Extreme weather, water shortages and imperiled polar bears: The effects of climate change are obvious and dire. To stem the tide — literally and figuratively — even educated experts are now pitching ideas straight out of science fiction.
On some level, it’s understandable. The grim reality of climate change poses some well-documented problems for humans. The biggest challenge, so far, has been convincing people to do less harm when it comes to the climate. Despite scientists’ plea to cool it with carbon dioxide (CO2) emissions — the most egregious of greenhouse gases contributing to climate change — CO2 levels continue to surge. Today, we put a whopping 20 times as much carbon into the atmosphere as our planet can remove naturally. To get back to healthy levels, we would have to cut our emissions by a staggering 98 percent.
“Could you imagine living on 2 percent of your annual income?” says David Battisti, an atmospheric scientist at the University of Washington. “That’s the problem: People can’t envision how you’d actually get this done.”
That line of thinking has led a cadre of scientists to explore alternative approaches to combating climate change. These approaches, known colloquially as geoengineering, take drastic steps to artificially manipulate the environment to help cool it. The techniques are big and brash; they are also very risky and in no way ready for prime time.
Despite being untested, and their consequences unknown, discussing such strategies has become less taboo of late, thanks, in part, to an increased sense of urgency to find short-term solutions.
These are the five most-discussed ideas in geoengineering to combat climate change:
1. Fake a volcanic eruption
When particularly explosive volcanoes erupt, they blast ash and sulfuric acid droplets into the atmosphere, which then morph into tiny reflectors that shield Earth from the sun. The result of this natural cycle is a global cooling effect. To mimic this process, scientists have proposed injecting a layer of sulfur dioxide particles into the stratosphere, most likely via aircraft. All things considered, the process is relatively straightforward and affordable. The estimated price tag is measured in the tens of billions of dollars, compared to the coming annual costs of climate change projected to be between $200 billion to $2 trillion annually.
In abundance, however, these particles gradually chip away at the ozone layer, reducing its ability to absorb the sun’s rays and allowing dangerous radiation through. Another problem: Once injected, the particles tend to spread around the globe and linger for years, making the process hard to undo if things go awry.
2. Make clouds brighter
Clouds keep things cool by reflecting the sun’s rays away from Earth. The whiter the cloud, the better it is at reflecting the sun. By seeding certain clouds with whitening materials — basically tiny particles of saltwater taken from the ocean below – we can transform them into natural sunshields. This cloud-brightening method costs about as much as the fake volcanic eruption option — roughly the amount Facebook paid for WhatsApp. It’s also less risky than injecting particles into the stratosphere because a weather system’s impact is regional, not global.
But lowering temperatures by blocking the sun’s rays is not without problems. Reducing the heat from the sun also means less water from Earth’s surface evaporates back up into clouds. That means when the clouds drift toward other parts of the world as part of a normal weather pattern, areas expecting rain might not get it anymore. The impact could be devastating and experts warn that altering weather patterns could spark water wars.
3. Fling a giant sunshield into space
You know those accordion-like sunshades made for car windows to keep the interior cool during summer? Scientists have proposed using that same principle to cool Earth. This technique would launch an enormous set of particle-based reflectors into space, positioning them between the sun and Earth to act as a giant parasol.
We know that this technique could cool Earth efficiently and relatively quickly, but the logistics and cost are serious obstacles. One proposal, for example, would launch a 60,000-mile-long shield containing 15 trillion reflective discs, each roughly 2 feet across, nearly a million miles into space. Even if we could pull that off, once the shade is up there, it’s up there for good.
4. Scrub the air of CO2
The goal here is to separate CO2 molecules from the air by passing it through chemical filters of a sort, which absorb CO2. This technique actually makes a lot of sense if you’re trying to filter carbon dioxide from, say, the smoke stack of a coal plant before it gets released into the atmosphere. If you try grabbing air out of your backyard, however, things get tougher: only about half a percent of that air is CO2. That’s not a great return rate, as you’d have to put a tremendous amount of air through a filtration process to have much of an impact. “The cost of doing this is astronomical,” atmospheric scientist Battisti said. “We’re talking about a good chunk of the U.S. GDP.”
5. Enrich the ocean with iron
Studies have shown that dumping iron dust into the ocean encourages the growth of blooms of phytoplankton — microscopic drifting plant life — that absorb atmospheric CO2 from the ocean. The hope is that after these tiny ocean plants die, they descend to the seafloor and take the carbon with them. The more phytoplankton, the more carbon they’ll pull down to the bottom, the thinking goes.
The problem is when phytoplankton sinks, other small ocean organisms consume and excrete them. This recirculates the carbon up to the ocean surface and ultimately back into the atmosphere as CO2. Scientists demonstrated that ocean enrichment, which would require depositing hundreds of tons of iron into the sea, would work, but its effect on temperatures and atmospheric levels of CO2 would be minimal, making the risks associated with mucking around with ocean ecosystems not worth taking.
So, yes, some of these ideas are bonkers and could potentially spark environmental issues much more atrocious than the ones we have now. But the fact that some of these are even on the table should be indicative of an even more terrifying reality: We need a solution to climate change, and we need one fast.
Julia Calderone is a science journalist living in Brooklyn, New York.