More than 10 years ago, Dr. Roy Spencer explained (1) in detail with examples why the climate models are wrong. All models were overstating climate sensitivity to greenhouse gases. The models were all (at the time) too sensitive to radiative forcing because they had misunderstood feedback processes, that is, feedback is an effect of radiative forcing, not a cause. His blockbuster revelation was that ALL feedback from radiative emissions from greenhouse gases is negative.
This note confirms Dr. Spencer’s conclusion at the molecular level. In the troposphere, the layer of air closest to earth’s surface, a greenhouse gas molecule, for example CO2, re-emits the long wave infrared radiation (LWIR) it absorbed from earth’s surface on average in about 300 picometers (0.00000001181102 of an inch) when it collides with another air molecule. But, when that emitted radiation is absorbed by another greenhouse gas molecule or earth’s surface, the radiation intensity is reduced by at least 50%, and so on for all subsequent absorption-collision-emission events.
In other words, radiative emission of LWIR from greenhouse gases is negative feedback, a cooling process not a warming process, resulting from the forcing of LWIR emissions up-dwelling from earth’s surface.
Long wave infrared radiation emitted and up-dwelling from the earth is broad spectrum IR radiation and varying in intensity, radiating from a bulk source on the surface which is usually continuing to radiate over some extended time interval.
In contrast, absorption of LWIR by a greenhouse gas molecule occurs at a specific intensity (watts per square meter) and at discrete, characteristic wavelengths of the greenhouse gas molecule. Relative to the tiny gas molecule, the earth’s surface is a large plane which is probably still emitting, especially during the day, when no more radiation can be absorbed by saturated greenhouse gas molecules. The bulk surface area of the earth emits a broad spectrum of LWIR wavelengths at varying intensities, but in contrast the greenhouse gas molecule can only absorb LWIR at discrete wavelengths and intensity. The radiative emissions (forcing) from the earth’s surface and the molecular absorber are very mismatched. LWIR radiation flux density from earth’s surface is astronomically large compared to the possible LWIR absorption by a gas molecule at any distance above the surface; the steradian geometry of LWIR from the surface is negligible.
Subsequent to the absorption event by the greenhouse gas molecule, the greenhouse gas molecule probably collides with a nitrogen or oxygen gas molecule, which usually causes the greenhouse gas molecule to emit its LWIR and relax to its ground state. Essentially a point source of light emits radiation at one or more discrete, characteristic wavelengths in a discrete intensity (or quanta) as an instantaneous pulse into 3D space. The intensity of that radiative emission is spread across 3D space. The intensity of the LWIR upon incidence on the next molecules or surfaces will be reduced by the inverse square law (the inverse of the square of the distance between the radiating greenhouse gas molecule and each of the receiving molecules or surfaces.) The radiation received at the next molecule or surface could be absorbed, reflected, scattered or transmitted transparently, but in all cases, the intensity of the LWIR radiation is reduced according to the inverse square law.
After a single radiative absorption event, the radiation from a molecule of greenhouse gas is emitted in a distribution spread across 3D space as determined by steradian geometry. Multiple other greenhouse gas molecules at different distances could absorb some of that radiation, or the earth’s surface could absorb some of that radiation, or the liquid and aerosol water in clouds could absorb some of that radiation, and some radiation could be transmitted to outer space. Every subsequent absorption event in the cascading series of absorption-emission-absorption events following the initial pulse of radiative emission from earth’s surface receives much less intense radiation than the absorption event that preceded it, never more intense radiation. This means that all feedback from radiative emission from greenhouse gases are negative (cooling) events, in agreement with Dr. Roy Spencer (1). Energy is being distributed in progressively lower amounts. There is no warming after the initial LWIR from the surface. Increasing the concentration of greenhouse gases (dominantly water vapor and clouds and minimally CO2) delays the rate of cooling by 3D steradian distribution of the LRIR radiation.
When the emitting greenhouse gas is very close to earth’s surface at least 50% of its emission is radiated away from the surface at varying steradian angles, and about 50% is radiated toward the surface at varying steradian angles. Radiative emission intensity from water vapor and clouds will always be significantly less than the radiation absorbed by the water vapor and clouds from the earth’s surface. Down-dwelling LWIR cannot warm the surface.
