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.