00:00When it comes to fighting climate change, some scientists are not talking about something that sounds straight out of science fiction, dimming the sun.
00:09The idea is simple, at least on paper.
00:12Cool the planet by scattering sunlight reflecting particles high up in the atmosphere.
00:18It's called Stratospheric Aerosol Injection or SAI.
00:22And while this concept has been discussed for years, new research from Columbia University says it might be far riskier and far less predictable than many people think.
00:35So how does it work?
00:37Now the principle comes from nature itself.
00:40Volcanic eruptions like Mount Pinatubo in 1991 blasted millions of tons of sulfur into the air, blocking sunlight.
00:49For a couple of years after, global temperatures actually dropped by about 1 degree Celsius.
00:56Scientists thought that if nature can do it, maybe we can too.
01:01But as it turns out, it's not that simple.
01:04Researchers at Columbia's climate school say the computer models studying SAI are too idealized.
01:12They assume perfect particles floating at perfect places in perfect amounts.
01:17Reality, they say, is messy.
01:20The atmosphere does not follow instructions.
01:23Dr. McNeil, an atmospheric chemist, puts it bluntly.
01:27The range of possible outcomes is a lot wider than anyone imagined.
01:32The study points to countless unknowns.
01:35From how and where to release particles, to who would even control such a planetary scale experiment.
01:41Let's picture it.
01:43If particles are released near the Earth's poles, it might throw tropical monsoons off balance.
01:49Do it near the equator and it could disrupt jet streams that govern global air circulations.
01:55And so this isn't just about cooling the Earth.
01:58It's also about potentially reshaping rainfall, shifting winds and altering climate zones with unpredictable consequences.
02:06And then there is politics.
02:09SAI would have to be done in a highly coordinated global effort.
02:13One country acting alone could trigger tensions or worse, retaliation if others suffer from side effects.
02:21The Columbia study also draws lessons from volcanoes.
02:25Yes, Mount Pinatubu cooled the planet, but it also disturbed the Indian monsoon and reduced rainfall across South Asia.
02:32Those were real social and ecological costs.
02:36So if sulphates come with these risks, can safer materials do the job?
02:42Researchers have tried to find alternatives.
02:44Calcium carbonate, alumina, even exotic options like cubic zirconia and yes, diamond.
02:51Now some of these reflect sunlight well, but they also bring new problems on the table.
02:57Most are scars, costly to produce or clump together into larger particles that simply do not work.
03:05Dr. Miranda Hack, the study's lead author, notes that few people have asked the practical question.
03:12Can we even produce and inject trillions of these tiny particles every year?
03:17The short answer seems to be no.
03:19Even the best materials, scientists say, may not stay stable in the atmosphere.
03:25They could scatter sunlight unevenly or fall out of the sky faster than expected, creating acid rain or soil contamination.
03:34This brings us to what the Columbia team calls a strategy full of uncertainty.
03:40They also warn that solar geoengineering might look like a quick fix for global warming, but the trade-offs could be enormous.
03:48As economist Gernot Wagner puts it, in real life, it won't unfold like it does in the models.
03:55So while the dream of cooling Earth sounds tempting, the reality could be far more chaotic.
04:02For now, scientists agree on one thing.
04:05Before we dim the sun, maybe we should think twice about the darkness it could bring.
Comments