When the world talks climate change—as is currently under way in Durban, South Africa—the main issue is carbon dioxide emissions. CO2 is emanating from the negotiators' mouths and the power plants and cars of their home countries—and that simple molecule is responsible for the bulk of global warming to date.
But CO2 isn't the only molecule trapping heat in the atmosphere. The warm conditions of the earth get a big boost from water vapor as well as several other culprits, some of which never existed in the atmosphere prior to human influence. Together, the other greenhouse gases account for roughly a third of the molecules trapping heat in the atmosphere — and more than a third of the overall warming of average temperatures globally.
What's more, cleaning up emissions of some of these other greenhouse gases may prove quite a lot simpler than cutting back on CO2—forestalling catastrophic climate change. In fact, some of the measures—such as capturing the methane released during oil production—actually save money in addition to the climate. The United Nations Environment Program estimates that cutting back on methane and soot emissions alone could prevent 0.7 degree Celsius of additional warming by 2040—and those cooling benefits could come faster than comparable cuts in CO2.