Now that every scientist who isn't part of the lunatic fringe agrees that human greenhouse gas emissions significantly alter the world's climate, the debate on Capitol Hill has shifted from science to policy. And that debate has proved even more complex than Congressional fights over the stimulus package, car company bailouts, and the decision to invade Iraq.

On Friday, the House of Representatives passed HR 2454, the American Clean Energy and Security Act of 2009, by a margin of 219 to 212, with three abstentions. The bill is the first legislative attempt to regulate carbon emissions, and the first bill to directly finger humans as the cause of climate change.

The Obama administration is expected to announce that California's strictest-in-the-nation gas mileage and emissions standards will now become a national standard. And surprisingly, U.S. automakers are actually happy.

Despite all the talk about carbon capture, carbon footprints and carbon trading, carbon dioxide only causes nine to 26 percent of the greenhouse effect. That means that the majority of warming results from gases with a much lower media profile than the paparazzi-trailed starlet of global warming, CO₂. In honor of last weeks’ report in the Journal of Geophysical Research, which identified a brand new greenhouse gas, PopSci.com counts down the gases that bring us bikini weather in Antarctica and beachfront property in Montana.

Less than two weeks before scientists from around the world gather in Copenhagen to issue recommendations for a new global climate-change treaty, the results from the two-year International Polar Year survey have arrived. They are not pleasant.

Common sense says that burning a plant you regrow every year is better for the atmosphere than spewing out carbon dioxide that’s been buried underground for eons. But the truth behind biofuels and petroleum often seems to defy common sense. Neither ethanol nor gasoline bubbles out of the ground ready to put in your tank. So to figure out which one does less environmental harm, you have to calculate all the energy that goes into making it.

Plans for cap-and-trade, carbon taxes, and other financial tools to curb global warming may float in and out of the national forum. But on a more local level, a price has already been placed on greenhouse gas emissions; it's $3.07 per ton.

In a lush pasture near Buenos Aires, this cow and its compatriots are digesting important information: how much methane—a greenhouse gas 20 times as potent as carbon dioxide—is released by the country’s 55 million bovines. Researchers from Argentina's National Institute of Agricultural Technology connected inflatable tanks to the cows’ first stomach, where methane is made, through a small hole between their ribs.

On Tuesday, G8 leaders in Japan made an agreement that sounds great – by 2050, they’ll cut the number of worldwide greenhouse gas emissions by half. It’s an improvement to Kyoto Protocol, at least, which the United States refused to adopt (and refused to apologize about). But developing nations, including China and India, were quick to criticize the accord, insisting that the G8 cut their emissions by more than 80 percent.

Getting carbon dioxide out of the atmosphere is just one step. After plants and trees pull CO2 out of the air, some of the surplus carbon is funneled down into the soil, where it can then re-enter the atmosphere or seep into groundwater. To trap this excess carbon, Newcastle University scientists are trying to design new kinds of soils that would transform the stuff into calcium carbonate, keeping it down in the ground.