According to a theoretical Greenhouse Gas Effect of 0 with 0ppm CO-equivalents the global temperature were 0°F or -18°C.
Due to the fact, all natural systems tend to show a maximum threshold value instead of infinite growth I wonder if there is a value of CO-equivalents that causes the maximum Greenhouse Gas Effect related to the current Energy output of the sun.
If there is an investigation or estimation on this value, how high is it and how high is the resulting rise in temperature?
Assuming a theoretical scenario with:
Energy Output of Sun = constant
Circulation System of Earth = constant
time = infinite
CO-equivalents = infinite
More thoughts from my side:
Is it valid to say we have a 84% GHG-Effect with respect to current albedo etc. ?
(333/396) W/m² ? Thus one could claim 100% GHG-Effect results in a plus of at least 6,3°C.
For the 'Greenhouse Effect' to saturate it is required for the atmosphere to reach a point where every wavelength emitted by the Earth will be either under complete or zero absorption.
I haven't seen any research on a greenhouse effect 'maximum'. I have seen only a paper concluding that the greenhouse effect on Earth now, is far from close to reaching saturation. I haven't read it in detail yet: Article The greenhouse effect and carbon dioxide
In realistic scenarios it seems it won't saturate and 6,3°C seems too low for maximum, but I have no idea if it is even possible in a non realistic scenario. Where the numbers on you comment come from?
Another thing is the case of Venus. Very thick atmosphere, most of it CO2, also has got some H2O and the result is mean temperature higher than 450 °C. It's closer to the Sun, but its albedo is around 0.7, so that doesn't help so much on this extreme warmth compared to Earth. Actually, its effective temperature is a bit lower than the Earth's.
It shouldn't matter for Earth some centuries or millenia ahead (maybe for all its lifetime) whether the greenhouse effect can reach hypothetically a maximum or not.
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Let's say the greenhouse gases reach so high concentrations that they can fully absorb their spectral absorption bands. The Earth most likely will be already much warmer than now and will get even more. Which means its spectrum maximum will have moved at a lower wavelength and its intensity would be increased.
If the spectrum change is big enough, then in some wavelengths of the current Earth's spectrum that are absorbed by greenhouse gases, emission could become negligible. However, Earth would emit in shorter wavelengths it now doesn't. So, other gases or other bands of the same gases could start contributing to greenhouse effect in this scenario.
For example, H2O can absorb parts of the Near-IR coming from the Sun. If Earth was so warm to have any significant emission in those bands, CO2 and H2O would still contribute to further warming even if the bands contributing now were saturated or a negligible part of Earth's spectrum. That would require the Earth to be warmer than Venus though.
The existence of so many gases (either greenhouse or not in the current conditions), the difference in some parameters like temperature and pressure with respect to altitude, phenomena like convection and atmospheric circulation etc. make this issue more complicated. The thinning of the atmosphere as we go higher for example, helps the IR radiation emited from lower layers to escape into space.
Yes i assumed my result also to be a very low estimation. my numbers are widely used for surface radiation and downwelling radiation, also in the first fig in the paper you cited.
My approach was to calculate the ratio of both of them and then assume, that a ratio of 1 was equal to a "100%" GHG-Effect where all the radiation is absorbed and reflected downwards. But I assume I lack alot of understanding where these numbers come from.
You mentioned Venus. Are there similar estimations for W/m² for our neighbour planet? If we have a GHGE of +33°C, then how strong is it on Venus? How much of the 450°C does the GHGE contribute.
So, according to higher IR with rising temperature, the heating is actually a potential feedback-loop by itself? Weak after all, but you say it's there. I did not know that! Thanks!
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