Since the seminal paper by the Nobel Laureate Paul Crutzen in 2006, there have been serious discussions on whether current climate change could be arrested or reversed using so-called “solar geoengineering methods” as outlined by Ken Caldeira and colleagues in 2013 and by the National Research Council in 2015. By definition, solar geoengineering refers to the intentional large-scale engineering solutions that are proposed to cool the planet by increasing the amount of solar radiation reflected by the planet.
Solar geoengineering methods are also known as solar radiation management (SRM), and in some instances, for brevity, we also use the term “geoengineering” to refer to solar geoengineering. Placement of mirrors in space, injection of reflective aerosol particles into the stratosphere, and brightening of marine clouds using sea salt aerosols are some examples of solar geoengineering methods. Hundreds of research papers have been published in the last decade by both natural and social scientists on the feasibility, effectiveness, cost, and risks, and the ethical, legal, social, political, and governance dimensions of geoengineering. In this article, we present a brief account of scientific research into solar geoengineering in India in the last decade.
Rahman and colleagues pointed out in 2018 that developing countries should have a major role in solar geoengineering research, discussion, and evaluation for political and moral reasons, as they are projected to bear the brunt of climate change: disappearance of small island nations due to sea level change, declines in food production in many parts of Asia, water stress across Africa, and major loss of biodiversity in South America. As a matter of climate justice, therefore, it was suggested that the nations that are most vulnerable to climate change should actively participate in discussions of research, ethics, and governance. Further, a southern research perspective may be valuable because the climate, ecosystem, culture, and moral values there are broadly different from those in the western world. Thus, collaborations between developed and developing countries to discuss common solutions to this problem are needed. A step in this direction is the recent call for applications by the Solar Radiation Management Governance Initiative (SRMGI; www.srmgi.org) to a $400,000 fund called Developing Country Impacts Modeling Analysis for SRM (DECIMALS), to which developing-world scientists can apply to model the solar geoengineering impacts that matter most to their regions.
At present, the desired CO2 emissions reductions to check climate change are not taking place rapidly. Almost every new study about climate change suggests that we have less time, and that the impacts are likely to be bigger and occur more quickly than we previously thought. In this context, Parker and Geden in 2016 argued that the ambitious target, set by the Paris Agreement, of limiting global warming to 1.5°C above the preindustrial temperature level is difficult to achieve without the implementation of geoengineering. One of the key aspects of solar geoengineering is that it can cool the planet rapidly; for example, modeling studies by MacMartin, Tilmes, and others in 2017 suggest that it takes only 4–5 years to reach desired temperature reductions. The cost of solar geoengineering is also estimated to be much less than the costs associated with climate change impacts such as droughts, floods, heat waves, sea level rise, etc. Many scientific bodies including the American Meteorological Society (AMS; www.ametsoc.org/ams/index.cfm/about-ams/ams-statements/statements-of-the-ams-in-force/geoengineering-the-climate-system/) have advocated research into solar geoengineering so that it could contribute to a comprehensive risk management strategy to slow climate change and alleviate some of its negative impacts. The leading proposal among the solar geoengineering schemes is the injection of aerosol precursors such as SO2 into the stratosphere to form sulfate aerosols and deflect about 1%–2% of the incoming solar radiation. Climate modeling studies have consistently confirmed that solar geoengineering can markedly diminish regional and seasonal climate change from anthropogenic CO2 emissions. Lowering of temperature by geoengineering would reduce some of the worst effects of climate warming such as sea level rise and the increase in heat waves and extreme rainfall events.
While solar geoengineering schemes such as sulfate aerosol injection are “supposedly” cheap and can rapidly cool the climate system, they do come with some undesirable side effects such as weakening of the global water cycle when implemented on a larger scale and in large magnitude, as found by several studies, including Bala and colleagues in 2008 and Tilmes and others in 2013. There could be changes in stratospheric chemistry and dynamics with impacts on the ozone layer, as shown by Tilmes and others in 2009. These schemes do not address ocean acidification, which could be detrimental to marine life, and they also commit us to maintain them for decades to centuries until atmospheric CO2 levels fall to sufficiently lower values. Further, the risk of such schemes if they fail or are halted is that the planet could be subjected to a significant warming within a very short period of time as discussed, for instance, by McCusker and colleagues in 2014: the rate of warming could be many times that of the current warming. Thus, human and natural systems could be subjected to extreme stress following an abrupt termination, although Parker and Irvine very recently argued that a resilient system could be designed against all but the most extreme catastrophes.
It is true that most of the solar geoengineering research is being done in the universities of Europe and North America. However, modest efforts have started in the developing world as well. For instance, China started its regional geoengineering program anchored at Beijing Normal University in 2015. The dialogue and research about geoengineering started in India almost 10 years ago, as evidenced by several publications from that country since 2009 on the topic. Climate modeling studies conducted in India by Bala and others have investigated the impacts of solar geoengineering on the global water cycle, extreme events, and cyclones in the Bay of Bengal. Indian researchers have been collaborating with foreign scientists in climate modeling to understand the climate processes and impacts related to the various methods of solar geoengineering.
