One way to counteract the rise in greenhouse gases in the atmosphere is to make use of known chemical reactions to capture carbon dioxide from the atmosphere and store it underground or use it to make something useful like hydrocarbon fuels or plastics. The process is similar to what plants do as they convert carbon dioxide into roots and leaves, but using industrial processes might make it happen faster and on a larger scale.

The question is whether this can be done cheaply enough to be worthwhile. Some have argued that the existing processes are too expensive, and that what's needed is basic research to find chemical reactions that require less energy, among other things. Meanwhile, it's better to try capturing carbon dioxide from smokestacks, where it's much more concentrated, making the capture process cheaper.

David Keith, director of the energy and environmental systems group at the University of Calgary, argues in next week's issue of Science that air capture (as capturing carbon dioxide from the atmosphere is often called) could be cheaper than people think, and that it may make more sense than other methods of offsetting carbon dioxide that are being used today.

He's careful to point out that the economics are by no means certain at this point. Indeed, he argues that what's needed now is funding for some large-scale tests to determine how much various processes really will cost. But his early research, including preliminary work with a startup company, suggests that costs for at least one part of the process--collecting carbon dioxide molecules from the air--will be cheaper than once thought, he says. What's more, such systems could be located anywhere in the world, making it possible to choose a location with low construction costs and easy access to geological structures for storing the carbon dioxide, both of which would make the process cheaper. Carbon dioxide capture from smokestacks, in contrast, must be done near existing power plants, where construction costs and the cost of transporting carbon dioxide to storage sites are higher.

Carbon dioxide capture from smokestacks will probably still have the edge, he says. But air capture may prove cheaper than other methods that are being funded now, such as putting solar panels on roofs in dark regions (Germany, for example), where payback times for the solar panels are very long.

Whether or not it makes sense to fund demonstration projects or to focus on basic research, air capture will likely play an important role in addressing climate change in the coming century. Even with strict emissions cuts in place, the carbon dioxide already in the atmosphere could cause serious problems. Air capture could provide a way to actually reduce greenhouse-gas concentrations, rather than merely stopping their growth.

As prices for wind and solar power drop, some experts say that the biggest barrier to making renewable energy dominant is the need for cheap and reliable storage.

A new Department of Energy agency, the Advanced Research Projects Agency for Energy (ARPA-E), seems to be listening. It could soon start a new funding round devoted exclusively to energy storage technologies, according to Imre Gyuk, a program manager for energy storage research at the Department of Energy. As a first step, it has also announced a workshop on grid scale energy storage to be held in Seattle on October 4.

Solar and wind technologies seem headed to the point where, in the next several years, they will be able to generate electricity at costs comparable to those of conventional sources.

But there's a catch. Electricity from wind turbines and solar panels isn't worth as much as electricity from coal or natural-gas-fired power plants or from nuclear reactors because it's not always available. When clouds cover the sun, or the wind stops blowing, utilities have to turn to conventional power plants to make up the difference. And, of course, solar doesn't work at all at night.

As the cost of solar comes down--and if researchers can develop cheaper storage--one day it might be practical to build extra solar panels and store the electricity they produce for use on cloudy days and at night. Then, because there's more than enough sunlight for all our energy needs, solar could become a primary source of electricity.

A draft of the Senate's version of a climate bill has been released. The official version is scheduled to be unveiled officially today in the Senate.

The move comes on the heels of President Obama's speech to the United Nations in which he called for action on climate change. A House climate bill passed back in May, but since then climate change has taken a back seat to health care reform. There's been some concern that no climate change legislation will be passed before a meeting in Copenhagen this December where world leaders are supposed to work out a new climate change treaty. With no law in hand, U.S. negotiators may find it hard to sell other countries on strict emissions reductions.

The draft bill tightens emissions caps somewhat compared to the House bill, calling for a 20 percent reduction in emissions by 2020 compared to 2005 levels, rather than a 17 percent reduction. It also contains sections devoted to reducing emissions specifically from transportation sources, as well as incentives for emissions reducing technology such as carbon capture and sequestration, nuclear power plants, and renewable energy.

But much work remains before the bill can become law. For example, some parts of the bill have only placeholder language, awaiting action from committees. Nevertheless, Senate Majority Leader Harry Reid (D-NV) has reportedly said that the bill is on track to be passed by the Senate before the Copenhagen meeting. That's not to say it will become law by then, of course, as it will still have to be reconciled with the House Bill.