The Kyoto Protocol sets binding reduction targets on greenhouse gas emissions, such as carbon dioxide, but it expires next year. That's why reaching a new agreement is a top priority for diplomats attending the annual United Nations-sponsored climate talks in Durban, South Africa beginning Monday.
The world's climate negotiators agree that they want to reduce emissions linked to climate change, but are having a hard time reaching consensus on the necessary steps.
Alden Meyer, the director of climate strategy and policy at the Union of Concerned Scientists in Washington, says the Kyoto Protocol is in jeopardy.
"The European Union has said they're willing to continue in Kyoto if there's a process launched to create a broader framework down the road that would include not only the United States but China and other major developing countries. Japan, Canada and Russia have indicated already they don't want to stay in Kyoto beyond the end of next year when their current commitments expire. So this'll be one of the major issues in Durban - what happens to Kyoto after 2012," Meyer said.
Only developed countries among nearly 200 parties that signed the Kyoto Protocol are bound by it to reduce emissions. That's based on the idea that they are largely responsible for the industrial activity that releases greenhouse gases into the atmosphere.
But some developing nations are heavy polluters, too, says climate scientist Todd Sanford of the Union of Concerned Scientists.
"If you still look at a per capita basis, the U.S. is still far ahead of everyone else. But growth in India and China have really put the developing world past the developed world at this point in terms of total emissions," Sanford said.
The United States is committed to making voluntary cuts, U.S. negotiator Jonathan Pershing said earlier this year.
"As part of that commitment, we stand behind President Obama's pledge to reduce our greenhouse gas emissions in a range of 17 percent below 2005 levels by 2020 as inscribed in the Cancun agreements [of 2010]," Pershing said.
The issue is international consensus, says Australian lawmaker Mark Dreyfus.
"I think it's hard to get 200, nearly 200, countries to agree and what we're finding is that a lot of countries are doing more domestically than perhaps they're prepared to agree to internationally," Dreyfus said.
Rachmat Witoelar is the Indonesian president's envoy for climate change. "So we have to learn how to take and give, and Indonesia is trying to do so by voluntarily lowering our emissions," Witoelar said.
The United States, the world's second-largest carbon emitter, never ratified the Kyoto agreement, in part because it placed no limits on developing nations such as China, the world's chief polluter.
U.S. President Barack Obama addressed that issue in Australia in mid-November.
"If we are taking a series of steps, then it's important that emerging economies like China and India are also part of the bargain. It doesn't mean that they have to do exactly what we do. We understand that in terms of per capita carbon emissions, they've got a long way to go before they catch up to us. But it does mean that they've got to take seriously their responsibilities as well," he said.
No agreement now exists to extend or succeed the Kyoto international climate agreement.