“We Need To Take CO2 Out Of The Sky: To Keep below Two Degrees, We’ll Need to Dramatically Reduce Current Emissions and Simultaneously Remove 10–15 Gigatons of CO2⁄yr from the Atmosphere by 2050. Read on for What That Means, Why, and How We Might Do It.”, 2020-02-22 (; backlinks; similar):
We’re putting enough of these gases into the sky that we’re changing the thermal properties of the atmosphere, trapping more heat. This is the greenhouse effect, which is the main contributor to climate change…There’s international agreement around 2℃ as maximum acceptable risk. With that in mind; there are two general approaches to keep warming to below a certain level:
Reducing emissions
Removing previous emissions from the sky
If you remember one thing from this piece, it should be that we need to do both. Gone are the days where optimistic emissions reductions kept us below a 2-degree warming target.
How to take CO2 out of the sky: For a more comprehensive but still accessible overview, I recommend Adam Marblestone’s Climate Technology Primer and primary sources in my Negative Emissions Reading List, especially the Summary section of the National Academies Report. Stripe’s Negative Emissions Commitment blogpost includes a brief overview of these and other technologies as well as some important context on adoption curves.
Briefly: there are plant-based, mineral-based, and chemical options:
Trees and forests
Direct air capture (DAC) + sequestration
Doing things with biomass: Bio energy with carbon capture and storage (BECCS) and Biochar
Enhanced weathering and carbon mineralization (For a more technical overview of this topic, I highly recommend “An Overview of the Status and Challenges of CO2 Storage in Minerals and Geological Formations”.)
Conclusion:
10-gigaton-scale negative emissions are necessary in essentially every emissions reduction scenario. We have no choice but to fund, research, and deploy them if we’re serious about keeping warming to 2°; or close to it. We are not even close to on track.
Negative emissions have been dramatically underfunded in proportion to their importance. This needs to be fixed if we’re going to have a shot at reducing the cost enough to make 10-gigaton-scale deployment possible by mid-century. It will take likely take years or decades for basic research and pilot projects to scale and get cheap enough; so we need to start right now.
It’s very unlikely any one category of technology, or any one natural approach, will scale enough. We should think of a portfolio across all the approaches outlined here, as well as more I didn’t discuss or have yet to be discovered.
We face the defining problem of our generation; of the entire human project thus far. Climate spans physics, chemistry, ecology, geology, policy, technology, land use, human rights, and more. It’s time we take this seriously as a gigantic opportunity for human progress, and rally to solve it!