Reflecting Sunlight to Cool the Planet: Can We Safely Experiment?
The world's warming fast, with 2024 being the first full year above 1.5°C hotter than the 19th-century average. Emissions continue to rise, and fossil fuel use is expected to hit a new high in 2025. While cutting emissions and scaling carbon removal are crucial, they may not be enough.
One idea being explored is reflecting a small fraction of incoming sunlight to reduce warming. This concept has been around since 1965 when Lyndon B Johnson's science advisers proposed it as the only way to cool the planet. Earth already reflects about 30% of incoming sunlight; raising this fraction slightly could strengthen the planet's natural heat shield.
The idea gained traction after Mount Pinatubo's eruption in 1991, which sent sulfur dioxide into the stratosphere and cooled the planet by about 0.5°C. This inspired the concept of stratospheric aerosol injection (SAI), with models suggesting it could offset 1°C of warming with around 12 million tonnes of SO₂ per year.
However, SAI is not a substitute for cutting emissions, and any deployment would need to be carefully managed. Research has been criticized for its lack of clarity, but careful, open research can clarify whether SAI could ever be used safely and effectively. In fact, research acts as a guardrail – not a slippery slope.
To verify the predictions, researchers propose conducting phase-gated programs similar to clinical trials in medicine. Phase one would involve releasing small amounts of SO₂ and measuring its evolution using various instruments. This early test would offer an opportunity to study how aerosols form and behave, helping identify key uncertainties and potential issues with current projections.
Phase two experiments could be larger, still much smaller than volcanic eruptions, allowing researchers to study how aerosols mix and distribute. Observational capabilities required for these tests would also detect unauthorized deployments.
The ultimate goal is to generate real-world evidence before a crisis forces our hand. The UK's Advanced Research and Invention Agency (Aria) program is a step in the right direction, while organizations like Reflective are working to support open science and careful coordination across the field.
By conducting outdoor research, we can ensure that any future decision – whether to move forward or reject the idea entirely – is based on facts, not fear or wishful thinking. The real danger isn't asking the question; it's waiting too long to learn the answer.
The world's warming fast, with 2024 being the first full year above 1.5°C hotter than the 19th-century average. Emissions continue to rise, and fossil fuel use is expected to hit a new high in 2025. While cutting emissions and scaling carbon removal are crucial, they may not be enough.
One idea being explored is reflecting a small fraction of incoming sunlight to reduce warming. This concept has been around since 1965 when Lyndon B Johnson's science advisers proposed it as the only way to cool the planet. Earth already reflects about 30% of incoming sunlight; raising this fraction slightly could strengthen the planet's natural heat shield.
The idea gained traction after Mount Pinatubo's eruption in 1991, which sent sulfur dioxide into the stratosphere and cooled the planet by about 0.5°C. This inspired the concept of stratospheric aerosol injection (SAI), with models suggesting it could offset 1°C of warming with around 12 million tonnes of SO₂ per year.
However, SAI is not a substitute for cutting emissions, and any deployment would need to be carefully managed. Research has been criticized for its lack of clarity, but careful, open research can clarify whether SAI could ever be used safely and effectively. In fact, research acts as a guardrail – not a slippery slope.
To verify the predictions, researchers propose conducting phase-gated programs similar to clinical trials in medicine. Phase one would involve releasing small amounts of SO₂ and measuring its evolution using various instruments. This early test would offer an opportunity to study how aerosols form and behave, helping identify key uncertainties and potential issues with current projections.
Phase two experiments could be larger, still much smaller than volcanic eruptions, allowing researchers to study how aerosols mix and distribute. Observational capabilities required for these tests would also detect unauthorized deployments.
The ultimate goal is to generate real-world evidence before a crisis forces our hand. The UK's Advanced Research and Invention Agency (Aria) program is a step in the right direction, while organizations like Reflective are working to support open science and careful coordination across the field.
By conducting outdoor research, we can ensure that any future decision – whether to move forward or reject the idea entirely – is based on facts, not fear or wishful thinking. The real danger isn't asking the question; it's waiting too long to learn the answer.
I mean, they're literally changing my downward-facing dog game! 
I just got back from a super relaxing trip to the beach and I'm hooked on these new eco-friendly mats. They're so comfy and they come in all these awesome colors! 
I'm thinking of starting a blog about outdoor adventures and sustainable living... what do you guys think? 
We could totally explore more ideas like SAI (stratospheric aerosol injection) and how it can help with climate change, but let's be real, who needs facts when you have a good pair of yoga pants? 
Just kidding, sorta. 
... Reflecting sunlight to cool the planet sounds like something straight out of a sci-fi movie, but at the same time, we gotta consider it as an actual option 
... We're not even close to cutting emissions and carbon removal, so this could just be another Band-Aid on a bullet wound 
. The problem is complex, and we need solid research, like these phase-gated programs, before we start making any big decisions.
... It's better to be proactive and try new things than to just sit back and wait for the planet to, you know, burn 
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I mean, don't get me wrong, it's convenient and all that, but sometimes I wish we could just disconnect and be present in the moment... anyway, back to this whole climate thing...
this is like totally amazing!! Reflecting sunlight to cool the planet? That's genius! 
I'm so down for any idea that can help us reduce our carbon footprint and slow down climate change. And yeah, we need to do this ASAP! The fact that they're talking about stratospheric aerosol injection (SAI) is so cool! 
Like, who wouldn't want to study how to make the planet's heat shield stronger? 
Can we do a group discussion on this in Discord? 
... gotta be done with careful planning & research tho 
. But at the same time, if it could really help mitigate some of that warming, I'm all for exploring it further 
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. It's like they're saying, "Hey, let's make sure this doesn't go haywire before we try to change the game." And honestly, that makes so much sense to me 
. Let's get to the bottom of this and see if it's a real game-changer 
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We're not even talking about that. This is just more of their plan to control us through science 
. I remember when I was a kid, we didn't think about all this climate stuff, but now it's like, super obvious that we need to act fast 
? 
. We can't rely on nature alone; we need to use science to figure this out 
. But what if the results are inconclusive? What if it's too little, too late 
?
. The planet is our home, and we gotta take care of it, even if it means taking some risks 
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. But seriously, 30% of sunlight being reflected already sounds right? We dont wanna play around w/ 1°C temp diff tho 
its not gonna make a big diff in the grand scheme. I'm all for open research tho 
lets get those phase-gated programs goin & see what we can learn 
️ I mean sure, there are risks and uncertainties, but come on, we've been playing catch-up with climate change for decades 
it's time to think ahead and try something new 
let's get behind this research and see where it takes us 
. While Earth already reflects about 30% of incoming sunlight, raising this fraction slightly could strengthen its natural heat shield. However, the potential risks and uncertainties surrounding stratospheric aerosol injection (SAI) are significant 
. Research has been criticized for its lack of clarity, but I firmly believe that careful, open research can clarify whether SAI could ever be used safely and effectively 
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, as long as it's being done in a way that's transparent and open. Like, they're proposing these big experiments where they'd release tiny amounts of particles into space and see what happens 
... but at the same time, we can't just sit around waiting for someone to tell us what to do 
. Can't we just focus on cutting emissions instead of trying to manipulate the climate like it's some kind of game 
?