Atmospheric pressure may have been over 2.0 bar during the Jurassic, which may explain why Antarctica was a densely vegetated rainforest during that time.
It has long been understood that atmospheric pressure is one of the primary determinants of a planet’s temperature, with higher pressure (for example, Venus at 92 bar) yielding warmer climates due the increase in heat capacity with mass (Chemke et al., 2016, Chemke et al., 2017), and lower pressures (Mars at 0.006 bar, Earth at 1.0 bar) yielding cooler climates (Goldblatt et al., 2009, Sorokhtin et al., 2007).
Image Source: Goldblatt et al., 2009, Sorokhtin et al., 2007
What we know about the requisite physics for the aerodynamics of flight (e.g., how heavy is too heavy for lift-off) serves as a robust proxy for atmospheric pressure variations of the ancient past.
For instance, the “giant birds of the Miocene,” with wingspans of “6.5 m or more,” could not take flight with today’s air densities (Cannell, 2020). Knowing what we know about flight physics, a minimum air pressure of 1.3 bar “would have been necessary for these birds to fly.”
Image Source: Cannell, 2020
Using known size and flight physics for large-winged predators, scientists have concluded the Late Permian and Middle to Late Jurrassic may have had atmospheric pressures of over 2 bar (Cannell and Nel, 2023). This could explain the polar warmth allowing for an Antarctic rainforest near the South Pole ~90 million years ago (Klages et al., 2020).
Image Source: Cannell and Nel, 2023
A new study provides a visual for just how much pressure may have varied in the past, ranging from 0.5 bar ~350 Ma to ~2.5 bar 300 Ma, and then almost 2.0 bar ~100 Ma, or during the time of the dinosaurs. (See the chart provided.)
As mentioned, one salient effect of atmospheric pressure variations is the size of animal and plant species, with higher pressures and greater warmth yielding 60-70 m tall trees, giant wing-extended (volant) insects and birds, alligators and magnolias thriving at the North Pole during the Eocene (~50 Ma), etc.
An interesting section of the paper suggests that not only does a planet’s atmospheric pressure determine the global temperature and the size of its creatures, it also may determine atmospheric CO2 levels and how alkaline or acidic the oceans get.
As noted in another recent paper, global temperatures and atmospheric CO2 are significantly negatively correlated (r = -0.76) over the last 210 million years (Davis, 2023). Likewise, high CO2 levels are associated with cooling periods like the End Permian extinction event, but not with ocean acidification periods. This strongly suggests atmospheric CO2 levels are not the determinant of the oceans’ pH balance nor global temperature – as we are led to believe.
“Periods of high atmospheric CO2, such as the Devonian, but with non-acidic oceans…are of particular interest. Oceans absorb a large amount of CO2 (currently ~50 times that of the atmosphere) due to the relatively high solubility of this gas in seawater, as expressed by Henry’s constant. A reduction in atmospheric mass therefore leads to massive outgassing of fractionated CO2 into the air and relatively alkaline seas. This is seen in the Devonian, at the end Permian and the Triassic-Jurassic transition, as well as in many major cooling events that take place together with an increase in CO2. Conversely, an increase in atmospheric pressure increases absorption and leads to lower levels of atmospheric CO2, but more acidic seas.”
Kenneth Richard wrote:
“As noted in another recent paper, global temperatures and atmospheric CO2 are significantly negatively correlated (r = -0.76) over the last 210 million years (Davis, 2023). Likewise, high CO2 levels are associated with cooling periods like the End Permian extinction event, but not with ocean acidification periods. This strongly suggests atmospheric CO2 levels are not the determinant of the oceans’ pH balance nor global temperature – as we are led to believe.”
Absolutely… CO2 is a (weak) net atmospheric radiative coolant, not a “global warming gas”.
https://www.patriotaction.us/showthread.php?tid=2711
The climatologists have flipped thermodynamics on its head. They did this via a misuse of the Stefan-Boltzmann (S-B) equation, using the idealized blackbody object form of the equation upon real-world graybody objects.
For instance, the Kiehl-Trenberth ‘Earth Energy Balance’ graphic (which represents the results of the maths in an Energy Balance Climate Model (EBCM)) does exactly this. Later ‘Earth Energy Balance’ graphics (and thus later EBCMs) go so far off the rails that they posit 398 W m-2 surface radiant exitance, which is physically impossible at their claimed 288 K, even if one treats the surface as an idealized blackbody (emissivity = 1, emission to 0 K) to inflate radiant exitance.
https://i.imgur.com/QErszYW.gif
[1] Idealized Blackbody Object form (assumes emission to 0 K and ε = 1 by definition):
q_bb = ε σ (T_h^4 – T_c^4)
= 1 σ (T_h^4 – 0 K)
= σ T^4
[2] Graybody Object form (assumes emission to > 0 K and ε < 1):
q_gb = ε σ (T_h^4 – T_c^4)
Because the idealized blackbody form of the S-B equation assumes emission to 0 K by the very definition of idealized blackbody objects, this artificially inflates radiant exitance of all calculated-upon objects.
The S-B equation for graybody objects isn't meant to be used by subtracting a wholly-fictive 'cooler to warmer' energy flow from the real (but too high because it was calculated for emission to 0 K) 'warmer to cooler' energy flow, it's meant to be used by subtracting cooler object energy density from warmer object energy density to arrive at the energy density gradient, which determines radiant exitance of the warmer object. This is true even for the traditional form of the S-B equation, because temperature is a measure of radiation energy density, per Stefan's Law.
