As Congress struggles over a bill to limit carbon emissions, a cap-and-trade program is already operating in 10 Northeastern states. But the regional project's mixed success offers a cautionary warning to U.S. lawmakers on how to proceed.

Two prominent — and iconoclastic — environmentalists argue that current efforts to tax or cap carbon emissions are doomed to failure and that the answer lies not in making dirty energy expensive but in making clean energy cheap.

Over the past two decades, mountaintop removal mining in Appalachia has obliterated or severely damaged more than a million acres of forest and buried more than 1,000 miles of streams. Now, the Obama administration is showing signs it plans to crack down on this destructive practice.

The days of freely dumping greenhouse gases into the atmosphere are coming to an end, but how best to price carbon emissions remains in dispute. As the U.S. Congress debates the issue, Yale Environment 360 asked eight experts to discuss the merits of a cap-and-trade system versus a carbon tax.

For spurring the transformation to a low-carbon economy, the federal and state governments, universities, and the private sector must join together to create a network of energy research institutes that could speed development of everything from advanced batteries to biofuels.

In an interview with Yale Environment 360, Bill McKibben explains why he’s now focused on organizing a citizens movement around climate change — and why he believes this effort is critical for spurring world leaders into action.

With global warming pushing some animals and plants to the brink of extinction, conservation biologists are now saying that the only way to save some species may be to move them.

With carbon cap-and-trade legislation now on Washington’s agenda, companies and interest groups have been hiring lobbyists at a feverish pace. For every member of Congress, there are now four climate lobbyists, many of them hoping to derail or water down the effort to reduce greenhouse gas emissions.

Secretary of State Hillary Clinton’s trip to China could be the first step in forging a partnership between the world’s largest emitters of greenhouse gases. A leading China expert sets forth a blueprint for how the U.S. and China can slow global warming and strengthen their crucial relationship.

NASA’s Robert Bindschadler, a leading expert on glaciers and ice sheets, is part of an international team monitoring a large and fast-moving glacier in West Antarctica. In an interview with Yale Environment 360, he explains the dramatic impact this unstable mass of ice could have on global sea levels.

If crucial climate negotiations later this year in Copenhagen are to have any chance of success, the U.S. must take the lead. To do that, President Obama needs to act boldly in the coming months.

Key developing countries have long been exempt from efforts to reduce greenhouse gas emissions. Now, as global climate talks move forward, that policy must change.

In response to industry pressure, the U.S. Food and Drug Administration has failed to set adequate restrictions on mercury levels in fish. Now the Obama administration must move forcefully to tighten those standards and warn the public which fish are less safe to eat.

Europe’s backpedaling last month on toughening its carbon trading system may have signaled the end of its leadership on climate change. Now, with a new administration and Congress, America appears ready to commit itself to tackling global warming.

Environmentalists from Bill McKibben and Paul Hawken, to Fred Krupp and Frances Beinecke offer President Obama their advice on the priorities he should set for the first 100 days of his administration.

In evaluating an economic recovery package, the new U.S. administration and Congress must weigh any proposed spending on highways or mass transit or wind-power transmission routes on the basis of clear criteria that would assess just how green the projects will be.

In an interview with Yale Environment 360, Amory Lovins, co-founder and chairman of Rocky Mountain Institute, says that world's biggest untapped energy source is efficiency. And retooling for energy efficiency will require "barrier-busting" at many levels. And government, Lovins says, "should steer, not row."

As he assumes the presidency, Barack Obama must make climate-change legislation and investment in green energy top priorities. And he must be ready to take bold — and politically unpopular — action to address global warming.

The next U.S. president should not wait for Congress to act on climate-change legislation. Instead, he should make use of the Clean Air Act to begin controlling greenhouse gas emissions and to implement a national cap-and-trade program.