If I understand correctly what I have been reading is that increases in CO2 will slightly warm the air which will allow water vapor a much more potent greenhouse gas to hold more moisture and trap more energy from the sun in earths atmosphere. But some of the other articles I read speak of another effect water vapor has which is to reflect sunlight back away before it ever come in. From what I can determine science still does not know the ratio of the two effects and can’t determine which would have the most effect. But preliminary indicators are is that it is about equal and the atmosphere may have the ability to regulate it’s own temperature. Is this true or valid science?
No. If it were true, we wouldn’t be experiencing climate change. The part that’s true is that water vapor enhances the effect of CO2. There is no such thing as water vapor “reflecting sunlight away”, unless you’re thinking of enhanced cloud formation. However, this doesn’t appear to be the case to any significant extent, either in reality or in climate models. Clouds also have both warming and cooling effects depending on their type and altitude. In general, high cirrus clouds tend to contribute to more warming by absorbing and re-emitting infrared radiation from the surface, while low clouds tend to create cooling by blocking sunlight from reaching the surface.
If as you say is true wouldn’t that start a never ending spiral of warming?
No, that’s a common misconception. Water vapor feedback stabilizes because of cooling by increased IR loss from outgoing blackbody radiation as the temperature rises. The heat loss to space from radiative flux per unit temperature rise is about twice that of water vapor feedback warming, so it’s a self-stabilizing feedback.
The Earth does have feedback systems in the atmosphere, but I would be very hesitant to say that these mechanisms work well enough for the atmosphere to maintain a constant temperature like a thermostat.
Water vapor has both positive and negative feedback consequences for the atmosphere. What this means is that as you increase the cloud cover, the temperature does drop, but the clouds also trap heat, making the temperature rise. Exactly which of these will have the greater effect is a matter of debate, but it’s my understanding that most scientists think that it’s either roughly a wash or that the overall effect will be slightly positive (meaning that increased clouds will lead to increased temperatures, which further increases clouds and further increases temperatures).
Wikipedia has a decent article about the atmosphere’s many feedback mechanisms, both positive and negative, which gives a better idea of the atmosphere’s complexity.
Also, if you look at graphs of the Earth’s temperature over millions of years, the temperature isn’t all that stable. If the negative feedback systems in the Earth’s atmosphere were strong enough to keep the temperature regulated reasonably well, then this graph would be a lot smoother.
The Earth doesn’t regulate its temperature well enough to call it a natural thermostat. At different periods in Earth’s history, the Earth has either become too hot for life around the equator or so cold that the entire surface of the Earth froze solid. Both of these were associated with mass extinction events.
While there are enough negative feedback mechanisms in the Earth’s atmosphere to prevent it from going into full-out psycho runaway greenhouse mode like our neighbor Venus, these mechanisms aren’t strong enough to prevent mankind from pushing the Earth’s atmosphere into a state where the polar ice melts and the equatorial regions become a dead, uninhabitable desert.
Just a few additional points for clarity. While water vapor is necessary for cloud formation, clouds and water vapor are of course distinct phenomena with different properties; clouds are condensed water droplets or ice crystals. Atmospheric water vapor itself is strictly a positive feedback, arising from the fact that the absolute amount of tropospheric water vapor is directly a function of temperature. What effect that may have on cloud formation, and on what types of clouds, is unclear, though as you correctly point out the net effect on balance doesn’t appear to be very significant (even though the two opposing effects of clouds are independently quite large).
I might add to my own previous post to say that while water vapor feedback is a strong positive feedback in the climate system, as I mentioned later, for any given CO2 level and tropospheric average temperature it self-stabilizes around an equilibrium point. In feedback terminology this would be called a negative feedback loop – one which has an intrinsic damping effect. The opposite would be a self-reinforcing positive feedback loop which is inherently unstable. Major loss of polar ice cover, and methane releases from thawing Arctic permafrost and undersea methane clathrates are several potential examples of positive feedback loops that could create runaway climate change – they could be self-reinforcing for a significant period of time.
This is not merely theoretical, as examples of tipping points creating rapid climate change (like Dansgaard-Oescher events, for instance, one of numerous examples of abrupt climate change) are found in the paleoclimate record. Earth may never turn into another Venus, but by continuing to release carbon from fossil fuels, carbon that’s been sequestered for millions of years, we could well set ourselves on the road to an eventual return to the climate of the Cretaceous. Regardless, the extremely rapid rate at which we’re forcing the climate is itself inherently destabilizing and dangerous.
The bottom line here is that there is ample evidence that the Earth does NOT have any effective self-regulating thermostat, and hence the concern over climate change and its long-term consequences.
Would it be possible to do a test using something like a warehouse for example where the humidity could be regulated and we could test how well light penetrated at various humidifies? I would imagine tons of these tests have already been done I just don’t know where to find them.
That’s totally not the issue and a warehouse experiment would be useless. The physics is clear.
What’s unclear is how all the thousands of factors, including the ones we don’t know interact collectively. There’s only one place to run that as an experiment: the whole planet. We can model most of the ones we understand, and move the experiment into a safer venue: a pile of RAM in a supercomputer.
@LSLGuy nailed it. First of all there’s not a lot of question about the spectral absorption properties of water vapor, which are well understood. And secondly even if there was, the optical thickness of water vapor in a warehouse or any man-made containment vessel is insignificant compared to that of the atmosphere. So yes, as noted, the behaviors of the climate system as a whole are what needs to be further studied – things like potential effects of water vapor on cloud formation, drifting of water vapor from the troposphere into the stratosphere, creation of water vapor in the upper stratosphere from methane oxidation, and the effects of the lapse rate feedback – the fact that the cooling temperature gradient with increasing height in the atmosphere diminishes with increased global warming. Among a great many others.
There is speculation that the living biosphere (total life on a planet en mass) itself can and ‘does’ alter the planet in ways that would tend to stabilize the climate and make it better for life. So a planet with life, according to this, the life on it tends to stabilize the climate. If so this would act as a thermostat, but take time and might go astray if things line up wrong, though the odds are for it to go right and it’s a large number problem. This assumes no fossil fuel burning species evolves there, or immigrates from other in system planets or other star systems and sets up colonies.
https://history.aip.org/climate/biota.htm
As for the liquid/gas system, it would seem like the water cycle would have to have an effect, after all we use water cooling for many things, some of them involve converting liquid to gas and back, and some at normal temperatures such as swamp coolers. But this effect alone would be to diminish the change, not try to reverse it. So I would not say it’s a true thermostat.
Now the effects of water vapor/clouds/CO2, that’s a crap(py) shoot. As clouds can reflect light, water absorb, different wind patterns, different cloud pattern and storms. I think that’s still in the stage where we know it will do something but not sure what.
CO2 does more than “slightly” warm the air. Just ask Venus. Water vapor does not reflect heat. Neither of those assertions is remotely close to valid science. In addition, as the earth warms, pockets of frozen methane thaw and reenter the earth’s atmosphere. Methane is a significantly more powerful greenhouse gas than even CO2.