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Venus and a Thicker-Atmosphere Earth

(fourth post in a series dedicated to the planet Venus as “example” of runaway greenhouse warming)
Venus post #1: Venus: Cool Greenhouse?
Venus post #2: Venus Warming Revisited
Venus post #3: Venus Missing Greenhouse Warming
Venus post #4: Venus and a Thicker-Atmosphere Earth

In reply to this comment

Ok n-g I presume we can now do assuming all niceties instead of repeating our thanks ūüėé so let’s try to clarify a few points.

To my mind, they act very differently

the rest of my question was “Wouldn’t moist convection for example drastically change the consequences of an increase in atmospheric CO2?”.

And the point was: when people say, look at Venus to see what GHG warming can do, the scientific answer should be that no comparison can be done with Earth as the whole mechanism of “warming” is very different (whatever CO2 may or may not be doing…if only because we have so much water vapor).

May I dare say we agree on this point?

When you’re looking at the planetary energy balance, the single number albedo is not just the starting point, but also the ending point

But surely an atmosphere, say, with low albedo in UV and high albedo to visible and IR does not behave as an atmosphere that is the other way around?

Earth’s for example is able to keep a bit warmer by the presence of UV-absorbing ozone in the stratosphere. That would mean a lower albedo in UV than in visible light, wouldn’t it?

The dry adiabatic lapse rate depends only on gravity and heat capacity

If the greenhouse effect is so strong on Venus, why isn’t the lapse rate much larger, and much larger than Earth’s, given the fact that the amount of CO2 decreases a lot between the surface and the height of 60km?

Surely the lower one gets, the more GHG there are, the higher the ability to trap heat.

Suppose there were no greenhouse effect on Venus

As you say, this is an argument, not proof

The fact that the IR emissions from Venus come from the atmosphere and not from the surface constitutes the proof

The fact that visible light comes from the atmosphere and not from the surface only proves there’s lots (lots!) of clouds on Venus. Why would the same observation regarding IR mean something else?

If the atmosphere of Earth were 100 times more massive

Let’s imagine Earth had a 10-km deep, reasonably large crater in the middle of a continent, with no liquid water on its bottom at all. What would be the temperature at the bottom of the crater? With a lapse rate for saturated air of 5.46K/km, 288+5.46*10=342K or 70C. Right? Wrong?


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