Day 52: Future not so bright if Earth’s gotta wear shades

Yes, it's come to this. A University of Arizona researcher has solid support for his idea to launch mirrors into space to deflect some of the sun's light in a climate emergency. Credit: Roger Angel

Thankfully, some researchers are pulling away from the is-it-is-or-is-it-ain’t global warming debate, and moving ahead with solutions to our undeniably nasty habit of fouling our global nest. 

But the reality is, such solutions are in their infancy — and it’s hard to tell, at this point, which ideas could help mitigate damage to Earth and which could backfire.

Seeding the oceans with iron to combat acidification, and pumping carbon dioxide underground, are two recently proposed solutions that come to mind. Here’s another one: adding things to the atmosphere to deflect some of the sun’s heat, so it doesn’t get trapped by excess greenhouse gases in the first place. Recently, orbiting mirrors and particulates have been suggested to fill such a role.

Each proposed solution comes with a projected price.

The idea to delay global warming by adding particles into the upper atmosphere comes in part from large volcanic eruptions, such as Mt. Pinatubo’s in 1991. Airborne sulfur hovering in the stratosphere cooled the Earth for about two years following that eruption.

But Daniel Murphy, a scientist at NOAA’s Earth System Research Laboratory in Boulder, Colorado, has studied that 1991 eruption, and his results predict unintended consequences of trying to mimic them.

Atmospheric particles reduce the amount and change the nature of the sunlight that strikes the Earth. On average, for every watt of sunlight the particles reflect away from the Earth, another three watts of direct sunlight are simply scattered in the atmosphere.

But most large-scale solar plants — the kind that can contribute to electricity grids — rely on direct sunlight and can’t use diffuse light. In sunny locations such systems, which use curved mirrors or other concentrating devices, generate electricity at a lower cost than conventional photovoltaic, or solar, cells. (Smaller-scale and photovoltaic cells can use both direct and diffuse sunlight.)

After the eruption of Mt. Pinatubo, peak power output of Solar Electric Generating Stations in California, the largest collective of solar power plants in the world, fell by up to 20 percent, even though the stratospheric particles from the eruption reduced total sunlight that year by less than 3 percent.

“The sensitivity of concentrating solar systems to stratospheric particles may seem surprising,” said Murphy. “But because these systems use only direct sunlight, increasing stratospheric particles has a disproportionately large effect on them.”

Murphy thinks seeding the atmosphere with sunlight-deterring chemicals could unintentionally reduce peak solar power by as much as one-fifth. The findings appeared online March 11 in Environmental Science and Technology. 

Hm … adding a pollutant to the atmosphere to counteract the effects of another pollutant … while compromising a truly green answer to our reliance on fossil fuels? I’m probably going to vote against that plan. 

But then, Roger Angel, an astronomer at the University of Arizona, has proposed something even more radical. He wants to fire trillions of sun-deflecting mirrors a million miles beyond Earth using a huge cannon with a barrel more than half a mile across. He’s already got NASA funding for a pilot study, and he’s commissioned an inventor. He knows the cost will be steep — around $350 trillion — but he thinks we could get the job done in 20 or 30 years.

Angel notes that his idea is for a climate emergency. And I hope we don’t get there. 

Seems a lot cheaper, healthier and responsible to rein in our vehicle emissions and learn to consume within our global means. Yes?

Sources: Press release on the atmospheric particle seeding and an article and press release about the giant sunshade.