Solubility of CO2 in Water vs. Greenhouse Effect?

[magnemoe]

I believe the reason for Venus' atmosphere and extreme conditions is due to its closeness to the sun, but not primarily due to the amount of radiation it receives. In the very early days of the solar system it was much like Earth now, but as the Sun warmed up to its current temperature and brightness, this triggered a runaway greenhouse effect resulting in the hellhole we all know and love today.

Main effect is the dense atmosphere, Venus might have started with one and it gradually gotten denser or the trigger might have been volcanoes, it looks like Venus kind of boils over every 200 million years.

Now once you get up to 100 degree the water boils off adding more insulation it also stop carbonizing so its no way to remove co2 from the atmosphere so it collects.

And no Earth has no chance at all becoming like Venus, if so it would have happened during all the beating the planet had taken the last billions years. The stress testing was far more brutal than the current 30% above normal co2 levels. How about forested polar regions who was standard at the age of the dinosaurs after the super continent broke up? Stable for 100 million years.

600 million years ago it looked like earth froze over.

Nobody serious says that Earth might become like Venus anyway, it was some talk about it back then global warming was recognized as an problem but it disappeared once they did some calculations.

[arkie87]

Watch the tempers, please. No need to treat fellow forum members as enemies.

ugghhh. this is exactly what i said i DIDNT want to happen...

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Now if we could get this thread back on track...

The real question is the relation between temperature and CO2 level. yes its an effect, however we also have other effects.

One weird effect on the 400.000 year graph was the stable temperature 120.000 years ago while co2 and ch4 level was falling hard.

Yes this can be measurement errors too but interesting.

Yes, that would be my next point. If, for some reason im not seeing from this graph (or from other external evidence or simulations) we can show that the feedback mechanism is responsible, then i have two additional questions:

(1) why does it reach a new steady state at only a few degrees higher temperature? i.e. what additional negative feedbacks exist that overpower the positive greenhouse effect?

(2) why isnt it always followed (as you pointed out). Why dont small rapid increases in temperature always result in a departure from an ice age or vice versa?

[AngelLestat]

What WedgeAntilles wants to said when he mentions that venus is twice as hot than earth, is because he takes 1 bar of pressure in both places..

If you want to compare temperatures of different planets, you need to do it at equal pressure.

Venus at 50km height which is 1 bar aprox, it has 67 to 80 celcius degree.

Which is more than twice earth temperature. But we need to take into account at least 5 big factors here:

1-Extra solar radiation.

2-Very reflective clouds of SO4 that are above this height, this counter the extra solar radiation, they are good to reflect sun light but they let escape long waves that comes from the layers below.

3-Atmosphere mix 98% co2, this help to trap more heat.

4-Convective heat that may come from lower layers..

5-Extra heat that comes from evaporation (is very dry, so this is not a big effect)

4-5: depends on how temperature was measure it.

Not sure if I forgeting something. I am not a expert. But I can said one thing with certain.. Not even experts can make good calculations to compare venus with the earth, because the information that we have from venus is very limited, our models does not make very good predictions in venus, because our climate models are not complete yet.

So it will not help in nothing to compare with venus to reach conclusions in this discussion. Venus is important to understand much better the greenhouse effect and improve all our predictions here on earth.

But well, our climate models may have some flaws, but they make better predictions here on earth, so we should focus with the things we got.

Edited August 5, 2015 by AngelLestat

[GeneralVeers]

The center cannot radiate heat, and started hotter than the outside, and cannot function as a heat-sink.

Night side of the planet can.

Don't straw-man me, I wasn't questioning the inverse-square law.

You didn't say what you WERE questioning. You merely said "that's BS" and "thermodynamics doesn't work that way. But you didn't explain what was actually wrong with my theory, or how thermodynamics DOES work. You just handwaved it. As with AEIOU--you really need the "why". And you're not the only person who did that.

Tell ya what, I'm gonna settle this Venus thing once and for all. I just found a nugget of pure gold:

What WedgeAntilles wants to said when he mentions that venus is twice as hot than earth, is because he takes 1 bar of pressure in both places..

Pressure......thank you very much, Angel--you gave me a brainstorm.

