by Sheena Alingig, Claudine Batimana, and Jyra Melo

Did you know that the 1991 volcanic eruption of Mount Pinatubo had a significant cooling effect on the Earth’s surface? 

Approximately 15 million tons of sulfur dioxide reached the stratosphere, creating small aerosol particles. These particles traveled worldwide on strong winds and stayed in the stratosphere for two years, resulting in a decrease in the average global temperature.

This cooling effect is similar to the concept of Solar Radiation Management (SRM), which is an intervention to reduce the amount of sunlight reaching the Earth’s surface to counteract climate change. 

However, there is an issue of lack of studies, particularly from Global South countries, regarding the long-term impacts of such volcanic events on climate and ecosystems. 

Despite the cooling effect of the Mount Pinatubo eruption, subsequent analyses conducted by scientists at NASA’s Goddard Institute for Space Studies (GISS) indicate that the Earth’s average global temperature has risen by at least 1.9°F (1.1°C) since 1880, with 2022 ranking as the sixth warmest year on record since 1880 according to NOAA temperature data. 

These temperature records have implications for the Philippines and its vulnerability to climate change, as rising global temperatures can contribute to extreme weather events and impact on the country’s ecosystems and communities.

In light of the escalating consequences of climate change, including rising temperatures, sea-level increases, and more intense natural disasters, experts worldwide are now exploring the potential of a technique akin to the cooling effect witnessed after the eruption of Mount Pinatubo in 1991. These include the studies conducted by The National Academic Press, Harvard, Rutgers, and Indiana University and other research institutions. 

In October 2021, the Philippines received funding known as the Degrees Modeling Fund (DMF) to research the potential effects of SRM in the region. The funding was provided by the Degrees Initiative, a non-government organization that supports research projects modeling the effects of SRM in developing nations.

Dr. Patricia J. Sanchez and her team at the School of Environmental Science and Management (SESAM) of the University of the Philippines Los Baños (UPLB) are researching the effects of SRM on agriculture. They are studying how SRM may alter rainfall patterns, intensity, temperature, and water-related disasters. They are also investigating how these changes could impact the growth and productivity of crops in the country.

The process of SRM

To gain a comprehensive understanding of Dr. Sanchez’s research and its implications on agriculture, it is important to explore the concept of SRM and understand how it works. 

SRM is like putting on a giant sunshade for the planet, providing a temporary relief from rising temperatures. This approach involves injecting sulfate aerosols into the stratosphere to reflect some solar energy back into space, thereby lowering the global temperature.

Sulfate aerosols are tiny particles made up of sulfur compounds suspended in the air, formed through the reaction of sulfur dioxide (SO2) with other substances in the atmosphere. These particles can scatter and reflect sunlight, leading to a cooling effect on the Earth’s surface. This definition of sulfate aerosols was given by researchers from environmental research letters in 2011 which aimed to determine the public understanding of SRM.

Aside from spraying reflective aerosol particles into the upper atmosphere, another method of SRM involves spraying seawater into the air directly above the ocean. This seawater is lifted into low-lying clouds, making them more reflective. 

The Institute for Advanced Sustainability Studies (IASS) in Potsdam, Germany proposed other techniques, such as brightening the sea surface and land, or putting reflectors into space. However, these techniques are receiving less attention from scientists due to concerns over feasibility and effectiveness.

SRM is mostly hypothetical

Despite the outlook of SRM in terms of reducing global temperatures and mitigating climate change risks, most of SRM’s techniques are still hypothetical. To date, SRM is limited to computer modeling, natural analogs or studies of natural events, and laboratory experimentation. 

Large-scale testing has not been conducted mainly due to concerns about potential risks associated with implementation. SRM techniques still need thorough evaluation and understanding of the risks before considering real-world application.

Global public perception of SRM was generally negative

SRM’s public perception and media portrayal is also generally negative, based on a 2021 review article by Kaitlin T. Raimi, an environmental psychologist at the University of Michigan. Dr. Raimi’s review aimed to provide an overview of public perceptions regarding the current global discussions on SRM, particularly in the field of social science. This included perspectives from scientists, policymakers, and the general public.

According to Dr. Raimi’s review, a major concern about SRM is that its discussion might make people, including policymakers, think that it replaces the need to reduce emissions. This concern is shared by both experts and the general public, as they fear that focusing too much on SRM could reduce support for emission reduction efforts.

Similarly, climate researchers Adam Corner and Nick Pidgeon found that many experts believe that merely researching and discussing SRM could undermine a country’s dedication to emission reduction. This phenomenon is often referred to as the moral hazard effect and it remains one of the longest-standing objections to SRM. 

