Why will we need so much carbon removal? The science is clear that to stop the world from continuing to warm, we need to get emissions to “net zero.” But there will always be some remaining emissions and some greenhouse gasses will be extremely difficult and costly to fully eliminate. Our models suggest we will need at least a few billion tons of carbon removal each year to counterbalance the remaining hard-to-eliminate emissions. Emerging technologies have the potential to meet this need.
The climate, and the world, are changing. What challenges will the future bring, and how should we respond to them?
It is also increasingly likely that the world will pass 1.5 degrees Celsius — our most ambitious climate target — in the next decade or so. In the recent IPCC report, more than 96 percent of scenarios that limit warming to 1.5 degrees Celsius above preindustrial levels by the end of the century overshoot it on the way there. Once we overshoot 1.5 degrees Celsius, even getting emissions all the way down to zero will not cool the world back down. This is the brutal math of climate change, and it means that the only way to bring global temperatures back down in the future is through the large-scale removal of carbon dioxide from the atmosphere.
To date, carbon removal efforts by companies and governments have largely relied on trees and soil. But even under a best-case scenario, these can only provide around half of the removal needed. We only have so much available arable land in which to plant the number of trees we need to store enough carbon.
While carbon removal is often conflated with carbon offsets, the vast majority of offsets currently sold pay someone else to avoid emissions rather than removing carbon dioxide from the atmosphere. Offset markets are plagued by hot air, with many actors gaming the system by claiming carbon credits for actions they were already planning to take, such as building a clean energy project or not cutting down a forest they own. In one case, an environmental group even provided offsets that were sold to oil companies, making the dubious claim that they would otherwise allow the forests they own to be logged.
Permanent removals, on the other hand, are harder to game. There is little market value to permanently removing carbon dioxide from the atmosphere, so it is much easier to prove that money spent actually results in removal. And the risk of accidental rerelease is orders of magnitude smaller. That’s why the well-respected Science Based Targets initiative only allows measures that permanently remove carbon from the atmosphere to offset remaining emissions — and only alongside deep emissions reductions.
The private sector can help jump-start permanent removals by purchasing them today. For example, Frontier — a recently announced initiative — will purchase nearly $1 billion of permanent carbon removal over the next nine years to help support early-stage technologies and figure out what approaches work and can scale in decades to come. But voluntary investments by the private sector can only take us so far; ultimately, removing carbon from the atmosphere will have to be incentivized by government policy, either through a price on carbon or subsidies for carbon removal.
The scale of permanent carbon removal that will be needed to meet our most ambitious climate goals is staggering compared to the small amount of removal that has taken place to date. We are playing catch-up here, as we are on many climate fronts. We need to use this decade to figure out what works and what can scale in the decades to come: experimenting with a wide variety of approaches like direct air capture, enhanced rock weathering, ocean alkalinity enhancement, biomass carbon removal and storage, and ocean biomass sinking among others.
To tackle climate change, we need to reduce emissions as quickly as possible. But we also need to invest in bringing down the cost of technologies to remove billions of tons of carbon dioxide from the atmosphere in the future. Trees and soil are not a panacea for removing carbon. While governments should be encouraged to enhance the amount of carbon stored in trees, plants, and soil, we should be skeptical of claims that rely on temporary removals to justify additional “forever” emissions.
Zeke Hausfather was a contributing author to the IPCC Sixth Assessment Report. He is the climate research lead at Stripe and a research scientist with Berkeley Earth.
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