I can't believe I'd never thought of this before. Basic gas dynamics. Compress a gas, and it gets hotter. Venus = 90 atmospheres = a whole lot hotter. Case closed.

(1) why does it reach a new steady state at only a few degrees higher temperature? i.e. what additional negative feedbacks exist that overpower the positive greenhouse effect?

The most significant negative effect is this: as something gets warmer, it radiates heat faster.

But there's something else going on that hardly anybody ever notices: the principle of diminishing returns. Most people assume "X amount of CO2 produces Y degrees of warming". And it doesn't work that way. If you start with a planet that's a CO2-free ice cube, the first kilogram of CO2 you add to the atmosphere will produce considerable warming. The second kilogram, much less. The third kilogram, even less than the second. Why? Because you've got more CO2 molecules competing for the same amount of heat. And the molecules don't play nice; they circulate around and on top of each other, jostle each other, steal heat from each other, and occasionally insult each others' mamas.

(2) why isnt it always followed (as you pointed out). Why dont small rapid increases in temperature always result in a departure from an ice age or vice versa?

There are probably several reasons, but I've got a theory for you which you've probably never heard:

Right now, Earth's global mean temperature is about 288 degrees Kelvin. Which is above freezing, but kinda chilly. Obviously, Earth isn't the same temperature everywhere......but what if it was? What would happen? Well, then the ENTIRE planet would be above freezing, both polar ice caps (and all other ice everywhere else!) would melt completely, and there would not be much rejoicing. A completely different result than we actually have today--yet the global mean temperature is the SAME.

In order for the planet to get out of an Ice Age (or to start one!) it's not enough to add heat. It matters where the heat goes. If it stays near the equator and the poles get colder, that would allow the ice caps to advance. If it's more evenly circulated for whatever reason, more heat would reach the poles, and it would be bye-bye Ice Age.

Bottom line: when people worry about global warming and note the planet's mean or average temperature going up, that doesn't tell you what's actually going to happen. You need to ask more questions.

Edited August 5, 2015 by WedgeAntilles

[arkie87]

Tell ya what, I'm gonna settle this Venus thing once and for all. I just found a nugget of pure gold:

Pressure......thank you very much, Angel--you gave me a brainstorm.

I can't believe I'd never thought of this before. Basic gas dynamics. Compress a gas, and it gets hotter. Venus = 90 atmospheres = a whole lot hotter. Case closed.

That's not how it works. I have a tank of 2000 psi nitrogen in my lab (~136 atmospheres in pressure). It is at room temperature. It is not as hot as venus just because it is under high pressure.

If you compress a gas, it gets hot, sure. But it will cool down to its steady-state temperature. Venus's steady state temperature is hot, so that is caused by something else.

In addition, one might think that the elevated pressures are caused by the high temperatures, but this is incorrect too. Pressure is caused by the weight of the atmosphere from the surface to space, and together, pressure and temperature cause density from ideal gas law.

The most significant negative effect is this: as something gets warmer, it radiates heat faster.

That is true, except that in our case, it radiates heat faster, but that heat is absorbed increasingly better by the atmosphere. So the fact that it gets hotter doesnt help, since the radiation does not escape the control volume of the planet. The planet should not stop heating up and the rate of heating up should accelerate as the atmosphere becomes more opaque to IR. The only way its possible to have negative feedback is if the wavelengths of the emitted radiation shifts significantly, which only occurs at really elevated temperatures.

Edited August 5, 2015 by arkie87

[AngelLestat]

Yeah there is some misconceptions about why venus is hot..

When you compress a gas, you are producing work, this procedure has some energy loses in form of heat. But if you let it cool, then you have big pressure without heat.

The venus case is different. We can imagine like if we have different blankets by height, which each one represent 1 bar of atmosphere and it allow through a big % of light.

Imagine that you are in a bed under 90 blankets vs 1 blanket, there are kinda transparent and you are under the sun. Is not exactly like that but might help to understand.

That is why we always compare jupiter-earth-saturn-venus temperature at equal pressure.

These are the temperatures that planets should have at 1 bar without greenhouse effect:

These are the real temperatures they have, take a look at 1 bar:

[GeneralVeers]

If you compress a gas, it gets hot, sure. But it will cool down to its steady-state temperature. Venus's steady state temperature is hot, so that is caused by something else.

