Climate change is “perhaps the most comprehensive challenge that mankind has ever faced,” declared David Crane, the CEO of NRG Energy, as a group of 26 big companies and five big environmental groups came together on Capitol Hill this morning to offer Congress a blueprint to tackle global warming.

It’s hard to argue with his assessment. The question is, is the blueprint being put forward by Big Business (GE, DuPont, Alcoa, Dow, Duke Energy, Xerox, Shell, Conoco Phillips, the three automakers, etc.) and Big Green (EDF, NRDC, the Pew Center, World Resources Institute and Nature Conservancy) up to the challenge?

The 24-page document from the U.S. Climate Action Partnership, also known as USCAP, emerged from nearly two years of negotiations. You can read it here. “We don’t view this as a perfect document,” said GE’s Jeff Immelt. “We view this as a catalyst for change.” Congress now gets to tackle the issue. Henry Waxman, who heads the House committee dealing with greenhouse gas regulation, said today he wants to get a bill out of committee by May.

USCAP is proposing a cap-and-trade scheme (as opposed to a carbon tax), which adds multiple layers of complexity to the inevitably complex issue of climate change. Far be it from me to judge whether this blueprint will do the job. But here are a few of my first impressions:

A scientific problem, a political solution: The Intergovernmental Panel on Climate Change has estimated that to have a 50% chance of preventing the worst effects of global warming (and keep warming below 2 degrees C), developed nations as a whole must cut emissions by 25-40% from 1990 by 2020 levels and 80-95% reductions by 2050. The emissions reductions targets recommended by USCAP, while not precisely comparable, fall short of that. Nevertheless, Fred Krupp of EDF said, “This gives us the certainty we need that the atmosphere will be protected.” I don’t know if he’s right, but it’s fitting that the blueprint was introduced in the Cannon House Office Building—it was clearly the product of  compromise.

The dilemma of rising energy costs: A key goal of the cap-and-trade program put forth by USCAP is to put a price on carbon emission, to provide economic incentives for companies and individuals (i.e., all of us) to cut back on use of polluting fossil fuels and make cleaner fuels more afforable by comparison. That makes perfect sense. But (and this is a big but) companies are understandably worried about the impact that higher energy prices will have on the economy, and politicians are fearful of being blamed for higher gas and electricity rates. So they want to raise energy prices—just not by too much! This is one reason why U.S. Cap calls for a massive giveaway of the permits to pollute, to avoid putting too big an immediate burden on companies or their consumers. One CEO says the hope is to create a “bearable slope” of rising energy prices. Do you thing Washington can get that right?

A victory for clean coal: I defy any layman to read the coal section of the blueprint and explain what it means. I doubt many congressmen will be able to understand it. (Here’s a sample sentence: “Require all new coal and other solid fueled facilities emitting more than 10,000 tons of CO2 per year that are initially permitted after January 1, 2015, to emit no more than 1,100 lbs of CO2 for MWh; and require all new coal and other solid fueled facilities above this size threshold that are initially permitted after January 1, 202, to emit no more than 800 lbs of CO2 per MWH–provided that USCAP’s CCS direct cash payment funding recommendations are adopted and provided further….etc etc) Trying to translate all that into English, Jim Rogers, the CEO of coal-burning Duke Energy, said that USCAP has concluded that clean coal technology is crucial to solving the problem of global warming. Not only does the U.S. have abundant supplies of coal, he noted, but so does China, whose economy is growing fast and energy hungry. So USCAP calls for massive subsidies for clean-coal plants and rapid adoption of rules to permit the capture and storage of CO2 in underground caverns. “We cannot take coal off the table,” Rogers says. “We must find ways to remove CO2 from coal use.” Good luck.

No news on nukes: Exelon, GE, NRG Energy, Siemens and other big companies in USCAP  believe that nuclear energy should be a key part of the low-carbon energy mix of the future. The enviros won’t go there. So there is a barely a word about nuclear power in the blueprint. This will be a big issue for Obama and the Congress to resolve.

Offsets, global and domestic: These are allowed in substantial numbers, to help hold down energy prices. “Offsets are an important part of the blueprint,” said Bob Lane, CEO of John Deere. The idea here is that companies that find it too expensive or technologically difficult to cut their own emissions can pay others to cut theirs. Farmers could be paid to trap methane gas given off by cows and pigs. Poor people in the developing world could be paid to preserve forests. This is controversial, but probably a good idea, provided the offsets are determined to be real, additional, measurable, enforceable and permanent–no easy feat.

The bottom line: USCAP and Congress are trying to do something that’s really, really, really hard—engineer a dramatic transformation of the U.S. company in ways that aren’t needlessly disruptive. The goal, all agree, is to move from an economy that relies on low-cost, high-carbon fossil fuels (oil and coal) to one that runs on high-cost, low-carbon fuels (wind, solar power, geothermal, and, yes, clean coal).

The politicians and CEOs want to move slowly. The science tells us to move fast. Therein lies the problem.

Jeff Immelt of GE and Jonathan Lash of WRI introduce USCAP two years ago.