Terrestrial globe on top of an induction stove, demonstrating that man-made global warming is a proven fact. Try it yourself!
I’m a meteorologist and this is a short explanation of the effect of carbon dioxide (CO2) in the atmosphere. There is a lot of alarmist rhetoric about a “crisis” due to human industry – human industry that has brought us out of the Dark Ages, doubled our life expectancy, and made the world greener. What’s not to like about that? Oh, yeah … the claim that we’re going to roast the planet.
Adding CO2 to our atmosphere is no more likely to harm humanity, or Nature, than adding more insulation in the roof of your house will set the place on fire. Understanding this requires some recall of High School physics.
The Earth, warmed by the Sun, emits infrared radiation, at wavelengths between about 9 and 14 micrometers (millionths of a meter). Everything on our Earth, including us, emits some amount of infrared radiation. The numbers I’ve quoted come from Wien’s Displacement Law – yes, you can find it easily on the web – that relates the peak wavelength of emission to the temperature of the emitter.
Normal Earth surface temperatures range between 310 K (Kelvin), or a little less than body temperature, and 210 K, or the air temperature outside a transcontinental aircraft. Brrrrrrr.
Let’s think of Earth’s emitted radiant energy in the form of photons, little discrete energy units, headed upward – some straight up, some off to an angle, and each at a wavelength determined by the temperature of the object it came from. Most of these photons (about 85%) will be absorbed by a molecule of greenhouse gas, either water vapor (H2O) or CO2. That means some of the electrons circling the atoms in these molecules will briefly rise to a higher energy state – an “orbit” farther from the nucleus. We say the atom has been “excited.”
This is where the “global warming” alarmists get excited too, making claims about “trapping” heat in the atmosphere. Ah, no! Atoms don’t remain in an “excited” state, any more than you do (as when the bank tells you the checking account is overdrawn). In a couple of nanoseconds (billionths of a second), the greenhouse gas molecule dumps the energy imparted to it in the form of a new (infrared) photon.
The original photons, from the Earth, were headed upward; which way do the new photons go?
Anyway they want – half up, half down. The ones that go up continue to space, and the Earth has cooled itself. The ones that go down return some – less than half – of the energy lost. That returned energy, that didn’t get away, is the “greenhouse effect” (GHE). No heat has been “trapped.”
In our atmosphere/Earth system, the GHE gives back about 33 degrees C, or 59 degrees F. About 30 C (54 F) of that is due to GHE from H2O, and about 3 C (5 F) is GHE from CO2. Note that no new energy has been added to the system; the Earth released (say) 100 photons, and got back less than 50.
The “greenhouse effect” doesn’t warm the Earth; it just slows the cooling, like the insulation in the roof. The insulation won’t burn the house down; it won’t even warm the house by itself.
That should be a relief; in addition, there are other reasons GHE from CO2 is not dangerous.
The alarmist story gives the impression all photons are alike, to a CO2 molecule. Not true; CO2 molecules have “favorite” wavelengths of photons. Physicists measure absorption “lines” and “bands”, specific wavelengths that a particular molecule responds to. The one and only CO2 absorption line in Earth’s emission spectrum is around 14.78 micrometers. Ouch; according to the Wien Displacement Law, that’s a photon that comes from an object at a temperature around -77 C, about the temperature at South Pole on a bad day. CO2 just doesn’t absorb – or return – many photons, because there aren’t many photons emitted from cold surfaces. It doesn’t “see” the warm photons at all, because they’re the wrong wavelength. Only about 5% of Earth’s emitted energy is “visible” to CO2; only half of that can be returned.
Another weakness in the “global warming crisis” argument is the Law of Diminishing Returns, a.k.a. Logarithmic Response. Remember, the energy returned to Earth by atmospheric absorbing gases comes entirely from molecules that have been lucky enough to catch an Earth-emitted photon in the first place. How much more “greenhouse” energy would we get if we add one more molecule of CO2 than is needed to absorb all the upwelling photons?
That last CO2 molecule is out of luck; all the upwelling photons are absorbed by the CO2 that’s already in place. It’s the end of the GHE. Until then, every added molecule of a greenhouse gas has only half the effect of the previous molecule, with which it competes. The GHE looks like the logarithmic curve (base 2) on the right. We are long past the “knee” of the CO2 GHE curve, and on the flat part. After all, volcanoes and decomposing vegetation have been adding CO2 to the atmosphere for eons. At the end of this article are some references to the vanishing effect of CO2.
Since 1997, we’ve increased the CO2 content of the atmosphere by about 10%.
It’s presently 400 molecules per million, or 0.04% of the atmosphere. (Water vapor, on a nice Summer Florida day, is about 40,000 molecules per million, or 4%.) Astoundingly, in spite of all that added CO2, there has been no warming of the atmosphere in the last 17 years. NOAA, NASA, the UK Meteorological Service, and the Intergovernmental Panel on Climate Change (IPCC) all agree. The CO2 we add today, and tomorrow, and next year, and in your grandchild’s lifetime will have the same, undetectable, effect.
Let me summarize this article with two points:
The lack of any warming for 17 years – and counting – might be due to diminished solar output. Or it might be due to more clouds in the atmosphere, due to more cosmic rays, or it might be due to the 60 year cycle of the Pacific Ocean (the Pacific Decadal Oscillation), which has gone into its cold phase, as it did in the mid-1940’s. But none of these potential reasons are included in the scores of climate models for which the Federal government has paid billions of our tax dollars. In the politicians’
models, only CO2 is admitted to control the climate. So the politicians have no justification to claim they have “settled science” on their side. Don’t let them turn off the heat and the lights for no reason – or just to control our lives.
And, whatever controls the climate – we don’t know – the simple physics you’ve just read tells us added CO2 is not “catastrophic.” You can’t produce catastrophic warming from the logarithmic added insulation of a minor constituent that merely slows the loss of 5% of Earth’s emitted radiation.
EDITORS NOTE: The featured image is an edited version of a photo taken by Quod Scripsi Scripsi, which is described as a, “Terrestrial globe on top of an induction stove, demonstrating that man-made global warming is a proven fact: Do it yourself!” This file is made available under the Creative Commons CC0 1.0 Universal Public Domain Dedication