The United States and China have resolved a key dispute in climate negotiations, but details suggest that differences could re-emerge over reporting of carbon cuts.
In an agreement at the U.N. climate conference in Cancun, Mexico on Dec. 11, industrialized and developing nations settled on a process to "measure, report, and verify" efforts to curb greenhouse gas emissions.
The issue known as "MRV" has been a point of contention with China for the past two years because of doubts about the accuracy of the country's official reports.
China has insisted that reviews of its data "must respect the national sovereignty," while resisting legally binding commitments for a treaty to replace the Kyoto Protocol.
Developed countries have been reluctant to make binding pledges of their own under such conditions. But a breakthrough at Cancun has bridged differences over the MRV dispute.
Elliot Diringer, vice president for international strategies at the Pew Center on Global Climate Change, called the accord "a basic agreement on the process that will be used to look at what countries report."
The agreement, based on a proposal by Indian Environment Minister Jairam Ramesh, calls for developing countries to report their emissions and reduction efforts for "international consultations and analysis" every two years.
Reviews will be conducted "in a manner that is non-intrusive, non-punitive, and respectful of national sovereignty," the Cancun accord says.
The compromise is seen as an important step, although it falls short of the binding and verified pledges that China critics have urged.
The deal formalizes the role of international reviews by a technical group, "making it much more difficult for China to back out," said Michael Levi, senior fellow at the Council on Foreign Relations, in a blog posting.
China's role is critical as both the largest developing country and biggest emitter of greenhouse gases. Concerns have been raised about its reporting on several counts.
The country has promised to cut 25 to 40 percent of its carbon emissions from 2005 levels by 2020, but only per unit of GDP.
Since China's economy is growing at 10-percent annual rates, emissions are expected to rise despite the proportional cut. Much also depends on whether China's economic statistics are overblown.
China's claims in a similar campaign for energy efficiency have been troubling.
Last month, the National Development and Reform Commission (NDRC) said China's energy use per unit of GDP fell 3 percent during the first nine months of the year, at a time when added power consumption outstripped GDP growth by nearly 70 percent.
The contradictions have put critics on guard about accepting China's data for a new climate treaty.
But Diringer argued that binding pledges are not necessarily enforceable, in any case. International examination may prove just as effective.
"Once you've seen it all laid out, then countries can make judgments whether they're doing an adequate job," Diringer said.
Developing countries also won another key concession on the MRV issue. Only "internationally supported" efforts will be subject to outside checking, while domestically funded measures will be reviewed only by their home countries.
The MRV process could affect the willingness of industrialized countries to fund new technology for developing countries and compensate them for keeping forests intact.
The Cancun agreement establishes a "Green Climate Fund" to administer U.S. $100 billion in annual support from richer nations, which would contribute U.S. $30 billion in 2010-2012.
China is expected to need only minimal foreign funds, but poorer countries will rely on aid for their emissions and reporting programs.
The huge costs may raise doubts about whether developing nations can continue to qualify for funding if they fail to submit verifiable reports. The Cancun agreement does not answer the question specifically.
Joanna Lewis, an assistant professor at Georgetown University, said the "non-punitive" condition implies that "a country can't be penalized in any formal way, including restricting their access to funds."
But individual developed countries could still find ways to restrict the use of their funds if they cannot substantiate the emissions reports, Lewis said.