For the billion-plus people inhabiting the Indian subcontinent, Indian climate and summer monsoon rainfall are synonyms, and an assessment of the impact of solar geoengineering on the Indian regional climate largely implies an assessment of the impacts on the monsoon. The rainfall associated with the South Asian monsoon has such a large impact on the resources of the region that even today the Indian economy is a gamble on the quantum of seasonal summer monsoon rains. A modeling study by Alan Robock and colleagues in 2008 on stratospheric sulfate geoengineering claimed “both tropical and Arctic SO2 injection would disrupt the Asian and African summer monsoons, reducing precipitation to the food supply for billions of people.” This finding of major disruptions to Asian monsoon rainfall has not been simulated in other modeling studies. Earlier and later modeling studies have consistently indicated that solar geoengineering could significantly reduce disruptions to temperature and precipitation caused by climate change. However, we caution that the regional pattern of precipitation could be altered. A 2018 climate modeling study by Nalam and others has shown that regional geoengineering such as Arctic geoengineering could shift the mean position of the Intertropical convergence zone (ITCZ) southward and reduce rainfall in the Northern Hemisphere monsoon regions, including the South and East Asian monsoons. More recent studies by Kravitz, MacMartin, Tilmes, and others in 2017 and 2018 point to new strategies that are likely to reduce some side effects of geoengineering. For instance, these studies have shown that the shift in the ITCZ can be prevented if injections are placed outside the equator and are annually controlled to reach refined global surface temperature goals.
On the issue of governance, the Council on Energy, Environment, and Water (CEEW) based in New Delhi has organized three international conferences since 2011 to discuss the governance of solar geoengineering research and technologies. The 2011 and 2016 events were held in cooperation with SRMGI. These discussions have attempted to identify the role of India in developing regional and global governance frameworks on solar geoengineering (for laboratory research, field experiments, and large-scale deployment).
The Indian government has also taken initiatives in geoengineering research. The Department of Science and Technology (DST) of India has been supporting an active climate modeling research program in geoengineering over the last five years at the Indian Institute of Science under the umbrella of a broader climate change research program. In 2017, DST launched a major research and development program (MRDP) to understand the implications of geoengineering on developing countries like India. One of the major scientific objectives of the MRDP is to study the sensitivity of the tropical hydrological cycle (particularly in the South Asian monsoon region) to stratospheric sulfate geoengineering. The research will identify and work on geoengineering-relevant climate physics problems using climate models (Fig. 1). A roundtable discussion on geoengineering funded by DST was also organized in New Delhi on 23 June 2017 to seek views of Indian experts and policymakers on the issue of geoengineering and whether and how geoengineering is likely to impact India. The meeting was attended by about 35 scientists from 14 Indian institutions, and it brought physical and social scientists together for an inclusive dialogue on geoengineering. A second roundtable meeting was organized in July 2018 in Bengaluru and was attended by about 40 participants from 17 institutions. These developments clearly indicate that India is already actively engaged in solar geoengineering research, evaluation, and discussion.
NCAR CAM4 (slab ocean) simulated equilibrium global mean (a) temperature and (b) precipitation changes relative to the preindustrial simulation. (c),(d) Corresponding changes in the tropics (20°S–20°N). In the “2xCO2” experiment, CO2 is doubled from preindustrial levels. All other experiments are geoengineering simulations where the CO2 is doubled and an amount of 20 Mt of either volcanic (prefix “Volc”; larger particles) or background (prefix “Bg”; smaller particles) SO4 aerosols are uniformly prescribed in the stratosphere around the globe. The suffix indicates the pressure level at which the aerosols are prescribed. The gray shading indicates ±2 standard deviations estimated from the preindustrial simulation. These experiments demonstrate that the smaller particles are more effective than larger particles in cooling the climate system. Also, volcanic aerosols at higher altitude are more effective. Global mean precipitation decreases in all geoengineering simulations. The tropics cool more and are drier than the global domain in all geoengineering experiments.
Citation: Bulletin of the American Meteorological Society 100, 1; 10.1175/BAMS-D-18-0122.1
NCAR CAM4 (slab ocean) simulated equilibrium global mean (a) temperature and (b) precipitation changes relative to the preindustrial simulation. (c),(d) Corresponding changes in the tropics (20°S–20°N). In the “2xCO2” experiment, CO2 is doubled from preindustrial levels. All other experiments are geoengineering simulations where the CO2 is doubled and an amount of 20 Mt of either volcanic (prefix “Volc”; larger particles) or background (prefix “Bg”; smaller particles) SO4 aerosols are uniformly prescribed in the stratosphere around the globe. The suffix indicates the pressure level at which the aerosols are prescribed. The gray shading indicates ±2 standard deviations estimated from the preindustrial simulation. These experiments demonstrate that the smaller particles are more effective than larger particles in cooling the climate system. Also, volcanic aerosols at higher altitude are more effective. Global mean precipitation decreases in all geoengineering simulations. The tropics cool more and are drier than the global domain in all geoengineering experiments.