One of which I already mentioned. Venus is closer to the Sun.

Plus, its atmosphere is partially transparent at infrared and ultraviolet wavelengths (and UV delivers more energy than infrared or visible light!), there's constant lightning, there's exothermic chemical reactions involving the sulfuric acid in the planet's atmosphere, and also the planet has no magnetic field and is constantly getting bombarded with high-energy solar wind (which is not only heating Venus more than Earth, but also slowly stripping Venus of its atmosphere!) There's actually lots of things that could do it. I've never been able to find exact values for most of them (because nobody knows), but it's enough to make me think twice about the real reasons our sister planet is such a hothead........

In addition, one might think that the elevated pressures are caused by the high temperatures, but this is incorrect too.

Disagree. Temperature is the cause of pressure. The reason a gas has pressure is because the molecules are moving around and bouncing off each other. Increase the temperature? The molecules bounce faster and harder, causing the pressure to go up.

Increasing the pressure increases the temperature, increasing the density increases the pressure and temperature. The factors are all interactive. But when Venus' atmosphere formed (or changed, or whatever caused it to turn into pea soup) the increase in pressure was definitely at least partially responsible for the increase in temperature.

That is true, except that in our case, it radiates heat faster, but that heat is absorbed increasingly better by the atmosphere.

Not true. When the atmosphere absorbs heat and warms up? The atmosphere itself becomes the radiator. More so when high-altitude winds are constantly circulating heat from the surface to the cooler upper atmosphere and to the dark side of the planet.

Ooh, hey--here's something interesting for you to chew on. You're familiar with the fact that water vapor is a greenhouse gas? One of the strongest ones, too. So then, why is it that areas with moist air (i.e. coastlines) are warmer at night.....and COOLER during the day? As opposed to deserts, which in general are blazing hot during the day and FREEZING COLD at night? Most people forget that about deserts. And this isn't just true about deserts; most areas of the Earth with dry air have wider temperature swings.

That's what greenhouse gases actually do. Your sweater doesn't know which is inside and which is outside; it insulates equally in all directions. Greenhouse gases don't only keep heat in--they also keep it out.

When you compress a gas, you are producing work, this procedure has some energy loses in form of heat.

Gravity = constant application of work.

Imagine that you are in a bed under 90 blankets vs 1 blanket, there are kinda transparent and you are under the sun.

The environment under the blankets warms to body temperature and stabilizes approximately there.

That's why the traditional Middle Eastern desert dress is what appears to be a paradox; fairly heavy full-body covering. It's hot under there, but less dangerous than exposure to the even hotter desert.

Side note about your picture of the planets, by the way: I've read theories that with no greenhouse effect, Earth would actually be about twenty degrees colder than the 279 Kelvin listed on your chart.

Edited August 5, 2015 by WedgeAntilles

[AngelLestat]

The reason a gas has pressure is because the molecules are moving around and bouncing off each other. Increase the temperature? The molecules bounce faster and harder, causing the pressure to go up.

Increasing the pressure increases the temperature, increasing the density increases the pressure and temperature.

You are mixing concepts here.

In a close system, if you increase the temperature, the gas expand, if it cant, the pressure rise.

The temperature in a gas depends on the average kinetic energy of each molecule in the gas, but it does not have nothing to do with pressure.

That's what greenhouse gases actually do. Your sweater doesn't know which is inside and which is outside; it insulates equally in all directions. Greenhouse gases don't only keep heat in--they also keep it out.

No, because they let sunlight pass, but when touch ground or sea, is emitted at a different IR frequency which bounce against co2, methane, water vapor, and other greenhouse gases.

The contrary happens with sulfuric acid, it reflect the sunlight and let pass IR frequencies from lower layers of venus, so the heat escape.

But venus has 98% of co2 too, so these two effect fight each other.

One plan to fight global warming here on earth is to spray sulfuric acid to our atmosphere, just with a tiny amount it will be enoght to decrease the temperature.. But of course, even a tiny amount might have bad secundary effect that we may not know about it.

Gravity = constant application of work.

