Climate talks are underway, but saving the world might be harder than we thought

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“If I sound a little testy,” says David Hawkins, sounding testy, “it’s because I see 20 complaints a day about this idea, and I don’t think it’s very helpful at this point.” Hawkins, director of climate programs for the Natural Resources Defense Council, has been fighting a mostly uphill battle to get the American political system to deal seriously with global warming. Just in the past few months, he has seen signs of progress, including new power-plant regulations from the Environmental Protection Agency and a few cracks in the Republican Party’s monolithic opposition to action on climate change.

Leading up to the long-awaited global climate summit in Paris, starting today, both China and India have said they would be cutting their projected emissions of carbon dioxide, a major step in itself that incidentally undercuts the argument made by Sen. Marco Rubio, R-Fla., at the second presidential debate, a significant Republican talking point: that it’s pointless for America to regulate carbon emissions because the rest of the world won’t go along.

So at this critical juncture, the last thing Hawkins wants is a bunch of noisy zealots proclaiming that saving the world requires a multitrillion-dollar project not just to reduce emissions of carbon dioxide, but also to actually remove the carbon dioxide that’s already in the air. You read that right: to run some substantial fraction of the Earth’s atmosphere through a network of machines to extract carbon dioxide and put it back underground — in effect, putting the entire fossil-fuel industry, built up over a century and a half of furious industrial activity, into reverse. If so-called “net negative emissions” could be achieved easily, it would be the greatest thing that could happen to the environmental movement — and, for that matter, to the fossil-fuel industry, which would no longer be on the hook for causing global warming. But to Hawkins, the idea is at best a costly distraction from the more achievable and urgent goal of moving toward renewable, “net zero” energy sources. “We’ve got fully proven technologies that we know the costs of,” he says, “so our priority should be on making them attractive to private industry.”

So-called “carbon removal” is a step further even than the not-yet-perfected technology for “carbon capture” — scrubbing CO2 directly from power-plant flue exhaust, where it is relatively concentrated. Even that is difficult to do today at a reasonable cost — but carbon dioxide in the ambient air is 300 times more dilute, making the problem even harder (although, for technical reasons, not 300 times harder). But that’s exactly what a growing number of climate scientists are urgently calling for. The view has been gathering support at least since 2009 when scientists from the National Oceanic and Atmospheric Administration concluded that “the climate change that is taking place because of increases in carbon dioxide concentration is largely irreversible for 1,000 years after emissions stop.

Or, as Tim Kruger of Oxford University explained at a World Economic Forum conference last year, carbon dioxide levels in the atmosphere, now around 400 parts per million and rising, will remain well above the safe level of 350 by the end of this century even “if everybody on the planet dies.”

That realization has spawned a host of new university programs, such as the Oxford Geoengineering Programme, which Kruger heads; the Center for Negative Carbon Emissions at Arizona State University; and the Center for Carbon Removal at Berkeley. It has given impetus to a number of technology startups with names like Global Thermostat, Joule Unlimited and Infinitree LLC, many of which are competing for the $25 million Virgin Earth Challenge prize, established by entrepreneur Richard Branson for a workable system to remove greenhouse gases from the air. As the owner of an airline, Branson has an obvious interest in the issue: Jet planes are a significant source of carbon dioxide pollution, and a particularly intractable one since, unlike cars, they can’t run on batteries. Branson announced the prize in 2007, and although the entrants have been winnowed to 11 finalists, a winner is by no means imminent. “Hopefully we’re not on the same time scale as the Longitude Prize,” said David Addison, who coordinates the Earth Challenge for Virgin, referring to the 18th century competition to build a reliable shipboard timepiece, which lasted around half a century.

In principle, there is nothing difficult about getting carbon dioxide out of the atmosphere. Trees do it naturally, by photosynthesis, locking up carbon in their wood and leaves, which is why reforestation is one weapon against climate change, except there’s not enough land for all the trees necessary, if people still want to eat. Klaus Lackner, director of the negative-carbon program at Arizona State, has designed what he calls a synthetic tree: It uses a chemical compound that soaks up carbon dioxide from the air, then releases it when treated with water. The CO2 can be collected at high concentrations and the chemical then reused. Most other processes work on some variation of this idea: Some use either solar-powered fans to suck air past a chemical bed or chemicals that recharge themselves with heat rather than water.

