Geoengineering could raise the risk of malaria for 1 billion people

In 2018, a commentary in Nature Climate Change by Colin Carlson and Christopher Trisos, then postdoctoral fellows at the National Socio-Environmental Synthesis Center (SESYNC), a University of Maryland center funded by the National Science Foundation, cautioned against the aftereffects of geoengineering, as it could significantly impact global health. 

Now, Carlson, Ph.D., an assistant research professor at the Center for Global Health Science and Security at Georgetown University Medical Center, and Trisos, Ph.D., a senior researcher at the University of Cape Town in South Africa, have confirmed their hypothesis in a study published in Nature Communications.

Their findings concluded that geoengineering the climate would result in enormous repercussions for the health of billions of people at the risk of malaria who live in tropical countries. 

The first of its kind study particularly focused on solar radiation management (SRM), a 'quick fix' to reduce the impacts of climate change. And one of the methods that have been proposed is injecting aerosols into the stratosphere that reflect incoming sunlight, leading to "pausing" global warming temporarily.

Though SRM has been touted as the step to reduce climate injustice, its impacts on health have not been studied. 

'Tinkering' with the Earth's temperature

Over the past 5,000 years, global temperature increased by a total of 4°C to 7°C. This has intensified weather patterns and fueled droughts, heatwaves, and wildfires. The Paris Agreement has set a goal of limiting warming by 2100 to less than 2°C.

But what if we could be proactive and meddle with the Earth's thermostat, controlling radiation from the sun? 

In its 5th Assessment Report, the UN's Intergovernmental Panel on Climate Change defined the 'tinkering' as geoengineering. It said that geoengineering was "a broad set of methods and technologies operating on a large scale that aim to deliberately alter the climate system in order to alleviate the impacts of climate change". 

These techniques can be divided into categories such as solar radiation management (SRM), which intends to cool the Earth by reflecting sunlight into space; and carbon dioxide removal (CDR), which aims to remove and permanently sequester carbon dioxide from the atmosphere, resulting in negative emissions.

“Geoengineering might save lives, but the assumption that it will do so equally for everyone might leave some countries at a disadvantage when it comes time to make decisions. If geoengineering is about protecting populations on the frontlines of climate change, we should be able to add up the risks and benefits — especially in terms of neglected health burdens, such as mosquito-borne disease," said Carlson, lead author of the study.

No clean chit for geoengineering

A team of eight researchers from the United States, Bangladesh, South Africa, and Germany used climate models to simulate what malaria transmission could look like in two future scenarios, with medium or high levels of global warming, with and without geoengineering.

The models were used to identify which temperatures are most suitable for transmission by the Anopheles mosquito and identify how many people live in areas where transmission is possible.

While medium- and high-warming scenarios revealed that malaria risk could shift significantly between regions, the high-warming scenario revealed that a billion extra people were at risk of malaria in the geoengineered world.

“On a planet that’s too hot for humans, it also gets too hot for the malaria parasite,” said Carlson. “Cooling the planet might be an emergency option to save lives, but it would also reverse course on those declines.”

“The potential for geoengineering to reduce risks from climate change remains poorly understood, and it could introduce a range of new risks to people and ecosystems,” said Trisos, senior author of the study.

There's more to climate injustice

The findings also revealed potential trade-offs between regions. In both scenarios, the authors found that geoengineering could reduce the risk of malaria in the Indian subcontinent, even compared to the present day.

But, at the same time, that protective effect would be offset by an increase in risk in southeast Asia. This could likely complicate the geopolitical reality of climate intervention for decision-makers. 

“We’re so early in this process that the conversation is still about increasing Global South leadership in geoengineering research. Our study highlights that the frontlines of climate injustice aren’t one monolithic bloc, especially when it comes to health,” said Carlson.