The moral hazard effect occurs when the discussion of solar geoengineering creates the perception that it can replace the need for reducing greenhouse gas emissions. This is crucial since global greenhouse gas emissions have already reached their highest recorded levels, as revealed by a study from the Earth System Science Data journal.  

Without substantial emission cuts, the planet’s average temperature will continue to rise, resulting in more frequent and severe heat waves, droughts, storms, and rising sea levels. SRM may temporarily lower global temperatures and mitigate some climate change effects, but it does not address the root cause of climate change which are excessive greenhouse gas emissions.

What are the current commitments to reducing greenhouse gas emissions? In 2015, countries worldwide agreed to the Paris Agreement, aiming to limit the global average temperature increase to below 2°C from pre-industrial levels, with efforts to achieve a 1.5°C target. However, current projections indicate that meeting the 2°C goal is highly unlikely, and reaching the 1.5°C target seems nearly impossible. The world is off-track in fulfilling its international climate change objectives, and the consequences of climate change are intensifying. Without significant changes to climate policies, global warming is expected to exceed 2.5°C. Reducing greenhouse gas emissions remains the primary strategy to mitigate global warming, while adaptation efforts aim to manage the risks associated with rising temperatures.  Scientists are exploring whether Solar Radiation Management (SRM) could potentially mitigate the impacts of climate change.

Risks and unintended consequences of SRM

Why does this concept spark so much debate?

There is a lot of uncertainty about how SRM would affect different regions in terms of temperature and precipitation.

“Yung mga existing na studies, in general, sinasabi nila na yung temperature bababa, kasi yun naman yung goal ng SRM.Sinasabi rin nila na yung global rainfall, bababa din siya in general. Pero regionally—for example sa Pilipinas, sa West, sa China, or sa US—iba-iba yung potential impacts ng SRM (the existing studies, in general, indicate that the temperature will decrease, as that is the goal of SRM. They also suggest that global rainfall will generally decrease. However, regionally, such as in the Philippines, the West, China, or the US, the potential impacts of SRM may vary)” said Keane Carlo Lomibao, a civil engineer focusing on hydrologic modeling components of the Philippine SRM project.

One result of using SRM techniques could be a decrease in global rainfall. This might be good for areas constantly being battered by typhoons but the impact on agriculture remains a concern as Lomibao said. There are too many possible impacts and implications, he added.

The studies that Lomibao refers to have long been extensively discussed in the realm of SRM. According to a 2019 study by The Royal Society, a renowned scientific organization in Britain, SRM might cause anomalies in temperature and precipitation in some regions. SRM can still make certain areas of the world hotter or colder than they should be, resulting in unusual temperature changes and unpredictable shifts in rainfall patterns. These sudden changes in temperatures and rainfall patterns can then lead to additional societal challenges and complications.

According to a 2021 study by Aaron Tang and Luke Kemp, research suggests that SRM could decrease peanut yields in India or counteract the advantages of lower temperatures. Although the specific agricultural effects are not yet fully understood, experts believe that these effects would vary across different crops and regions. 

SRM’s influence on temperature and rainfall patterns can also affect public health. According to a 2020 study by Colin J. Carlson and Christopher H. Trisos, the different effects of SRM on temperature and other ecological factors in different regions could impact the transmission of diseases. For example, reductions in monsoon rainfall caused by SRM might increase the risk of cholera, while changes in temperature can affect the transmission of vector-borne diseases such as malaria.

SRM also poses additional environmental risks. According to Hannah Jose, a licensed Agricultural and Biosystems Engineer and one of the researchers of the Philippine SRM project, “Some of the environmental risks na na-identify ng ilang climate—and even SRM—scientists and researchers ay yung effect [ng SRM] sa ocean acidification. Mayroon din siyang potential to contribute more sa air pollution.”

(Some of the environmental risks identified by certain climate and SRM scientists and researchers include the effect of SRM on ocean acidification. It also has the potential to contribute further to air pollution.)

Ocean acidification refers to the ongoing process of increasing acidity in the Earth’s oceans. It occurs when carbon dioxide (CO2) from the atmosphere dissolves in seawater. It harms coral reefs, shellfish, plankton, fish, and the entire marine food web. 

“Once na magkaroon nga tayo ng SRM, yung mga mai-introduce niya pang particles, mga aerosols, magre-react pa siya lalo dun sa i natin kaya nga magkakaroon pa ng more acidifciaton, magiging more acidic pa ung oceans natin,” said Jose.

(Once we have SRM, the introduced particles, such as aerosols, will further react with our oceans, leading to increased acidification. Our oceans will become even more acidic.)

