Our choices on global warming are painful. And they're only getting worse.

We all think other people ought to lose weight and drive more carefully; we all think other people should do something about global warming. That seems to be the state of the greenhouse debate. Everyone you ask about global warming professes to be concerned, but by their behavior, hardly anyone is willing to do anything.

Americans keep buying mega-SUVs and pickup trucks, these gas-guzzlers being the single worst Western factor in greenhouse gas accumulation. American petroleum use has increased almost 20 percent in the last decade, with almost all the rise attributable to SUVs and pickup trucks, which now account for more than half of the automotive market. There isn't any prominent national politician who favors a revenue-neutral gasoline tax increase, which most economists, including N. Gregory Mankiw, George W. Bush's chair of the Council of Economic Advisors, think is the simplest and most economically efficient way to reduce petroleum waste. (Income or payroll taxes would be reduced to the same degree gasoline taxes were increased; consumers would then make their own decisions about what kind of vehicles to buy, rather than having a regulatory scheme dictate this. The argument for a revenue-neutral 50-cent increase in the gasoline tax can be found here.) Meanwhile demand for electricity keeps rising, which means more coal and natural gas burned at generating stations, which means more greenhouse gas accumulation.

The Kyoto greenhouse gas treaty, which never had any chance of being ratified by the U.S. Senate, is about to go into effect for the European Union, Russia, and a few other nations. Assuming the European Union actually implements Kyoto--this is a big "if," since the treaty has no meaningful enforcement mechanisms or penalties--European consumers, at least, must reduce their per-capita energy consumption. No such requirement is in view for Americans, who continue who demand the cake-and-eat-it-too condition of unlimited energy use without political or climate consequences. At the Rio Earth Summit in 1992, George H. W. Bush was roundly denounced for offering a deal that would have (this is a simplification) frozen U.S. greenhouse gas emissions at the level of 1990 in perpetuity. Editorialists and environmentalists demanded deep, dramatic cuts. Today editorialists and environmentalists would take Bush's 1992 offer in a minute, as U.S. greenhouse gas emissions have risen about 15 percent since 1990 and continue to rise.

Of course, global warming science remains fraught with uncertainty. World temperature increases so far (about one degree Fahrenheit in the last century) have done no one any harm; figures for projected future temperature increases are highly speculative; the evidence from nature is hardly undisputed, the lower 48 states having just completed the sixteenth-coolest summer on record. Still, there is an increasingly strong scientific consensus that artificially triggered climate change is a danger. A few months ago Thomas Karl, director of the federal National Climatic Data Center and once a leading greenhouse skeptic, declared that "anthropogenic climate change is now likely," with impacts "quite disruptive" to agriculture and global economics. In 2002, the National Academy of Sciences warned that "abrupt" climate change is possible, and that unpleasant effects might include a rise in sea levels of as much as 30 feet. When the industrial era began, Earth's atmosphere had 280 parts per million of carbon dioxide, the most important greenhouse gas; today the figure is 370 parts per million, a 32 percent increase. Current trends suggest that carbon dioxide levels in the atmosphere will rise to at least double the pre-industrial level, perhaps triple. Logically, all the additional greenhouse gases must eventually have some impact, and we're not likely to be happy about it. Reform seems prudent.

John Kerry's proposed energy policy (described in detail here) would reduce U.S. greenhouse emissions, mainly by seeking a one-third improvement in the fuel efficiency of cars, SUVs, and pickups. Kerry, at least, proposes action--George W. Bush has tried to punt all global warming issues by the dodge of advocating further research. Bush and other administration figures now talk not of greenhouse gas reduction but of the declining "carbon intensity" of the economy, meaning less fossil fuel used per dollar of economic output, because "carbon intensity" figures are pleasingly negative. But the carbon intensity of the U.S. economy has been in decline since Herbert Hoover. Total emissions, not ratio of emissions to production, are what matter to climate. Although there are ever-lower greenhouse-gas emissions per unit of GDP, ever-higher growth in GDP swamps the intensity reduction, resulting in higher total amounts of greenhouse gases.

If enacted, Kerry's energy policy would reduce growth in U.S. greenhouse emissions, but still be a drop in the bucket compared to the global picture, especially as greenhouse gas emissions from the developing world keep increasing. Full international implementation of all Kyoto rules would reduce greenhouse gas levels in the atmosphere only by about one percent by 2050; Kerry's mileage plan might have, on its own, a similarly modest impact.

But we've got to start somewhere. Initial goals must be to keep the accumulation of greenhouse gases in the atmosphere from reaching runaway levels, while creating economic incentives for people to invent the kinds of technological devices, free-market trading, and developing-world clean-energy programs that will lead to significant greenhouse gas reduction.

To put into perspective the magnitude of the challenge, consider calculations recently done by Robert Socolow and Stephen Pacala of Princeton University. Socolow and Pacala calculated what changes in energy policy would be necessary to stop atmospheric greenhouse gas accumulation at about 500 parts per million--almost double that of when the industrial era began--by the year 2050. Taking into account global fossil fuel use trends, especially in the developing world, they devised 15 policy options. Here are the options, which I have simplified to plain words that specialists won't like:

1. Increase the mileage of all new passenger vehicles to 60 MPG.
2. Ration driving; allow only one-half as many annual miles per driver as today.
3. Reduce by 25 percent the energy used by the world's buildings for heating, cooling, and appliances.
4. Double the generating efficiency of all coal-fired power plants. (Technically possible but extremely expensive.)
5. Close 1,400 coal-fired power plants and replace them with natural-gas fired power plants.
6. Build 3,500 large facilities to inject carbon from power generation back into the earth.
7. Increase global manufacture of synthetic fuel to 200 times the current level. (Technically possible but extremely expensive.)
8. Double the number of atomic power plants, retiring a large coal-fired power plant for each new reactor commissioned.
9. Build 50 times more wind-power turbines than now exist.
10. If wind is used to make hydrogen for cars, build 100 times more wind turbines than now exist.
11. Build 700 times more solar-power converters than now exist.
12. Increase biofuels production to 100 times the current level.
14. End all tropical deforestation.
15. Increase "conservation tillage," a form of farming that keeps carbon in soil, to 10 times the current level. (Worldwide use of genetically engineered crops would be required.)

Probably you are thinking, whew, those are tough options, but we'll choose one and do it. Here's the rub. The world must do seven of the above 15 things merely to hold greenhouse gas accumulation at double the pre-industrial level.

Whoever wins in November, an opportunity to reform U.S. energy policy will present itself, because shortly after the election the National Commission on Energy Policy will recommend sweeping changes in U.S. energy use. Yes, the phrase "national commission" inspires yawns, but this commission is a true bipartisan effort--members include the chairman of ConocoPhillips and Andrew Lundquist, author of Dick Cheney's energy plan. There's a strong chance the National Commission on Energy Policy will say it is time to begin real action regarding greenhouse gases. It is time. Long journeys begin with small steps; if we don't take the initial actions to moderate greenhouse gas emissions now, the problem will be worse when we are eventually given no choice but to act.

Gregg Easterbrook is a contributing editor for The New Republic specializing in public policy issues.

By Gregg Easterbook