You may have noticed that a lot of folks seem to be in a panic about Climate Change. This concern rests on the assumption that increased atmospheric CO2, presumably from human activity, will cause increased heat retention in the atmosphere, leading to potentially dangerous over-heating of the planet.
The principle is pretty straightforward. Incoming radiant energy from the sun, consisting of infrared, visible, and ultraviolet wavelengths, passes with little resistance through the atmosphere and strikes the surface, warming it. Some of the heat is transferred downward, deeper into the earth, some of it is transferred directly to the atmosphere by contact, but much of it is re-emitted in the infrared portion of the spectrum. It is called “outgoing long-wavelength radiation,” OLR for short. Unimpeded, OLR would head straight to space.
But atmospheric gases, including CO2, absorb and re-emit, in all directions, some amount of the OLR, delaying its return to space. It is in essence a faint secondary reflection of the incoming radiant energy. The backscattered OLR transmits some amount of radiant energy back toward the surface, warming it by some amount. More CO2 means more energy captured and re-radiated by the atmosphere, meaning more heating of the surface and atmosphere. Or so goes the thinking.
But the energies involved are actually comparatively small. The IPCC estimates that increasing the concentration of CO2 from 280-ish ppm to 420-ish over the last 150 years has added the equivalent of 2.5 Watts of radiant energy for every square meter of surface.
To put that in context, a typical flashlight bulb emits around 5 Watts of energy. The clear-sky summer sun at noon delivers about 1400 Watts of radiant energy per square meter of surface, while the whole-earth, 24/7 average is about 342. Incoming solar radiation also fluctuates by as much as 90-plus Watts per square meter over the course of an average year because the Earth’s orbit is slightly elliptical, with perihelion (closest to sun) occurring in January and aphelion (most distant) occurring in July.
So if the IPCC’s figures are accurate, then the additional CO2 has increased the radiant energy reaching the surface, on average, by only about 0.7 percent. Energetically speaking, that’s the difference between having a chicken salad sandwich for lunch and having that same sandwich plus a quarter of a potato chip. Or increasing the power output of an automobile engine from 142 horsepower to 143. Or to put it another way, it is about one fortieth the amount of annual variation caused by the Earth’s elliptical orbit.
OK, so maybe it’s not really a problem right now. But if you add a bunch more CO2, this smallish value will become a much larger one, right?
Maybe, maybe not. Let’s take a closer look.
The “absorption spectrum” of CO2, meaning the wavelengths it absorbs and re-emits, is pretty patchy. The gas absorbs very strongly in only one narrow band centered on about the 15 micrometer wavelength, pretty close to the center of the OLR spectrum.
By contrast, water vapor, which is very abundant throughout most of the lower atmosphere, has numerous absorption bands across the OLR spectrum, including the 15 um band, though it does not absorb quite as efficiently as CO2 at this particular wavelength.
CO2 absorbs this wavelength so strongly that it is effectively blocked, even at very low concentrations. This leads to sharply diminishing returns as the concentration of CO2 increases. At 50 ppm CO2 captures maybe 80 percent of the available 15 um band, at 100 ppm a few percent more, at 200 ppm yet a couple percent more, and so on. By the time you get to 400 ppm, more or less the current value, greater than 90 percent of the OLR that can be captured, has been. If you double again to 800 ppm you capture just a couple percent more of the available radiant energy. Full saturation, meaning 100 percent capture, theoretically occurs around 4000 ppm.
Which incidentally was about the level of atmospheric CO2 during the Cambrian Period around 500 million years ago. During the Cambrian, the abundance and diversity of multicellular life forms expanded dramatically. Just for grins, google “Cambrian explosion.”
The principle of diminishing returns is central to the issue of climate change, because if it is accurate, then CO2 has very nearly reached the limit of its ability to add heat to the atmosphere. Any further increase of CO2 in the atmosphere, no matter how large, will add only a minuscule amount of heat. It follows that people panicked about “global boiling” are working themselves into a lather over nothing.
This knowledge, widespread in the field of atmospheric science, has been unknown to the general public, and ignored by those pushing climate alarm for fun or profit. There’s a really good reason for this omission, too. Because a LOT of money is on the line, not to mention careers and reputations and many hundreds of millions of dollars in government grants. And what would the media do to grab eyeballs if it lost one of its favorite surefire Narratives?
Climate Change is now a trillion-plus dollar international business. Goldman-Freaking-Sachs for crying out loud is sinking billions into it. They are not doing this because they are nice people who care.
With so much money, prestige, and power on the line, any contrary data is likely to be ruthlessly suppressed. And that’s exactly what has happened over the last couple of decades.
But the walls are starting to crack. Here and there scientific publications that still have some integrity have published original research that goes against the grain. One recently published article, by a trio of Polish physicists, verifies the principle of diminishing returns, first established by Happer and Wiijngarden some years ago. You can find a summary of it it here. The article referenced, a summary of this paper, also contains a link to the original.
For some folks, this is heresy, literally. Others are threatened by a finding that imperils their gravy train. So there will be pushback, and it will be vicious. Don’t be surprised if the article is eventually withdrawn on some pretext after a coordinated pressure campaign waged by the usual suspects, who want to keep the fear alive, no matter what, because this is the basis of their power.
And their profits.