Carbon-dioxide is certainly the highest-profile greenhouse gas out there, but it's hardly the only one. There are also, for instance, hydrofluorocarbons (HFCs), which are used to make refrigerants and have become a popular substitute for ozone-layer-destroying CFCs, which have been phased out under the 1989 Montreal Protocol. HFCs don't chew through the ozone layer, but they do warm the planet—some types are thousands of times more effective at trapping heat than CO2. And, while HFCs are fairly rare at the moment, their use is set to skyrocket in the coming decades—if left unchecked, HFC production would easily overwhelm any progress made on curbing carbon-dioxide.

So much for the gloomy stuff. The good news is that HFCs would be relatively simple—and inexpensive—to phase out. It could be done under the existing Montreal Protocol, a treaty that's been hugely successful at eliminating the use of CFCs and other dangerous chemicals for decades. As David Sassoon of SolveClimate reports, junking HFCs could be done for as little as $4 billion through 2050, making this far and away one of the most cost-effective steps we could take to reduce the rate that the planet's heating up.

So why isn't this being done? Read Sassoon's story for the full details, but the short answer is that China and India realize they could get paid a lot more if HFC destruction was included as part of a new climate treaty, rather than merely as an add-on to the old Montreal Protocol. So, like everything else at Copenhagen, it's become just another poker chip. But there's a potentially massive "easy" win on climate here, as close to a gimme as it gets, and the issue deserves more attention than it's received so far.

(Flickr photo credit: DCvision2006)