How Satellite Data Explains the Dynamic Energy Balance of the Earth in Space, and How Surface Temperatures Must Change to Maintain that Balance. No Models Required
An answer I just gave to a question in Quora
The question I answered , in spades, was : How do satellite measurements of IR emission help us understand the impact of greenhouse gases like CO2 compared to gases like nitrogen and oxygen?
ANSWER: Massively. Here’s why…..
The radioactive long wave infrared spectrum from the Earth measured from space defines the total cooling energy that is leaving Earth to maintain the dynamic balance with incoming solar energy that is absorbed by the atmosphere and terrestrial surface - so that the balance is always maintained, as it obviously must be, determined by whatever level the solar insolation is currently at, as our cyclically changing orbit around the Sun varies the distance between Earth and Sun.
The outgoing long wave infra red LWIR energy spectrum we observe shows us the effects of greenhouse gases that limit the transmission of energy from the surface back to space, hence requiring a higher surface temperature to maintain this balance.
The radiative spectrum shows the characteristic frequencies that GHGs affect . The largest effect is by water vapour and the lesser effects of carbon dioxide, there is no radioactive absorption in nitrogen and oxygen, so no effect on the outgping LWIR. There is no debate about the reality of the greenhouse effect as we see it from space but the dominant effect is from water vapour and the effects of CO2 have become very limited at current levels due to the band saturation effect - which is nothing to do with heavy metal and you can study at your own leisure. In short more CO2 has little effect above the lowest level at which plants can survive, and hence humans.
For detail graphical details including the measured satellite spectra and the full paper on this see:
The reason the theoretical spectrum of the radiative black body Plank curve is changed is because the GHE reduces heat loss from the surface and atmosphere. Hence the gap in the radiative spectrum at the GHG binding energy levels/frequencies. The GHE does not directly warm anything. It reduces cooling. The necessary response to the loss of cooling by all the sources of re-radiated solar energy is what warms things up, as a consequence of increased GHE creating a positive imbalance in the Earth’s balance system.
The greenhouse effect doesn’t warm anything directly, it insulates the surface from space so its harder for particular frequencies of radiation to leave and cool earth. So the planetary surface and atmosphere is warmed by the imbalance caused by the GHE increase UNTIL all the radiation losses to space combined increase enough to restore the energy balance. Again, this is dominated by water vapour, well seen in the satellite record. Water vapour increase creates a much larger cooling effect than its other warming feedback of its greenhouse effect. Water vapour release by oceanic evapoartion increases by 7% per deg SST, that latent heat enrgy reaches space as radiation after being released to the atmosphere as latent heat on condensation. This negative feedback to warming is three times as powerful as its positive feedback, but NAS and other conveniently include the GHE while ignoring the larger radiative cooling that must also result from the water vapour formation. The cooling evaporative enrgy loss is 3 times the warming greenhouse effect for water vapour alone.
All observed as real in the satellite spectra, which is why they are so important in understanding the big picture from space. Just the facts. No models required. The overall empirical assessment of Earth’s energy balance in space is in the satellite radiative spectra, well studied and reported, quantified as an overall radiative balance in space here:
Catt, Brian, An Empirical Quantification of the Negative Feedbacks of Earth's Energy Balance (January 01, 2025). http://dx.doi.org/10.2139/ssrn.5220078
NB: An important difference between water vapour and CO2’s smaller greenhouse effect is that CO2’s is well saturated before 200ppm, and becomes more saturated, less sensitive as CO2 levels increase. The CO2 GHE degrades logarithmically. So any given doubling in CO2 has the same temperature effect on the surface of earth. 200–400ppm has the same effect as 2000–4000ppm. And both levels are perfectly safe for humans, so we have a LOT of headroom. Also, CO2 is not a pollutant, it is a natural gas essential to plant and human life that depends on burning carbon based food to generate the energy required to live. We are made of 20% Carbon CO2 absorbed from the atmosphere as CO2. The carbon cycle most people are taught at school but most seem ignorant of, forgot or didn’t listen? More is measurably good for crops.
No bad things have happened because of more CO2, per the UN IPCC itself (IPCC AR6, Page 1856, fig 1212). Only good things we can measure.
The earth has absorbed so much CO2 that only 4 parts in 10,000 are left in the atmosphere, close to the death of plants level during ice age glacial phases between the short warm periods like now, because when its coldest the oceans absorb more CO2. The oceans currently hold 98% of all the CO2 on the surface of earth in absorbed forms, been there since the oceans formed and sucked it up from the atmosphere 4Billion years ago or so, BTW. CO2 is mostly not in the air, it’s in the water, also bound up in limestone and chalk and generally at a low level, but with its CO2 GHE already well saturated by 200ppm, and the remaining possible effect relatively small for the reasons above.
Just the facts we have measured. No models required. Real science versus fairy tales.
That's mostly wrong in the science fact.
All enrgy leaving the surface is passed to space as radiation, see NASA energy budget.
Radiated LWIR, and indeed incoming EMR, is not warmed or absorbed by N2 or O2, they are ideal gasses that are transparent to this frequency of radiation and their molecular structure does not have multiple binding energy modes. That is simply false. KInetic enrgy is thermal, unrelated.
GHG radiative scattering happens throughout the affected frequencies path to the tropopause, the GHGs inhibit radiation passing through the Troposphere to space, nothing is warmed or captured in a such scattering process of quantum excitation and relaxation, no enrgy loss occurs within the atmosphere as a result of it.
As regards thermal enrgy, the latent heat of evaporation becomes thermal energy in the Troposphere and that is in turn released to space as photonic energy, yes. THis has nothing to do with the radiative Greenhouse effect.
The CO2 band saturation effect is described as logarithmic throughout the literature. Because it is. Read it. Nobody describes it as logistic? There is even an expression that defines it. Can't type it here. It simply an inverse log function, decaying not expanding, there are two types.
See real scientific papers for details, Pierrehumbert's is good, as I reference.
You are of course right regarding how the radiative spectrum measured from space gives an indication of the altitude in the Troposphere a particular frequency of radiation has come from, if you know the lapse rate where it departed for space.
Great Article Brian. I normally pester Howard , but he is busy today. So a couple of queries. Firstly,
I thought the incoming EMR could heat O2 and N2 to a small extent through Photoionisation and Photodissocition? And if so, do you know how much? Or is that wrong? And secondly, I can never totally comprehend the NASA Energy Budget. I get the approx Quarter total incoming solar radiation of 340.4 W/m2 and the balance of Absobed and Reflected energy. All Good. But where does the 398.2 Emitted or the 340.3 Back Radiation come from? Thin air? Surely an emitted Photon of IRR redircted downwards by a Mol of CO2 in the narrow band of 14 to 16.5 Mu must have at best equal, but probaly less Energy than the Surface it came from. Therefore it could not possibly "Heat" the surface, let alone "cumulatively heat" the surface, causing more evaporation of H20, and warming the planet, as stated by the IPCC. Unless I've misundestood Thermodynamics ?? And isn't LWIR reflected by H2O anyway, so the Oceans couldn't be Heated by the redirected LWIR ? Your thoughts?? Cheers David D