My daughter Ren celebrated her 25th birthday last summer. She's a member of what I call Generation B, where B stands for "bonfire." Since her birth, more than half of all the fossil fuel consumed in human history has been burned, and more than half the greenhouse gas emissions humans have ever produced has gone skyward. 

As it steadily accumulates in the atmosphere, this enormous plume, now measuring 30 billions tons each year, is enough to melt glaciers, strand polar bears on sea ice, shrink the Colorado River, and alter the climate on which life depends.

Earlier this year, hopes for a national policy that would finally tackle global warming ran high, and prospects for an international climate treaty looked promising. But though the House passed a climate bill in June, the Senate (motto: "Where good ideas go to die") has kicked the can down the road while it struggles with health care reform. And since the Chinese, now the world's largest polluters, are reluctant to reduce their emissions, December's climate summit in Copenhagen, Denmark, seems unlikely to produce much more than "provisional targets" and "tentative promises."

Lately, I've begun to wonder whether that's all bad. Indeed, we may already have most of the climate policy we are ever going to have, an ad hoc and accidental assemblage of energy policies and economic realities that may prove surprisingly effective at further reducing emissions.   

Although global emissions are still rising, and the climate problem is far from solved, U.S. emissions are falling, fast. Since 2007, they are down 9 percent, in large part because Americans are using 2 million barrels less oil each day. Lester Brown of the Earth Policy Institute believes that "the United States has entered a new energy era. Peak carbon is now history. What had appeared to be hopelessly difficult is happening at amazing speed."

Economic devastation is one cause of lower emissions: Burdened with debt and starved for credit, the growth engine has seized. Across the West, construction is at a standstill, sprawl on sabbatical. In my once-thriving valley, storefronts are blinking out and idle architects are brewing beer in their bathtubs. The federal government will borrow $1.4 trillion this year, trying to "stimulate" the economy. But the Phoenix is not rising: Ten percent of Americans are unemployed and 30 million are on food stamps. With many families underwater on their mortgage, it's a season not for Jingle Bells but for jingle mail.

Other elements of our de facto climate policy include an informal moratorium on new coal plants -- coal power accounts for about 30 percent of U.S. emissions -- aggressive efficiency and renewable energy standards, and higher gasoline prices. Moratorium may be too strong a word, but new coal plants are becoming increasingly difficult to permit, finance and build. Nearly 100 proposed plants -- including some in Montana, Utah, Nevada and Arizona -- have already been cancelled or put on hold.

Over the coming decades, coal is likely to lose market share to wind, solar and natural gas. Thirty-four states have adopted renewable electricity standards, and some of them are quite aggressive. California hopes to reach 33 percent by 2020, which means that on some days wind, sun, and geothermal will need to provide half the state's electricity. Achieving that lofty ambition will require enormous investments in new power plants and associated transmission lines in that state and adjoining Nevada, Arizona, Oregon and Washington.

Although the recent "cash for clunkers" program was poorly executed, it indicates a renewed focus on resource conservation. Saving energy, water, soil and carbon -- plugging the leaks -- will be essential if we hope to reboot the economy; some economists argue that future growth will be impossible without it. About 60 percent of the energy that currently flows into the U.S. economy is lost, generally as waste heat. All across the landscape -- power plants, cars, planes, big-screen TVs, buildings, light bulbs, air conditioners -- there's massive room for improvement.

Thrift was once an American virtue and will, of necessity, be so again. Our contemporary civilization was designed around $10-a-barrel oil, but that's long gone. Higher gasoline prices, courtesy of a coming collapse in Mexican petroleum exports and booming car markets in Asia, will further reduce U.S. oil imports and kick-start hybrid-electric and all-electric vehicles. We now buy 1 million barrels a day of Maya crude, but by 2015 Mexico likely won't be exporting any oil because its largest field, Cantarell, is crashing. In years to come, U.S. motorists who pull into a service station will be bidding against millions of first-time drivers in India and China.

For decades, Westerners have boisterously celebrated and vociferously complained about growth. Besieged by its impacts, we debated whether "slow growth" or "smart growth" might be better. But now, for the first time in 30 years, the American bonfire is not growing. This is the new normal, a strange operating condition most of us have never experienced. 

The economy may be stuck in the ditch, but on climate, says Brown, "We are headed in the right direction." Still, he adds, we have a ways to go: "We do not yet know how much we can cut carbon emissions because we are just beginning to make a serious effort. Whether we can move fast enough to avoid catastrophic climate change remains to be seen."