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.

In a new review article in Nature Geoscience, two scientists say that black carbon, the stuff that gets kicked up into the air from biomass burning and diesel engines, among other things, could account for as much as 60 percent of the warming effect of carbon dioxide. That's three to four times greater than most estimates, and more than that of any greenhouse gas save CO2.

I live in a hundred year-old house where most everything is original: the windows (drafty), the walls (uninsulated), the furnace (burns oil). I need only look at my heating bill every month to deduce what the Commission for Environmental Cooperation has determined through a two-year study—homes and office buildings in North America account for over one-third of the continent's greenhouse gas emissions. They are terribly inefficient.

Where: Near Greenland

Cost: $50 billion

Carbon Challenge

It is increasingly accepted that rising levels of greenhouse gases are
contributing to changes in the world's climate. One of the main culprits is carbon dioxide. We exhale carbon dioxide when we breathe. Our cars, homes, factories, and the power plants that light our streets, all release carbon dioxide into the air. It's also emitted when fossil fuels are burned for energy. But that's about to change.

The ultrathin atmosphere, cold climate (average - 67�F), and consequential lack of the liquid water that is required for life make Mars an inhospitable planet. But by 2100, scientists predict, Mars colonists will say goodbye to their spacesuits, thanks to a geoengineering scheme that puts greenhouse gases to good use. The process, called terraforming, employs robots to mine 130 million tons of fluoride and sulfur deposits from Martian quarries each year and transport them to factories.

For the sake of the scoop, Ben & Jerry's managed to do what no refrigerator manufacturer has: jolt into development the world's most eco-friendly ice-cream freezer. Unveiled for Earth Day 2004 at a Manhattan scoop shop, the chiller relies not on greenhouse gases but on sound waves to keep the precious stuff cold. Research on thermoacoustic refrigeration limped along for 20 years or so until the ice cream duo forked over $600,000 to a Penn State team, which made the prototype in two years.

When will the next ice age occur?
Jessica Myers
Glen Ridge, N.J.
If historical patterns repeat themselves, within about 2,000 years. But that's an extremely big "if." Over the past several million years, Earth has spent most of its time sheathed in ice. But about every 100,000 years, the planet thaws. These warm spells, called interglacial periods, usually last between 15,000 and 20,000 years. We've been enjoying our current interglacial period for about 18,000 years-giving us roughly 2,000 to go before the next deep freeze.

During the 1980s, A diesel-powered Volkswagen Rabbit was briefly part of my household fleet. It was a particularly frigid Detroit winter, and we had to plug in the Rabbit's engine block heater if we were parked for even an hour or it absolutely refused to start. Even on warm days, our Rabbit hesitated at the touch of the ignition key. Its lack of power necessitated long-term planning for the simplest highway passing maneuvers. The engine clattered, smoked, and smelled like a city bus. The car's sole saving grace was that it traveled miles and miles on a single tank of fuel.