Tinkering with the Earth's thermostat at the cost of human lives

On the Texas-Mexico border, T.R. Schmidt builds a launcher to fire sulfur into the stratosphere to cool the planet.

Known as a stratospheric aerosol injection, a form of solar geoengineering, the technique would introduce aerosols into the stratosphere, replicating the after-effects of a volcanic eruption and creating a global cooling effect. This is similar to the impact of the eruption of the Mount Tambora volcano in Indonesia in 1815. This massive eruption emitted enough small particles of ash and aerosols into the atmosphere that it reduced sunlight to such an extent that average global temperatures dropped by as much as three degrees Celsius. 

But, Schmidt's plans don't go as well as expected. While the solar radiation modification (SRM) method was found to help a few low-lying areas, it threatens others with drought.

Fortunately, the above situation is fiction - the plot of Termination Shock, a science fiction novel by Neal Stephenson, takes place in a future unrecognizably altered by climate change.

Unfortunately, this fictional future could soon become a reality if we don't take a second look at our climate policies.

For the past few years, climate engineering, or geoengineering —the large-scale manipulation of environmental processes to affect the earth's climate — has been a subject of much debate between supporters and critics. Some argue that the science is untested, and the results of tinkering could create another kind of, more damaging, climate change. Others argue that it would help us achieve the goals of the Paris Climate Agreement, without an expensive and challenging mass reduction in carbon use. At the very least, we can say that the benefits or costs of geoengineering for human and planetary health are almost entirely unknown.

While meddling with the Earth's thermostat might well cool down the planet, it likely comes with massive repercussions - one of which is a potential increase in infectious diseases.

A first-of-its-kind study titled "Solar Geoengineering could redistribute malaria risk in developing countries" appeared in Nature Communications on April 20 and contained alarming findings. The research revealed that geoengineering the climate would put the health of billions of people who live in tropical countries at risk of malaria.

Getting a seat at the global table

The study had an interdisciplinary team behind it. Led by lead author Colin Carlson, Ph.D., assistant research professor at the Center for Global Health Science and Security at Georgetown University Medical Center, and senior author Christopher Trisos, Ph.D., a senior researcher at the University of Cape Town in South Africa, the research team included an epidemiologist, climatologist, and a microbiologist.

"People have been thinking about geoengineering for a while, a very tight-knit group of people, disproportionately from the United States and Europe - this is something that's been commented on a lot," Carlson tells IE. 

Their project is part of a broader initiative called DECIMALS [Developing Country Impact Modelling Analysis for SRM), "which is specifically about studying the impacts of geoengineering in developing countries. We've researchers from South Africa, Bangladesh... and what we are trying to do is broaden the horizons another way, and think about health and social impacts that so far have not been brought into the geoengineering conversation," he continues.

Sure, we've been thinking about the health impacts of climate change for decades. But we're kind of starting from square one when it comes to tackling it, feels Carlson. 

Anything that 'solves' climate change is not a win for the planet

"A lot of geoengineering research operates with the assumption that because climate change will be catastrophic for human health, anything we do that goes in the other direction must be a win. And I think that speaks to potentially a lack of concern about the ground reality of what lives this saves or doesn't," says Carlson.

Although all human life is priceless, this type of meddling could have significant unintended consequences for some. "We think about all of the processes of documenting and telling these stories and valuing human life as intrinsically urgent. We're working uphill convincing people that unintended consequences particularly matter if they are in communities in the global south that are on the frontlines of climate injustice," he says.

Carlson's approach to thinking about the issue of climate change, and climate correction, more holistically meshes with other development goals. As the Johannesburg Declaration on Sustainable Development states, “the adverse effects of climate change are already evident, natural disasters are more frequent and more devastating and developing countries more vulnerable.” Though a global phenomenon, climate change disproportionally affects poorer countries, primarily because of their high dependence on natural resources and limited capacity to cope with climate extremes. 

"And so, I think there's something particularly heinous about being dismissive out of hand about the possibility that even a small unanticipated consequence might follow this community. Global Health is a field that is good at dealing with those complexities and thinking about the value of human life. And we're hoping to bring some of that ethos into this," says Carlson. 

Malaria does not have a linear relationship with temperature

Carlson and his team used computer modeling to simulate malaria transmission in two future scenarios for Earth's climate, with medium or high levels of global warming and with and without geoengineering.

The models identify the temperatures which contribute to increased transmission by the Anopheles mosquito and determine how many people live in areas where transmission rates would increase.

The optimal temperature for malaria transmission varies from model to model but is generally thought to be around 25 degrees Celsius. Thus, mindlessly deploying SRM strategies could result in a situation wherein tropical countries could have lower temperatures than today, which are actually more conducive to malaria transmission. 

In both medium- and high-warming scenarios, malaria risk was predicted to shift significantly between regions, but in the high-warming scenario, simulations found that a billion extra people were at risk of malaria in the geoengineered world.

"There's a tonne of other infectious diseases we should be bringing into the space. We started with malaria because it probably has the highest burden of anything that is climate-sensitive, at least in terms of mortality," says Carlson. 

Surprisingly, the research also revealed that the risk of infectious disease in these simulations varied between different regions. For instance, in both scenarios, while geoengineering might reduce the risk of malaria in the Indian subcontinent, the risk was increased in countries of Southeast Asia. 

"What is striking though, is that there are very localized anomalies that come with geoengineering. And so, there are places that experience very unexpected outcomes relative to even the world we live in today," says Carlson. 

According to the study, "if geoengineering deployment cools the tropics, it could help protect high elevation populations in eastern Africa from malaria encroachment but could increase transmission in lowland sub-Saharan Africa and southern Asia. Compared to extreme warming, we find that by 2070, geoengineering would nullify a projected reduction of nearly one billion people at risk of malaria."

The cost of inaction

Carlson's research has important consequences for policymakers. "One is to inform decisions about geoengineering - to show some of the potential unanticipated consequences - and say that there might be more things like this we don't know and any decision made today could be made in the absence of that evidence."

The other is to inform people in the health sector "and say that this might be a decision that gets made without them," he tells me. 

"My worst fear about geoengineering, from the health sector, is not catastrophic impacts, but that we wake up on day one, and we haven't thought through anything. There are practical challenges that come up if we have to pivot global health infrastructure between regions. We've been planning for more than a decade on the shift of malaria from West to East Africa over time - we've been moving infrastructure and building adaptation capacity in East Africa. We could wake up tomorrow and find that all of that planning is for a reality that is now completely reversed." he says.

Carlson and his team hope to conduct similar research with more infectious diseases and health impacts while simultaneously supporting other teams undertaking similar work. 

"I think we don't necessarily want to build the entire global health infrastructure around the possibility of geoengineering. The best thing we can do is know how bad this could be. So that if it happens, from day one, we're starting with solutions, not with measurement," he adds.