If that it would be true, we will be able to harvester energy just with 1 static machine using gravity..´

Gravity is a field, you get work only moving through the field, if you rise you get potential energy, if you let it drop you gain kinetic energy.

But if you are static, nothing happens. Atmospheres are static, they move only because the sun provides energy.. not the gravity field.

The environment under the blankets warms to body temperature and stabilizes approximately there.

No, you never enter in a car which was under the sun?

If you increase the glasses layers, you will see that the temperature keeps rising by each layer.

The same with plastic sheets , if you have 1 big plastic piece (like this) in your house, take a thermometer, and put it in the sun, then cover it with 1 layer of plastic, then with 3, then with 6. Lets see what happens.

That's why the traditional Middle Eastern desert dress is what appears to be a paradox; fairly heavy full-body covering. It's hot under there, but less dangerous than exposure to the even hotter desert.

The fabrics they use does not act as greenhouse effect, and you cover the skin from sun burns.

Also the climate is dry, so if you drink extra water, you cool your self by sweating in a more efective way.

Side note about your picture of the planets, by the way: I've read theories that with no greenhouse effect, Earth would actually be about twenty degrees colder than the 279 Kelvin listed on your chart.

Yeah, is the same shown there

Edited August 5, 2015 by AngelLestat

[arkie87]

Disagree. Temperature is the cause of pressure. The reason a gas has pressure is because the molecules are moving around and bouncing off each other. Increase the temperature? The molecules bounce faster and harder, causing the pressure to go up.

This is true for gasses in a constant volume: if you increase the temperature, you increase the pressure due to the reasons you mentioned. However, planets are not constant volumes; their atmospheres actually expand and contract as mean atmospheric temperature changes (see: Scale Height). When temperature increases, the atmosphere gets bigger, but the pressure on the surface stays the same. The pressure on the surface is ONLY dependent on the weight of the atmosphere above; not on temperature.

Increasing the pressure increases the temperature, increasing the density increases the pressure and temperature. The factors are all interactive. But when Venus' atmosphere formed (or changed, or whatever caused it to turn into pea soup) the increase in pressure was definitely at least partially responsible for the increase in temperature.

While your statements regarding kinetic theory of gasses is true, it has nothing to do with the steady-state temperature of Venus. The steady-state temperature has to do ONLY with how much heat is absorbed by the planet vs. how much is emitted to space. The only fluxes that matter are those that cross the planetary control volume. These effects you describe would only be temporary. These gasses should have cooled down already, if they were only heated due to compression in the past.

Not true. When the atmosphere absorbs heat and warms up? The atmosphere itself becomes the radiator. More so when high-altitude winds are constantly circulating heat from the surface to the cooler upper atmosphere and to the dark side of the planet.

The very top of the atmosphere becomes/is a radiator, and as less and less of the surface heat reaches the top, less and less of the upper atmosphere remains a radiator, since it takes less and less distance to become opaque.

Ooh, hey--here's something interesting for you to chew on. You're familiar with the fact that water vapor is a greenhouse gas? One of the strongest ones, too. So then, why is it that areas with moist air (i.e. coastlines) are warmer at night.....and COOLER during the day? As opposed to deserts, which in general are blazing hot during the day and FREEZING COLD at night? Most people forget that about deserts. And this isn't just true about deserts; most areas of the Earth with dry air have wider temperature swings.

Moist air also has more enthalpy, so it has more thermal mass. Not sure if you can isolate that affect.

That's what greenhouse gases actually do. Your sweater doesn't know which is inside and which is outside; it insulates equally in all directions. Greenhouse gases don't only keep heat in--they also keep it out.

Greenhouse effect doesnt quite work the same way. It only insulates heat coming from cold sources (i.e. long wavelength light). Like glass: it is transparent to visible light but opaque to infrared.

Gravity = constant application of work.

Gravity doesnt do any work. It takes no energy to keep a gas under pressure, just force. Gravity isnt actively doing work on anything or compressing anything to increase its temperature.

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You are mixing concepts here.

In a close system, if you increase the temperature, the gas expand, if it cant, the pressure rise.

The temperature in a gas depends on the average kinetic energy of each molecule in the gas, but it does not have nothing to do with pressure.

