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    CALIPSO and similar satellites. NASA

    Scientists Propose Using Lasers to Fight Global Warming From Space

    Written by

    Brian Merchant

    Senior Editor

    At the world's first major geoengineering conference, two separate scientists put forward proposals to use lasers to modify the Earth's climate and fight global warming, from space.

    One suggested that a satellite equipped with a high-powered laser could grow clouds in the atmosphere below; the other proposed lasers that would blast greenhouse gases from orbit to effectively erase the agents of climate change. 

    The highly theoretical proposals are still in their early stages, and easily count as the more radically ambitious of the already radically ambitious climate engineering schemes discussed by scientists. These plans don't concern gadgets that absorb carbon pollution or spreading particles in the sky, after all—we're talking about space lasers powerful enough to alter the climate.

    And European Space Agency fellow Isabelle Dicaire studies them full time. She traveled to Berlin this week to discuss how a satellite equipped with high-powered LIDAR lasers may prove useful for researching—and maybe eventually actually orchestrating—climate engineering.

    LIDAR is remote sensing technology that blasts a laser at a target, then analyzes its reflection to accurately measure distances. It's already widely used here on Earth (on things such as Google's driverless car), and by NASA's CALIPSO satellite. Dicaire is interested in what we could do with a much more powerful LIDAR positioned in space; theoretically, it should be able to better detect the movement of particles in clouds, and maybe even make new ones.

    this would be the first step if you'd like to do laser cloud seeding

    Among the most widely discussed geoengineering ideas of recent years is so-called cloud-brightening. A cloud is just a mass of water vapor that's condensed into droplets around particles floating in the air—and the more droplets in a cloud, the more sunlight gets bounced off of them. 

    So, geoengineers figure that if you can increase the surface area of clouds, or seed more of them altogether, you could begin to reflect back enough sunlight to cool the globe. Research into the subject has been limited, and Dicaire says a powerful LIDAR would help scientists better understand the science. Beyond that, it could be used to carry out the cloud-seeding itself.

    "Another application is to use the effects that are happening inside the plasma filaments to do some exotic stuff. For instance, laser-based cloud seeding," she said. Researchers at the University of Geneva, Dicaire says, have demonstrated that lasers can produce droplets.

    "They are generating nano-sized water droplets from the laser," she said. They're doing it in a lab, though. "I'm monitoring the field to see what we could do from space."

    So, theoretically: "You can use the Earth Observation System to target or find where you have your clouds, what kind of clouds you would like to seed, and then from that, aim the beam towards these clouds." Bear in mind that the idea ESA is examining here is entirely theoretical, and no laser even exists in orbit capable of performing such a feat. But it's not unthinkable, technologically speaking—the political and economic hurdles are probably larger.

    "So far you can only find these laser sources on the ground. Eventually, if someone would like to put them in a satellite, they would have to space qualify them. So this is something that some industries are looking into. And this would be the first step if you'd like to do laser cloud seeding."

    This would likely be a pretty expensive way to make clouds brighter—older proposals suggest using boats to spray seawater skyward—and you'd need an awful lot of cloud-growing laser satellites. But Dicaire, for now, is more interested in the underlying research LIDAR could help scientists perform.

    Image: NASA

    "It's a very basic concept. The only one looking at it at the moment is ESA, and it's very preliminary. We just want to see if it's possible to send your beam from the satellite to the ground. If it's possible then, yeah, we'll look more closely into this," she said.

    Alternatively, we could use another type of laser-toting satellite to blast away the greenhouse gases already in the atmosphere. That's what Aidan Cowley, a professor at Dublin City University, proposes, anyhow. He believes that a solar-powered satellite equipped with a plasma laser could hone in on heat-trapping gases in order to get them to break apart into less harmful ones.

    "We've already observed here on earth that plasma ionization approaches, for example, air plasmas, can essentially dissociate long-lived pollutants: SF6, carbon dioxide. This is something we've observed, and it's been well reported in literature," Cowley told me. "Plasma essentially will excite whatever gas it's traveling through, and just by giving energy to these gases, these molecular species, they'll break up—in the case of SF6, they'll become S, and become more benign greenhouse gases."

    It's an alluring idea, of course; SF6 is a potent and long-lasting greenhouse gas. And our immense CO2 output is driving climate change toward a cliff; it'd be convenient if we could just zap them away with a laser. So why haven't we done it already, if plasma ionization has proven to scatter the building blocks of our climate crisis?

    "The problem about using [lasers] as a means of actually addressing climate, greenhouse gases per se, is that the energy used to strike those plasmas has to be generated here on Earth. So essentially you're burning fuel to destroy the emissions that you're producing anyway, and it ends up being a net positive to the emissions profile anyway. So you have to come up with a low cost, energy-free scenario that frees you from that paradigm. And that's where the idea of using space solar power to do so comes into it."

    A satellite outfitted with high-efficiency solar panels should do the trick.

    there's nothing crazy about it, solar power in space

    "Essentially by using abundant power that's available in orbit, to drive ionization phenomenon in the atmosphere, you can neatly size up the problem of doing the same thing here on the ground, and you have a nearly unlimited supply of energy to do so. You just need to develop the technology and tap it for that," he said.

    Now, there are other pitfalls here; those greenhouse gases are already pretty diffuse in the atmosphere, so it'd be hard to target them effectively with a laser. Cowley says you'd probably need multiple units to do it effectively. Then there's the vast expense of building, testing, and deploying the machines, of course.

    Cowley also says his satellite would be useful for creating ozone, to patch up the holes we've left by overusing aerosols. "You could use it to create ozone, too," he said. "Pretty strong pedigree for producing ozone. It's a very easy trick." Then again, he adds, the technology could be used to the reverse effect, too.

    "Conversely, from a military perspective, you could also use it to destroy the ozone as well, if you do it the right way," he said. "It could potentially open the holes in the atmosphere of your not too friendly neighbors."

    So does Dr. Cowley think his greenhouse gas-blasting satellite is feasible?

    "I still think it will take a long time. It's got an underground movement to a certain degree, so I think it will continue to be developed, going forward. Space solar power has got a fairly good future for certain applications, and, I think, eventually, like most technology, it will be the niche that drives the mainstream adaptation," he said. "Find one good niche and make it work, and people will go, 'oh that's not so crazy after all.' And there's nothing crazy about it, solar power in space. It's not science fiction."

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