A sunscreen for Earth? Assess the risks first

Mint

24-04-2025

More than a dozen private companies around the world are looking to profit from extreme measures to combat global warming—filling the sky with sunlight-blocking particles, brightening clouds or changing the chemistry of the oceans. We live in precarious times when it's not hard to find the technology and money to change the Earth's climate. The problem is that nobody knows how to control the unintended consequences.
Some scientists who've studied and modelled the complexity of Earth's oceans and atmosphere say any 'geo-engineering' scheme big enough to affect the climate could put people at risk of dramatic changes in the weather, crop failures, damage to the ozone layer, international conflict and other irreversible problems.
Environmental lawyer David Bookbinder is more afraid of geo-engineering than he is of climate change. 'The consequences of geo-engineering could happen a lot faster and with much less warning," he said. 'And could provoke a really bad geopolitical crisis."
The world got an early warning about this Wild West situation in 2022 when a small startup called Make Sunsets caused a scandal by launching a small balloon-borne experiment over Mexico to spray sulphur dioxide into the atmosphere. Now, it's joined by richer, more serious players, including an Israel-based company called Stardust, which is researching a plan to dim the skies with a particle of undisclosed chemistry.
In theory, sulphur dioxide or similar chemicals can cool the planet by forming suspended particles of sulphuric acid that act to scatter sunlight. When I wrote about the Make Sunsets incident, the company's founder said he thought it could profit by selling carbon credits under the belief that its actions would offset emissions.
They won't. Such a particle release does nothing but mask the effect of the carbon build-up in the atmosphere. If those releases are abruptly stopped, the temperature could rise suddenly in what's been called 'termination shock."
Bookbinder said that presidents, governors or even private individuals might be authorized to make such decisions. 'Right now, anyone can… There are literally no rules." He warned that if a cooling scheme initiated in one country coincided with floods, droughts or crop failures in another, the affected country might retaliate without direct evidence that the geo-engineering caused the problem.
One justification for geo-engineering comes from the 2015 Paris Agreement, which included an imperative to keep warming below 1.5° Celsius. We've already surpassed that mark. Preventing us from reaching even more dangerous temperatures will require more than just stopping carbon emissions. We might need to find a way to pull carbon out of the atmosphere on a global scale.
That was the stated goal of California businessman Russ George back in 2012 when he released iron into the Pacific Ocean off the coast of British Columbia. The iron, in theory, would fertilize algae, which would absorb carbon. There was never any documented scientific evidence that it helped.
Now, several companies, such as Canadian startup Planetary Technologies and US startup Vesta, are beginning to dump chemicals into the oceans in an attempt to increase the pH level of the water. This should, in theory, trigger more carbon uptake from the atmosphere. Planetary Technologies has found a way to make money by selling carbon credits.
With for-profit organizations already releasing chemicals into the oceans, it's important for scientists with no financial stake in this industry to collect data, said geo-chemist Adam Subhas of the Woods Hole Oceanographic Institute. The American Geophysical Union believes monetary gains should not be prioritized in small-scale research either.
There's a catch, according to Stanford's Jacobson. Small-scale experiments won't detect damage that might ensue if the projects were scaled up enough to actually affect global warming. In his view, we aren't coming close to realizing the world's potential to switch our energy needs to renewable resources. He convincingly argues that it makes no sense to resort to exotic and dangerous solutions when we haven't fully exploited what we know is safe and clean.
Right now, some of these companies have sunk millions of dollars in investor money, giving them incentives to convince the public and politicians that their particular brand of geo-engineering is necessary to save the world. What we need instead is more scientific data and some rules to protect us all from rash decisions and their unintended consequences.
©Bloomberg
The author is a Bloomberg Opinion columnist covering science.