No, because they let sunlight pass, but when touch ground or sea, is emitted at a different IR frequency which bounce against co2, methane, water vapor, and other greenhouse gases.

The contrary happens with sulfuric acid, it reflect the sunlight and let pass IR frequencies from lower layers of venus, so the heat escape.

But venus has 98% of co2 too, so these two effect fight each other.

One plan to fight global warming here on earth is to spray sulfuric acid to our atmosphere, just with a tiny amount it will be enoght to decrease the temperature.. But of course, even a tiny amount might have bad secundary effect that we may not know about it.

If that it would be true, we will be able to harvester energy just with 1 static machine using gravity..´

Gravity is a field, you get work only moving through the field, if you rise you get potential energy, if you let it drop you gain kinetic energy.

But if you are static, nothing happens. Atmospheres are static, they move only because the sun provides energy.. not the gravity field.

No, you never enter in a car which was under the sun?

If you increase the glasses layers, you will see that the temperature keeps rising by each layer.

The same with plastic sheets , if you have 1 big plastic piece (like this) in your house, take a thermometer, and put it in the sun, then cover it with 1 layer of plastic, then with 3, then with 6. Lets see what happens.

The fabrics they use does not act as greenhouse effect, and you cover the skin from sun burns.

Also the climate is dry, so if you drink extra water, you cool your self by sweating in a more efective way.

Yeah, is the same shown there

I was Ninja'ed

[AngelLestat]

Yeah, it happens to me all the time, but your english is better and you explained in a different way. So is always good had different approaches.

[GeneralVeers]

Heheh. Ninjas do their evil work without ever being seen. If Angel was indeed a ninja.....his post would be invisible.......<cue spooky music>

Anyhow: we're starting to see the part where repeated quoting causes messages to get longer and longer, so I'm going to skip a bunch of stuff and just grab some fun things to reply to. If I skipped something important, just pretend I disagreed angrily with it.

No, because they let sunlight pass, but when touch ground or sea, is emitted at a different IR frequency which bounce against co2, methane, water vapor, and other greenhouse gases.

The above effect does happen, but it's minor; the effect of ALL atmospheric gases, greenhouse or not, absorbing heat from the ground via direct contact is more significant.

Carbon dioxide is a different process. It absorbs infrared in two pretty specific frequency bands, warming the gas (which, like all heated objects, re-radiates the energy at a lower frequency). But like the sweater example I posted earlier, carbon dioxide doesn't care which way is up and which is down. In the same way it keeps some of Earth's heat from escaping, it also prevents some of the Sun's energy from reaching the ground--absorbing it higher up where it more easily radiates back into space. But carbon dioxide is a red-headed stepchild greenhouse gas. Time to meet the Big Bully:

Water vapor is yet another different process. Water (in vapor and liquid form) has a high specific heat. It takes a lot more heat to produce an actual temperature change in water than, say, concrete. This effect cools the air during the day (because energy is converted into a smaller temperature change than if the energy was in the ground). Then, at night, the water vapor cools down more slowly (again, because of its high specific heat) keeping the nighttime warm. That's why the California coast is so nice and the Mojave Desert is a scorcher followed by an ice cube. Lack of water vapor allows the Sun to incinerate desert ground--and then lack of water vapor allows all that heat to radiate out at night.

No, you never enter in a car which was under the sun?

Bad example. Car windows are darn near blackbody absorbers; they reflect very little (look at an ordinary car with non-tinted windows and notice how dark it actually is). And then the car interior only heats up to dangerous levels if the windows are closed. Earth's albedo is much higher than a car window, and the figurative windows are always open. Once the sunlight hits the ground, the air circulates upwards, contacting colder air in the upper atmosphere--which obviously can't happen in a car. Circulation is a big factor.

The same with plastic sheets , if you have 1 big plastic piece (like this) in your house, take a thermometer, and put it in the sun, then cover it with 1 layer of plastic, then with 3, then with 6. Lets see what happens.

Pardon me if I sound like I'm nitpicking.....but you did say the plastic sheets were partially transparent. Meaning lots of them stacked on top of each other are very close to zero transparency. End result: your body heat becomes the primary heat source. Same result as further up: the real reason things warm up under a plastic sheet is because the air under it isn't allowed to circulate. Car windows and plastic sheets (and the glass walls of an actual greenhouse) interfere with air circulation; greenhouse gases do not.

