The National Research Council (NRC) is underscoring the need to reduce emissions of carbon dioxide before exploring ways to modify Earth’s climate. Altering the climate, sometimes called geoengineering, would require significant additional research and global coordination, NRC concludes in two reports released on Feb. 10.
The first priority should be cutting greenhouse gas emissions, NRC says. Next, the possibilities for altering the climate are carbon dioxide removal (CDR) and solar radiation management (SRM), the reports say.
Neither of these theoretical approaches to address climate change has ever been scientifically tested or applied in the environment.
CDR involves several strategies. They include increasing the uptake of atmospheric CO2 by boosting photosynthesis through land management strategies and ocean iron fertilization, burning of biomass for energy coupled with carbon capture and storage, and direct air capture of CO2. In contrast, SRM would involve injecting sulfur dioxide or other gases into the atmosphere to reflect the sun’s rays into space and thus reduce solar warming of the planet.
If more fully developed, CDR has the benefit of removing the causes of climate change and ocean acidification. In contrast, SRM would only offset the warming effects of greenhouse gases and not stem acidification from ocean uptake of atmospheric CO2, the reports say.
Methods for cutting greenhouse gas emissions are far more developed than either possibility for intervening in the climate, the NRC reports emphasize.
“Environmental risks vary among CDR approaches but are generally much lower” than the risks associated with SRM, the reports say. “However, it is also less risky environmentally to avoid a given CO2 emission to the atmosphere than to emit it with the expectation that it will be purposefully removed from the atmosphere at some later time.”
The NRC committee that compiled the reports urges policymakers to first reduce emissions, next explore CDR, and only then move to examine the potential of SRM after significant research and monitoring. “The Committee considers it to be irrational and irresponsible to implement [SRM] without also pursuing emissions mitigation, carbon dioxide removal, or both.”