-3
$\begingroup$

Lets assume a sea level temperature increase 2c/3c. Then, what is the temperature increase at 10 km altitude? Temperature increase at 30 km altitude? Temperature increase at 70 km altitude? And Temperature increase at 500 m below sea level? etc. etc. Please give full description of global temp increase with special regard to C02 as night time insulator and water as night time heat source. Structure of CO2 molecule. How does it do it?

  1. Is it true that increases in CO2 slow down the atmosphere's cooling rate per kilometre of altitude by trapping progressively larger amounts of infra-red energy within the body of the atmosphere?
  2. Is it true that the temperature increase resulting from CO2 emissions ultimately occurs at the top of the atmosphere, which is close to space and heat loss?
$\endgroup$
  • 1
    $\begingroup$ Yes, simple physics tells you that increasing levels of CO2 is a problem for the planet. And, the temperature increase can be and is observed right down here on the surface of the earth, as well as in the oceans. $\endgroup$ – Jon Custer Oct 30 '18 at 19:31
  • 2
    $\begingroup$ The oceans are indeed huge thermal reservoirs. But they are not magic: if you pour energy into the ocean it will warm. So the answer to your question (3) is clearly no: I'm not sure why you would think otherwise. $\endgroup$ – tfb Oct 30 '18 at 20:51
  • $\begingroup$ @JonCuster, it's no longer "simple physics" when so many variables are involved in the problem. Considering only the fact that CO2 absorbs infrared radiation misses the fact that the CO2 absorption band is already saturated, so adding more CO2 has much less effect than one would think. In addition, if warming causes more water vapor in the atmosphere, there will be effects on atmospheric convection, and albedo from cloud cover and possibly more snow fall. $\endgroup$ – David White Oct 30 '18 at 21:00
  • 1
    $\begingroup$ No. That radiation previously escaped to space. $\endgroup$ – tfb Oct 30 '18 at 22:42
  • 1
    $\begingroup$ @DavidWhite: By 'previously' I meant 'compared to the state with a lower CO2 concentration in the atmosphere': the amount of heat in the atmosphere is obviously not a conserved quantity so if part of it becomes warmer as a result of a greenhouse effect another part does not have to cool! $\endgroup$ – tfb Oct 31 '18 at 9:22
4
$\begingroup$

Without any CO$_2$ in the atmosphere the earth would be a very cold place, about 40 or 50 centrigrades colder than now. Trace molecules in the atmosphere radiate about as much energy to the surface as the sun.

It is sometimes argued that the greenhouse effect is saturated. And it is true that the effect of doubling the CO$_2$ content is "small": it gives an increase of the radiation with just 4 % or so. And to radiate that away, the surface temperature would just increase by $1$ % (Stefan-Boltzmann $T^4$ law).

But $1$ % of 300 K means an increase of 3 centigrades, which is catastrophic.

The top of the troposphere remains at the same temperature, 260 kelvin or so, or marginally cooler. The earth radiates as much as it absorbs from the sun. (Or actually slightly less until steady state is reached.) The only way this would change if when the albedo of the earth would change.

The sea is becoming warmer. At least the top layers. More moisture in the atmosphere, more energy in hurricanes.

(Very approximate numbers here.)

$\endgroup$
  • 1
    $\begingroup$ @DavidWhite why doesn't this increased intensity lead to enough temperature change to bring the ocean temperature back to its "lower CO2" equilibrium temperature? Obviously, energy conservation dictates that the hurricane must carry away thermal energy from the ocean. But why do you think this should lead to the ocean maintaining some arbitrary temperature? It will simply shift to a new equilibrium point. $\endgroup$ – Oscar Bravo Oct 31 '18 at 9:23
  • 1
    $\begingroup$ @DavidWhite: it's rather fortunate for us that not all the energy in raised SSTs is carried away by hurricanes! $\endgroup$ – tfb Oct 31 '18 at 9:29
  • 1
    $\begingroup$ @PhysicsDave: the energy from the core is tiny: it's something like $0.1\,\mathrm{W/m^2}$ which is utterly negligible compared to solar radiation. It is more than human energy generation however! $\endgroup$ – tfb Oct 31 '18 at 13:07
  • 1
    $\begingroup$ @Pieter, I agree. I expect the same thing that you do. However, my expectations have been wrong before, and it's best to actually collect real world data to verify expectations and hidden assumptions. $\endgroup$ – David White Oct 31 '18 at 18:22
  • 1
    $\begingroup$ @DavidWhite: That's not what I meant: you can do Fermi estimation on this. Assuming a mixing depth of 20m (which I think is conservative) then I get about $3\times 10^{22}\,\mathrm{J}$ to heat the mixed layer of the oceans by a degree. The power in a hurricane (most of which is rainfall) seems to be $6\times 10^{14}\,\mathrm{W}$ so this is about 18 months of hurricane. That's actually not as bad as I thought, but it's bad. $\endgroup$ – tfb Nov 2 '18 at 9:55

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.