In addition, the wavelength of the radiation absorbed by the greenhouse gas is lengthened by the steradian angle of incidence of that radiation at earth’s surface. The intensity of the down-dwelling radiative emission at its point of incidence the surface is reduced by more than 50% and its wavelength is lengthened in every case except where the point of incidence is 90 degrees perpendicular beneath the radiating molecule. At all other steradian angles, the LWIR wavelength is lengthened. The LWIR spectrum is between about 7.5 microns and 14 microns. Above 14 microns is the microwave spectrum. At wide steradian angles of incidence on the surface, the LWIR radiation that was originally emitted from the greenhouse gas molecule is lengthened into the microwave spectrum where different physical phenomena occur, which will not be discussed here. But, the long wave IR from the original radiative emission from earth’s surface has been cooled to microwave wavelength by the radiative emission from the greenhouse gas molecule. Thus, the wavelength lengthening process from the radiative emission by a greenhouse gas is also reducing the energy feedback, i.e. negative feedback to the initial forcing caused by the LWIR radiative emission from earth’s surface.
Radiative re-emission or feedback from a cloud or greenhouse gas can never warm the surface or the object or the molecule that was the source of that radiation, consistent with the laws of thermodynamics. The source will always be at a much higher intensity than the feedback re-emitted radiation. As the re-radiating molecule moves farther from the source of the LWIR, the 3D steradian angle increases, which further reduces the intensity. Feedback from greenhouse gases such as CO2, methane, clouds and water vapor results in a time delay in cooling and reduction in intensity of the long wave IR radiative emissions.
In the case of one greenhouse gas molecule absorbing radiation from another greenhouse gas molecule, for example, a water vapor molecule absorbing radiative emission from a CO2 molecule, the water vapor molecule absorbs (if those energy bands are not already occupied) a specific intensity of radiation at CO2’s characteristic wavelengths which overlap with water vapor. Subsequently, If that water vapor molecule then re-emits that radiation, the intensity of that re-emitted radiation is distributed into 3D steradian space. That is, the intensity of the radiation received from the water vapor molecule by the next molecule is much less (following the inverse square law) than the energy that was initially absorbed by the water vapor molecule. The energy does not disappear, but it is broadly distributed in 3D space and time delayed.
Potential energy in a greenhouse molecule is the relative motions of one atom and its electrons relative to another atom and its electrons within a single molecule. The potential energy in one greenhouse gas molecule can be translated to potential energy in another greenhouse gas molecule by a collision under specific collision dynamics and geometry conditions. The gas molecules must have identical vibration modes where one molecule is at ground state and the other molecule is at its elevated vibration state. Also, the potential energy in one elevated greenhouse gas molecule can be translated to kinetic energy in another greenhouse gas molecule in specific collision dynamics and geometries. These are relatively rare collisions compared to a greenhouse gas molecule colliding with molecules of non-greenhouse gases N2, O2 and Ar which make up about 98% of air molecules. In the troposphere, neither IR radiation nor the potential energy associated with the elevated potential energy resulting from absorption of IR be absorbed by or translated to a gas molecule which does not have a dipole moment, for example, oxygen, nitrogen or argon.) LWIR radiative emissions from greenhouse gases cannot warm the non-greenhouse gases that comprise 98% of the molecules in the air. Nor can LWIR radiation from any source warm the 99% empty space that surrounds gas molecules in air.
Ignoring other important effects and considering only radiative feedback effects, if the water vapor and clouds are low altitude where air pressure is higher, then water vapor and clouds will have a relatively higher insulating effect (i.e. more delay in cooling) as compared to higher altitude water vapor and clouds, where air pressure is less, intermolecular distances are greater, collisions are less frequent and reduction in intensity due to distance is larger.
In all cases of radiative emission and absorption by greenhouse gases, the intensity of the radiation absorbed at one greenhouse gas molecule is substantially less than the intensity of the radiation that was absorbed by the prior greenhouse gas molecule which emitted that radiation, and the radiation becomes progressively less intense at each subsequent absorption event. For example, radiation absorbed at 1 picowatt per square meter at one greenhouse gas molecule is absorbed by the next greenhouse gas molecule at a small fraction of 1 picowatt per square meter.
In Summary, greenhouse gases are distributing energy rather than trapping energy. Radiative emissions from greenhouse gas molecules are spread over 3D space and spread over time. LWIR radiation from earth’s surface is delayed on its path back into outer space. This is delayed cooling, not warming, like wearing a stocking cap on a cold day.
