When it comes to the climate emergency, heat-trapping gases like CO2 and methane are the cause but not the problem. The problem is the buildup of heat that is changing global weather at an alarming rate.
So maybe we should be trying to reduce the heat as well as the greenhouse gases. How? By reflecting sunlight back into space with mirrors on the ground, of course!
That’s the crazy-sounding idea being tested in a field at NHTI and alongside the airport in Plymouth. I don’t use the adjective “crazy-sounding” lightly.
“That’s the first reaction I had, the first reaction of everybody I’ve introduced the idea to,” admitted Lisa Doner, associate professor of environmental science at Plymouth State University, who is leading the New Hampshire experiments of Mirrors for Earth’s Energy Rebalancing or MEER. “But the more we explore the idea, the more we think that sometimes these simple solutions can be more effective than you give them credit for.”
Doner has overseen the installation of 235 mirrors on glass rods laid out in various patterns on a field roughly three football fields long and one field wide next to the Plymouth airport, which was the only field they could find that wasn’t shaded and didn’t get mowed for hay. Under those mirrors are a whole network of buried sensors to record what happens to the temperature and moisture in the soil in coming years.
A similar series of arrays are being installed near the Sycamore Community Garden at NHTI. Tracey Lesser, a professor of chemistry at Concord’s community college, who coordinates its Environmental Science and Sustainable Agriculture program, was out there last week overseeing students placing stands and mirrors and sensors.
“We’re hoping to have some data pulled by the spring, maybe in time to start analyzing for (students’) capstone research project,” Lesser said.Greenhouse effect
MEER is the brainchild of Ye Tao, an engineer with a physics degree from MIT who has been refining it and talking about it for a couple of years. (I heard him on David Roberts’ podcast “Volts” and as soon as he mentioned New Hampshire I said “Oh boy – there’s a column idea!”)
As you know, the greenhouse effect occurs because visible light from the sun can penetrate our atmosphere quite well to reach the ground but gets reflected back up as ultraviolet light – heat – which cannot penetrate our atmosphere very well. That light-turned-into-heat is increasingly trapped, just like within a glass greenhouse.
Tao’s idea is simplicity itself: Build a bunch of upward-facing mirrors that will reflect the light back up, so it can travel out through the atmosphere without heating us. In other words, increase the planetary albedo.
This is basic physics. You’ve probably heard of a variant called White Roof Project, which paints the top of buildings white so they’ll reflect more light, reducing their internal heat. It’s also the physics behind atmospheric geoengineering, which would release clouds of tiny particles from airplanes so they could reflect sunlight before it becomes heat.
The crazy part of MEER is that it needs to build and install enough mirrors to make a global difference. Tao has estimated that it must cover at least 10% of the planet’s surface, which would require more mirrors than the world can build. That last point is why part of MEER involves developing highly reflective thin films as a replacement.
But even if MEER is crazy, Tao believes we have to try. A big part of his pitch is that so much excess heat has already been accumulated since the start of the Industrial Revolution that cutting emissions, while vital, isn’t enough to avoid disaster.
“Even if we switch to 100% renewables tomorrow, we will still pass the heat thresholds” that could make the planet uninhabitable, he told the “Volts” podcast. Keeping out heat is necessary to give us time to transition the world to a carbon-free economy, he argues.Local effects
Like all good climate mitigation efforts, MEER also holds out hope for local benefits.
After all, everybody is attracted to the shade when it’s hot and ground-mounted mirrors provide it. It seems feasible that an array of mirrors could provide enough shade to help nearby people or crops survive an increasingly hot and dry world, even if they never do much for planetary climate.
Enter the New Hampshire field sites. Their main purpose is to quantify the very local effect of arrays and gather some data about construction methods and layout arrangements.
“It has been really effectively modeled but never ground-truthed,” said Lesser. “Tao was looking for a group – citizen scientist, undergraduates … He approached CCSNH (community college system) and UNH system, invited a bunch of us to a Zoom meeting where he outlined ideas.”
Donor and Lesser jumped at the possibility, seeing a mix of scientific value, student interest (college students know they’ll be living with increasing climate emergencies so they perk their ears up at mitigation) and hands-on experience with experiment design and construction.
“Environmental students don’t usually get a lot of chance to do fabrication and materials testing,” said Donor, who noted that the project’s tools and equipment took over an entire meteorology lab last summer.Controlled experiments
The PSU and NHTI experiments will be testing slightly different things, although there’s considerable overlap.
“We are testing arrays at different heights. Plymouth is doing it at different densities” of arrays, said Lesser.
They’ll also be gathering basic information about local effects of arrays through controlled setups. Concord, for example, will have one field of arrays featuring black, heat-trapping glass and one of clear glass to compare what happens under the mirrored arrays.
NHTI will be installing its mirrors soon – PSU’s have been up for a while – but is already getting feedback on mundane issues like wildlife.
“We have woodchucks in our experiment; they don’t seem disturbed by us at all,” said Lesser. Birds, on the other hand, are an issue. “Turns out the birds really like to perch on them. Their ability to reflect light is affected if they’re covered in bird poop.”How about weather?
“Our site is significantly windier than PSU,” Lesser said, which will affect construction. “Snow is a great question – do we just let it go and see what natural conditions are, or clear it? That’s one of the questions we’ll be looking at,” she said.
Many of these questions have been answered by ground-mounted solar arrays, of course, but there’s a difference. MEER has to be really cheap to build if it has any hope of making an impact.
“The goal is to make them as sustainable and easily sourced as possible and easily put together – something that could be deployed world-wide in developing and developed nations,” said Lesser. That even includes using twine at times.
PSU’s completed arrays hold 60-by-60-centimeter mirrors made of reflective film between thin tempered glass, held on cedar blocks by suction cups. The blocks are mounted at 25 degrees (the angle of the summer solstice sun) atop meter-long glass rods half buried in the ground.
Glass seems an odd choice for a support. But, the professors told me, unlike wood it can’t be chewed through for the five years or more the experiment will run, and unlike metal it doesn’t conduct heat into or away from the soil, which would affect the results. Real-world MEER installations would have more traditional supports.
PSU has already found some issues. For example, round supporting rods can be easily rotated by wind and soil movement so different cross-section shapes are needed.
“We are finding some fallacy in the methods. That’s part of why we’re doing this experiment, finding out the barriers for people doing something like this on a local scale,” said Doner.
And what about the possibility of MEER actually making a global difference? Is that crazy?
“I think about this a lot. I think it is (feasible),” Doner said. “If you just look at the number of mirrors needed it’s daunting, on the scale of a trillion mirrors to redirect the trajectory of climate warming … but that’s not to say that something even 1/1000th of that scale won’t help. Every reflective surface has an impact in changing climate.”
Importantly, she added, MEER is accessible. “It doesn’t take an engineering degree to stop this experiment, and it doesn’t take an engineering degree to start it.”
“One of the biggest takeaways, besides being a feasibility experiment, is it introduces folks to the concept of climate mitigation in a way that’s very reachable, very visible,” Doner said. “Education is important.”
“…visible light from the sun can penetrate our atmosphere quite well to reach the ground but gets reflected back up as ultraviolet light – heat…”
I thought it was infrared, not ultraviolet, radiation that was heat. No?