The idea that we might be able to "geoengineer" the planet to purposefully change the climate has clearly moved from the fringes into the mainstream. Momentum has been building in recent years: an essay in an academic journal by a Nobel Prize winning scientist in 2006, articles in the Wall Street Journal and Foreign Policy, a largely private gathering of researchers at Harvard.

Recently things have really broken out. In addition to multiple articles and books in the popular media, the United Kingdom's Royal Society, the authoritative national academy of science there, issued an in-depth review of geoengineering and President Obama's science advisor, John Holdren, has repeatedly stated that geoengineering must be on the table as a possible approach to addressing climate change.

Yesterday, the House of Representatives' Committee on Science and Technology held a hearing that its chairman, Bart Gordon (D-TN), said was, "the first time that a congressional committee has undertaken a serious review of proposals for climate engineering."

Gordon was quick to say that this doesn't mean he supported geoengineering, and that the consensus at the hearing seemed to be that no one should deploy geoengineering until we've done a lot more research. But the very fact of the hearing confirmed that influential people are starting to take geoengineering very seriously. It's no longer just a subject for gee-whiz fascination, with science-fiction-like scenarios such a vast parasol launched into space to shield the earth from the sun. Now scientists are formulating detailed research plans, start-ups are inventing new geoengineering technologies, and politicians and foreign policy experts are considering what all of this might mean for international relations.

So, why the sudden enthusiasm for proposals to tinker with the climate? These ideas aren't new, but until recently they've been largely kept under wraps while attention has been focused on reducing greenhouse gas emissions. There are probably three main reasons for the change. First, some view geoengineering as a cheap way to avoid costly conversions to zero-emissions technology, a potential technological fix that could help them stave off climate legislation. With geoengineering as an option, they argue, there's less of a rush. We'll just cool the planet until we can get around to switching to cleaner forms of energy.

But this could be mind-blowingly stupid. One of the most popular geoengineering approaches--shading the earth with a haze of sulfate particles in the upper atmosphere--would very likely lead to severe droughts. There are other potential side effects, but a purposeful act that causes the failure of crops for potentially hundreds of millions or billions of people could also lead to international conflict. Even geoengineering enthusiasts have admitted there's a chance of war.

The second reason why geoengineering is getting a serious hearing is that scientists are growing increasingly concerned that, even if we commit to drastically cutting emissions, we've already waited too long. By the time we actually reduce emissions, enough greenhouse gases will have accumulated to cause serious climate disasters. We may need geoengineering, then, in addition to fast cuts in emissions.

The third reason is that geoengineering is cheap, so cheap that a wealthy individual could do it. There's growing concern that unless we develop a science-based international consensus about the real dangers of geoengineering, someone will go off and do it on their own.

These last two reasons seem to have been in the back of Gordon's head during his opening remarks. "Geoengineering carries with it a tremendous range of uncertainties, ethical and political concerns, and the potential for catastrophic environmental side-effects. But we are faced with the stark reality that the climate is changing, and the onset of impacts may outpace the world's political and economic ability to avoid them," he said. "This issue is too important for us to keep our heads in the sand. We must get ahead of geoengineering before it gets ahead of us."

Not everyone is taking things seriously though. Just before the committee got underway, the ranking Republican on the committee, Ralph Hall (Texas), turned to Gordon and asked, "You can stand a little fun about that outrageous thing we're going to talk about today?" Then, during the hearing he compared geoengineering to "flying elephants."

Last week researchers and policy experts gathered at MIT to talk about geo-engineering--a subject that's becoming more popular in the face of concern over inaction on climate change.

The upcoming United Nations climate change convention in Copenhagen seems unlikely to produce the binding and stringent agreement needed to sharply curtail greenhouse gas emissions. Meanwhile, greenhouse concentrations continue to mount, driving scientists who were once opposed to the idea of tinkering with the planet to reconsider it.

Now they've got another reason to be worried. Earlier this year a climate bill that would've limited greenhouse emissions and helped renewable energy sources compete with fossil fuels seemed well on its way. In June a version passed the House. But then other matters--mostly health care reform--distracted Congress, and a Senate version of the bill got bogged down. The Senate recently took up the bill again, but yesterday a report in the Washington Post declared that "there is almost no hope for passage" of the bill.

