We have spent the past decade debating a scientific consensus on global warming instead of taking action to fix it. The time is now to move from talk to action. For too long, we have allowed our national dialogue on this looming crisis to be distorted by a small group of special interest-funded naysayers. They have stalled as the evidence mounted along with worldwide temperatures. Powerful interests have deployed an unending cascade of hollow arguments and manipulations to enable a flood of toxins into our rivers, farmland, neighborhoods and communities -- often with the support and sympathy of the Bush administration. But Americans have had enough. People across this country grasp the scientific reality that we are in the middle of a crisis. The Earth's poles and virtually all points in between are heating up at a frightening and potentially catastrophic pace. Recently, the most comprehensive study to date confirmed that manmade global warming is real -- and underscored the danger we all face from it. According to the Intergovernmental Panel on Climate Change (IPCC) -- a network of more than 2,000 scientists -- we now know with a scientific certainty of greater than 90 percent that most of the observed warming over the past half-century is caused by human activities. No doubt, we in politics must work to solve these problems from 30,000 feet -- with bold new ideas for national solutions -- but the drive to address global warming will only succeed if Americans continue to stand up and protect the ground beneath their own two feet. San Francisco blazed a new trail in the fight to keep America clean and green -- and earned worldwide headlines -- when it banned the use of plastic shopping bags at large supermarkets and chain pharmacies. Around 180 million plastic bags are distributed each year at San Francisco shopping venues. This is a major step -- and it sends a powerful message that more of the same just won't cut it. Even among Republicans, the reign of "hear no science, see no science, speak no science" politicians is eroding. Right here in California, Gov. Arnold Schwarzenegger signed a law capping California's carbon emissions. The good news is that America has met great challenges in the past and can surely do so again. Simply put, we have no choice. It is time to do away once and for all with the myth that fixing the environment is bad for business. In the long run, the opposite is true. General Motors Vice Chair Bob Lutz recently told Business Week that "Being known as the technology laggard is not conducive to selling automobiles." Government needs to help America's automakers create cleaner, more efficient vehicles -- and to help America maintain its dozens of new "green" markets that will inevitably spring up to meet this challenge. Why shouldn't these new businesses be American businesses? Each of us can do something, and we need to insist on leaders who will. We wouldn't elect someone who said terrorism wasn't a threat, but for too long we've tolerated those who treat the threat of energy insecurity and the truth of global climate change as inconvenient myths. Well, from now on, every American who walks into a polling place can and should vote to kick out of office anyone standing in the way of solving either threat. Together, we have written a book about the changing face of environmentalism called "This Moment on Earth" -- the book explores what's at stake and explains what people are doing about it. In the Senate, Kerry's bipartisan proposal calls for the biggest reduction in greenhouse-gas emissions. The bill establishes an economy-wide cap-and-trade program for greenhouse-gas emissions. Such systems use the power of the marketplace to reduce emissions in a cost-effective and flexible manner. In practice, cap-and-trade systems create a financial incentive for emission reductions by assigning a cost to polluting. A key advantage is that it gives companies flexibility in the manner in which they may achieve their emission targets. Another advantage is that it sets a clear limit on emissions. The Kerry-Snowe bill freezes emissions levels in 2010 and then gradually reduced each year until we hit 65 percent below 2000 greenhouse-gas emissions levels by 2050. Such reductions are in line with what the science tells us we need to achieve in order to avoid catastrophic climate change. While it's not easy for a Red Sox fan to quote legendary Yankees catcher Yogi Berra, he was right when he warned that "it gets late early out there." The truth is, it's late already. But it's not too late if we get serious about tackling global climate change. No more cheap talk. No more dodging the issue. The time has come for America to do what America always did in times of 20th century challenge -- it is now time to face the greatest challenge this planet faces in the 21st century.