[ ♪ Intro ].

Scientists agree that climate change is happening and that Earth is getting warmer. And while that means we all need to get serious about limiting our carbon dioxide emissions, for real this time, it also means scientists are looking for plan B.

Because we might need it. Many researchers are thinking about changing the climate with climate engineering or geoengineering. We’ve talked about some of these ideas before—like throwing a bunch of stuff in the air to reflect sunlight and cool the planet.

But big things like this would have huge downsides, like changing rainfall patterns, and probably other stuff we can’t even predict. That has some researchers searching for yet another way, like by using the Earth to clean up our messes for us. Here are three ways we could do that.

Plants are great for the environment because they can suck CO2 out of the air and give us oxygen in return. But the simple fact is that, between farming and other uses of land, we don’t have the space to plant enough trees to solve our climate change problem. Still, we do have oceans, and they’re good at growing plants, too.

Seaweed, for instance, grows extremely quickly, some 30 to 60 times faster than land plants. And it’s relatively easy to grow in bulk. So, some folks are proposing seaweed farms as a solution to our carbon woes.

You’d grow the seaweed, and then it could be turned into a biofuel and used to power something like a car. One research group estimated that if you devoted 9% of the ocean to growing seaweed, you could provide all the biofuel the world needs. And as long as you captured any emissions from that fuel, you could still remove about as much CO2 as the world spits out every year.

They project this would offset all our emissions by 2035, and even get us back to the level of carbon dioxide that scientists say is safe—about 350 parts per million—by 2085. For comparison, we’re at about 410 parts per million now, which is not so great. By removing CO2 dissolved in water, seaweed would even help with ocean acidification, which can make life hard for creatures like coral.

Still, if this all seems like a longshot, you’re right. Massive seaweed farms aren’t exactly an investor’s dream, and to make it truly work, you’d need to figure out how to capture carbon emissions efficiently. But it sure beats planting a few forests, which would never be able to scale up like this.

So we could always try this on a small scale and see how it works. As wonderful as seaweed is at fixing carbon, some engineers and start-ups are trying to take that a step further. They want to improve on Mother Nature by creating artificial trees and plants.

These machines would take carbon dioxide out of the air directly, using so-called direct air capture technology. Different machines work differently, but most use specialized materials that bind CO2 more tightly than other molecules. Then, the systems either store the gas indefinitely, or use it for biofuel.

Some, including one running prototype in Iceland, even turn the CO2 into stone. They piggyback on the fact that carbon dioxide will react with certain rocks, like basalt, to form carbonite minerals. That keeps the CO2 out of the air basically forever, which sounds awesome.

Other designs call for pumping the captured gas into greenhouses to grow crops. Still, the biggest problem with all of these is cost. We have prototypes that work, but they don’t work very well, and they’re just too darn expensive.

Right now, it takes some $200-$600 to get one metric ton out of the air, so it would take billions of dollars to solve our climate problem. We’d need to cut that cost way down to flood the world with these super trees. Another option might be to skip the plants and pseudo-plants entirely, and just freeze carbon dioxide right out of the air.

This might be the strangest proposal of all, but the idea is relatively simple. First, go to a place where it’s super cold, like Antarctica, where carbon dioxide almost freezes on its own already. Then, build freezers to bring the temperature down to about 140° Celsius below zero.

Depending on the pressure, that’s enough to turn the CO2 into snow so you can store it in a frozen landfill forever. Still, to make this work, the energy for the freezers would have to come from a renewable source, like a nearby wind farm. One group of scientists thinks 16 or so wind farms would do the trick.

They’d power 450 snow plants and pull 1 billion metric tons of CO2 out of the atmosphere every year. That’s only a small fraction of what we emit, but, hey, it's a start. There’s also a variant on this idea that involves making CO2 basically rain out of the sky.

You’d fling a compound called monoethanolamine into the air, which is great at binding CO2. Then, it would grab the carbon dioxide and fall to earth, where it would collect on the ice sheet of East Antarctica. I mean, it’s not like we’re doing much down there anyway.

This plan is still super hypothetical, but it goes to show just how strange these ideas get. Compared to true geoengineering efforts, all of these ideas are somewhat small-scale, so they’d have to be ramped up in a huge way to make much of an impact on our carbon levels. But because they’re less risky, they’re more likely to be tried than any major project.

And, at this point, that might be the most important thing. Thanks for watching this episode of SciShow! If you’d like to learn more about some of those extreme geoengineering solutions to climate change, you can watch our episode all about it. [ ♪ Outro ].