## onsdag 2 januari 2013

### Lapse Rate by Thermodynamics

In the previous post I asked Roy Spencer about the correct description of the GreenHouse Gas Effect GHGE, which he claims is misunderstood by many people, but got no answer.

It seems that Spencer, WUWT, Lubos and of course all climate alarmists, take the existence of a GHGE for granted, maybe because it has an acronym, while the nature of this effect remains elusive, which makes serious scientific discussion difficult or even meaningless.

Spencer gives the hint that GHGE "is an infrared effect" which connects to the common (mis)conception that the GHGE is an effect of radiation, more precisely, that the lapse rate, or temperature drop with atmospheric altitude, is determined by radiation.

This connects to the question of the lapse rate of a thermally isolated column of air subject to gravitation, to which Loschmidt answered the dry adiabatic lapse rate of 10 C/km, while Maxwell and Boltzmann claimed zero lapse rate or isothermal air, without ever reaching any conclusion.

The observed lapse rate of the atmosphere is 6.5 C/km which keeps the Earth surface at a comfortable + 15 C, while the temperature at the tropopause at 10 Km is chilling - 50 C.

The surface temperature is thus determined by the temperature at the tropopause and the lapse rate. What determines then the lapse rate? Thermodynamics or radiation? I argue that it is thermodynamics, while people assuming that the GHGE is real seem to argue that it is radiation.

In a previous post I gave an argument in favor of thermodynamics, which I here return to. Consider thus the column air discussed by Loschmidt and Maxwell/Boltzmann:

If the column is isolated without heat supply and the air is still, then heat conduction will equalize the temperature into zero lapse rate in accordance with Maxwell/Boltzmann. However, if there is a (small) heat supply Q at the bottom of the column, then by conduction in still air a linear any lapse rate - dT/dx will be established by the balance equation
• - alpha x dT/dx = Q
where alpha is a (small) coefficient of heat conduction. With alpha sufficiently small, this will make -dT/dx bigger than the dry adiabatic lapse rate of 10 C/km, and convective overturning will be initiated (to eventually give an observed lapse rate of 6.5 C/m).

If the coefficient of heat conduction in still air is small, which is the case, then a small heat source at the bottom will prior to convective overturning establish a lapse rate equal to the dry adiabatic lapse in accordance with Loschmidt, a lapse rate thus determined by thermodynamics and not radiation.

To sum up: Loschmidt was more correct in the setting of the Earth atmosphere, since the Earth surface is heated, and the lapse rate is thus determined by thermodynamics and not by radiation. A GHGE based on a lapse rate determined by radiation, is just an acronym and no a real effect.

With the lapse rate determined by thermodynamics and not radiation, the role of GHG is limited to an effect on the temperature at the tropopause, which may not easily be changed by small perturbations in the radiative properties of the atmosphere, thus suggesting small climate sensitivity as discussed in previous posts.

#### 6 kommentarer:

1. Very good again. But it could be even better by saying that radiation is a part of the thermodynamics and that the parameter determining the amount of heat trapped is likely to be the mass.

2. Hi Claes!
I just want to say I find your work really interesting and illuminating, especially your idea of 'gravitational forcing'.

In my mind I'm seeing an atmospheric heat-storage mechanism by dint of lifting molecules higher (against gravity). This is expressed in the pressure of the atmosphere, which dissipates the heat. Gravity IS the greenhouse effect.

Weirdly, pretty much the only effect of CO2 seems to be cooling. If CO2 and H2O did not cool the atmosphere by radiation to outer space, the atmosphere would get hotter and hotter, and higher and higher, and boil away.

More CO2 means more cooling. A doubling of the CO2 in the atmosphere doubles it's partial pressure, increasing it's emissivity. The Effective Emission Height as a heat trapping mechanism is fallacious.

The lapse rate is driven by the non-isotropic radiative heat exchange at TOA. IR is radiated out, but none is fed back at TOA which creates the cooling from TOA down.

Thank you.

Peter Grimshaw, Uk

3. In a vertical column of air, imagine it has neither -
1. Heat source at base, nor
ie, it is an energetically closed system ..
then the air will be isothermal?
All the molecules share their momentum by random collisions.
The energy is spread equally throughout the system as a mix of Potential Energy + Kinetic Energy.

