The Obama administration seems ready to resuscitate relations with Russia, including by renewing nuclear-arms-reduction talks. Even before the inaugural parade wound down, the White House Web site offered up a list of ambitious nuclear policy goals, with everything from making bomb-making materials more secure to the eventual abolition of nuclear weapons.

That's welcome news, but for such goals to be realized, the White House will need to be prepared to reimagine and reshape the nuclear era and, against strong opposition, break free from cold war thinking and better address the threats America faces today.

George W. Bush actually started down this road. He reached an agreement with the Kremlin in 2002 to cut the number of operational strategic warheads on each side to between 1,700 and 2,200 by the year 2012, a two-thirds reduction. Washington is likely to reach that goal ahead of schedule. President Bush's efforts were propelled by the Nuclear Posture Review - a periodic reassessment of nuclear forces and policies - in December 2001. While still grounded in the belief that nuclear weapons are the silver bullets of American defense, the review let a little daylight into the nuclear bunker by acknowledging that nuclear-weapons policy had to be readjusted to deal with rapidly changing threats. Soon, however, the president's initiatives were overshadowed by the wars in Afghanistan and Iraq, his administration's absorption with the threat of terrorism and the gradual breakdown in relations with Russia.

President Bush's agreement with Moscow, which was built upon weapons reductions made by Presidents Bill Clinton and George H. W. Bush, is President Obama's starting point. But rather than settle for the next level - 1,000 active weapons seems to be the likely goal - the White House should reconsider the entire superstructure of nuclear-weapons strategy. This won't be easy. The mandarins of the nuclear establishment remain enthralled by elaborate deterrence theories premised on the notion that the ultimate defense against a variety of military threats is a bristling nuclear arsenal.

It's true that America's nuclear weapons still offer the hope of deterring attacks from countries like North Korea and, if it soon goes nuclear, Iran. But it is hard to imagine how they would dissuade a band of elusive, stateless terrorists from making a nuclear bomb and detonating it in New York, Washington or Los Angeles.

One provocative road map for moving away from nuclear deterrence comes from a quartet of cold war leaders - Henry Kissinger and George Shultz, former secretaries of state; William Perry, a former secretary of defense; and Sam Nunn, a former chairman of the Senate Armed Services Committee. Two years ago, they bridged their ideological differences to call, improbably, for the abolition of nuclear weapons, and they proposed a series of interim steps to reduce nuclear dangers, stop the spread of bomb-making materials and lay the groundwork for a nuclear-free world.

Even the quartet recognizes that "getting to zero" will be exceedingly difficult. But the issue today isn't whether the elimination of nuclear weapons is feasible. That's a distant goal.

An achievable immediate goal should be to cut the United States' and Russia's nuclear stockpiles down to the bare minimum of operational warheads needed to backstop conventional forces. As long as these two countries have far and away the most nuclear weapons, Washington looks hypocritical when it lectures other nations about the size of their arsenals or their efforts to develop nuclear weapons.

There's reasonable disagreement among experts about the minimum number of nuclear weapons the United States and Russia should maintain. The more emphasis you put on nuclear deterrence, the more potent you think the arsenal should be. And the more you want to engage the world in arms reduction and prevent proliferation, the more you consider radical cuts. To bring the number down below 1,000 would require determined presidential leadership.

The president's determination will be measured by how effectively he makes the case for Senate ratification of the 1996 Comprehensive Nuclear Test Ban Treaty. Leading scientists say that technological advances over the past decade have erased doubts about whether an international monitoring system can detect and locate underground tests outlawed by the treaty. The scientists also say that the United States has the technical expertise and tools to maintain the effectiveness of its nuclear weapons without underground testing, as has been successfully demonstrated since the United States stopped testing in 1992.

Ratification of the test-ban treaty would help build momentum for a 2010 review of the Nuclear Nonproliferation Treaty, the increasingly frail 1968 accord aimed at limiting the spread of nuclear weapons and eventually eliminating them. American leadership is essential to reinvigorating the treaty and buttressing nonproliferation efforts. The best way to avoid nuclear terrorism is to prevent terrorists from acquiring the highly enriched uranium needed to make the simplest nuclear bomb.

Listening to the discussion at a recent nuclear-weapons conference in Washington, I felt as though I had slipped back in time to the cold war and its arcane, often surreal debates about waging nuclear war and the doctrine of mutual assured destruction. It's heartening to see President Obama and his national-security team promising to elevate nuclear-weapons policy and free it from the shibboleths of cold war nuclear theology. Now they must put their words into action.

