Funny "debate" about water vapour

[YNM]

Am I to understand the Earth "sweats", carrying heat from the surface into the upper atmosphere and space? If so, would higher humidity result in more heat loss?

The basis of greenhouse gases is that they stay long enough in the atmosphere and absorb fair amount of heat before finally being dumped off (either in precipitation or loss to space). Water condensates pretty easily - it'd require enourmous amount of heat being present in the lower atmosphere to prevent them precipitate, and making them lost to space needs even larger amount of heat. The reason why Venus is hellish is because their CO2 are hard to precipitate, and they're heavy, so runaway greenhouse effect is more prominent - once cloud cover is there, the surface is very hot already that precipitation is sealed off (that's why they don't have CO2 rain).

[GeneralVeers]

The basis of greenhouse gases is that they stay long enough in the atmosphere and absorb fair amount of heat before finally being dumped off (either in precipitation or loss to space).

This doesn't actually tell you anything. In fact, the average lifetime of a CO2 molecule in Earth's atmosphere (which is quite long if I recall accurately) is a misleading statistic used by environmental radicals to scare people. It's used to make CO2 seem more threatening than it is. In reality CO2 is a very weak greenhouse gas. Cue my previous comment where I compared CO2 and Imperial Stormtroopers.....

What matters is the rate at which the substance in question is being introduced into the atmosphere, IN ADDITON TO the amount currently in the atmosphere, IN ADDITON TO the rate at which it's being taken out. You MUST take all three numbers into account or you end up with meaningless/deceptive/bogus results.

[YNM]

This doesn't actually tell you anything. In fact, the average lifetime of a CO2 molecule in Earth's atmosphere (which is quite long if I recall accurately) is a misleading statistic used by environmental radicals to scare people. It's used to make CO2 seem more threatening than it is. In reality CO2 is a very weak greenhouse gas. Cue my previous comment where I compared CO2 and Imperial Stormtroopers.....

What matters is the rate at which the substance in question is being introduced into the atmosphere, IN ADDITON TO the amount currently in the atmosphere, IN ADDITON TO the rate at which it's being taken out. You MUST take all three numbers into account or you end up with meaningless/deceptive/bogus results.

Well, I only say that to determine whether a particular molecule can induce greenhouss effect or not, apart from their specific heat capacity ! A whole lot different for inducing runaway greenhouse effect, which is waay more complex.

[GeneralVeers]

Yeah......not gonna happen on Earth. The greenhouse effect is not gonna run away from home and is not gonna end up on a milk carton.

Random thing I just started wondering: does anybody know the albedo of a solar panel? Cause when you look at one, it's generally darker than its surroundings, which means it's taking sunlight and turning it into HEAT instead of reflecting it. Which is a bad thing when you're trying to keep the planet's heat level down.....

[peadar1987]

This doesn't actually tell you anything. In fact, the average lifetime of a CO2 molecule in Earth's atmosphere (which is quite long if I recall accurately) is a misleading statistic used by environmental radicals to scare people. It's used to make CO2 seem more threatening than it is. In reality CO2 is a very weak greenhouse gas. Cue my previous comment where I compared CO2 and Imperial Stormtroopers.....

What matters is the rate at which the substance in question is being introduced into the atmosphere, IN ADDITON TO the amount currently in the atmosphere, IN ADDITON TO the rate at which it's being taken out. You MUST take all three numbers into account or you end up with meaningless/deceptive/bogus results.

Ugh, we've been through this before. atmospheric lifetime is important, as it determines the response speed of the system. Water has a short lifetime, so the system responds quickly, and returns to equilibrium. CO2 has a long lifetime (because carbon sequestration is far slower-acting than rain) and so it has far more time to cause damage before it leaves the atmosphere. Yes, eventually anything will find an equilibrium point, regardless of atmospheric lifetime, but nobody with any sort of knowledge of the subject is claiming otherwise.

Yeah......not gonna happen on Earth. The greenhouse effect is not gonna run away from home and is not gonna end up on a milk carton.

Again, prove this, and there'll be a shiny Nobel prize waiting for you in Stockholm. Earth won't become Venus, but the world's top climate scientists are still unsure of the magnitude and effect of the various feedback loops. Things could indeed run away to something very bad, like 6+ degrees of warming, even if that's not the most likely scnario.

[Wesreidau]

Not quite. The main way the Earth loses heat is by radiation, (mostly in the far IR band[1]), with only a small amount by 'evaporation', (the loss of lightweight gas molecules). Most of that radiation is generated on the surface and in the lower atmosphere.

While increasing the heat capacity of the atmosphere would increase the amount of radiation that can get out, (a photon generated 10km up is more likely to end up in space than one generated at sea level[2]), adding more water to the atmosphere wouldn't really do anything but create more rain. The atmosphere is just about saturated with water vapour anywhere but right near the surface where the ground warms it.

[1] This is one reason why CO2 is such a big deal, it has an absorption peak that is just about bang on Earth's emission peak.

[2] Well, more likely to result in a photon escaping. In reality most of those photons will be absorbed and re-radiated many times on the way up.

To be clear I am referring to water vapor from the sea level or ground absorbing that ground heat, ascending to higher altitudes, and then radiating off that heat to space or otherwise higher altitudes. This compared to dry air with less heat capacity. Not gas loss.

[Nikolai]

Trying to be charitable here... maybe the teacher didn't have it clear in his/her head what a "climate forcer" versus a "climate follower" gas is?

Water vapor is a greenhouse gas, but its presence in the atmosphere is more a function of temperature than a cause of that temperature. Maybe the teacher had it confused in his/her head that only "climate forcers" should be properly thought of as greenhouse gases.

[GeneralVeers]

Niko gave me a brainstorm.

"Hey, class, instead of me telling you what water vapor actually does, here's how we can try and figure out what it does....."

Translation: how about our teachers teach students HOW to think, not WHAT to think?