Once again Mick Jagger is right: “You can’t always get what you want/But if you try sometimes you just might find/You get what you need.”

The House of Representatives is poised for its first-ever floor debate and series of votes on a landmark measure to reduce global warming pollution. This bill is revolutionary in its intent and, while imperfect in its means, it deserves the support of progressives.

The American Clean Energy and Security Act would establish binding greenhouse gas pollution limits, set the first national renewable electricity and efficiency standards for utilities, and improve efficiency standards for buildings and appliances—creating 1.7 million new jobs and spurring $150 billion in investments. At the same time the bill would also make ratepayers whole while protecting low-income families for the cost of less than a postage stamp.

The original draft of this bill included a more aggressive 2020 greenhouse gas reduction target and a higher renewable electricity standard. Both were lowered to reach a fragile compromise between environmental champions in the House of Representatives and others members concerned about local industries. Despite these changes, this bill starts the critical transition to a low-carbon economy. It sets a hard cap on emissions—something the previous administration was dead set against—that will be lowered over time so we can achieve the emissions reductions climate science demands over the next few decades.

In the short term, the cap will reduce emissions by the equivalent of removing 500 million cars from the road by 2020. The cap will also set a price on carbon pollution, reflecting the costs of dirty coal-fired electricity. It will spark more clean-energy innovation and private investment in energy efficiency and alternative energy, including wind and solar energy.

Passing this bill is the first arduous step toward energy transformation. Senate passage of similar legislation will be more difficult, and the Senate Energy Committee is off to an inauspicious beginning by passing an energy bill that would do little to boost investments in renewable electricity. The bill would allow oil drilling in an area only 45 miles off the Florida Gulf Coast and worsen global warming by lifting the prohibition against the federal government purchase of oil from Canadian tar sands, which produce twice as much greenhouse gas pollution as regular oil. The Senate bill is weak, toothless, and unacceptable, and it must be improved before it passes.

The U.S. political system has never attempted to solve a problem as complex as climate change, with all its scientific, economic, energy, security, and humanitarian dimensions. The congressional will to act lags far behind the scientific evidence that there is little time left to avert the worst impacts of global warming.

President Barack Obama’s determination to speed our energy transformation has brought defenders of the status quo out in force. Opponents of change understand that now is the best opportunity for our success. We have a new, very popular president, a dedicated speaker of the House, a determined Senate majority leader, and the numbers in both bodies to realize this clean-energy vision. Opponents know they must block these changes now or it will be too late. Conservatives joined by big oil and coal lobby groups have unleashed a massive campaign to block these measures.

Some of my allies in the progressive community worry about worst-case implementation scenarios that might eviscerate the American Clean Energy and Security Act ’s greenhouse gas pollution reductions. Because of these fears they believe that inaction is preferable to this action. I do not question their sincerity, but their strategy could prove disastrous. Without meaningful action in Congress, the Obama administration will lack the credibility to cajole developing nations to reduce their growing emissions as part of the Copenhagen global warming talks this December. The chance to adopt meaningful clean-energy and global warming policies will evaporate for at least two years.

Some advocates argue that congressional inaction is preferable because the Environmental Protection Agency can use its authority under the Clean Air Act to require power plants to reduce their emissions. I strongly believe that if Congress cannot muster the votes to pass a decent energy and climate bill, then the EPA can and indeed must act to regulate carbon dioxide emissions under the Clean Air Act. But I also know that approach is rife with peril. It would face legal assaults that would significantly delay implementation of any such reduction rules.

What’s more, the EPA lacks the authority to adopt and implement other important near-term pollution reduction tools, such as a national renewable electricity and efficiency standard. Relying on the EPA is an important fail-safe strategy, but that administrative path is rocky and long.

The American Clean Energy and Security Act is not all that environmentalists and progressives want. But we must pass this bill so that we can get what we need: a clean-energy law that creates jobs, reduces oil use, and cuts global warming pollution.