That wholly-fictive 'cooler to warmer' energy flow is otherwise known as 'backradiation'. It is nothing more than a mathematical artifact due to the misuse of the S-B equation. It does not and cannot exist. Its existence would imply rampant violations of the fundamental physical laws.
Temperature (T) is equal to the fourth root of radiation energy density (e) divided by Stefan's Constant (a) (ie: the radiation constant), per Stefan's Law.
e = T^4 a
a = 4σ/c
e = T^4 4σ/c
T^4 = e/(4σ/c)
T = 4^√(e/(4σ/c))
T = 4^√(e/a)
where:
a = 4σ/c = 7.5657332500339284719430800357226e-16 J m-3 K-4
where:
σ = (2 π^5 k_B^4) / (15 h^3 c^2) = 5.6703744191844294539709967318892308758401229702913e-8 W m-2 K-4
where:
σ = Stefan-Boltzmann Constant
k_B = Boltzmann Constant (1.380649e−23 J K−1)
h = Planck Constant (6.62607015e−34 J Hz−1)
c = light speed (299792458 m sec-1)
σ / a = 74948114.502437694376419756266673 W J-1 m (W m-2 / J m-3)
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The traditional Stefan-Boltzmann equation for graybody objects:
q = ε_h σ (T_h^4 – T_c^4)
[1] ∴ q = ε_h σ ((e_h / (4σ / c)) – (e_c / (4σ / c)))
Canceling units, we get J sec-1 m-2, which is W m-2 (1 J sec-1 = 1 W).
W m-2 = W m-2 K-4 * (Δ(J m-3 / (W m-2 K-4 / m sec-1)))
[2] ∴ q = (ε_h c (e_h – e_c)) / 4
Canceling units, we get J sec-1 m-2, which is W m-2 (1 J sec-1 = 1 W).
W m-2 = (m sec-1 (ΔJ m-3)) / 4
[3] ∴ q = (ε_h * (σ / a) * Δe)
Canceling units, we get W m-2.
W m-2 = ((W m-2 K-4 / J m-3 K-4) * ΔJ m-3)
One can see from the immediately-above equation that the Stefan-Boltzmann (S-B) equation for graybody objects is all about subtracting the energy density of the cooler object from the energy density of the warmer object.
You will note that σ = (a * c) / 4… the S-B Constant equals Stefan’s Constant multiplied by the speed of light in vacua divided by 4.
[4] ∴ q = (ε_h * ((a * c) / a) * Δe) / 4 = (ε_h * c * Δe) / 4
Canceling units, we get J sec-1 m-2, which is W m-2 (1 J sec-1 = 1 W).
W m-2 = (m sec-1 * ΔJ m-3) / 4
————————-
The Stefan-Boltzmann equation in energy density form ([3] above):
σ / a * Δe * ε_h = W m-2
σ / a = 5.6703744191844294539709967318892308758401229702913e-8 W m-2 K-4 / 7.5657332500339284719430800357226e-16 J m-3 K-4 = 74948114.502437694376419756266673 W m-2 / J m-3.
Well, what do you know… that's the conversion factor for radiant exitance (W m-2) and energy density (J m-3)!
It's almost as if the radiant exitance of graybody objects is determined by the energy density gradient, right?
Energy can't even spontaneously flow when there is zero energy density gradient:
σ [W m-2 K-4] / a [J m-3 K-4] * Δe [J m-3] * ε_h = [W m-2]
σ [W m-2 K-4] / a [J m-3 K-4] * 0 [J m-3] * ε_h = 0 [W m-2]
… it is certainly not going to spontaneously flow up an energy density gradient.
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Note 2LoT in the Clausius Statement sense:
"Heat can never pass from a colder to a warmer body without some other change, connected therewith, occurring at the same time."
'Heat' [M1 L2 T-2] is definitionally an energy [M1 L2 T-2] flux (note the identical dimensionality), thus equivalently:
"Energy can never flow from a colder to a warmer body without some other change, connected therewith, occurring at the same time."
That "some other change" typically being external energy doing work upon the system energy to pump it up the energy density gradient, which is what occurs in, for example, AC units and refrigerators.
Remember that temperature is a measure of energy density, equal to the fourth root of radiation energy density divided by Stefan's Constant, per Stefan's Law, thus equivalently:
"Energy can never flow from a lower to a higher energy density without some other change, connected therewith, occurring at the same time."
Or, as I put it:
"Energy cannot spontaneously flow up an energy density gradient."
My statement is merely a restatement of 2LoT in the Clausius Statement sense.
————————-
Do remember that a warmer object will have higher energy density at all wavelengths than a cooler object:
https://i.stack.imgur.com/qPJ94.png
… so there is no physical way possible by which energy can spontaneously flow from cooler (lower energy density) to warmer (higher energy density). 'Backradiation' is nothing more than a mathematical artifact due to the climatologists misusing the S-B equation.
The above completely destroys AGW and CAGW, because they are predicated upon the existence of "backradiation" (radiation spontaneously flowing up an energy density gradient) as the causative agent for the climatologists' claimed "greenhouse effect".
————————-
By the same token, far from a "global warming gas", water acts as a literal refrigerant (in the strict 'refrigeration cycle' sense) below the tropopause, which I explain at the link above.
In fact, CO2 is the most prevalent atmospheric radiative coolant above the tropopause, and the second most prevalent (behind water vapor) below the tropopause.
Thus, the misuse of the S-B equation has flipped thermodynamics on its head, designating polyatomics as "global warming gases" and monoatomics as inerts… in reality, the monoatomics and homonuclear diatomics are the true "global warming gases" (they dilute the radiative polyatomics), and polyatomics are net atmospheric radiative coolants… again, explained at the link above.
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