Jose noted that SRM can also contribute to air pollution because it introduces additional particles. “Though sabi naman ng mga researchers from other countries…yung added aerosols…hindi niya significantly ii-increase yung level ng pollution,” said Jose. “But yung level kasi ng pollution natin ngayon sa air…medyo hindi na siya safe. Any additional aerosols or particles na magco-contribute pa dun sa pollution will be damaging na talaga,” Jose added.

(SRM can also contribute to air pollution because it introduces additional particles. However, according to researchers from other countries, the added aerosols will not significantly increase pollution levels. Nevertheless, our current air pollution levels are already quite unsafe. Therefore, any additional aerosols or particles that contribute to pollution will indeed be detrimental.)

In a study published in 2012, Christopher Preston, a Philosophy professor at the University of Montana, highlighted concerns among experts regarding the public perception of SRM. These experts fear that SRM could exacerbate challenges for future generations, who would have to face both the risks associated with SRM and the consequences of past greenhouse gas emissions.

The need for expanding SRM research

Amidst the debate and controversy, one of the most important criticisms against SRM is its limited research. As noted by Visschers’s study on public perceptions of SRM, most of its research has taken place in Western countries, specifically the US, the UK, and different European countries. 

In February 2023, over 110 scientists worldwide penned an open letter advocating for research on the potential of expanding SRM. “Where possible, governments, philanthropists, and the scientific community must seek ways to expand scientific capacity for Global South researchers to both engage in and direct research on SRM,” the scientists wrote in the letter.

What was the open letter in support of SRM? More than 110 scientists from the US, Canada, and Europe have written an open letter expressing concern about the world’s ability to limit global warming to below 2 degrees Celsius.  While the scientists emphasize the importance of reducing emissions as the main priority, they argue that it is crucial to fully understand the potential consequences of solar radiation management (SRM) before any country considers implementing it as a desperate measure. James Hansen, a respected former NASA climate researcher, led the group of scientists. Hansen is recognized for raising awareness about the alarming rise in global temperatures during the 1980s.

In his book “The Ethics of Solar Radiation Management” published in 2012, Preston points out that just as developing countries are expected to bear the brunt of the impacts of climate change, they would also be the most affected by the potential harms of solar geoengineering. Preston refers to this amplified inequality as a “moral deficit”.

For Preston, it is crucial to involve researchers from diverse geographical areas, including both developing and developed countries. These researchers can help make sure that climate models and policies consider the needs and interests of people in different regions since they would have a better understanding of the specific challenges faced by those in the global South.

Expanding participation in SRM Research

While SRM research has traditionally been dominated by Western countries, there are now positive developments taking place, often made possible by scientists from Malaysia, Vietnam and other developing countries. 

One of these developments is the Degrees Initiative, a non-government organization providing funding—called the Degrees Modelling Fund (DMF)—for research projects that model the effects of SRM in developing nations. Since 2018, the Degrees Initiative has been awarding DMF funds to various research teams across the world. They have already worked with more than 150 researchers to explore the effects of SRM on various areas, including droughts in Southern Africa, dust storms in the Middle East, and the spread of cholera in South Asia. One of the objectives of the project is to identify the potential impacts of SRM in water-related disasters.

The two main project sites of SRM in the Philippines are Laguna De Watershed and Lanao Lake Watershed. With these two watersheds being the main water body utilized by the people living near the areas, it would be effective to collect and gather information during the conduct of the study as they are most likely the ones to be affected. This would also mark the beginning of localizing simulations on the GeoMP scenarios to the Philippines, specifically the Laguna and Lanao Lake areas, which is also one of the objectives of the study.

While the study is still ongoing, it is expected that the continuous efforts of the researchers would potentially yield results considering that this study is not solely based in the Philippines. There is an existing collaboration with other researchers from other countries, particularly Africa and the US. Since SRM was introduced to address the risks of the worst-case scenario, it is expected that the possible outputs would answer the questions and address the criticisms of SRM.  It is also important to note that it would be explored but not necessarily used in the future.

“Eventually, makakakuha tayo ng scientifically fact na judgement ng SRM at kung makita man natin in the future na yung SRM ay hindi pala ganun kaganda, maghahanap tayo ng best course of action para i-address ang global warming at climate change“. Engr. Lomibao said.

(Eventually, we will acquire scientific facts for  judgment on SRM, and in the future, if we can actually see that SRM is not feasible, we will find the best course of action to address global warming and climate change.)

SRM continues setting its objectives and long-term goals not only in agriculture but in other aspects as well. According to Simon Nicholson, an Associate Professor in the School of International Service, the study of SRM is said to be the idea born out of desperation. It demands public consideration considering the fact that this is research led by many geoengineering advocates with the research trying to find solutions to some global problems. As SRM is still not deployed, the current study of SRM is entirely theoretical.  The result of this study would not only be beneficial to agriculture, but this can also lead to finding true solutions to climate change.