Scientists reject aerosol geoengineering
[NEW DELHI] Geoengineering schemes that could help some countries deal with global warming could have the opposite effect in others, according to a study.
Geoengineering refers to large-scale interventions, such as capturing greenhouse gases, aimed at tackling global warming. Some climate scientists have suggested adding aerosols to the atmosphere to deflect the sun's rays in what they call 'solar radiation management' (SRM).
Previous studies only examined a small number of scenarios for SRM and did not look at how those impacts would differ on regional level.
But a study published in the August issue of Nature Geoscience examined the effects of 54 different approaches to deflecting solar radiation on 23 macro-regions of the world and found that the impacts of SRM could vary at regional levels.
Pumping aerosols into the atmosphere, for example, would have different effects on climate in China and India. The differences would grow with time, posing challenges to international governance of such interventions.
The analysis showed that while a given action could restore climate in both countries to the baseline before man-made global warming, by the 2070s, the strategies needed to achieve the same results in different countries would conflict with each other.
"Our results demonstrate that not only would 'optimal' SRM activities imply different things for different regions, but that international negotiations over the amount of SRM could become inherently more difficult the longer such activities were used," the paper said.
"It is a far-fetched assumption that a single engineering intervention will alter the overall dynamics of such a complex system," Anand Jayaraman, director of National Atmospheric Research Laboratory in India, told SciDev.Net.
He said scientists first need to fully understand the system, and then improve prediction of the monsoon that is crucial to the agriculture, before working out geo-engineering solutions to global warming.
"Projections of climate change at the local and regional scale is a challenging task," Govindaswamy Bala, professor at the Centre for Atmospheric and Ocean Sciences at the Indian Institute of Science, Bangalore, who was not involved with the study, told SciDev.Net. "This is where the knowledge gap exists for both climate change and geoengineering research."
"We should note that this is a single modelling study," Bala said. "Comparison of multiple models will be required to test the robustness of results obtained in this study."
Nature Geoscience doi: 10.1038/ngeo915 (2010)