We actually have a good understanding of what SO2 does in the atmosphere thanks to both volcanic eruptions and (until recently) the large amounts of particulate sulfur emitted from oceangoing ships. I think the more interesting question is how much risk we're willing to tolerate versus doing nothing at all. The risk of letting sea level rise continue unabated seems much worse to me than a (temporary!) intervention while we figure out full decarbonization.
It turns out that we've been accidentally doing geoengineering like this for years, and we've suddenly stopped due to regulations: RhodesianHunter posted this link in a different thread: (https://www.thedailybeast.com/weve-been-accidentally-geoengi...)
As per the website: "Just one gram of our clouds offsets the warming effect of one ton of CO₂ for a year."
I would wager that politicians and business leaders who read such a statement would be relieved to hear that they no longer have to worry about a cure because the symptoms are treatable.
Of course these sorts of things have always killed people and right now the statistical increases are small enough that it's not unreasonable to believe that they're just fluctuations within normal historical bounds. It would take significantly larger increases in severity and intensity for many people to accept climate change as a contributing factor.
So it's not just that we have to wait for people in wealthy countries to die, it's that we have to have to wait for them to die in high enough numbers that the average citizen acknowledges that there is a problem.
SO2 is a short-term, fast-acting, and reversible cooling option. That is why we need to massively adopt it ASAP.
I get the impulse for unilateral techno-optimist solutions but continually releasing sulfur dioxide into the air is not a sustainable option in any respect. Sustainability and "more, faster" ideologies are not compatible. You will be imposing health risks on plants and animals that many simply will not be able to mitigate for themselves. It is always apparent very quickly in conversations like this that the people proposing such "solutions" spend most of their time indoors in filtered air.
The impact of SO2, including its effectiveness and atmospheric residence time, varies based on its deployment location (latitude, longitude, altitude), concentration, and particle size.
For instance, the International Maritime Organization (IMO) 2020 regulations have reduced SO2 emissions from cargo ships in the troposphere, leading to decreased respiratory illnesses near ports and less acid rain. However, this reduction in SO2 has also warmed ocean shipping lanes, prompting discussions about reintroducing sulfur into the troposphere. [1]
Deploying SO2 in the stratosphere, above most of the atmospheric water vapor and where winds reach speeds of 200kph, allows it to spread globally and remain airborne longer (1 to 3 years). This higher placement necessitates less frequent applications for the desired reflective effect. The 1991 eruption of Mt. Pinatubo demonstrated this, injecting 20 million tons of SO2 into the stratosphere [2], cooling the Earth by 0.5°C and, according to some models, temporarily reversing decades of warming.
Stratospheric aerosol injection (SAI) is likened to Earth's sunscreen, [3] a temporary measure to reflect the Sun's energy and mitigate warming while we address the larger challenge of removing over a trillion tons of greenhouse gases emitted since the 1850s and transitioning away from fossil fuels.
Climate change demands immediate action, and SAI offers us the critical time needed to live in a world with fewer catastrophic climate events.
[1] https://docs.google.com/document/d/1vGEDuEn6uikvGZpR9oZplPPh...
[2] For reference, estimates suggest that global SO2 emissions were around 131 million tons in 1970 and continued to rise, peaking at approximately 150 million tons by the late 1980s in the troposphere.
[3] https://twitter.com/MakeSunsets/status/1741336520366444822
Source: https://www.nytimes.com/2023/01/09/climate/ozone-hole-restor...