How much carbon dioxide removal do we actually need?

Sucking carbon from the sky is a key climate solution. But how much we lean on it depends on our political choices.

Ships pass in front of smokestacks belching smoke and steam into a cloudy sky. The light is hazy.
Laying a strong foundation that brings more people into the CDR fold will open up options for how it’s deployed, including how much we need.
Chris LeBoutillier / Unsplash

Silicon Valley’s favorite climate solution is still decades away from being deployed at scale, if it will ever be ready. Yet the moment carbon dioxide removal is having right now is really something to behold.

Over the past few weeks, the Intergovernmental Panel on Climate Change offered up an extensive chapter on sucking carbon from the sky, and Big Tech and venture capital committed more than $1.2 billion to it in two separate announcements last week. “There's never been a better time to start a carbon removal company!” Ryan Orbuch, Lowercarbon Capital’s carbon removal lead, tweeted while announcing the VC firm’s $350 million fund.

Indeed, there’s a lot of money out there and a lot of interest in a climate solution we know we’ll need in some form. But as we enter the era of exploring carbon removal in earnest, it’s worth asking just how much we need — and what “need” even means.

It’s a matter of scale

There’s no shortage of ways to pull carbon from thin air. Planting trees is perhaps the most basic way to do it, though even that comes with complications. There are exotic solutions, too, like growing kelp, adding crushed up rocks to soil, growing crops and building fanciful machines. Some companies turn that captured carbon into oil or rocks that can be stored underground while others reuse it for things like vodka. (Believe it.)

Yet all these efforts currently sequester a few thousand tons of carbon dioxide a year. All the money pouring into carbon dioxide removal — known as CDR in the climate world — would help scale up these nascent efforts or spark new ones. But right now, in a world where more than 36 billion tons of carbon dioxide were emitted last year, it’s the equivalent of using an eyedropper to bail out the Titanic.

We need a full-blown pump system in addition to a crew working 24/7 to repair the breach in the atmosphere’s hull if we’re going to keep from drowning. How fast that crew gets to work on the hull will be one of the deciding factors in how much CDR we need.

The IPCC report identifies the tools we need to do the repair work, including the usual climate solution suspects: renewable energy, battery storage, electric vehicles, reduction in energy demand and a slew of other tools we have available to us right now. The IPCC shows we need financing for stuff to increase anywhere from three to six times over current levels to get on the right track. Policies that support more rapid renewable deployment and provide people with options to live lower-carbon lifestyles — or in the case of the rich, forcing them to reduce their profligate carbon footprints — are also vital to ensuring this decade doesn’t put us further behind the eight ball. And the report makes it clear we need to rapidly phase out the use of fossil fuels.

All this will still only get us part of the way to staving off the worst impacts of climate change. The IPCC also shows that by midcentury, we’ll need to rapidly scale up CDR. Using modeling, the report calls for removing about 5.8 billion tons of carbon dioxide from the atmosphere by 2050 through a variety of techniques. That assumes we limit warming to 2 degrees Celsius, the main Paris Agreement target.

It’s also political

Choosing that as a target is a political choice, though. Another report from the IPCC published in 2018 showed the difference between 2 degrees and 1.5 degrees Celsius of warming is life and death for hundreds of millions of people as well as ecosystems throughout the world.

The IPCC isn’t the only game in town, however. Other groups have included carbon removal in their modeling. Another assessment from the United Nations pegged CDR needs at 10 billion tons a year by midcentury. Shell — yes, that Shell — puts it around the same total.

The underlying assumption in models calling for CDR is that we keep burning fossil fuels for longer. To revisit our boat analogy, the assumption is we take our sweet time repairing the breach, forcing us to rely on a more elaborate pump system we don’t have the instructions to even build in the first place.

Toly Rinberg, an applied physics doctorate student at Harvard, said that these high numbers are “weaponized by polluting interests” to constrain how we think of the future — and the present.

“People calling for 10 or 20 gigatons of removal per year, why are they doing that?” he asked. “It reduces political pressure to decarbonize.”

Rinberg, along with fellow applied physics doctorate student Andrew Bergman, took a different “bottom-up approach” in “Carbon Dioxide Removal Primer,” a book and website, published last year. Rather than modeling a bunch of scenarios where the oil keeps flowing, the analysis looked at what are known as “hard-to-abate” emissions. That is, sectors of the economy like air travel and cement manufacturing that are going to be tough decarbonization nuts to crack. That yields a far lower — and by Bergman and Rinberg’s own estimation, “conservative” — range of 1.5 to 3.1 gigatons of carbon we’ll need to remove from the sky each year.

What these ranges show is that the idea of what we “need” when it comes to CDR isn’t set in stone. Bergman told Protocol any attempt to say we “need” a certain amount of carbon being pulled from the sky “merges a political choice that's complicated with a technical limit that makes one sound like the other and that undermines our ability as a society to actually talk about the choices.”

The same is true in letting Silicon Valley dictate the terms of the nascent industry. “Right now, the trajectory of scalability of this industry is not on track to be in the public interest,” Rinberg said.

Bergman added that a way to get it on track would be startups having community members where CDR projects are sited on their actual board and not advisory boards or companies like Stripe and Microsoft that are buying carbon removal services voicing support for unionization efforts at startups or mandating certain labor practices.

Ultimately, laying a strong foundation that brings more people into the CDR fold will open up options for how it’s deployed, including how much we need. The same is true for the climate solutions we have available now. And the track record isn’t super great so far. But there’s never been a better time to turn a page.

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