“Solar geoengineering” can exacerbate malaria

Mount Pinatubo, 1991 eruption In the Philippines, nearly 20 million tons of sulfur dioxide are injected into the sky.This sudden gas explosion in the atmosphere reflected sunlight from Earth and lowered the average temperature of the planet. About 1 degree Fahrenheit A little longer than a year.If humanity wants to limit the worst effects of global warming, it simply has to be It, By plane, indefinitely.

That is at least the idea of ​​solar geoengineering. For its supporters, mimicking a large volcanic eruption is an ethical need and a way to mitigate the impact of climate change. “Perhaps the biggest reason to take cooling seriously is that profits are likely to come to the poorest countries,” said David Keith, a professor of applied physics at Harvard University. I have written of New York Times last year. “Poor people tend to live in hot places.”

The technology required for geoengineering has never been successfully demonstrated, but many economists are already convinced that it will happen at some point in the century. This is because the theoretical cost is only a few flights, a sprayer, and millions of tonnes of sulfuric acid. Yes, it’s expensive, but it’s out of the reach of millionaires interested in the average island nation and climate.

But geoengineering is far from a sure bet. To that criticThis technique runs the risk of recreating some of the worst mass extinctions in the history of the planet. This was the result of the boost. both Atmospheric carbon dioxide levels When Its sulfate level.We are already pumping CO₂ Towards the sky, they insist. Why is adding sulfate not counterproductive?

A New research Solar geoengineering suggests that it will be even more complex than its proponents are aware of. Every year, tens of millions and even hundreds of millions of people can be exposed to malaria. “There is a lot of research on the potential of geoengineering to reduce the dangers of extreme heat and rising sea levels.” Christopher TrisosThe co-author of the study and director of the Institute for Climate Risk at the University of Cape Town, South Africa, told me. “But we cannot assume that geoengineering universally mitigates risk. Man.. “

In the extreme worst-case scenario where humans try to raise the temperature of the Earth several degrees by 2070 and then return it to 2020 levels, geoengineering could increase the risk of malaria for perhaps one billion people. Research has found that geoengineering can remodel major risks around the world, even in less extreme scenarios. Although humanity has achieved zero net carbon pollution by the middle of the century, more mild simulations still trying to bring temperatures back to 2020 levels remain a difficult problem.In this world, West African countries such as Nigeria and Ghana gain A total of about 100 million people are at risk of malaria.However, in East African countries such as Ethiopia and Kenya, geoengineering reduce Malaria risk of about 100 million people.

Many scientists are worried that climate change will exacerbate the spread of mosquito-borne diseases such as dengue and yellow fever. However, malaria itself falls into the category. In 2020 Over 627,000 people He died of malaria and about 241 million people were infected with malaria.Malaria remains 6th highest cause of death In low-income countries, more people die than car accidents, HIV / AIDS and tuberculosis. In the words of the study’s authors, no other mosquito-borne virus is making “remotely comparable” sacrifices to the illness and death caused by malaria.

The trade-off between geoengineering and malaria appears for two reasons. First, solar geoengineering does not completely restore the Earth’s climate clock. Adding enough sulphate aerosols to completely counteract the amount of warming caused by carbon pollution is changing the physics of climate rather than restoring its previous state. Many geoengineering simulations experience strange phenomena such as “tropical supercooling.” In this phenomenon, the land near the equator is cooler than expected, even though the area near the poles remains much hotter. The latest intergovernmental panel reports on climate change show that these regional and seasonal distortions appear “reliably” in many types of geoengineering models.

This is a problem because malaria has no linear relationship with temperature. Plasmodium is spread by mosquitoes. Mosquitoes are warm-blooded animals and depend on the ambient temperature to set the pace of metabolism. Therefore, the risk of malaria tends to increase as the temperature rises. Maximum temperatures are 25 degrees Celsius and 77 degrees Fahrenheit, Colin Carlson, a professor at Georgetown University and co-author of the dissertation, told me. However, as temperatures continue to rise, mosquitoes become more and more non-functional and begin to “fall out of the air” at about 34 degrees Celsius and 93 degrees Fahrenheit. This means that there is a severe heat peak in mosquito survival and along with malaria transmission.

This study found that tropical supercooling and the ideal temperature for malaria infection can interact in a nasty way. In some parts of the world, geoengineering was done in places that were too hot for mosquitoes to survive, returning them to the point where they could survive. Elsewhere, it has restored the temperature near 25 degrees Celsius required for mosquitoes to breed.

Of course, mosquitoes are not the only ones struggling to cope with extreme heat. The same is true for humans. If it’s too hot for humans and animals to survive, geoengineering may just make sense. But reality can have much more subtle nuances. “I think it’s gambling to sum up the catastrophic biological risks. [of high temperatures]What you have is not better than other factors, “Carlson said.

One of these other factors can be meningitis, a dangerous and sometimes fatal infection of the tissues surrounding the brain and spinal cord. The disease is most prevalent in Africa’s Infestation, as small particles of dust can increase the risk of meningitis. Meningitis beltPeople are regularly exposed to aerial sand and dust from Sahara. Seasonal monsoons often wash dust out of the air. However, some geoengineering simulations could weaken the monsoon season, expose more people in sub-Saharan Africa to dust, and increase the risk of meningitis, Carlson said. increase.

Even if geoengineering reorganizes the geography of malaria, increasing infections in new areas and eliminating them in old areas without increasing the total number, it will cause public health problems. In certain parts of the world, we are preparing health and medical infrastructure for malaria. If the burden of illness moves to new locations, those locations do not have the same accumulated expertise and institutional factors designed for it. The disease will cause higher casualties, at least initially.

Keith, a professor at Harvard University who calls geoengineering the “worst” way to cool the planet, says the study and its broader efforts to quantify the health effects of warming are worthwhile. Told me. But he suspected that mathematics would be against geoengineering. “it’s good [that] People are watching it, “he said. “But don’t be surprised that solar geoengineering doesn’t improve your health evenly. Global warming It does not uniformly harm the health consequences. He did a little mental arithmetic: the destructive power of heat life is expected to cause about 5 million deaths a year by the end of the century, he said. By comparison, malaria kills about 500,000 people annually, and that number has declined since the turn of the century. Malaria has plenty of room for exacerbation before it can match the burden of heat at the end of the century.

In a broader sense, this study shows that solar geoengineering can worsen people’s lives even in poor countries where it may be most useful. “What’s worrisome about the geoengineering trade-off is that it’s at the forefront of climate change, and it’s being discussed as if there’s something called the” Global North “that benefits from a” solution. ” That’s what Carlson said. “This is the first trolley problem we’ve seen,” he said, in studying the effects of climate change. “There are winners and losers in this.”