Democrats are divided over the bill, and Republicans have been vocally opposing it. If the report is right, countries meeting in Copenhagen will have even more reason to criticize the U.S. for inaction, and to use that as a reason to delay a climate treaty or water it down.

That's one way to look at it, at any rate. Here's another: Copenhagen is probably doomed already--why the rush to push legislation through? That's essentially what Republican Senator George Voinovich (Ohio), who opposes the current bill, reportedly said last week, "Wouldn't it be smarter to take our time and do it right?"

It certainly is hard to be against getting something right. But will slowing things down lead to a better climate bill? Probably not, as long as the chief objection is that the bill will make energy more expensive, something that seems unavoidable. But if the delay can lead to a better system for distributing those costs equitably, and if along the way inefficient subsidies can be weeded out and emissions caps tightened (wishful thinking?), it could be worth the wait.

The Advanced Research Projects Agency-Energy (ARPA-E) is finally getting off the ground. Although created during the Bush administration, the agency only recently got its first director and this week its first funded projects were announced. But there are serious questions about whether the agency can succeed.

Its mission is to identify "revolutionary advances in fundamental sciences," then translate these advances into "technological innovations," particularly in areas where industry won't do this on its own because the technology is considered too risky. In some ways ARPA-E is supposed to be for energy technologies what DARPA (Defense Advanced Research Projects Agency) is for the military. That agency had its hand in the development of a number of revolutionary new technologies, including Arpanet, the precursor to the Internet.

The first batch of ARPA-E projects is certainly fascinating. It includes projects that could improve the performance of current energy technologies by many times, slashing the cost of solar panels and batteries, for example. If they succeed, the world could be a different place. Renewable energy could out-compete fossil fuels without the help of subsidies and long-range electric cars could become widely affordable, challenging the dominance of the internal combustion engine.

By design, the program managers at ARPA-E have picked risky projects. But have they picked the best risky projects? That would require reviewers that have an unusual combination of skills and experience. Ideally you'd have people who are both the very best scientists in their fields and who have had extensive experience in industry. The latter is particularly important because academics often aren't privy to the latest advances in industrial labs. They sometimes publish work tackling problems industry has already solved. Conversely, people with only industrial experience might not be open to radically new ideas as an academic free to explore longer-term, and riskier, possibilities.

The problem is that the ARPA-E process, by necessity, disqualified some of the very best potential reviewers. Many brilliant academics are likely to have founded their own companies that might compete with applicants. Quite rightly, those connected with potentially competing companies were banned as reviewers--but as a result, some of the best potential technologies may have slipped through the cracks, while some companies that have almost no chance of success may have received money.

The other issue is in the difference between the energy industry and the military. The military is willing to pay top dollar for radical technologies that give it a significant advantage. It's also more authoritarian--it can dictate changes from the top.

In energy, you've got to create technologies that are cheap and convenient enough to take on entrenched fossil fuel power plants and internal combustion engines and so on, which already have extensive infrastructure in place. You've also got to produce something that utilities--which are extremely risk averse--are willing to take on. And you've got to deal with consumers who are reluctant to change their routines.

All this could mean some really exciting possibilities simply won't work--because the materials required are too expensive, for example, or can't be found in large enough quantities, or because the technology would require consumers to change habits too much. For example, a very cheap and efficient new engine might not succeed if it requires consumers to take the simple step of filling two separate fuel tanks with two different fuels. The point is that projects funded DARPA-like, with an eye for really radical ideas, might lead to technologies that won't succeed in the market.

So, anyway, these are the challenges--and I'm curious what people think about them. I know for example that some people have good arguments as to why the energy industry versus the military differences might not really be a big problem--I just can't remember those arguments, or where I heard them.

And having just enumerated the challenges, I still can't help but be excited about these ARPA-E projects. Maybe they'll all fail. But if even one succeeds it could transform society. So in the next several weeks, look for a series of stories from TR digging into some of these projects.