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The inside scoop on solar geoengineering

This article is from The Spark, MIT Technology Review’s weekly climate newsletter. To receive it in your inbox every Wednesday, sign up here.

Sometimes, as a reporter following climate technology, I feel like I have a front-row seat for some of the hottest topics on the planet. 

That’s how I’ve felt watching the news about solar geoengineering unfold over the past several months. Thanks to a few big news events, efforts to cool down the planet by reflecting some sunlight back into space are suddenly a huge part of the public conversation.

But some people have been watching this show for years. And lucky for me, I get to work with one of them: James Temple, senior editor for energy here at MIT Technology Review. James has been following the field of geoengineering for nearly a decade, and he just published an in-depth essay about what all these recent developments could mean for the future of the climate. So for the newsletter this week, let’s take a look at the world of solar geoengineering. 

What is solar geoengineering, anyway? 

Geoengineering is an umbrella term that covers a wide range of efforts to alter the Earth, usually in some way related climate change. Propping up a melting glacier, for example, could be considered a form of geoengineering. 

Solar geoengineering, as you might guess from the name, involves sunlight. Reflecting some of the sun’s radiation back into space could help cool the planet, counteracting the warming caused by greenhouse-gas emissions. 

The solar geoengineering approach that’s gained the most attention involves using aircraft like balloons or planes to release gases or small particles into the atmosphere that would reflect sunlight, easing warming. Other potential paths include brightening clouds over oceans or even launching elaborate sunshades. By the way, this is all mostly theoretical so far, since nobody can really agree whether we should even be studying solar geoengineering, much less doing it. 

So what’s all the buzz about? 

Some academic groups have been trying to research solar geoengineering for years. But these efforts have hit roadblock after roadblock, and scientists are facing public opposition to even small-scale experiments designed to better understand how efforts to reflect sunlight might work. Caution here is understandable: tweaking the climate at a big enough scale can have huge effects, and some are concerned that even relatively modest actions could have unintended consequences.

Recently, though, a few people have just gone ahead and … launched stuff anyway. In December, James broke the news that a person named Luke Iseman had reportedly released a balloon in Mexico that contained a few grams of sulfur dioxide. This amount of material is tiny—far less than what’s released in a single transatlantic flight. It’s also not clear whether this really did anything, or even if the material made it into the stratosphere, because there wasn’t great monitoring equipment on the balloon.

But in any case, the moment made waves across the tech and climate communities. Iseman later founded a startup called Make Sunsets. The Twitter response was wild, and the media coverage of this startup following the initial story has been fascinating—after you read James’s piece from December, check out this story in Time, where the writer went along with the startup on another launch. 

And guess what? Make Sunsets may not be the only project that’s gone ahead with small-scale geoengineering efforts: in March, James found out that a group in the UK had apparently launched a balloon with a few hundred grams of sulfur dioxide in September 2022. (It feels important to share with you that this balloon was called “Stratospheric Aerosol Transport and Nucleation,” or SATAN for short.)

Why is all this happening now? 

I posed this question to James in a recent chat about his solar geoengineering coverage, because even though I had followed the news through his work for a few years, all the recent hubbub in the last six months still took me by surprise. 

While the tide of geoengineering has been rising for a while, with more papers being published and more researchers getting engaged, “I think that we’ve just kind of reached this societal tipping point on the topic of climate change,” James told me. 

Basically, people are starting to see the effects of climate change and to understand that it’s a big deal—that we need to make big moves, and quickly. James pointed to the 2018 UN climate report emphasizing the importance of limiting global warming to 1.5 °C over preindustrial levels, ands the school strikes that same year, as big turning points. I’d personally also add the floods in Pakistan in 2022, an especially tragic disaster that put climate damages front and center. 

Where is all this going? 

Small-scale efforts to tweak the climate have now happened. “We’ve moved into this at least slightly different world,” James told me. But, he adds, it’s not clear exactly what this will mean for the future of the field. 

Some folks think these small-scale actions could open the dam on geoengineering, with DIY efforts multiplying and more people trying to monetize them. Or they could end up slowing things down. Earlier this year, Mexico (where Iseman launched his balloons) announced it planned to restrict geoengineering and would encourage other countries to do the same. 

In a new essay published last week, James took a step back to reflect on the state of geoengineering and consider the flawed logic of rushing out extreme climate interventions. 

“I think we have time to properly have a democratic debate over what solutions we want to use and what sets of trade-offs we’re okay with,” he told me. “I’m not saying we should engineer the planet, but I am saying that climate change is really bad and going to be much worse, and we really do have to be careful about taking options off the table.”

Related reading

Check out James’s recent essay, where he spoke with some of the biggest voices in solar geoengineering and shared some of his takeaways about recent developments in the field. 

Some nonprofits and academic groups want to expand who has a say in debates about solar geoengineering. 

In case you missed them, here’s James’s story about Make Sunsets, and here’s the one about the UK test flights. 

Dilapidated wind power station with spare parts of wind turbines in the foreground


Another thing

Wind turbines, and the renewable energy they provide, are going to be key in addressing climate change. The problem is, old turbines are starting to pile up in landfills.

The good news is that materials researchers are on the case: a lab in Denmark recently developed a process to break down the fiberglass that makes up wind turbine blades and recover some of the material’s key building blocks. Read more about the new research, and what it would take to make this method work on millions of tons of old equipment, in my latest story.

Keeping up with climate  

Swedish battery maker NorthVolt is joining the race to build batteries powerful enough for planes. (Bloomberg)

→ The company’s highest-performance batteries come in at an energy density of about 400 watt-hours per kilogram, well below a commonly cited target for short flights, 1,000 Wh/kg. Read more about why batteries for planes may still have a way to go. (MIT Technology Review)

California just passed aggressive emissions rules for trucks that will boost electric heavy-duty vehicles. How this plays out could be a key indicator of just how quickly vehicle supply and charging infrastructure can ramp up. (Canary Media)

Airbnb is starting a program to help hosts pay for heat pumps in Massachusetts. The incentives are on top of state money, as well as federal tax rebates. (Canary Media

→ Here’s some background on how a heat pump works, and just how expensive one can be. (MIT Technology Review)

While trucks in the US keep getting bigger, people like farmers who use them for work are clamoring for something different. Now, some rural Americans are importing tiny Japanese pickup trucks. (The Economist)

The ocean is really, weirdly warm this year, and climate scientists are worried. (Wired)

→ A warming atmosphere and hotter oceans could have surprising effects, like potentially disrupting key currents in the Atlantic. (MIT Technology Review)

The European Union just passed huge rules for new aviation fuels. Low-carbon fuels will need to make up 6% of supply in 2030, a steep jump from today. (CNBC)

An energy company in Texas is building a power plant that it says can burn a mixture of natural gas and hydrogen. The approach is gaining steam because of tax credits and upcoming rules for power plant emissions, though the technical details are still fuzzy. (Washington Post)

In the latest development in the gas stove saga, a budget proposal in New York state could ban natural-gas hookups in new buildings. (New York Times)