This isothermal tendency, the tendency for molecules to equalize momentum between them is what drives heat into the upper atmosphere after radiation has cooled it? And is this what sets up the lapse-rate?

Peter Grimshaw

4. Have you worked out how much energy is driven into the upper atmosphere by thermal convection?

A very rough calculation gives me a rate of 1m3 of air is heated by 1C (0.75C) per second by the sun at zenith? Very roughly 1000J/s.

This is more than enough to drive thermal convection, especially if the sun is over the sea.

If all this energy is transported to the upper atmosphere, and stored in the potential energy of the raised gas, which is then dissipated throughout the atmosphere by weather, and then slowly radiated out to space by the SB effect, how much energy is actually being directly transferred to TOA by radiation?

Peter Grimshaw

5. Would you have time to review this piece?
Inspired by your site amongst others..

Does Dalton’s Law turn the Greenhouse Gas effect on it’s head?
Is Carbon Dioxide is an atmospheric COOLANT?

The key mechanism Anthropocentric Global Warming (AGW) thinkers describe is to use is something called EEH, Effective Emission Height.
This is real.

It is fair to say EEH IS generally believed to be the ‘Global Warming’ mechanism.

It works as AGW proponents say it does.
It uses the decrease in temperature as you go higher in the atmosphere to reduce radiation.
It can be subtle and tricky to compute or explain (http://clivebest.com/blog/?p=4597) but it works, and it would REDUCE IR emissions from CO2 leaving the atmosphere, IF a fixed amount of radiation was flowing through the atmosphere.
Essentially, the CO2 ‘fire’ of upward IR gets a bit colder, and less IR.

But a mistake that AGW scientists make is
1. Trying to explain heat transfer using radiation.
2. Thinking of radiation as a fixed quantity of energy being transported.
3. Not realising the implications of CO2 being a trace gas increasing in quantity.

As CO2 levels in the atmosphere increase, the IR fire actually gets bigger.

Radiation is partly a factor of the QUANTITY of gas. Emissivity increases.
Double the gas, and pretty much, you double the radiative output, and this is NOT factored in to most AGW calculations, (including Clive – see link – above, Clive forgets this).

Dalton’s law says that double the molecules of CO2 will double it’s partial pressure and all its attributes in the atmosphere (https://en.wikipedia.org/wiki/Dalton%27s_law).

Radiation within the atmosphere is independent of the amount of IR “upwelled”.
Radiation from a gas is described by the SB (Stephan-Boltzman) rules and is dependent on the temperature of the gas and the quantity (or ’emissivity’), NOT the amount of radiation upwelled or that it receives. Radiation has little to do with heat ‘transfer’.

Increasing CO2 in the atmosphere has two effects, and they are both to do with what might be called a ‘grey’ body becoming a bit more ‘black’. The trace gas becomes a bit more opaque, and bit denser, a bit more solid.
1 An increase in EEH, which is real and lowers outgoing IR a bit, the fire cools, a bit.
2. An increase in IR from an increased amount of CO2. The IR fire almost doubles.
So the IR fire cools, but gets lots bigger.

The key heat transport mechanism is not radiation, it is convection at the equator, where the sun is hottest. So we can let go of the idea of any heat being ‘blocked’. Rising air transports massive amounts of energy from the bottom to top of atmosphere where it is stored as potential energy. This creates atmospheric pressure, and is slowly released by radiation. Think tropical thunder storms for heat transport. And compare with cold ice caps where there is little sun. Radiation doesn’t create thunder storms, sun + convection does, and this transports loads of energy to TOA where it is stored as potential energy. If someone knows how much that would be good.
The met office even has a name for this heat-storage mechanism is CAPE – Convective Available Potential Energy https://en.wikipedia.org/wiki/Convective_available_potential_energy

Thinking in terms of radiation transporting heat and being ‘blocked’ does not well describe how our atmosphere works and confuses thinking. Convection is the main heat transport.

CO2, believe it or not, is only ever a coolant.

Here is a table which describes increasing CO2 emissivity with increase pressure/density
More CO2 means More IR will leave our atmosphere.
These figures were calculated about 60 years ago by a man called Hottel.

http://www.biocab.org/Emissivity_CO2.html
More partial pressure = More radiation.
More CO2 cools the air even more.

Peter Grimshaw