The fabrics they use does not act as greenhouse effect

Of course they do. They keep your body heat in--and the hotter desert air around you out. When it's below 100 outside, it's time to take off some layers......(bow chigga wow wow)

Yeah, is the same shown there

Uhhhhh.....I meant twenty degrees colder than that number that is on the chart. The theory was (I forget where I found this) that the Earth would be around two hundred and fifty degrees Kelvin if there were no CO2 in the atmosphere (which would mean even lower if there were no greenhouse gas at all, as your chart said). No big, that theory I found was exactly that--a theory.

While your statements regarding kinetic theory of gasses is true, it has nothing to do with the steady-state temperature of Venus. The steady-state temperature has to do ONLY with how much heat is absorbed by the planet vs. how much is emitted to space. The only fluxes that matter are those that cross the planetary control volume. These effects you describe would only be temporary. These gasses should have cooled down already, if they were only heated due to compression in the past.

Yes, Arkie, I'm giving you less face time (well, keyboard time) than I gave to Angel. Sorry about that. Don't worry, this is a good one that will probably surprise you. It surprised me; I just learned something new.

Check out the Kelvin-Helmholtz mechanism: https://en.wikipedia.org/wiki/Kelvin%E2%80%93Helmholtz_mechanism

It is estimated that Jupiter radiates more energy through this mechanism than it receives from the Sun, but Saturn might not.

Surprise! Jupiter is producing heat via compression alone.

You're right--the heating from pressure is temporary. And you're wrong--Venus' gases have no reason why they "should have cooled already". All the planets (including Earth!) are cooling down. But the process is far from done.

An unrelated but interesting (and scary!) fact: our Sun is doing the opposite! The Sun is gradually shrinking....and heating up. Through out its main-sequence life, as more helium accumulates in its core, the pressure in the fusion zone has been increasing--and therefore the rate of fusion is accelerating. As a result, the human race doesn't have five billion years left--in less than one billion, the hotter Sun will render the Earth uninhabitable. Cue the violin.

[arkie87]

Carbon dioxide is a different process. It absorbs infrared in two pretty specific frequency bands, warming the gas (which, like all heated objects, re-radiates the energy at a lower frequency). But like the sweater example I posted earlier, carbon dioxide doesn't care which way is up and which is down. In the same way it keeps some of Earth's heat from escaping, it also prevents some of the Sun's energy from reaching the ground--absorbing it higher up where it more easily radiates back into space.

Yes, CO2 radiates heat up and down, but since the energy is radiated back into the atmosphere from the ground, the next effect is to lose energy to space (since space isnt giving it back).

Though, that is a good point, that even though opacity might approach 100%, there is still a finite layer in the upper atmosphere that is radiating heat into space. I wonder what the limit is i.e. what the maximum effective opacity can be, given that a layer at the end of the atmosphere will always be radiating heat: some back to the atmosphere and some to space?

Bad example. Car windows are darn near blackbody absorbers; they reflect very little (look at an ordinary car with non-tinted windows and notice how dark it actually is). And then the car interior only heats up to dangerous levels if the windows are closed. Earth's albedo is much higher than a car window, and the figurative windows are always open. Once the sunlight hits the ground, the air circulates upwards, contacting colder air in the upper atmosphere--which obviously can't happen in a car. Circulation is a big factor.

I dont see how circulation is relevant (or, more exactly, its effects would only be temporary). The control volume is around the entire globe. If the energy isnt radiated to space, then it stays in the globe and will warm it.

OR, is what you are saying that circulation warms the upper layer in the atmosphere, which increases the radiation temperature in the upper atmosphere, where the opacity is not 100%? Thus, even though the surface is radiatively insulated from the upper atmosphere due to greenhouse gasses, circulation can effectively bring heat up there, through the radiative "blanket". That makes sense. I dont know if anyone has quantified the strength though?

Yes, Arkie, I'm giving you less face time (well, keyboard time) than I gave to Angel. Sorry about that. Don't worry, this is a good one that will probably surprise you. It surprised me; I just learned something new.

