Climate policy can’t wait any longer.

On Capitol Hill, some are saying legislation on the economy must come first, or health care or education — suggesting that Congress does not have the time or bandwidth to deal with climate and energy this year, too. Others say the brief cooling period we’ve had in the United States — driven by the El Niño-La Niña cycle — undermines the urgency of action. Still others say the United States should reach an international agreement before enacting new domestic legislation.

These arguments might have merit at another time. But the latest science is telling us that action to reduce emissions and make the switch to clean energy sources just can’t wait.

Powerful and accelerating forces are already at work: The Greenland ice sheet, which holds enough water to raise global sea levels by 20 feet, is melting at an alarming rate. The Arctic Ocean — engine of the Northern Hemisphere’s weather — could be ice-free in summer within five years, absorbing more sunlight and thus warming even faster.

Drought is increasing the amount of forest lost to fire, releasing more carbon into the atmosphere. The world’s tropical belt has already expanded toward the poles by two degrees of latitude — as much as had been predicted for the entire 21st century.

Our chance to stabilize greenhouse gas concentrations at an acceptable level is rapidly slipping away.

Modern society is structured around the climate we have — along coastlines that may be washed away by storms and rising sea levels; next to farmland and forests that will become less productive as water supplies decrease; at elevations cold enough to thwart insect-borne disease. The changing climate threatens the glue that holds humanity together.

Because environmental groups have been at the forefront of the fight against climate change, global warming has been considered an environmental issue and treated as if it could be managed like other forms of pollution. This framing is misleading — both because climate change threatens the world’s economic prosperity and security and because, unlike conventional pollution, it is in most respects irreversible.

Focus on that word for a moment: irreversible. No U-turn can take us back to the world we grew up in, or even the one we know today. When the Arctic ice cap disappears, our globes must replace white with blue — because there is no way to put the ice cap back. When Greenland releases the water it has stored in its glaciers for millennia, we will have to evacuate our shorelines — because there is no way to refreeze the ice sheet.

Every day and year that goes by, emissions of carbon dioxide and methane and other greenhouse gases contribute to the accumulation in the atmosphere and in the Earth’s oceans. These emissions stay in the “pipeline— and will not completely dissipate for thousands of years. We must act now to minimize the damage and try to avoid catastrophe. Climate policy can’t wait for a day when the legislative calendar is less crowded.

The good news, which bears emphasis, is that averting climatic disaster does not mean economic hardship and human suffering. Rather, it opens up a golden opportunity. As President Barack Obama said in his inaugural address, we can harness the sun, wind and soil to fuel our cars and run our factories. We can, and should, end our debilitating dependence on oil imports, which cost consumers $450 billion last year. We can bring forth new businesses — and create millions of new jobs that can’t be outsourced — by reducing the amount of energy we waste and turning to the renewable sources that we have in great abundance.

Congress recognized this opportunity in the stimulus package and again in the omnibus appropriations bill — allocating tens of billions of dollars to accelerate the clean energy transition, through the development and deployment of these rapidly evolving technologies.

But it does no good simply to wish these technologies luck against century-old incumbents who have long ago written off their development costs and who use the atmosphere as their dumping ground. It makes no sense to invest tens of billions of dollars in technologies and then fail to create the market conditions for them to compete economically.

Rep. Henry Waxman (D-Calif.), the new chairman of the House Energy and Commerce Committee, got it right from the beginning by promising to deliver a combined energy and climate bill to the floor by Memorial Day. That approach is not possible in the Senate due to divided jurisdictions, but Majority Leader Harry Reid (D-Nev.) has said he will bring the two bills together to the floor.

It is a platitude of American politics to say the U.S. has no energy policy. A more accurate statement is that the U.S. does indeed have an energy policy — to use the cheapest energy available at the fastest rate possible. What’s missing is an energy strategy. Advancing energy and climate policy together will produce a coherent and integrated strategy for the transition to a clean energy economy.

The international community has waited long enough for such a strategy to emerge. Since the United States abandoned its commitment in Kyoto in 1997 to reduce its greenhouse gas emissions, despite the United Nations climate treaty we ratified in 1992, the movement toward an effective global agreement on climate has only limped forward.

Obama’s election has renewed hope that the U.N. climate talks in Copenhagen in December will lead to a next phase of action to reduce emissions. Unless the United States arrives at the conference with evidence of a firm commitment to act, however, there is no chance that China, India and other emerging economies will do their part. To be credible at Copenhagen, the process must begin at home.

Congress must act so that the world will act, and the world must act if we are to preserve the planet as we know it, for our children and grandchildren. It’s as simple as that. Climate policy can’t wait any longer.

Timothy E. Wirth is president of the United Nations Foundation and a founder of the Energy Future Coalition. The Colorado Democrat served in the House and Senate from 1975 to 1992 and served as undersecretary of State for Global Affairs.