The potential pitfalls of sucking carbon from the atmosphere


PHOTO/Carbon Engineering

Last week, Canadian company Carbon Engineering published research findings that show how carbon dioxide could be sucked up from the atmosphere for less than $100 per ton. In 2017, the world emitted some 32.5 gigatons of the stuff. But hey—baby steps.

Scientists have long speculated that so-called “negative emissions” technologies like CO2 removal could not only slow the accumulation of carbon in the air, but even reverse it. Before last week, though, all that speculation was, well, largely speculative; nobody had convincingly demonstrated how to pull off negative emissions at scale. Previous estimates had pegged the cost of sucking carbon from the skies, for instance, at $600 per ton—way too pricey to qualify as a viable cleanup solution. The findings from Carbon Engineering, which appear in the latest issue of the journal Joule, point the way toward a future in which negative emissions are not only technically possible but financially feasible.

So yeah—it’s big, significant, encouraging news. But it’s not all blue skies and rainbows.

Carbon removal technologies, promising though they may be, are overhyped, says David Keith, an applied physicist at Harvard and Carbon Engineering’s founder. “And the overhyping has become a political trick.” That hype, he says, makes it easier for policymakers to avoid drafting near-term mitigation strategies and exceed their carbon budgets, in hopes that their debt will be repaid at some point in the future. What begets this trickery? Computer simulations.

When the Intergovernmental Panel on Climate Change modeled more than a thousand scenarios in search of ways to limit a rise in global temperatures, the most propitious projections relied heavily on the assumption that CO2 removal would one day swoop in and save our collective asses: Of the 116 IPCC scenarios found to limit warming to below 2° Celsius, 101 relied on negative emissions. “It enables policymakers to claim that we’re very close to keeping global temperatures below a 1.5 or 2 degree increase, while sweeping under the rug the hard work that remains to be done researching carbon dioxide removal,” Keith says.

Many people share his concerns. As a collection of climate researchers noted in a 2014 commentary published in the journal Nature: Negative emissions’ “credibility as a climate change mitigation option is unproven and its widespread deployment in climate stabilization scenarios might become a dangerous distraction.” An essay by climate researchers Kevin Anderson and Glen Peters, published in Science in 2016, leveled even harsher criticism: “Negative-emission technologies are not an insurance policy, but rather an unjust and high-stakes gamble,” they wrote. “The mitigation agenda should proceed on the premise that they will not work at scale. The implications of failing to do otherwise are a moral hazard par excellence.”

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