Reporting from Copenhagen — International negotiators are quietly making progress here on steps to reduce "stealth" pollutants that contribute to climate change, including soot, refrigerants and methane gas, which together account for nearly as much greenhouse gas pollution as carbon dioxide.
Carbon dioxide, of course, is the poster gas for global warming. Disagreements over how to reduce its emission from cars, factories and power plants have dominated the Copenhagen climate talks so far.
But carbon dioxide accounts for only half the world's greenhouse gas emissions. And while top leaders postured and negotiated over a host of issues related to carbon emissions in the first week of the summit here, behind the scenes diplomats have worked toward compromises on a few simple strategies to reduce the other pollutants that cause global warming.
Those sources include so-called black carbon, soot from incompletely burned fossil fuels and biomass, including that produced by ships and cooking stoves that collects in the atmosphere and on ice and prevents sunlight from being reflected back into space; hydrofluorocarbon chemicals, known as HFCs, used in refrigerators and air conditioners worldwide; and methane, which emanates from coal mines and landfills.
Many scientists and environmentalists say reducing the "forgotten 50%" of pollutants will be faster, easier and substantially cheaper than cutting carbon dioxide, and could buy the world time in its climate clock race.
"We can eliminate -- not just cut -- one of the six greenhouse gases this week," said Durwood Zaelke, a longtime environmental lawyer who is president of the Institute for Governance and Sustainable Development. "This can buy us more than a decade of delay" against the worst effects of climate change, he said.
Even as developing and developed nations have clashed over several issues, there has been broad support for the goal of reducing non-CO2 emissions. However, some nations are worried about moving to phase out HFCs before enough replacement chemicals are produced.
Negotiators here, however, are heavily focused on the high-profile issue of reaching a deal on CO2 emissions -- particularly the Obama administration, which stands to lose political capital at home and abroad if no such agreement materializes.
The administration appears loath to push provisions that could distract from the focus on carbon dioxide. At the same time, environmental advocates in Copenhagen say they worry that the "forgotten 50%" could slip out of a final agreement unless the United States champions their inclusion more vigorously.
"There is a huge political opportunity for a clear administration win on an issue where they desperately need one," said Paul Bledsoe, a former Clinton White House official who works on climate-change issues, and who joined Zaelke in urging the Obama team in January to act quickly on the "forgotten 50%" of emissions. "So far, they've left it languishing."
President Obama has repeatedly called for phasing out HFCs and the Environmental Protection Agency has taken strides to reduce the United States' black carbon output. American officials are set to unveil a modest black carbon spending initiative this week.
Because HFC regulation is handled through a decades-old treaty that aims to phase out pollutants that deplete the ozone layer, writing an HFC declaration into the agreement, a U.S. official said in Copenhagen, is "not something that we think is necessary."
Action on black carbon and hydrofluorocarbons is a particularly appealing goal for island nations concerned that the world may be nearing "tipping points" of global warming, in which increased greenhouse gas concentrations in the atmosphere start a chain reaction of temperature rise that would lead to their nations being swallowed by rising seawater.
The island nations are desperate for measures that will reduce warming in the short term. Black carbon is an ideal target because it stays in the atmosphere for only a few weeks, compared with 100 years for carbon dioxide, meaning that if black carbon emissions were eliminated, atmospheric heat-trapping would drop quickly.
In addition, the world has a successful track record of replacing harmful chemicals akin to HFCs, which replaced ozone-depleting refrigerants in the 1980s and '90s. Many scientists say HFCs could be replaced by either existing chemicals or those that chemical companies will quickly produce in the event of a phase-out, if the ozone treaty history is a guide.
Over the last week, Zaelke, Bledsoe and their allies in several national delegations to the talks have pushed to include a few sentences in a new climate agreement, which they say would allow the world to move swiftly against both substances.