There is considerable debate regarding the effectiveness of Solar Radiation Management (SRM) in mitigating global warming, with opponents arguing that it may be a “dangerous game.”
According to Reuters, as the world struggles to move away from fossil fuel combustion, scientists are exploring whether atmospheric geoengineering could help limit global warming and avert climate disasters.
One potential method—Solar Radiation Management (SRM)—aims to reflect sunlight back into space, with the most prominent proposal being the spraying of sulfur dioxide (SO2), a cooling agent, into the upper atmosphere.
There is significant debate about the effectiveness of this method—voices from the U.S., Europe, and various environmental groups have raised concerns about both opportunities and risks. Currently, discussions are largely theoretical, and there are only a few small-scale projects being implemented.
Heatwave in Miami, Florida (USA), June 26, 2023. (Photo: AFP/TTXVN).
What is the Current Stage of the Technology?
The idea of injecting SO2 into the atmosphere is not new.
The U.S. National Academy of Sciences proposed this concept as early as 1992, while scientists noted that volcanic eruptions release large amounts of SO2 into the air, which has a cooling effect on the planet.
Efforts to eliminate SO2 as a harmful air pollutant in China and elsewhere over the past decade have reduced its cooling effect and the “visible” heat caused by greenhouse gases, contributing to rising global temperatures.
The startup Make Sunsets, based in the U.S., is one of the few commercial ventures involved in this field. Last year, it released two weather balloons containing SO2 in Mexico, prompting the Mexican government to ban this activity in January.
Company founder Luke Iseman told Reuters that initiating projects in the U.S. is “simpler.”
However, aside from Make Sunsets, there have been only a handful of other research projects, including the release of high-altitude weather balloons in Southeast England in 2022 to test the viability of aerosol spraying devices.
Other projects have been canceled due to public opposition, including a joint venture between Harvard University and the Swedish Space Corporation in 2021.
Research has been conducted on less hazardous SRM technologies, including marine cloud brightening, which involves spraying seawater from ships to make clouds reflect more light.
While these methods are less invasive and less likely to cause harm compared to stratospheric aerosol spraying, they may be more expensive and energy-intensive—according to Benjamin Sovacool, a Professor of Earth and Environment at Boston University, who has researched the feasibility of deploying these methods at the Great Barrier Reef.
What Concerns Do SRM Opponents Have?
According to Reuters, dozens of scientists are calling for a “comprehensive international assessment” of the use of SRM to understand the associated risks and the regulations that may be necessary for broader implementation of this technology.
In a letter published in February, they argued that it may be challenging to reduce or eliminate carbon emissions quickly enough to keep temperature increases below 2 degrees Celsius, and that SRM interventions may be needed to avert climate tipping points.
Opponents of this method argue that while sulfate aerosol spraying may cool the planet, the side effects could be even more devastating.
A group of 60 scientists launched a global initiative last year to persuade governments to ban outdoor solar geoengineering experiments.
The group warned that the risks of SRM are too great and could impact weather patterns, agriculture, and “the provision of basic food and drinking water needs.”
Severe heat in New South Wales (Australia), March 2023. (Photo: AFP/TTXVN).
Critics point to models suggesting that SRM could disrupt monsoon patterns and cause droughts in Africa and Asia. Others argue that it could also slow the recovery of the ozone layer or lead to dangerously increased acid rain.
The United Nations Environment Programme (UNEP) warns in a report released this year that this technology could even be weaponized, creating new security and geopolitical threats.
Opponents also fear that this technology could be used as an excuse to delay the transition to net-zero greenhouse gas emissions.
Importantly, even if SRM interventions successfully reduce temperatures, they will not address other consequences of increased CO2 levels, such as ocean acidification.
Andrea Hinwood, Chief Scientist at UNEP, stated: “It is important for people to understand that SRM technology… does not address the climate crisis because it does not reduce greenhouse gas emissions or reverse the impacts of climate change.”
Its effects would also be short-term, increasing the likelihood that countries would be compelled to deploy SRM for centuries.
“Once you commit, you have to keep doing it. If you stop, you will see all the warming you ‘missed’, basically overnight on a climate timescale. So this is a dangerous game,” said Laura Wilcox, a climate expert at the University of Exeter in the UK.
