his Cabinet and inner circle with advocates who have pushed for deep mandatory cuts in greenhouse gas pollution and even with government officials who have achieved results at the local level.

The President-elect has said that one of the first things he will do when he gets to Washington is grant California and other states permission to control car tailpipe emissions, something the Bush administration denied.

And though congressional action may take time, the incoming Congress will be more inclined to act on global warming. In the House, liberal California Democrat Henry Waxman's unseating of Michigan Rep. John Dingell - a staunch defender of Detroit automakers - as head of the House Energy and Commerce Committee was a sign that global warming will be on the fast track.

Senate Environment and Public Works Chairman Barbara Boxer, D-Calif., vowed to push two global warming bills starting in January: one to promote energy efficiency as an economic stimulus and the other to create a cap-and-trade system to reduce greenhouse gas emissions from utilities. "The time is now," she wrote in a Dec. 8 letter to Obama.

Mother Nature, of course, is oblivious to the federal government's machinations. Ironically, 2008 is on pace to be a slightly cooler year in a steadily rising temperature trend line. Experts say it's thanks to a La Nina weather variation. While skeptics are already using it as evidence of some kind of cooling trend, it actually illustrates how fast the world is warming.

The average global temperature in 2008 is likely to wind up slightly under 57.9 degrees Fahrenheit, about a tenth of a degree cooler than last year. When Clinton was inaugurated, 57.9 easily would have been the warmest year on record. Now, that temperature would qualify as the ninth warmest year.

Associated Press writer Dina Cappiello contributed to this report.