NOTE:
A worthwhile study. I included only the portions explained in relatively easy to understand language. The full study with the math can be found at the link. I learned complex math while studying engineering in the stone age 1970s, but struggle with it today. Fortunately the text is easy to understand. I believe the conclusion that CO2 causes some global warming, but not that much, is reasonable.
I do NOT believe the authors' claimed precision, to one decimal place, about the past global average temperature effects of adding CO2 to the atmosphere. The technical name for that is the false precision fallacy. In climate science, however, false precision is a small problem compared with the usual always wrong wild guesses of the FUTURE climate! The alleged +1.5 degree C. temperature rise from pre-industrial tipping point, for one example, is baloney, not based on any science. If re-stated as +1.527 degrees C., that would be false precision, but the number would still be baloney. I say "baloney" because when rounded to the nearest 0.1 degree C. that "tipping point has already been reached twice during the peak temperatures from El Nino heat releases from the Pacific Ocean. Once in 1998 and again in late 2015 or early 2016 (I can't remember which right now). No one even noticed, except me!
Ye Editor
Source:
http://www.ijaos.org/article/298/10.11648.j.ijaos.20210502.12
"Abstract
It has long been accepted that the “greenhouse effect”, where the atmosphere readily transmits short wavelength incoming solar radiation but selectively absorbs long wavelength outgoing radiation emitted by the earth,
is responsible for warming the earth from the 255K effective earth temperature, without atmospheric warming, to the current average temperature of 288K.
It is also widely accepted that the two main atmospheric greenhouse gases are H2O and CO2.
What is surprising is the wide variation in the estimated warming potential of CO2, the gas held responsible for the modern concept of climate change.
Estimates published by the IPCC for climate sensitivity to a doubling of CO2 concentration vary from 1.5 to 4.5°C
based upon a plethora of scientific papers attempting to analyse the complexities of atmospheric thermodynamics to determine their results.
The aim of this paper is to simplify the method of achieving a figure for climate sensitivity not only for CO2, but also CH4 and N2O, which are also considered to be strong greenhouse gases,
by determining just how atmospheric absorption has resulted in the current 33K warming and then extrapolating that result to calculate the expected warming due to future increases of greenhouse gas concentrations.
The HITRAN database of gaseous absorption spectra enables the absorption of earth radiation at its current temperature of 288K
to be accurately determined for each individual atmospheric constituent and also for the combined absorption of the atmosphere as a whole.
From this data it is concluded that H2O is responsible for 29.4K of the 33K warming, with CO2 contributing 3.3K and CH4 and N2O combined just 0.3K.
Climate sensitivity to future increases in CO2 concentration is calculated to be 0.50K, including the positive feedback effects of H2O,
while climate sensitivities to CH4 and N2O are almost undetectable at 0.06K and 0.08K respectively.
This result strongly suggests that increasing levels of CO2 will not lead to significant changes in earth temperature
and that increases in CH4 and N2O will have
very little discernable impact."
Equilibrium Climate Sensitivity (ECS) is generally understood to be the increase in earth surface temperature resulting from a doubling of atmospheric CO2 levels after thermal equilibrium has been achieved (Zhong and Haigh 2013).
Values for ECS deduced from a variety of climate models show a high degree of uncertainty with a typical range remains a wide range of estimates of what the ECS could be.”
This is an unfortunate situation since world governments are implementing ambitious and expensive plans to limit the increase of global temperatures by reduction of CO2 emissions to atmosphere,
and to achieve a net zero carbon economy, in the belief that CO2 emissions are the main driver of global temperature increases.
In order to justify such a fundamental change to the global economy and indeed the associated risk to an “established way of life”
it is of paramount importance that an accurate value for ECS is determined.
To do this, it will be necessary to cut a swathe through the complexities of atmospheric thermodynamics and find a simple method of
accurately estimating ECS.
1.1. The “Greenhouse Effect”
The average temperature of the earth is determined solely by the energy balance at the top of the atmosphere (TOA).
At equilibrium, energy input from the sun is balanced by the energy radiating from the earth, which is a function of its temperature.
The term “greenhouse effect” is used to describe the process whereby short wavelength solar radiation is transmitted through the atmosphere,
whereas components of the long wavelength radiation emitted by the earth are absorbed by the atmosphere, thus limiting re-radiation into space with a consequential warming of the earth (Schwartz 2018).
The atmospheric gases which absorb this energy, principally CO2 and H2O, are collectively referred to as “greenhouse gases”.
In order to quantify this warming, it is first necessary to identify the key contributing variables.
1) Solar Radiation.
This is the radiated energy received by the earth from the sun.
It may be calculated from a knowledge of the sun surface temperature and the diameter and distance of the earth from the sun.
This value is corroborated by direct measurement from orbital satellites. (Trenberth et al 2009).
2) Earth’s Albedo.
The earth’s reflectivity to solar radiation.
This is a measurement of how much of the solar radiation is reflected into space, thus weakening the solar radiation input.
3) Earth’s Emissivity.
All bodies emit thermal radiation as a function of their temperature according to the Planck equation for black body emission.
The emissivity of the earth determines what fraction of that black body radiation is actually emitted by the earth.
4) Atmospheric Absorption.
