If you had to choose only one type of climate action to bet the planet on, it would probably not be carbon dioxide removal.

Rather, to stop the planet from getting ever hotter, we need to stop emitting carbon dioxide by burning fossil fuels for things like electricity, heat, and transportation. CDR, as it’s known, is a lousy substitute for this—no amount of tree planting, carbon-sucking machines, or crafty accelerated geologic processes can realistically compensate.

Yet to avoid the worst impacts of climate change, we need some amount of CDR. Indeed, the longer we delay, the more of it we’re depending on.

That’s one upshot from the latest edition of The State of Carbon Dioxide Removal, out this month from a team of researchers from the University of Oxford, the University of Wisconsin–Madison, and various institutes in Germany and Austria.

The report merits a close read. In discussing its findings, the authors circled a particularly knotty problem: For CDR to scale up meaningfully, it needs demand, likely driven by government policy. For this to work, it also needs ways to safeguard its credibility—a proposition that is anything but straightforward.

Monitoring, Reporting, and Verification (MRV)

The challenges of proving a CDR project is having a worthwhile impact for the climate are multifarious. For one thing, some approaches are more durable than others; yes, a tree takes in carbon dioxide from the air and stores it, but how long until that tree dies, or potentially catches fire? Avoiding double-counting is another problem. Then there are issues with lifecycle analysis.

The different approaches to CDR—the report considers 15 in all—often produce emissions of their own. For instance, planting seeds for an afforestation or reforestation project might involve a tractor. If that tractor is burning diesel, how does that cut into the project’s overall climate benefits? A similar question might apply if you’re using energy to run a machine to crush rocks for an enhanced rock weathering project.

This is just part of the headache with MRV, or monitoring, reporting, and verification of CDR. Another is that there isn’t one clear-cut standard for how things should be done—rather, the report identified 102 of them—and 40 percent of these protocols were developed in just the last two years.

Getting MRV right is crucial to protecting what one report author called CDR’s “social license,” which is key for demand to keep scaling and improving different approaches. 

One thing that might help clarify all this, the authors note, is a forthcoming CDR methodology report from the IPCC—currently slated for release in 2027. We’re all waiting.

Interested in CDR?

If you're curious about the wonky world of carbon dioxide removal—why we need it, why we'd do well to rely on it as little as possible, the different approaches, and the challenges with MRV—we have just the thing. We've made the reading material for our entire class on CDR free.

Think of this as the CDR chapter in the online textbook that accompanies our 12-week Learning for Action climate fellowship. Fellows also get regular live discussions with interested peers, instructors, and experts to help grow their knowledge of CDR—and a whole lot of other climate solutions.

New cohorts of the Learning for Action course start regularly, so don't wait to apply. Financial aid is available.