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Spraying Aerosols Into The Sky to Cool The Planet Is 'Technically Possible', Harvard Scientists Find

CARLY CASSELLA
27 NOV 2018

The idea was once taboo, but desperate times may just call for desperate measures.

If humans are able to spray millions of tons of sulfate aerosol into the sky, we could create a sort of chemical canopy that reflects heat from the Sun and takes the edge off global warming.

 

This kind of atmosphere-hacking could be dangerous, but as catastrophic climate change increases its grip on the planet, researchers at Harvard are beginning to take the idea of solar geoengineering more seriously.

"The fact that researchers at one of the world's top universities are costing the deployment of such a radical scheme shows how urgent the climate change problem has become," Peter Cox, an expert in climate system dynamics at the University of Exeter, told The Guardian.

The most detailed analysis of such a scheme to date has now revealed that while aerosol injection is highly uncertain and ambitious, it is "technically possible" from an engineering perspective.

It would also be "remarkably inexpensive" to fund. Using a fleet of specially-designed aircraft to periodically spray sulfate particles into the lower stratosphere, the Harvard research suggests we might be able to cool the planet at a price well within the reach of several nations.

If the program was launched in 2018, the authors predict it would cost about US$3.5 billion, with an extra $2.25 billion every year for program maintenance. To put that in perspective, the world currently spends about $500 billion a year on green technologies – an investment of far greater magnitude.

 

"Dozens of countries would have both the expertise and the money to launch such a program," the researchers conclude.

"Around 50 countries have military budgets greater than $3 billion, with 30 greater than $6 billion."

To realise this radical plan, one of the biggest expenses would be creating a new fleet of streamlined, sulfate-spewing jets.

The only cheap and reasonable option for distributing the aerosol is by aircraft. But an aircraft that can travel 20 kilometres high while also carrying a massive payload of aerosol? Nothing like that currently exists. And it needs to, if we want the sulfate particles to stick around in the atmosphere for more than a year.

Because of this, the researchers designed an entirely new plane that could serve such a purpose, featuring a narrow body and disproportionately large wings, as well as two extra engines.

Starting with a fleet of just eight jets – and ultimately ending up with almost 100 planes – a sulfate injection program would be able to complete over 60,000 missions a year in just 15 years.

But while this technology may help mask some of the symptoms of climate change, it won't solve the issue completely, leaving ocean acidification and other consequences to worsen. What's more, none of this even touches on the uncertainties and risks of deploying such a plan.

 

While solar geoengineering is often described as "fast, cheap, and imperfect", the Harvard study only supports the first two claims. Today, the imperfections of this technology remain unclear and, potentially, very dangerous.

Pumping enough sulfate into the atmosphere to mimic a volcanic eruption is risky business. It's also one of those solutions that, once started, cannot be stopped.

If the program is terminated for whatever reason, scientists think the rate of global warming would probably come back with a vengeance, rapidly raising global temperatures and leaving human society and ecosystems even less time to adapt.

As a solution to climate change, some scientists have compared it to throwing a bear into the arena with a lion: "You know, maybe they'll fight and kill each other. Or maybe they'll just both kill you."

Some experts have even gone so far as to call solar geoengineering a threat to democracy. After all, what happens if one country does take control of the global climate through solar geoengineering? And what if they do so without the rest of the world's consent?

In this regard, the Harvard study does offer a comforting thought. The findings suggest that a program of aerosol injection would require such widespread activity that keeping it secret from the rest of the world would be nearly impossible.

"No global SAI program of the scale and nature discussed here could reasonably expect to maintain secrecy," says Smith.

"Even our hypothesised year one deployment program entails 4,000 flights at unusually high altitudes by airliner-sized aircraft in multiple flight corridors in both hemispheres. This is far too much aviation activity to remain undetected, and once detected, such a program could be deterred."

Until maybe, one day, we decide that the risk is worth it.

This study has been published in Environmental Research Letters.