Greenhouse Effect 101

[drstuess]

I don't think anyone disagrees that above the mean radiating height the temperature cools with more ghg's. The question is whether, on an energy basis, it accounts fully for the warming during the transitioning to equilibrium.  However given that more ghg's raise the mean radiating height and that most of the atmosphere is below this height, it seems like the energy balance increases between equilibrium. 

There are several models on the UChicago site that demonstrate this: http://climatemodels.uchicago.edu/rrtm/

Here is a screenshot with 800 ppm.  Note that it has 400 ppm as the equilibrium amount, so if you set co2 at 400, the net flux is 0

 

[blizzard1024]

1 hour ago, drstuess said:

I don't think anyone disagrees that above the mean radiating height the temperature cools with more ghg's. The question is whether, on an energy basis, it accounts fully for the warming during the transitioning to equilibrium.  However given that more ghg's raise the mean radiating height and that most of the atmosphere is below this height, it seems like the energy balance increases between equilibrium. 

There are several models on the UChicago site that demonstrate this: http://climatemodels.uchicago.edu/rrtm/

Here is a screenshot with 800 ppm.  Note that it has 400 ppm as the equilibrium amount, so if you set co2 at 400, the net flux is 0

 

This makes sense but I believe the increase in energy is below the radiating layer... I don't see how a GHG can increase energy for the whole system. The flux to the Earth increases and creates an imbalance down below, but aloft there is less energy outgoing and hence the energy budget for the whole earth + atmosphere remains the same. GHGs radiate more energy downward at a lower temperatures and hence emission actually drops above. I made a mistake on this way back. 

[drstuess]

That is for the whole system, the effective radiating height is like 5km. 

[chubbs]

On 1/26/2017 at 8:31 PM, blizzard1024 said:

Getting back to the basic greenhouse effect, if the atmosphere gains greenhouse gases, they will absorb more outgoing long wave radiation and warm the Earth.

However, this will reduce the amount of OLR going to higher levels and hence there will be cooling above. This simple statement shows that a planet can't gain energy from its own

atmospheric gases.  The amount of energy that comes in, is balanced by the energy that leaves the system. How the energy is distributed is what GHGs do. There is no way the earth system including the ENTIRE atmosphere can gain energy. It can't happen. If you look at Venus, the higher atmosphere is much colder than the earth's because of the runaway greenhouse effect. See below...

 

 

The cooling you see way up in the upper 5% of the atmosphere of venus is due to greater emissivity to space due to higher CO2 in the upper atmosphere and the lack of an ozone layer due to the lack of oxygen. Radiation from lower levels has to be higher on venus than the earth as long as the yellow line is higher than the blue. The cooling in the earth's stratosphere is strong evidence for a ghg effect. There is increasing CO2 in the stratosphere, increasing the emissivity of the stratosphere so increasing the radiation from the stratosphere to space. If natural variability was driving temperature change the stratosphere would not be cooling.

[Jack Frost]

 

Excellent contribution to the discussion Chubbs.

Much better than: 

"Frosty the Snowman, knew the sun was hot that day,
so he said, "Let's run, and we'll have some fun now, before I melt away."

That was, well, let's be charitable and just say, odd. 

[Jack Frost]

 

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