Integrated assessment modeling of carbon removal at ICRLP

Authored by David Morrow, Director of Research, Institute for Carbon Removal Law and Policy

Bioenergy with carbon capture and storage (BECCS) is sometimes described as the only technology ever invented by modelers. There’s a grain of truth to this: the idea of combining bioenergy with CCS to produce a negative emissions technology rose to prominence because of its adoption by integrated assessment modelers in the early 2000s. Since then, these models have provided one important tool for thinking about how carbon removal might play a role in climate policy. The Institute for Carbon Removal Law and Policy is helping to push the boundaries of integrated assessment modeling of carbon removal with two ongoing projects.

What are integrated assessment models?

Before we get to ICRLP’s modeling projects, let’s back up a bit. What are integrated assessment models (IAMs)? Basically, IAMs are computer models that combine a model of the climate system with models of the economy, the energy sector, and land use to help researchers think rigorously about possible climate futures. For instance, researchers can use these models to ask questions like, “What would happen to the energy sector and the climate if coal were phased out worldwide by 2050?” or, “How would the energy sector change over time if the whole world put a gradually rising price on carbon beginning in 2040?” Researchers can also use these models to identify decarbonization pathways by which the world could meet various climate policy goals, such as the Paris Agreement’s goal of limiting global warming “well below 2°C.” When you read headlines saying that the world needs to cut its emissions in half by 2030 in order to limit global warming to 1.5°C, you’re reading a conclusion based in large part on integrated assessment modeling.

CarbonBrief offers an excellent introduction to IAMs and their role in studying climate policy. If you prefer to learn by doing, check out Climate Interactive’s EnROADS model, an IAM that’s fast enough to run in your web browser.

How are IAMs used to study carbon removal?

Integrated assessment modelers realized almost twenty years ago that they could combine two technologies that were already represented in their models—bioenergy and CCS—to model a technology that actively removes carbon dioxide from the atmosphere. Research over the past two decades suggests that developing and scaling negative emissions technologies makes it much likely that the world can keep warming below 2°C or 1.5°C. In fact, modeling studies suggest that unless the world reduces its greenhouse gas emissions extremely rapidly over the next two or three decades, it may not be possible to limit warming below 1.5C without large-scale carbon removal

Until recently, however, few integrated assessment modelers had incorporated any kind of carbon removal into their model besides BECCS and reforestation. (For some notable exceptions, see recent papers led by Jessica Strefler, Giulia Realmonte, and Jay Fuhrman.) As a result, BECCS has long operated as a kind of stand-in for the wide variety of approaches to carbon removal that have been proposed. Actually implementing BECCS at the scales projected in many IAM scenarios would likely be disastrous because it would require devoting such vast tracts of land to bioenergy. Overcoming the conceptual and technical hurdles to modeling other approaches to carbon removal would be an important step in understanding what role carbon removal can realistically play in just and sustainable climate policy.

Integrated assessment modeling at ICRLP

Earlier this year, ICRLP launched a project to produce a variant of the Global Change Analysis Model (GCAM), a major IAM developed by the Joint Global Change Research Institute. I’m working with Postdoctoral Researcher Raphael Apeaning to extend GCAM’s ability to model carbon removal. That involves both incorporating additional approaches to carbon removal, starting with direct air capture, enhanced weathering, ocean alkalinization, and soil carbon sequestration; and giving GCAM the capacity to model various policies for incentivizing and supporting carbon removal. We gratefully acknowledge the financial support of the Alfred P. Sloan Foundation for this project.

I’m also supervising an undergraduate in American University’s School of International Service, Garrett Guard, as he uses GCAM to write his senior thesis on the role of BECCS in climate policy. His thesis grew out of a research project he did for a course I taught last year on using integrated assessment models for climate policy analysis. Garrett’s research looks at what happens when the world tries to meet various climate targets if we exclude fossil fuel CCS, BECCS, or both from the climate policy portfolio, as well as how that varies across different socioeconomic pathways.

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