David G. Victor says a comprehensive, national-level climate change policy with bi-partisan support is necessary in the U.S. before engaging, seriously, with other nations. Although the Democrats control both the White House and Congess, previous landmark environmental legislation were authored under centrist Republican administrations. Furthermore, the Administration needs time to carefully construct a national policy that considers current, more stringent, policies at the state-level while balancing the economic crisis.

One effect of the new Obama administration's global charm is that America could be let out of the environmental doghouse. The Obama plan to restart the economy is stuffed full of green incentives, and the new president has earned global cheers for his promise to cut the gases that cause global warming. But hope and change are not easy to implement in Washington, and the first big disappointment is likely to come later this year when the world's governments gather in Copenhagen to replace the aging and ineffective Kyoto treaty.

In reality, the greenish tinge on nearly every economic recovery plan, even China's, show that this crisis offers green opportunity.

Pundits have been talking down the Copenhagen summit on the theory that the current financial crisis makes 2009 a tough time for governments to focus on costly and distant global goals like protecting the planet. In reality, the greenish tinge on nearly every economic recovery plan, even China's, show that this crisis offers green opportunity. The real reason Copenhagen will be a disappointment is that the new Obama administration can't lead until it first learns what it can actually implement at home. And delivering greenery in the American political system is harder than it looks-even when the same left-leaning party controls both the White House and Congress.

On environmental issues, America is barely a nation. Under a single flag it uneasily accommodates a host of states pushing greenery at wildly different speeds. In the 1970s and 1980s, this multispeed environmentalism propelled America to a leadership position. The key was truly bipartisan legislation, which allowed Washington to craft a coherent national approach. In fact, most of the major U.S. environmental laws did not arise solely from the environmental left but were forged by centrist Republican administrations working closely with centrist and left-leaning Democrats. Republican President Nixon created America's pathbreaking clean air and water regulations; Republican George H.W. Bush updated the air rules to tackle acid rain and other pernicious long-distance pollutants. In his more moderate second term, Ronald Reagan was America's champion of the ozone layer and helped spearhead a treaty-probably the world's most effective international environmental agreement-that earned bipartisan support at home and also pushed reluctant Europeans to regulate the pollutants.

Ever since the middle 1990s-about the time that the U.S. government was shut down due to a partisan budget dispute-such broad coalitions supporting greenery have been rare. In the vacuum of any serious federal policy, for nearly a decade the greener coastal states devised their own rules to cut warming gases. The United States as a whole let its green leadership lapse. (At the same time, the project to create a single European economy has shifted authority in environmental matters from individual member states into the hands of central policymakers in Brussels, where a coterie of hyperrich and very green countries have set the agenda. Europe, long a laggard on environmental issues, is now the world leader.)

The normal multispeed script was playing out on global warming as the Obama administration took power. Industry, worried about the specter of a patchwork of regulations, has lobbied for a coherent national strategy. But the Obama administration's first major policy on global-warming policy went in precisely the opposite direction: he reversed the Bush administration's decision that blocked California from adopting its own strict rules on automobile efficiency.

Today's challenge, which won't be solved by Copenhagen, is for Obama to stitch these many state environmental efforts together. That's no easy task. Global-warming regulation will probably have a larger impact on the nation's economy than any other environmental program in history, and any plan will have to allow enough room for some states to move quickly while also satisfying industry's well-founded need for harmony. Obama's Democratic Party controls both the White House and Congress, but that does not guarantee success. It will be difficult to craft a national policy that earns broad and bipartisan support while also taking the big bite out of the emissions that the rest of the world is hoping Obama will promise to the Copenhagen treaty. The difficulties aren't just in dragging along wary conservative Republicans. In fact, the most important skepticism about an aggressive national strategy has been from a coalition of centrist Democrats who fear the impact on jobs and economic growth.

One key to success will be crafting a deal with China and other developing countries to show that they, too, are making an effort. But serious efforts on that front are still in their infancy.

The big challenge for Copenhagen will be to find a way to allow negotiations to stretch beyond the unrealistic 2009 deadline while still keeping momentum. America's slowness in getting serious about global warming should be welcome because it is a contrast to its rushed behavior in negotiating the Kyoto treaty. At Kyoto, Bill Clinton's administration promised deep cuts in emissions without any plan for selling them at home, which is why the Bush administration could so easily abandon the treaty. Repeating that mistake would be a lot worse than waiting a bit for America to craft real leadership. If that's why Copenhagen falls short of the mark, then that's good news-real greenery, rather than fakery.