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This article is part of a Fortune Special Report: Business Faces the Climate Crisis.

For two decades, Klaus Lackner has been fixated on trees and how they pull carbon dioxide from the air. What if, the Arizona State University engineering professor theorized, you could create a machine that worked like a tree—but a thousand times more efficiently—thereby reducing the effects of climate change?

In January, Lackner’s first such artificial tree—which looks less like a real tree and more like a supersize lamp—came off the manufacturing line in Boston, and, along with more than 250 others, will be installed near Phoenix. Unlike a real tree, which absorbs 10 tons of carbon in its lifetime, these mechanical trees may one day each collect up to 32 tons of CO₂ in a single year—the equivalent of what seven passenger vehicles emit annually. “We need to start cleaning up after ourselves,” Lackner says.

Fake trees may seem like a far-fetched solution to climate change. But today they’re one of many sci-fi ideas gaining momentum amid ominous scientific studies showing rising earth temperatures and increasing carbon dioxide in the atmosphere.

An artificial tree designed by Klaus Lackner of ASU sucks CO2 from air that moves through the device.

These out-there technologies are part of a scientific field called geoengineering, which is aimed at manipulating the environment to offset the effects of climate change. Unlike, say, solar or electric vehicles, whose widespread adoption would depend on changing consumer behavior and established industries, geoengineering technologies attack climate change directly—and, theoretically, have an impact more quickly.

“The next decade is going to be another decade of disappointment, and if we’re serious about preventing climate change, we need to explore all the options,” says Jesse Reynolds, who researches geoengineering as a fellow in environmental law and policy at the University of California at Los Angeles law school.

But critics argue that such technologies may make it more difficult to curb the core problem because they remove any incentive for humans to stop emitting greenhouse gases. If we cool the earth with new technology, then companies and people will fail to reduce pollution, they say.

“There’s a moral hazard of giving people an excuse to not do anything about climate change,” says Joanna D. Haigh, emeritus professor of atmospheric physics at Imperial College London and former director of the Grantham Institute – Climate Change and Environment.

Adding to the backlash is the fear that large-scale interventions can negatively change the earth’s natural systems by altering rainfall and weather patterns or causing flooding and drought. And some of the possible effects can’t simply be turned off.

Nevertheless, projects like the Marine Cloud Brightening Project, an international collaboration led by atmospheric scientist Robert Wood and University of Washington researchers, are pushing forward. The team has built powerful nozzles that would be installed on boats and spray 3 trillion particles of seawater each, hundreds of feet into the air.

The technology mimics an already known phenomenon in which exhaust from oceangoing ships creates streaks in marine clouds and cools the earth temperatures below them. Salt particles are thought to work similarly but are a more environmentally friendly alternative.

Computer models suggest that spraying just 20% of the earth’s clouds could cool the entire planet by two or three degrees Celsius, says Kelly Wanser, adviser to the Cloud Brightening Project and executive director of SilverLining, a nonprofit that’s pushing for funding for geoengineering projects. But Wanser admits that clouds are complicated and that it’s difficult to predict what will happen.

Scientists are also exploring the idea of fertilizing the ocean with iron sulfate to stimulate the growth of algae, the sea life that absorbs carbon dioxide and releases oxygen. In 2012, for example, an American businessman dumped iron sulfate off Canada’s Pacific coast that created an artificial algae bloom over as much as 10,000 square kilometers. But such efforts are controversial because algae compete with other aquatic life and can reduce fish population. Meanwhile, in February, researchers at the Massachusetts Institute of Technology published a paper saying, in fact, that kick-starting beneficial algae growth on a global scale is nearly impossible.

Meanwhile, researchers are studying whether building massive underwater sand berms where glaciers meet the ocean could keep glaciers from disappearing, thereby preventing sea levels from rising. The sand would form walls around the submerged glacial ice and, theoretically, keep chunks from breaking off. The scientists, who hail from Princeton University, Beijing Normal University, and Finland’s University of Lapland, are also considering building artificial islands and large pumping stations that would channel cold water under glaciers, which, on land, slide on a thin layer of ice, to slow their movement.

Another idea, pushed in a paper published by Swiss scientists in 2018, is that switching the color of all roofs to white in every major city could cool the earth by up to two or three degrees Celsius. New York City actually introduced rules for white roofs into its building codes in 2012, and volunteers have been painting tar rooftops in the Big Apple, as well as in Chicago and Los Angeles.

At Harvard University, scientists are taking a cue from volcanic eruptions, which naturally spray sulfur dioxide into the stratosphere and cool the earth below. The researchers want to spray a shield of mist made of calcium carbonate—found in chalk and seashells—into the stratosphere and reflect sunshine back into space. They plan to test the theory by using a balloon sent into the stratosphere to release the light-reflecting particles, and then, if it works, deploy high-altitude planes to do the same thing on a larger scale.

Advocates of geoengineering say it can bridge the current political impasse in the U.S. over addressing climate change. While conservatives may balk at regulating fossil fuels, they’re generally more open to the idea of fostering innovation through research.

In December, Congress approved a $1.4 trillion spending package that includes some funding for geoengineering projects. The National Oceanic and Atmospheric Administration and the Department of Energy received at least $19 million for early-stage research.

Noah Deich, executive director of Carbon180, a think tank focused on carbon removal, says the key to the success of individual geoengineering projects will be largely determined by the market and not necessarily novel technologies. Companies that sell carbon-eating technology could generate revenue from existing incentive programs and additional ones experts expect will be implemented in the coming years. That landscape is starting to take shape. California already offers carbon removal credits and other incentives to companies that capture and bury harmful CO₂ underground—a technique that academic and government researchers deem safe.

Lackner, the artificial-tree designer, has high hopes that he can create a market for fake trees. He and Arizona State University signed a deal with Ireland-based Silicon Kingdom to manufacture his carbon-eating trees, install them on wind and solar farms, and then sell the liquid CO₂ the trees produce to beverage companies that want a supply of sustainable carbonation for their drinks.

The secret to economic success for Lackner’s tree, says Silicon Kingdom’s CEO Pol Móráin, may be its simplicity. The tree—which cost $30,000 to $100,000 each—require no special equipment to be installed or maintained, and they are small enough to mass produce and operate using solar or wind power.

Each tree is as about the size of a poplar, with carbon-absorbing “leaves,” or plastic-like discs, that feel like leather and look like shag carpet. The leaves drop down into the “trunk,” a barrel at the bottom of the system. Using heat inside the barrel, the tree converts the carbon gas to liquid CO₂ and then stores it underground using a series of small pipes.

Móráin says that a large carbon tree farm with 120,000 mechanical trees could capture 4 million tons of carbon annually. If 250 large-scale farms were created, they could suck up 3% of global carbon emissions, he says. “When we started, there was a lot of skepticism,” says Móráin. “But over the last six to seven months there has been a mindset change.”

A version of this article appears in the April 2020 issue of Fortune with the headline “Sci-Fi Tech Tackles Climate Change.”