Climate models yield incorrect answers in part because they assume a priori that feedback from greenhouse gases causes warming. Thus the models always overstate sensitivity to radiative emissions, CO2 concentration, water vapor, clouds and methane concentration. Climate modelers built greenhouse gas warming into their models. Michael Mann, Benjamin Santer and other scientists admitted in their 19 June 2017 paper in Nature Geoscience, “In the early twenty-first century, satellite-derived tropospheric warming trends were generally smaller than trends estimated from a large multi-model ensemble,” reads the first line of the abstract. “Over most of the early twenty-first century, however, model tropospheric warming is substantially larger than observed,” they added. In other words, the warming observed in real world temperature trends was “substantially” less than predicted by their climate models. (2)
Absorption and emission events in gases are not by and of themselves thermal events or heat. Neither the increase in energy due to absorption nor the decrease in energy due to radiation have changed the ability of the molecule to do work. Unless some other condition occurs, usually a collision, the greenhouse gas molecule is in thermodynamic equilibrium and in a natural, reversible state. Radiative absorption and emission in gases are changes in the motions of atoms and electrons/bonds within a single molecule. These are changes in potential energy, not kinetic energy. Thermal energy or heat is molecular motion, that is, directional motion of the entire molecule, or kinetic energy. Thermal energy is the molecule either moving at a velocity through space or the entire molecule vibrating or moving in contact with other molecules in a liquid or solid matrix. The radiative energy absorbed by greenhouse gas molecules causes already ongoing (i.e. ground state) vibrations of atoms and bond/electrons within the gas molecule to be increased by a discrete amount. The stretching and or bending oscillations/vibrations become higher frequency and farther; the outer electron shell expands. After a collision, or a change in condition such as the temperature or altitude, the gas molecule will emit that radiation at almost the same wavelengths and intensity in which it was absorbed, except the emission is into 3D steradian space but it was received in a discrete pencil-like or tube-like beam. Under certain conditions, for example very high pressure, there can be an extremely small amount of radiation emitted as scatter. It is not the gas molecules that are vibrating in space but it is the atoms and bonds/electrons inside the molecule which are vibrating. After the gas molecule emits its discrete quanta of radiation, it relaxes to its ground state vibrations, which are determined by temperature and pressure of the surrounding air.
Absorption and emission events are not in and of themselves thermal or heating events. The gas molecules do not change kinetic direction velocity as a result of absorption or emission. Collisions change kinetic energy which in turn usually causes emission of the energy held in the elevated state of internal vibration. The tropopause is the boundary between the troposphere and stratosphere. In the upper atmosphere above the tropopause, molecules are much farther apart, air is less dense, air pressure is lower, and CO2 spontaneously emits LWIR because its elevated energy state is out of thermodynamic equilibrium with the surrounding near vacuum. There is little water vapor and clouds in the stratosphere and in the other atmospheric layers above the tropopause which could block the LWIR emissions from CO2 into space. More than 50% of that radiative emission from CO2 will go into outer space. Again, radiative emission from CO2 is a cooling effect; the temporary absorption of LWIR by CO2 gas molecules is a delay in cooling.
Sunlight and infrared radiation are not heat in and of themselves. We perceive heat when the sunlight or infrared light cause the molecules in our skin to vibrate, which our nerves sense and our then brains perceive as heat. Or, the sunlight or collisions of moving molecules striking a thermometer cause the molecules in the thermometer to vibrate and expand, which we read on the thermometer as higher temperature.
Reference (1): Satellite and Climate Model Evidence Against Substantial Manmade Climate Change, by Roy W. Spencer, Ph.D. December 27, 2008 (last modified December 29, 2008)
Reference (2): Causes of differences in model and satellite tropospheric warming rates. Nature Geoscience. 19 June 2017. Benjamin D. Santer, John C. Fyfe, Giuliana Pallotta, Gregory M.Flato, Gerald A. Meehl, Matthew H. England, Ed Hawkins, Michael E. Mann, Jerey F. Painter, Céline Bonfils, Ivana Cvijanovic, Carl Mears, Frank J. Wentz, Stephen Po-Chedley, Qiang Fu and Cheng-Zhi Zou. NATURE GEOSCIENCE| VOL 10 | JULY 2017. P.478