Of course, the necessary scale is immense: Lackner estimates that to bring carbon dioxide levels back down to 350 parts per million would take on the order of 100 million of these machines scattered around the globe. But, he adds, although they are the size of a shipping container, they aren’t necessarily more complex or expensive than a car. The world builds 80 million cars and trucks a year.

And someday they could even make money. Carbon dioxide is a pollutant, but it is also a commodity with a number of commercial uses — in chemical synthesis, for carbonating soda, filling fire extinguishers and making dry ice. The biggest use, by far, is for injecting it under pressure into oil wells to force more oil to the surface. Even as carbon dioxide is accumulating, catastrophically, in the atmosphere, companies still mine it from underground and sell it. Delivered in bulk by pipeline, it’s worth around $100 a ton. Or you can buy it in 50-pound tanks, for which one supplier quoted a price, delivered in New York City, of around $1 a pound. At that price, the average adult gives away around $15 in CO2 every week, just by exhaling.

Since the cost of transportation accounts for a large part of carbon dioxide’s price, Global Thermostat, a startup co-founded by Columbia University physicist Peter Eisenberger and economist Graciela Chichilnisky, is developing a carbon-removal technology that can run off the waste heat of anything that burns fuel — a small generator, say, or a commercial bakery — and be located where there’s a use for CO2. Infinitree, based in New York but with a demonstration project under way in Sacramento, wants to sell CO2 to farmers. Carbon dioxide promotes plant growth. Growers already use it in greenhouses, and there’s research suggesting it can work on fruit and vegetable crops in the field. Given enough cheap energy, you can even turn carbon dioxide back into a liquid fuel that can be burned like gasoline.

But all of this technology combined accounts so far for only a fraction of the world’s emissions of CO2. And even if it could be perfected — if, say, every gallon of gasoline or ton of coal burned could be replaced by an equivalent amount of fuel synthesized from atmospheric CO2, using renewable energy from windmills and solar cells — it wouldn’t necessarily remove carbon dioxide permanently from the atmosphere. Carbon dioxide removed from the air to make fuel goes right back out when the fuel is burned, obviously. That’s better than burning fossil fuel (which adds carbon dioxide to the atmosphere), but at best it can achieve net-zero emissions — not the net-negative emissions some climate scientists think is necessary. Negative emissions require extracting carbon dioxide and getting rid of it forever. There are only a few ways to do this — by burying it underground or binding it chemically in a form that does not break down — and the technology to do that affordably on the necessary scale is still in the future.

Which explains why the issue is so sensitive for the big environmental groups and government agencies. The EPA website’s climate-change page discusses carbon capture from flue gas as one approach, but doesn’t mention ambient-air carbon removal. Most of the mainstream environmental organizations avoid discussing it. “We’re happy to see research on these approaches,” Hawkins says, “but they’re not the first order of business, which is to deploy the techniques we have today to reduce and eliminate emissions.” Lackner, for his part, considers that a head-in-the-sand position: “This is a disruptive technology in many ways,” he says, “so it’s hard to gain traction. Many in the environmental community are not aiming at solving the climate change problem as such, but stopping fossil fuels. They see any discussion about getting carbon out as a distraction from those goals. They hate the oil companies, so they don’t want carbon-neutral gasoline.” They want bicycles.

Hawkins acknowledges that part of his problem with the carbon-capture industry is the risk that people will say, “We’ve got this miracle solution, so we don’t have to do anything now, just wait 20 years for it to come to fruition.” That’s the “moral hazard” argument, referring to the temptation to take risks knowing that someone else will pick up the tab. There is also, though, what Oxford’s Kruger calls the “morale hazard”: the danger that the idea of pulling CO2 from the atmosphere, billions of tons of it, almost literally molecule by molecule, is so daunting, so improbable-sounding, and so expensive, that the political system may decide it’s beyond our capacity and essentially give up on doing anything. And that, everyone agrees, is the one thing we can’t afford.