Posts Tagged ‘Tropics’

Global Warming: a Cheap, Easy, Temporary Fix

August 29, 2012

I’ve been thinking about global warming. The US Meteorological Service has now changed its official stance and states that global warming is at least partially caused by human activity. That got me to thinking, and so I’ve now posted an idea in two Facebook groups I’m a participant in.
Global warming means that we will see more drought, more intense and more giant storms, and a general change to the surface of the Earth with disruption of food supply and probably an increase in hunger for those who live in marginally-productive countries. I suspect that in time we’ll find a long-term solution, but in the short term, there’s going to be a lot of human misery and death and loss of wealth among the developed nations. So even a temporary fix would be useful, until the science and engineering is available to provide a longer term solution.
I know how to fix global warming.  The worst problem I foresee is not cost or efficiency, but the resistance of people and politicians.  This idea needs no new science, but it does need an reinterpretation of existing science.

I’ll begin with an overview of the greenhouse effect. Global warming depends at bottom on that.  Global warming is simply a slight rise in efficiency of the trapping process of the insolation.

So what is the greenhouse effect, and why does it work? Much solar radiation passes through the atmosphere without being absorbed; that’s how we can use it to see. This radiation has a certain set of bandwidths, the colors that can be separated by a prism or rainbow. There are also ultraviolet and most interesting for our viewpoint, infra-red radiation. This is, in essence, radiated heat. It’s easy to demonstrate; you can feel it on your skin, and you feel its absence when a cloud shades the sun. It strikes the earth and is differentially absorbed or radiated back to space. Dark farmland, for example, absorbs heat quite efficiently; water less so, although what is absorbed is also released in the form of latent heat in evaporation (this is what fuels hurricanes, and usually begins off the coast of Africa in the northern hemisphere). Sunlight striking sand is partially reflected, and that which strikes snow and ice is almost totally reflected.
Reflected sunlight, like incoming sunlight, is not efficiently absorbed by atmospheric gases. It’s still at the same frequency/wavelength as it was when it came in, so it passes through the atmosphere and back to space.  Photos taken from space use this reflected energy.
But what of the energy that strikes the ground and is absorbed? It heats the Earth’s surface. That’s easy to prove; take a walk on a warm day barefoot, you can feel it. I also once used the heat-trapping effect of color (black plastic tubing to design and build a solar heater for my swimming pool in El Paso; 300′ of 2″ irrigation tubing, coiled on the roof of my porch, then a system of pipes to connect this to the pool circulation pump, and so whenever I used the pool filter, I also got free heat. Very efficient; I often swam as early as February and as late as November in El Paso, in West Texas).
The Earth not only reflects incoming radiation, it also radiates. It must; this is how the Earth disposes of absorbed radiant heat and also heat from the interior.  But because it has a temperature that’s different from that of the sun, it radiates in a different bandwidth. The soil doesn’t glow, but you can feel the heat radiating in the evening; very pleasant. This radiation is at a wavelength that is readily absorbed by water vapor, Carbon dioxide, and Methane.  Absorption of radiated heat is the greenhouse effect.
So it occurred to me that the way to interrupt the greenhouse effect was to change the albedo selectively; to reflect, rather than to absorb, the incoming radiation. The best place to do this is in the band of deserts that surround the Earth, at about 30º north and south of the Equator. The tropics, the band from 23.5º north to 23.5º south through the equator, generates its own albedo change through cloud production. But the deserts are often clear; no clouds, no rainfall, just heat absorption.
If we could change that pair of desert zones from a strongly-absorbent to a reflective zone, it should reduce the greenhouse effect and hence reduce global warming.
This is the science.  Change not global warming, instead change the Earth’s greenhouse effect.

I came up with a way to do this.  It depends on the fact that not all parts of the Earth absorb energy equally.  Change the part that is most energy-absorbent, you have a much greater effect on the greenhouse effect than you would have if you attempted to change the greenhouse effect by, for example, working at the poles.

I would first begin with a small test unit and gather data; one day, then a week, then ideally  over the course of a year. What seems practical in theory might not work in reality.

So I intend to build a test unit.  I will then gather the data, interpret it, put it into graphs and then present it. Only data needed is temperature, preferably from electronic thermometers taking readings from under the reflective panel and one or more readings outside it but nearby.  Simply put, to change the planet’s temperature, I would build large numbers of frames, preferably of aluminum, but wood would also work. Across these I would stretch 2-mil reflecting mylar film (one roll, $35 from Amazon, 50″x50′). Support the panels above the ground. For the test plot, perhaps a meter above ground; for actual use, two or three meters up. Make small units, say 5m x 5m. Install, move on. They can be manufactured over Winter, begin installation in early Summer, hope to last a year at least. They should be installed for maximum effect around the world on all land surfaces that are currently desert. At the designed height, they would not interfere with passage of humans and animals below them. I would slant them at about 13º facing South in the Northern hemisphere, facing North in the Southern Hemisphere. It is not necessary to wrap the entire planet in these; the beauty of it is that it’s cheap and each installation has some small effect. The shaded land won’t be harmed; it’s desert, hence not used for anything except grazing.

Maintenance: if damaged, a frame could be reused and the mylar film simply replaced. I suspect it wouldn’t last more than a season, perhaps with luck two, before solar UV deteriorated it. But even fragments blowing along the ground are minimally useful because they reflect sunlight.
Incremental effect; each panel reduces insolation, the basis for the greenhouse effect, by a small fraction. Many of these, large fraction. Adjustment: getting too cold, close down some of the panels. Still too hot, glaciers melting? Put up more.  The effect is incremental and linear depending on the numbers of panels.
Proof: easy to construct a cheap panel farm. Take temperature readings  underneath the panels in the shade, and around them in full sunlight. Collect daily information, say at 8am, at 12 noon, and at 6pm. Do this for a year. Examine how much maintenance is required. Large winds will likely destroy a significant number of panels, but a ‘breakaway’ fastener on one side might alleviate that while still keeping the panel tethered. Deterioration from the Sun, a problem. It may turn out that 5mil or 10mil would be better, but the cost would be higher. Costs should be less for mylar than I quoted; that $35/50″x50′ is retail, so wholesale and economies of scale should reduce that.
End of the year: assemble the data, graph it, discuss and publish.  Budget for a full-scale test? Say $1 million.  Actual cost?  Less than $100 000.  The rest is reserve for unexpected expenses.I intend to set up the test plot, consisting of one or two panels and the land surrounding them, and begin collecting data.  I should begin to do this within two weeks.
Feel free to circulate the idea and run it by experts.  The only thing I ask is that if you’re using my work, I get credit for my input.
Update: I’ve now acquired three thermometers, one that measures minimum and maximum temperature values, another as a check on the first (both are digital and use probes for sensing), and a non-contact infrared based thermometer.

I built a test panel and installed it today, Sep 15 2012.   I used salvaged plastic and wood and fastened the plastic to the wood with staples, then wrapped the plastic once around the wooden end pieces to keep the staples from ripping through the plastic.  I put up four T-posts that I had on hand, installed guy ropes to stabilize and tension the panel, and then clamped the end boards to the T posts.  The panel is approximately 50cm above the ground.  I have posted photos on my Flickr page.

I took first readings this afternoon about 3pm.  The differences between the shaded ground and plastic (those read approximately the same) and the sunny ground alongside the panel were 12.5 C degrees.  I’ll be making more precise measurements using the sensors of the digital thermometers.  But I conclude that this afternoon I became the first person to deliberately reduce the greenhouse effect, and global warming, by a small but measurable amount.