In the face of several studies in recent years that have concluded that solar radiation management (SRM) geoengineering approaches might pose risks to food security, primarily by altering precipitation patterns, a new study in Nature Climate Change (J. Pongratz, Crop Yields in a Geoengineered Climate, Natural Climate Change, online, Jan. 22, 2012) seeks to assess the impacts of SRM on maize, wheat and rice production and yields. The study carried out three global climate simulations, including one with atmospheric carbon dioxide concentrations of 400ppm (control), a climate with doubled atmospheric carbon dioxide concentrations, projected within this century under some scenarios, and a climate with doubled atmospheric carbon dioxide with sulphate aerosol concentrations set at levels that stabilize global temperatures at the control level.
Among the take-aways:
- In the simulation of doubled carbon dioxide concentrations relative to the control climate, there are small negative impacts on maize crop yields and production, and positive changes in wheat and rice, with warming causing most of the climate-related reductions in yield;
- SRM could lead to increases under a 2x atmospheric carbon dioxide concentration scenario, with declines in yield found only for rice in high latitudes
- Maize, wheat and rice production would be generally higher under SRM, with especially beneficial impacts in terms of reversing projected losses of maize in northern mid-latitude regions under a 2x carbon dioxide concentration scenario;
- However, there may be more marked regional changes in productivity, both positive and negative
- Individual small regions may experience reductions in yield that “may pose a risk to local food security if subsistence farming prevails and adaptation is not possible;”
- Negative regional impacts may be primarily related to the effect of precipitation changes on yields, e.g. projected weakening of the Asian monsoon, with projected precipitation decrease of 10-14% in summers
- Changes in insolation and diffuse fraction associated with SRM deployment would likely yield additional positive benefits in terms of crop production
This would be an excellent student reading in a geoengineering module. Among the questions that could be asked:
- Would it be acceptable to deploy a technology that provides benefits to most regions of the world in terms of food production even if there are some negative regional impacts? Would a system of compensation for projected crop losses tip the balance of equities in favor of SRM deployment?
- While the study indicates that “multiple-model ensemble studies should be carried out to better characterize the effect of SRM,” given the abiding weaknesses of regional models, how confident can we be of results from such studies? What level of risk and uncertainty would be acceptable in deploying SRM technologies given potentially very negative impacts;