Question: Global average temperature and Gas Laws

[Euler07]

Hi all,

So I've been pondering over this and would like some feedback as to what is wrong with this hypothesis.

1) The Gas Laws state that temperature is proportional to pressure (

https://en.wikipedia.org/wiki/Gas_laws).

Basic high school stuff that we all learnt.

2) Wind is the movement of air, caused by the uneven heating of the Earth by the sun and the Earth's own rotation. (

https://education.nationalgeographic.org/resource/wind/).

Let's ignore the Earth's rotation in this analysis. Local increases in temperature increase the pressure of that region. The hot air reduces in volume/density, therefore rises, and cooler air rushes in from other regions and this causes wind. This is the effect of local changes in temperature.

3) If the air was contained in a physical chamber (which prevented an increase in volume and therefore increased the density/pressure), then the pressure would increase and the temperature would increase. Local wind occurs because the volume of air is able to increase (therefore reducing density and rising).

4) Atmospheric air is not contained in a chamber. Quite the opposite, there is a vacuum surrounding Earth. Therefore, the global volume of air is free to expand and contract without restriction.

5) Atmospheric pressure is caused by the gravitational attraction of the planet on the atmospheric gases above the surface and is a function of the mass of the planet, the radius of the surface, and the amount and composition of the gases and their vertical distribution in the atmosphere (

https://en.wikipedia.org/wiki/Atmospheric_pressure).

Atmospheric pressure is essentially the gravitational pull of the earth on the atoms in the atmosphere.

6) The movement of atoms from the Earth's crust into the atmosphere (eg. from volcanic eruption, the burning of fossil fuel, the melting of frozen methane etc) does not reduce the overall gravitational pull of the Earth+atmosphere since the overall number of atoms remains the same. In fact, it should theoretically reduce the gravitational pull of the Earth since more atoms are now above the ground level which will have a gravitational pull upwards. However, this movement of atoms is so small in comparison to the Earth's gravity that it is negligible.

7) If there is no restriction on the global volume of air, then the atmospheric pressure is based on the gravitational pull of the Earth.

8) If the gravitational pull of the Earth is constant, there is no restriction in the volume of the atmosphere, then this means that global average pressure and therefore global avereage temperature remains constant.

9) An increase in the global average temperature requires an increase in the global average atmospheric pressure, which is not possible unless there is an increase in the gravitational pull of the Earth.

 

[BrianPetersen]

No.

An increase in the temperature results in a reduction in density. If applied uniformly to the entire atmosphere, it would result in the entire atmosphere becoming "deeper" (the "thickness" would increase) but the total mass remains constant so the total pressure at the surface remains constant. The "lapse rate" - the rate at which pressure decreases with altitude - would change due to the reduction in density - same starting point, lower slope, extending out to a higher "thickness".

 

[BrianPetersen]

The thing that you are missing about the gas law PV=nRT is that although the two sides of the equation equal each other, they don't have to equal a constant. 5 = 5, 7 = 7, 2 = 2, etc. If you increase T and the number of moles of gas remain the same, then either P increases or V increases or any combination of both. Since the pressure at the surface is a representation of the amount of mass above the surface and that's constant, P (at the surface) remains constant, which means V increases, and that means the total thickness of the atmosphere increases.

 

[TugboatEng]

Technically, if the atmosphere became deeper the pressure at the surface would decrease because the effect from gravity decreases with distance. Is this significant? I don't know.

 

[rb1957]

why 4 ? why can't the atmosphere expand into space ? and we're talking very small changes to the atmosphere (1 or 2 degree) that may (before folks on either side of the argument lash out at me) or may not have significant effects on our biosphere.

but 1) the atmosphere is not an ideal gas.

I'd expect that the small change in temperature would cause a small change in pressure and a small change in density

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

 

[LittleInch]

Don't forget that temperature in the gas laws is measured in degrees K.

So an increase from say 15 C to 16C average is only an increase of 1/288 = 0.003% 0.3%

A search for air pressure over time basically shows no discernible increase from fixed weather station data

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Compositepro]

1/300= 0.003= 0.3%

 

[LittleInch]

Of course it is....

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[BrianPetersen]

Technically, if the atmosphere became deeper the pressure at the surface would decrease because the affect from gravity decreases with distance. Is this significant? I don't know.

The radius of the earth is about 6400 km. About 99% of the mass of the atmosphere is below 32 km above the mean surface radius. About 0.5%. I'll go with not significant.

 

[TugboatEng]

We are, however, constantly losing our atmosphere to solar winds. Bulking it up may not be such a bad thing in the long run. When we burn fossil fuels we sacrifice a little oxygen to make a lot of CO2 and H2O. Even better, neither of those two gasses are pollutants.

 

[Euler07]

If you increase T and the number of moles of gas remain the same, then either P increases or V increases or any combination of both. Since the pressure at the surface is a representation of the amount of mass above the surface and that's constant, P (at the surface) remains constant, which means V increases, and that means the total thickness of the atmosphere increases.

Thanks everyone. I think Brian has explained what I was missing. As temperature increases then volume increases but pressure remains the same.

Technically, if the atmosphere became deeper the pressure at the surface would decrease because the effect from gravity decreases with distance. Is this significant? I don't know.

Thanks Tugboat. I'm not sure if this is correct since the centroid of gravity is at the centre of the Earth and remains the same overall mass? But you're probably right.

why 4 ? why can't the atmosphere expand into space ?

Regarding point 4, I think you may have misread or I didn't write clearly. I agree that the atmosphere can expand into space. This is opposed to an actual greenhouse where expansion and convection are both prevented. I'm not sure why the earth's atmosphere is being modeled as a greenhouse.

but 1) the atmosphere is not an ideal gas.

I agree that it is not necessarily an ideal gas, but at least the gas laws are based off a reproducible experiment. Whereas the current 'science' I'm seeing in the world is all based off 'consensus' (once you censor, or remove funding to, those who disagree).

So an increase from say 15 C to 16C average is only an increase of 1/288 = 0.3%

Thanks. To be honest, I think an average change of pressure of 0.3% would also create hysteria in today's environment. The 'news' would probable tell us we need space suits within 12 years.

We are, however, constantly losing our atmosphere to solar winds. Bulking it up may not be such a bad thing in the long run. When we burn fossil fuels we sacrifice a little oxygen to make a lot of CO2 and H2O. Even better, neither of those two gasses are pollutants.

I'm of the mind that the earth has been here long before we have. It produced life of infinite complexity and innate intelligence. It's unlikely that the intelligence of the human brain is capable of understanding the complexity of the universe. It's more likely that the human brain is capable of mistakenly believing that is is capable of understanding the complexity of the universe. I simply look at each generation and see that each of them has an absolute belief that they know everything, only to be proven horribly wrong within a few more generations. And then the cycle repeats

 

[rb1957]

there are enough facts and counter-facts on both sides of the question... feel free to make your own consensus !

nobody knows all the climate interactions, and we're probably missing some significant ones. Our modelling is IMHO very crude.
the analysis (with the best of intentions) is IMHO laden with assumptions.

I think it is very odd ... we've moved into a social environment that demands answers from science (not questions) and demands certitude (hence consensus).

I wonder what the future will think when they look back on this episode !?

And this is not saying that we shouldn't have an eye on our use of FFs (and on our other interactions with the natural world).

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.