India and Atmospheric Sulfate Injection: a Double-Edged Sword

How the leading proposed geoengineering method could spark conflict where the world needs cooperation.

By Thomas Lutken

As the impacts of climate change become more apparent, many in the environmental community are turning towards the intentional manipulation of Earth’s climate to counteract the problem. One frequently touted method is atmospheric sulfate injection, which could cool our warming planet. However, the limitations of the technology should temper hopes of a miracle cure for climate change. Additionally, care must be taken that unintended side effects do not create divisions in the global effort to combat the climate threat.

Geoengineering is the manipulation of the Earth’s natural processes to change them. India has experimented with geoengineering in the past. As recently as 2005, several Indian states used cloud seeding to increase local rainfall. Geoengineering solutions to stop climate change primarily come in two forms - carbon dioxide (CO2) removal and solar radiation management.

CO2 removal methods range from simply planting trees to pumping liquid CO2 deep underground. Some researchers even propose fertilizing patches of ocean to cause a bloom of algae, whose bodies would then sink, sequestering carbon on the ocean’s floor.

Solar radiation management, on the other hand, is reducing the amount of the Sun’s energy that hits the Earth’s surface. This can be done in a few ways, but the most frequently proposed idea is atmospheric sulfate injection. This is also one of the most controversial geoengineering options, and the one with the most relevance to India.

The idea behind atmospheric sulfate injection is to inject small airborne particles (aerosols) into the stratosphere. These particles will reflect a small percentage of the Sun’s energy back into space, thereby cooling the planet. By inserting these aerosols above the troposphere (where rainfall occurs), they can stay in the atmosphere for about two to three years.

The “proof of concept” for this method exists in volcanic eruptions. Mt. Pinatubo erupted in June 1991, on the island of Luzon In the Philippines. This sent 2.4 cubic miles (10 cubic kilometers) of material into the atmosphere, reaching heights of 25 miles (40 km). Part of this cloud included 15 million tons of sulfur dioxide. The particles stayed there for two years, and the climate effects were clear; over the next 15 months Earth’s average temperature decreased by about one degree Fahrenheit, or 0.6 Celsius.

According to one study, by sending specially designed high-altitude airplanes on roughly 4,000 total sulfate injection missions a year, humans could replicate this same level of cooling. This has the potential to offset half of the warming expected over the study’s 15-year period and counteract billions of metric tons of CO2 emissions each year. At a cost of around $2 billion annually, even medium-sized economies could afford such a program. This price tag would also be far less expensive than the potential impacts of climate change. Take the United States: the 2018 US National Climate Assessment Report estimates the impacts of climate change damages will amount to “hundreds of billions of dollars annually” by 2090, making atmospheric sulfate injection an appealing solution.

Despite the climate cooling benefits of this technique, there are still possible side effects. The Intergovernmental Panel on Climate Change, for example, cites ozone depletion as a possibly harmful consequence of sulfate injection, which could undo decades of ozone recovery. Sulfate injection also fails to address ocean acidification, since the concentration of atmospheric CO2 will remain high and on an increasing trajectory.

Most relevant to India is the effect of these sulfate injections on global rainfall patterns. A recent study finds volcanic eruptions in the tropics decrease monsoon rainfalls, causing “a significant impact on rainfall distribution, water resources and the ecosystem.” Similarly, sulfate injection has the potential to alter India’s monsoon, leading to widespread crop failures in a country which relies heavily on its agricultural economy. If the international community began sulfate injections to address climate change, it would likely force India away from any cooperation and could even spark counter-geoengineering efforts from India.  If we are to use sulfate injections to slow climate change, India is a necessary and integral partner to that process.

Atmospheric sulfate injection could be a part of our solution to the climate crisis, especially as global CO2 emissions continue to rise. Because of the potential for harmful side effects to developing nations, care must be taken to ensure we don’t create division. The international community must cooperate to solve climate change and cannot afford to alienate critical partners like India. Sulfate injection must be better understood before it becomes part of the cure for climate change.

Thomas Lutken is a research intern with the Wadhwani Chair at CSIS. In this role, he has worked on Indian electricity policy and electric mobility. After CSIS, Tom will be moving to the National Bureau of Asian Research, continuing his career as a project associate studying energy and environmental affairs.