Citation: Bulletin of the American Meteorological Society 100, 1; 10.1175/BAMS-D-18-0122.1
NCAR CAM4 (slab ocean) simulated equilibrium global mean (a) temperature and (b) precipitation changes relative to the preindustrial simulation. (c),(d) Corresponding changes in the tropics (20°S–20°N). In the “2xCO2” experiment, CO2 is doubled from preindustrial levels. All other experiments are geoengineering simulations where the CO2 is doubled and an amount of 20 Mt of either volcanic (prefix “Volc”; larger particles) or background (prefix “Bg”; smaller particles) SO4 aerosols are uniformly prescribed in the stratosphere around the globe. The suffix indicates the pressure level at which the aerosols are prescribed. The gray shading indicates ±2 standard deviations estimated from the preindustrial simulation. These experiments demonstrate that the smaller particles are more effective than larger particles in cooling the climate system. Also, volcanic aerosols at higher altitude are more effective. Global mean precipitation decreases in all geoengineering simulations. The tropics cool more and are drier than the global domain in all geoengineering experiments.
Citation: Bulletin of the American Meteorological Society 100, 1; 10.1175/BAMS-D-18-0122.1
In the coming years, we envision an expansion of scientific capacity in geoengineering research in India. Such research in the country should focus on identifying if geoengineering would adversely impact the natural systems in India. Investigation into the robust response of the monsoon and Indian hydrology (represented by precipitation, evapotranspiration, and runoff) to solar geoengineering should be the top priority areas in this direction. Field experiments that study monsoon clouds, aerosol–cloud interaction, and intrusion of tropospheric aerosols into the stratosphere could provide crucial region-specific information on albedo modification. Indian climate scientists could use the Earth system model that is currently developed by the Indian Institute of Tropical Meteorology for performing solar geoengineering simulations to generate locally produced knowledge on the effects of geoengineering on the Indian climate.
One relevant issue of societal importance is to assess the ability of solar geoengineering to reduce the intensity of heat waves in the premonsoon season in India that cause thousands of deaths each year. Research should also assess if geoengineering would be beneficial to the regional forestry and agriculture sectors by reducing heat stress and extreme rainfall events, and to coastal zones by preventing regional sea level rise in India.
Glacier modeling studies should assess if solar geoengineering would help to reduce the accelerating mass loss in the Himalayan glaciers and avert the looming water crisis in the Himalayan valleys, where people heavily depend on the low-altitude glaciers for their water resources. The robustness and uncertainty in impacts should be assessed by using data from multiple climate models that participate in climate model intercomparison projects, such as CMIP6 (Coupled Model Intercomparison Project phase 6) and GeoMIP6 (Geoengineering Model Intercomparison Project, so named to be consistent with CMIP6), and output from the new Geoengineering Large Ensemble (GLENS) project. Research should also include large-scale engineering techniques to remove pollutants such as PM2.5 (particulate matter that has a diameter of <2.5 µm) from the polluted air in urban and industrial areas; the techniques are likely to be different from solar geoengineering.
Solar geoengineering is a controversial idea, and it may be societally and institutionally infeasible, as it is riddled with moral, ethical, legal, and challenging governance and political issues. In 2016, Morton provided an excellent account of the complex societal issues surrounding geoengineering. However, it may be worthwhile to develop an improved scientific understanding of the processes involved in geoengineering and its possible implications, globally as well as regionally. That is why several international agencies and scientific bodies, such as the U.S. National Research Council, the Royal Society, the American Geophysical Union, and AMS, have advocated research (but not implementation) into geoengineering. Our view is aligned with the position taken by these scientific societies, and thus we are of the opinion that India should also continue to engage in scientific research on geoengineering while its policy on the issue may be evolving. Further, we believe that geoengineering modeling research is indistinguishable from basic scientific research into climate change.
To conclude, solar geoengineering is not a panacea for all the adverse effects of climate change. It is not a substitute for CO2 emissions reductions, and it may never be implemented. Because solar geoengineering is entangled in a complex web of societal, moral, ethical, political, legal, and governance issues, it is certain that social scientists will have a central role in geoengineering discussions. Scientific research must, however, continue, and the global south, including India, should be actively engaged in solar geoengineering research, evaluation, and discussion.
ACKNOWLEDGMENTS
The grant (DST/CCP/MRDP/96/2017(G)) from the Department of Science and Technology for supporting the climate modeling research program in geoengineering is gratefully acknowledged. The authors thank Dr. Krishnamohan for technical assistance in drafting the figure for this article.
FOR FURTHER READING
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