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The End of Climate Change? The Pros and Cons of SAI

Understand the pros and cons of stratospheric aerosol injection (SAI), a solution that could fix climate change!


As the planet continues to warm, scientists and policymakers are exploring various drastic measures to mitigate the escalating threats of climate change. These include brightening clouds, releasing algae into the seas, and launching giant mirrors into space.

One of the most promising of these measures is stratospheric aerosol injection (SAI), a technique that injects reflective particles into the upper atmosphere to reflect sunlight and ultimately cool the planet.

While some experts believe that SAI could hold the key to solving climate change, others are scared of its efficacy and warn of potential risks. As we approach the critical threshold of 1.5°C of warming, it’s more important than ever to carefully evaluate all the benefits and drawbacks of SAI and consider how we can work together to combat climate change before it’s too late. So let’s take a look at the known positives and negatives of SAI, so we can decide together whether it could be the solution to climate change.

It’s fast and cost-effective

Unlike other climate change mitigation strategies, such as transitioning to clean energy or reducing greenhouse gas emissions (GHGs), SAI could be accomplished using our existing technology and infrastructure. All of this means we could potentially see results in a short amount of time, giving us the breathing space to implement longer-term solutions.

Recent studies have shown that even a small number of reflective particles injected into the upper atmosphere could offset climate change drastically. A recent paper by Wake Smith estimated we would only need around a hundred modified planes to spray the needed millions of tons of sulphur dioxide into the atmosphere each and every day.

Another benefit Smith points out is that SAI should be relatively inexpensive, costing only about $18 billion per year for each degree we want to avoid (in 2020 USD). This means we could potentially avoid 1.5°C of warming by spending about $27 billion per year, for the foreseeable future. To put this number into context, we spent around $9,000 billion on global fiscal support for covid-19.

It mimics natural systems

As SAI mimics what happens when volcanoes erupt, eruptions have become incredibly valuable in validating if SAI is safe and plausible. One of the largest eruptions in recent history was the Mount Pinatubo eruption in 1991, when 17 million tons of sulphur dioxide were injected into the upper atmosphere. The effect of this injection cooled a large part of the planet’s surface by 0.4°C in 1992–93.

It’s fully reversible

Unlike carbon capture and storage, SAI is a short-term approach, and therefore its effects can be reversed relatively quickly. This is possible as the sulphur dioxide particles injected into the atmosphere eventually fall back to the planet’s surface due to gravity. Once they fall back to the planet’s surface, generally within a few years, they no longer have a cooling effect.

This reversibility is significant because it means that if SAI were found to be causing unintended or negative consequences, such as changes in weather patterns or damage to the ozone layer, it could be stopped or reduced. This would allow the atmosphere to eventually return to its pre-injection state. In contrast, other climate change mitigation strategies that involve long-term storage of carbon dioxide, may not be easily reversed once they have been implemented.

It’s doesn’t solve everything

While SAI has the potential to mitigate climate change, there are many potential drawbacks that need to be carefully considered. Regrettably, SAI does not address the root cause of climate change, which is the build-up of GHGs in the atmosphere. It only provides a temporary solution to offset some of their climate change effects. These built up GHGs, such as carbon dioxide, would still have a nasty effect on the environment, like increasing ocean acidification, which is killing coral, shellfish, and plankton.

If we stop injecting sulphur dioxide into the atmosphere, the planet will quickly warm up again. Therefore, to truly address climate change, we need to take more comprehensive action to reduce our GHGs and transition to clean energy sources. Therefore, it is essential that the green transition still happens.

It may get in the way of other carbon strategies

It is possible that SAI research could divert funds from other well-known carbon-reduction strategies, like the investment in clean energy. Even the knowledge that we could cool the planet with SAI could possibly remove the incentive to decarbonize.

There may be unintended consequences

There is the possibility of unintended consequences, particularly as this approach has never been attempted before, and any alterations to our atmosphere could have far-reaching consequences for all living things on our planet.

One of the unintended consequences of SAI could be the negative impact on plants and crop yields. Since SAI decreases or scatters incoming solar radiation, many plants would receive less direct sunlight which they use for photosynthesis. This could result in less food production globally, and with a growing global population, this may lead to future famines and resource conflicts. Additionally, fewer plants and biomass would reduce the planets ability to absorb GHGs, which could further exacerbate the effects of climate change.

On the other hand, scientists have recently theorized that the cooling effect of SAI could benefit plants, potentially outweighing the negative impacts mentioned above. Interestingly, there are also some advantages to the scattering of solar radiation too, as it may actually increase plant growth under tree canopies.

Other potential unintended consequences of SAI, include adverse health effects for humans and animals due to the irritant properties of sulphur dioxide, and risks of increasing the acidity of rain, mist, and waterways. It’s also unclear how SAI would interact with other pollutants, buildings, and weather patterns on a larger scale.

There are many ethical issues to consider

There are many ethical questions associated with SAI. The decision to use this technology would be a decision to intervene in the natural processes of the planet and manipulate its climate (i.e., geoengineering). This raises questions about who should have this type of power.

Additionally, the benefits of SAI may not be equally distributed, and some regions of the world may benefit more than others. This means implementation of SAI should ideally be done through an international coalition, otherwise, we could create losers in the process.

It may be adopted to late

We would truly need an international agreement to start geoengineering our planet. An SAI program with substantial climate impact would lie well beyond the financial reach of most individuals economies, and would instead be the exclusive domain of large national economies or international coalitions. Additionally, due to the ethical considerations stated above, a truly international agreement would ideally be needed to make sure that the process remains fair.

As we have seen with the COP conferences, even with many years of scientific research, all actors may not agree in time. Negotiations could go on for decades. Therefore, even if SAI is proven to be effective with minimal downsides, it may come to late in our fight against climate change.


In conclusion, while SAI may have many benefits for mitigating the effects of climate change, it’s many negatives need to be evaluated carefully, as messing with the atmosphere could cause a lot of damage. Additionally, the ethical considerations and slow adoption of such global-reaching technologies make it difficult to imagine an easy implementation of SAI in the short term. However, the fact that SAI is a short-term solution that can be reversed relatively quickly is encouraging.

It is vital to note that SAI cannot be used as a replacement for other climate action, such as reducing GHGs and transitioning to clean energy. Ultimately, a combination of all these solutions and actions is needed to fight against climate change. Hopefully, SAI will be included in this fight. Only time will tell…


Wake Smith (2020) Environ. Res. Lett. 15 114004

IMF (2020) Tracking the $9 Trillion Global Fiscal Support to Fight COVID-19: by Bryn Battersby, Elif Ture, Raphael Lam, viewed on 25 Feb 2023.

United States Geological Survey (1999) The Atmospheric Impact of the 1991 Mount Pinatubo Eruption: by Stephen Self,1 Jing-Xia Zhao,2 Rick E. Holasek,1 3 Ronnie C. Torres,1 4 and Alan J. King1

Proctor, J., Hsiang, S., Burney, J. et al. Estimating global agricultural effects of geoengineering using volcanic eruptions. Nature 560, 480–483 (2018).

Science News (2018) Global dimming may mitigate warming but could hurt crop yields: by Carolyn Gramling, viewed on 25 Feb 2023.

Rich Munro

CEO & Founder

Rich is the founder of Ecorth. He has been working in the ESG industry for 10+ years.