Absorption of the long wavelength radiation emitted from the earth by atmospheric gases, in particular H2O and CO2, both possessing strong infra-red radiation absorption characteristics.
5) Retention of Absorbed Energy.
This is the key issue which contributes much to the uncertainty in determination of climate sensitivity.
What happens to the energy absorbed by the atmosphere?
There are only two possibilities;
some of the energy is reradiated through to space by the warmed atmosphere,
or the energy is retained by the earth and its atmosphere thus contributing to the planetary warming.
This energy retention is a function of complex atmospheric thermodynamics and its estimation is a major cause of the
wide variations in climate sensitivity estimations.
1.2. Retained Energy
Variables 1 to 4 in the list above are all easily identifiable and may be determined with reasonable accuracy.
Variable 5, Retention of Absorbed Energy, however, is in a different league.
Atmospheric thermodynamics are immensely complicated and to use them to determine an accurate estimate of the fraction of absorbed energy that is retained is near impossible in the non-linear chaotic system that is the earth’s atmosphere and is the primary contributor to the wide range of estimates of climate sensitivity (Stevens B. et. al., 2016) [8].
There is, however, an alternative method of determining this retained energy factor using the calculations of earth temperature.
6. Conclusions
In order to satisfy radiative equilibrium at the “top of the atmosphere” (TOA) at an average earth temperature of 288Kelvin, only 61.5% of the earth’s radiated energy should be transmitted through to space, leaving 38.5% to be absorbed and retained by the atmosphere/earth.
Use of the HITRAN data base of gaseous absorption spectra shows the current atmospheric absorption to be 73.0% of total radiative emissions of which 52.74% must be retained by the earth/atmosphere to satisfy the current TOA equilibrium.
This is a simple expression of the current earth temperature equilibrium.
The 38.5% retained radiation absorption comprises 35.3% attributed to H2O, 3.0% to CO2 and a mere 0.2% to CH4 and N2O combined.
From this it follows that the 33Kelvin warming of the earth from 255Kelvin, widely accepted as the zero-atmosphere earth temperature,
to the current average temperature of 288Kelvin,
is a 29.4K increase attributed to H2O,
3.3K to CO2 and
0.3K to CH4 and N2O combined.
H2O is by far the dominant greenhouse gas, and its atmospheric concentration is determined solely by atmospheric temperature.
Furthermore, the strength of the H2O infra-red absorption bands is such that the radiation within those bands is quickly absorbed in the lower atmosphere
resulting in further increases in H2O concentrations having little further effect upon atmospheric absorption and hence earth temperatures.
An increase in average Relative Humidity of 1% will result in a temperature increase of 0.03Kelvin.
By comparison CO2 is a bit player.
It however does possess strong spectral absorption bands which, like H2O, absorb most of the radiated energy, within those bands, in the lower atmosphere.
It also suffers the big disadvantage that most of its absorption bands are overlapped by those of H2O thus reducing greatly its effectiveness.
In fact, the climate sensitivity to a doubling of CO2 from 400ppm to 800ppm is calculated to be 0.45 Kelvin.
This increases to 0.50 Kelvin when feedback effects are taken into account.
This figure is significantly lower than the IPCC claims of 1.5 to 4.5 Kelvin.
The contribution of CH4 and N2O is miniscule.
Not only have they contributed a mere 0.3Kelvin to current earth temperatures,
their climate sensitivities to a doubling of their present atmospheric concentrations are 0.06 and 0.08 Kelvin respectively.
As with CO2 their absorption spectra are largely overlapped by the H2O spectra again substantially reducing their impact.
It is often claimed that a major contributor to global warming is the positive feedback effect of H2O.
As the atmosphere warms, the atmospheric concentration of H2O also increases, resulting in a further increase in temperature
suggesting that a tipping point might eventually be reached where runaway temperatures are experienced.
The calculations in this paper show that this is simply not the case. There is indeed a positive feedback effect due to the presence of H2O,
but this is limited to a multiplying effect of 1.183 to any temperature increase.
For example, it increases the CO2 climate sensitivity from 0.45K to 0.53K.
A further feedback, however, is caused by a reduction in atmospheric absorptivity as the spectral radiance of the earth’s emitted energy increases with temperature,
with peak emissions moving slightly towards lower radiation wavelengths.
This causes a negative feedback with a temperature multiplier of 0.9894.
This results in a total feedback multiplier of 1.124, reducing the effective CO2 climate sensitivity from 0.53 to 0.50 Kelvin.
Feedback effects play a minor role in the warming of the earth.
There is, and never can be, a tipping point.
As the concentrations of greenhouse gases increase, the temperature sensitivity to those increases becomes smaller and smaller.
The earth’s atmosphere is a near perfect example of a stable system.
It is also possible to attribute the impact of the increase in CO2 concentrations from the pre-industrial levels of 280ppm to the current 420ppm to an increase in earth mean temperature of just 0.24Kelvin, a figure entirely consistent with the calculated climate sensitivity of 0.50 Kelvin.
The atmosphere, mainly due to the beneficial characteristics and impact of H2O absorption spectra, proves to be a highly stable moderator of global temperatures.
There is no impending climate emergency and CO2 is not the control parameter of global temperatures, that accolade falls to H2O.
CO2 is simply the supporter of life on this planet as a result of the miracle of photosynthesis."