Natural gas burns cleanly, emits half as much carbon dioxide into the atmosphere as burning coal, and is extremely plentiful—especially due to new extraction technologies such as fracking. It seems like a perfect fuel for battling climate change.

But natural gas won't be enough to reach emissions levels thought to be necessary to keep warming below two degrees, according to a new report (pdf) from the International Energy Agency. What's more, it could have the negative effect of delaying the deployment of renewable power sources that could help reach those targets.

The report warns that cheap natural gas could cause government support for renewable energy, which has taken the form of mandates and other incentives, to waver.

Renewable energy is supposed to become more competitive as fossil fuels rise in price, due to increasing demand. But abundant new natural gas supplies, such as in the Marcellus Shale in the United States, could help keep natural gas cheap.

The report says that "lower gas prices may put pressure on some governments to review their policies and level of support" for renewables. In a press release, IEA executive director Nobuo Tanaka said: "Its increased use could muscle out low-carbon fuels, such as renewables and nuclear - particularly in the wake of the incident at Fukushima and the likelihood of a reduced role for nuclear in some countries. An expansion of gas use alone is no panacea for climate change."

So, if natural gas does erode support for renewables, it could delay the cost reductions that come with it, making it even harder for renewable power to compete.

Natural gas could, however, be good for energy security, since natural gas is widely distributed around the world, the report said. If production were developed around the world, it would make it less necessary to rely on sometimes fickle suppliers, which in particular have left Europe vulnerable to supply disruptions.

The report notes that demand for natural gas is expected to be particular strong in China, which in its 12th Five-Year Plan called for the tripling of natural gas consumption.

Even as the health care bill grabs headlines, details are beginning to emerge about a new energy and climate bill being pieced together in Washington by trio of U.S. senators. According to Energy Washington, an eight-page outline of the bill includes provisions for something called a "cap-and-refund" approach to reducing carbon dioxide emissions.

That's a alternative to the "cap-and-trade" system proposed in a climate and energy bill that pass the House last June. The Senate version of the bill has gone nowhere, prompting John Kerry (D-MA), Joseph Lieberman (I-CT) and Lindsey Graham (R-SC) to work on a new approach. The cap-and-trade system has been effectively branded as an energy tax by those who oppose it. But a cap-and-refund approach might be more appealing. Under such a system, utilities and other emitters would buy allowances for emitting carbon dioxide, with the number of allowances capped to ensure emissions will be gradually reduced over time. Then the proceeds would be mailed out to Americans in the form of refund checks. (It's a system featured in legislation already proposed by Senators Maria Cantwell (D-WA) and Susan Collins (R-ME)).

It's likely that not all of the proceeds will go directly back to the people. As much as half could be directed to fund energy research and other government programs.

Both cap-and-trade and cap-and-refund systems can be market-based, allowing emitters to trade allowances and offering them flexibility to cut emissions in whatever way is cheapest. Economists such as Robert Stavins, at Harvard University, say that such market-based systems would be cheaper than renewable energy mandates, which restrict emitters to using renewable energy such as wind and solar when other technologies could be cheaper (such as capturing and storing carbon dioxide).

The Senators haven't formally proposed the bill yet, but it there have been indications it could be unveiled by April 15th.

The prospect of geoengineering, the intentional large-scale manipulation of the climate to offset the effects of global warming, continues to draw the attention of top scientists and policymakers. The prestigious journal Science is publishing two papers on the subject in its next issue, and next week the Science Committee of the House of Representatives will hold its second hearing on the subject.

According to some climate models, climates could change very quickly as greenhouse gas emissions rise, such as when thawing permafrost releases methane (a powerful heat-trapping gas), or loss of ice causes the earth to absorb more heat. Such outcomes might not be very likely, but even the chance that they could happen has scientists worried, as they could lead to widespread severe drought and famine and rapid sea level rise, among other things. Even the most ambitious efforts to curb greenhouse emissions might not be enough to prevent disastrous climate change, some say. And ambitious efforts to cut emissions seem ever more unlikely, after the limited success of the recent summit in Copenhagen, and opposition to a climate change bill in the Senate.

In one of the Science articles, researchers say testing of geoengineering strategies may prove necessary, but before testing can occur, they say an international agreement should be reached. Such testing could cause changes in weather patterns that could hurt some countries, for example, and an agreement needs to be in place to establish standard testing procedures and methods for dealing with international disputes arising from such testing.

Such an agreement might be even more important if the argument of another Science paper proves to be correct. In that paper the researchers argue that the only way to effectively test geoengineering is through full scale implementation of a particular geoengineering scheme--and such a large deployment could have big, unforeseen consequences.