After seven years of bruising negotiations, repudiation by one of its early architects, and repeated pronouncements of its imminent demise, a 1997 pact to curb the growth of greenhouse gases tied to global warming is limping toward ratification.
Now comes the hard part: putting its complex rules into effect, and planning for what will follow once the agreement's first - and so far, only - formal commitment period ends after 2012.
"This is the most complicated, sophisticated effort at directed change" in international environmental policy ever attempted, notes Elliot Diringer, director of international strategies for the Pew Center on Global Climate Change. "Is it possible? We'll find out."
The pact in question, the 1997 Kyoto Protocol, requires countries signing the agreement to reduce global carbon-dioxide emissions by an average of 5 percent below 1990 levels by 2012.
Many atmospheric scientists agree that these emissions are at least partly responsible for an increase in average global temperatures. Those temperatures are expected to rise for the foreseeable future, with disruptive consequences worldwide.
Already, 126 nations have ratified the agreement - more than double the 55 needed. But the ratifying industrial countries only accounted for 44.2 percent of industrial-country emissions (55 percent are needed).
Last week, the final piece in that ratification puzzle appeared to fall into place when the Russian cabinet voted to ratify the accord. It now goes to the Russian Duma for the final vote, seen by many as a formality in the wake of the cabinet's decision.
Even if every signatory meets its emissions-reduction goal, the effort would barely slow the rate of increase of CO2 and have virtually no effect on climate.
By the end of this century, atmospheric CO2 is expected to double over preindustrial levels. That's because of the world's widespread use of coal, oil, and natural gas since the start of the Industrial Revolution as well as changes in land-use patterns.
Yet the value of the agreement lies less in its immediate effect on the atmosphere than on the political and diplomatic chemistry needed to deal with a problem that is likely to take decades to solve, some analysts say.
The 1997 accord "puts real pressure on countries to deliver on their commitments. Countries will demonstrate that it can be done affordably. And most important, ratification sets in motion the diplomatic machinery" to look beyond 2012, Mr. Diringer says.
He notes that the accord requires signatories to begin talks next year on a new round of targets and timetables for emission reductions.
"This is the first step in what will need to be a decades-long process," adds David Sandalow, a Brookings Institution scholar who has served as assistant secretary of state for oceans, environment, and science under President Clinton.
By most accounts, the European Union is in the vanguard of efforts to implement the Kyoto accords. The EU has set up a carbon-emissions trading scheme, which takes effect in January, according to David Victor, director of the Program on Energy and Sustainable Development at Stanford University in Palo Alto, Calif. In addition, it has developed a set of voluntary and binding regulations to cover households, transportation, and the building sector.
The EU is likely to fall a little short in meeting its Kyoto targets on its own, he says, but Russia's participation will come to Europe's rescue.
Because the Russian economy was in such shambles in 1990, the base line against which Kyoto targets are measured, Moscow's emissions targets are far above existing emissions. So Russia has carbon "credits" it can sell to EU members.
European countries can also earn credit against their emissions targets for helping Russia build cleaner, more efficient power plants and factories. Such "joint implementation" projects, permitted under Kyoto's ground rules, are expected to allow the EU to claim victory in meeting its targets by 2012.
Other industrial countries, such as Canada and Japan are further behind. Japan's biggest problem is emissions from autos, notes Philip Clapp, president of the National Environmental Trust, an environmental group in Washington, D.C. Three years ago, the country tried to lay plans for higher domestic fuel-economy standards to meet its Kyoto commitments, Mr. Clapp says, but the US threatened to challenge those standards before the World Trade Organization. Japan's move would constitute a trade barrier against American auto imports, the US argued.
Now, analysts say, Japan is said to be exploring an internal carbon-trading system, as well as taxes on emissions to help it meet its Kyoto targets.
In the end, Clapp says, "the countries that have ratified will comply" using the full range of mechanisms the pact makes available.
The big question, he continues, is what happens after 2012.
Next year, talks are set to begin on a post-2012 emissions-control regime. A key goal is likely to be a hunt for ways to get countries, including China and the United States, to buy in to a new agreement. That will require thinking outside the 1997 protocol box, some analysts say.
The challenge will be to overcome the inertia that could build behind Kyoto's existing mechanisms if they prove successful during the first commitment period. "When a model is seen as effective, it's hard to swim against the tide," Dr. Victor says.