James Temple quotes me in a story on a new LLNL/ClimateWorks report on California’s 2045 carbon neutrality goals. Although I like a lot in the report, I also have some concerns:
For one, Carnegie Institution researcher Danny Cullenward warns that the three major levers in the plan—land use, direct air capture, and hydrogen from biomass—are all “untested at scale.” He adds that the study may overestimate how cheap direct air capture will become and how much carbon the state’s forests and soils are likely to store. After all, in some recent years, including the major wildfire season of 2018, California’s forests have produced more carbon dioxide than they absorbed.
Cullenward also says reaching carbon neutrality presumes that California will achieve its goals in cutting emissions from electricity, transportation, and other sectors we know how to clean up. At the current rate of reductions, however, the state will miss its 2050 decarbonization target by a century.
There’s a lot to like in the new report, and I’m in complete agreement with lead author and LLNL senior scientist Roger Aines, who says now is the time to start working on negative emissions strategies.
But the report’s discussion of forest carbon isn’t sufficiently rigorous. It relies on an extremely optimistic study from researchers at The Nature Conservancy (Cameron et al., 2017, PNAS). My colleagues in the ecology community have repeatedly questioned how realistic these forest carbon scenarios are, and in any case the LLNL report doesn’t include climate feedbacks like drought, fire, and disease that make forest carbon storage a particularly challenging prospect in the Western U.S.
As a result, I’m inclined to write that part of the report off and focus on its main moving parts—negative emission technologies using biomass wastes from forest and agricultural systems, as well as novel direct air capture technologies. After all, these strategies produce about 100 of the 125 million ton CO2 per year negative emissions potential the report identifies for 2045, so they constitute the bulk of the study’s findings.
On these fronts the report provides a helpful roadmap for discussion. Not only will we need some or even all of these negative emissions technologies to work, but unlike most of the offsets-oriented discussion of forest carbon, these technologies could be deployed in California to deliver local jobs and economic benefits. Technology strategies with these features are much more realistic and robust—both in terms of the domestic prospects and the potential to inspire climate followers—so there’s a lot to like here.
Congrats to the LLNL team for an important contribution.