All eyes are on the United Nations Climate Change conference talks that kick off in Copenhagen, Denmark, this week. Known as the COP15 summit, the international negotiations will center on cap-and-trade and offset schemes to combat global warming, not a global carbon tax or strict regulation that are being called for by some sectors of the climate change movement.

"Governments going to Copenhagen claim to have [emission] goals for 2050, which they will achieve with the 'cap-and-trade' mechanism. They are lying through their teeth," wrote renowned climate scientist James Hansen in London's Observer last week. "Unless they order Russia to leave its gas in the ground and Saudi Arabia to leave its oil in the ground (which nobody has proposed), they must phase out coal and prohibit unconventional fossil fuels."

Back in the United States, one big environmental group does not seem to be listening to Dr. Hansen's plea. The Natural Resource Defense Council (NRDC) has long touted cap-and-trade as a realistic solution to solving the climate crisis.

The NRDC's position is rather simple: pollution allowances and other market mechanisms can help to reduce carbon dioxide (CO2) emissions, that great global warming pollutant, while simultaneously creating green jobs. The largest CO2 emitters in the United States are coal-fired power plants.

Dan Lashof, who serves as director for NRDC's Climate Center, believes that cap-and-trade is the best, most effective way to curb CO2 pollution - essentially a win for the environment and a win for the economy.

"Billions of dollars in allowances are at stake under the proposals to cap and reduce global warming pollution," said Lashof. "The value of pollution allowances should benefit consumers and smart programs that deliver real pollution reductions, not polluters."

Not everyone agrees with Lashof and the NRDC's position. Last week in New York, leading environmental economist and co-director of the Carbon Tax Center, Charles Komanoff, along with James Hansen and hundreds of other activists protested outside the NRDC's midtown offices for exactly the position Lashof espouses.

Most political arguments don’t really have a right and a wrong, no matter how passionately they’re argued. They’re about human preferences -- for more health care or lower taxes, for a war to secure some particular end or a peace that leaves some danger intact.  On occasion, there are clear-cut moral issues: the rights of minorities or women to a full share in public life, say; but usually even those of us most passionate about human affairs recognize that we’re on one side of a debate, that there are legitimate arguments to the contrary (endless deficits, coat-hanger abortions, a resurgent al-Qaeda). We need people taking strong positions to move issues forward, which is why I’m always ready to carry a placard or sign a petition, but most of us also realize that, sooner or later, we have to come to some sort of compromise.

That’s why standard political operating procedure is to move slowly, taking matters in small bites instead of big gulps. That’s why, from the very beginning, we seemed unlikely to take what I thought was the correct course for our health-care system:  a single-payer model like the rest of the world. It was too much change for the country to digest.  That’s undoubtedly part of the reason why almost nobody who ran for president supported it, and those who did went nowhere.

Instead, we’re fighting hard over a much less exalted set of reforms that represent a substantial shift, but not a tectonic one. You could -- and I do -- despise the insurance industry and Big Pharma for blocking progress, but they’re part of the game. Doubtless we should change the rules, so they represent a far less dominant part of it. But if that happens, it, too, will undoubtedly occur piece by piece, not all at once.

Moving by increments:  it frustrates the hell out of many of us, and sometimes it’s truly disastrous. (I just watched Bill Moyers’ amazing recent broadcast of the LBJ tapes in the run-up to the full-scale escalation of the Vietnam War, where the president and his advisors just kept moving the numbers up a twitch at a time until we were neck deep in the Big Muddy.)  Usually, however, incrementalism, whatever you think of it, lends a kind of stability to the conduct of our affairs -- often it has a way of setting the stage for the next move.

The Copenhagen climate change talks kicked off on Monday. A Q&A on the key areas that will define success or failure.

Copenhagen - Delegates left the Bali climate change talks in December 2007 with high hopes that a grand bargain on reducing greenhouse gas emissions would be secured by now.

But today, as the latest round of climate change talks begin with representatives from more than 190 countries gathered in Copenhagen, Denmark, expectations are far more modest.

The biggest decision – a binding international agreement on reducing greenhouse gas emissions – is likely to be pushed off until next December, when another round of climate talks are scheduled for Mexico City. Nevertheless, two weeks in Copenhagen will yield insights into global efforts to control industrial emissions and the warming of the planet.

Below are some key questions:

What might success in Copenhagen look like?

Low expectations at the start of the conference may not be a bad thing.

"I think there was a sense all along that we were not going to be able to reach an international binding legal agreement in Copenhagen," says Eileen Claussen, who heads the Pew Center on Global Climate Change in Arlington, Va. But only in the last week did leaders acknowledge this. The results may disappoint some, she said, but added that it's a more realistic track.