Earth's Energy Balance

[David H]

I have been told that the natural state of the atmosphere was it had a perfect balance of energy, which has now been put out of equilibrium by adding excess CO2.

I am not aware of any such theory and if correct how did nature magically manage to produce the perfect conditions to store and release energy equally and is so sensitive to change it takes so little to affect it if so?

[Canary42]

What's so "magic" about a balance - obviously conditions will continue to change UNTIL a balance is achieved. Upset the balance and chaos resumes.

[Old_Geezer]

Well more a new balance is found.
All balances are natural.
Not sure what it has to do with energy though. Perhaps if you had a link.

[wildwood]

Which energy are you referring to?

[jim360]

I'm not quite sure what you mean in this case, because the atmosphere hasn't really been in perfect balance ever. However there is a general answer that I'll try to set out.

Essentially the point is that balance is not magical but quite the opposite: it's desirable. In most if not all physical situations you can imagine starting things off in whatever starting condition you like, then sitting back and watching how things progress. Almost invariably the system will try to reach a balance. It's just easier, in some sense. Things are usually more stable, or it takes less effort to maintain the balance. This idea (or a variant of it) is one of the guiding principles of physics, and amounts to saying that "nature wants to take it easy".

At any rate it is no accident that, if left alone long enough, everything reaches a state of balance. The same is true for the atmosphere, for example. ("Left alone" doesn't mean "left alone by humans", but by anything that isn't part of the normal state of affairs. Asteroids colliding, or volcanic activity, also disturb the system.) What happens next, when you try to disturb the balance, depends a lot on how the system is set up. It's possible for a balance to be ideal and the system could easily return to it no matter how hard you try to move away; but in many cases the balance is just not stable and even a small kick will change things significantly. Unfortunately, the atmosphere is in the second category and is sensitive to change.

Not sure if that clears things up but hopefully it helps a bit. The point is that balance is nice, so that you'd expect to see it eventually, but not always easy to maintain.

[beso]

Balance, better known as equilibrium happens in any system where the rate of transfer is dependent on the concentration.

The side with the higher concentration, be that water, salt, heat or anything else will move more to the other side, down the concentration gradient by transmission, diffusion, conduction, convection or radiation as the case may be.

Equilibrium is reached when the rates of transfer are the same and the concentrations don't change further. When the relative concentration is changed or the rates of transfer enhanced or impeded then the process will begin towards a new equilibrium.

In the case of the atmosphere it is separating the Earth at about 300 kelvin from space at about four Kelvin and the Sun at about 6000K (though it does cover only a small area of the sky).

The heat flow is always from the hot to the cold. In the day the heat and light comes in from the Sun and straight through the atmosphere with some reflected by clouds.

On the ground the heat and light are absorbed making the ground or sea hot. At night the heat flows back toward cold space as infrared radiation but some gasses in the atmosphere absorb it so not all escapes. If it didn't we would quickly reach temperatures more like space overnight.

When we increase the concentration of those gasses, the surface temperature of the Earth must increase to radiate more to space until the new equilibrium is reached.

This is why it is futile to argue that the Earth's temperature is not rising. The decrease in the radiation back out into space has been measured and the temperate must rise to compensate. This is consistent with the knowledge that Carbon Dioxide absorbs infrared radiation.

Any arguments about where the heat is going and how fast the temperature is rising are just rearranging the deckchairs on the Titanic.

[David H]

Thanks beso, I'll process that as I can, and had I known any more initially I'd have explained more but was pretty much of a mystery to me.

[Old_Geezer]

That's the problem with what your mates claim in the pub. You can't link to the conversation :-)