Sucking carbon dioxide out of the sky - or "direct air capture," as it is known by experts and scientists - is a bit like a time machine for climate change. It removes CO2 from the atmosphere and stores it deep underground, almost exactly the reverse of what humanity has been doing for centuries by burning fossil fuels. Its promise? That it can help run back the clock, undoing some of what we have done to the atmosphere and helping to return the planet to a cooler state.
The problem with direct air capture, however, has been that it takes energy - a lot of energy. Carbon dioxide only makes up 0.04 percent of ambient air, making the process of its extraction chemically and energy intensive. According to the U.N. Intergovernmental Panel on Climate Change, by 2100 the world needs to remove between 100 and 1,000 billion tons of carbon dioxide from the air to meet its most ambitious climate goals - or between 10 and 100 times China's annual emissions. But if the energy powering that comes from fossil fuels, direct air capture starts to look less like a time machine than an accelerator: a way to emit even more CO2.