Check out the Kelvin-Helmholtz mechanism: https://en.wikipedia.org/wiki/Kelvin%E2%80%93Helmholtz_mechanism

Surprise! Jupiter is producing heat via compression alone.

I think i've heard of that before. The reason this effect is still significant is because its cyclical, so it is constantly being renewed. Venus does not undergo these contraction/expansions AFAIK, since it is a rockey planet (it seems like it only happens to stars/gaseous planets).

As a side, Jupiter is also under high pressure (much much higher than Venus), but the temperature is obviously way below that of Venus, and it is closer to it's blackbody temperature. So pressure has nothing to do with temperature.

You're right--the heating from pressure is temporary. And you're wrong--Venus' gases have no reason why they "should have cooled already". All the planets (including Earth!) are cooling down. But the process is far from done.

The planets are cooling from formation. Earth's core is still molten. Eventually, it will freeze, the magnetic field will stop, and life on earth will end. Mars's magnetic field is gone already since its core is frozen. Its core is frozen since the planet is smaller, and therefore, cools more rapidly.

If the atmosphere somehow compressed and heated up in the past, it should have cooled down already. It does not have nearly as much thermal mass as the planet does. Besides, based on the physics, its not possible for atmospheres to (permanently) compress/pressurize. The pressure is constant: the volume changes with temperature, not the pressure.

I wonder if K-H mechanism could explain long term variations in the Sun's power, that Milankovitch cycles cannot explain....

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Anyway, if we could get back on topic: is there any particular reason that those famous graphs of CO2 vs Temperature automatically indicate greenhouse effect, rather than just solubility of CO2 in water?

My main point is: if the greenhouse effect didnt exist, the graph would look the same (due to solubility), no? Thus, is it not a bad graph to show?

Edited August 6, 2015 by arkie87

[YNM]

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Anyway, if we could get back on topic: is there any particular reason that those famous graphs of CO2 vs Temperature automatically indicate greenhouse effect, rather than just solubility of CO2 in water?

My main point is: if the greenhouse effect didn't exist, the graph would look the same (due to solubility), no? Thus, is it not a bad graph to show?

No at all. Solubility, if any, actually goes down when it's hotter, plummeting to full vaporization (no solubility, in turn, making gas out of it) at boiling point. They won't look the same at all : we are recording air temperature. Had air consist of matter that doesn't absorb EM at all the Earth would be devoid of life, and Venus would actually be the women paradise. Rock planets did cools down, but at that time it's mostly nothing but super-thin atmosphere much like Moon or Mercury, that even don't count to be called an atmosphere as we know, feel, live, and breath with it.

Edited August 6, 2015 by YNM

[arkie87]

No at all. Solubility, if any, actually goes down when it's hotter, plummeting to full vaporization (no solubility, in turn, making gas out of it) at boiling point. They won't look the same at all : we are recording air temperature. Had air consist of matter that doesn't absorb EM at all the Earth would be devoid of life, and Venus would actually be the women paradise. Rock planets did cools down, but at that time it's mostly nothing but super-thin atmosphere much like Moon or Mercury, that even don't count to be called an atmosphere as we know, feel, live, and breath with it.

I am confused by your response: solubility of water goes down with temperature, making CO2 come out of the ocean and enter the atmosphere, thereby raising CO2 ppm with temperature. Thus, the graph would still look as is, no?

This effect occurs according to everyone, and global warming in the past actually depended on this effect according to the original paper to create a positive feedback loop, so i dont see how an informed person can dispute it...

[AngelLestat]

The above effect does happen, but it's minor; the effect of ALL atmospheric gases, greenhouse or not, absorbing heat from the ground via direct contact is more significant.

If you want to study the energetic process of an object, first you need to establish which are your energetic inputs and outputs.

For Venus or Earth you have only 3 inputs and 1 output.

Inputs:

-Sun heat transfer by radiation

-radioctive decay from heavy elements which mostly are located in the core.

-remaining heat since earth formation.

Output:

-Heat transfer by radiation to space.

Inputs and outputs should be in equilibrium (due how old is the earth)

But in earth, the heat transfer by radiactive decay is very low, if the sun disappear, the amount of heat radiated to space from earth will be very low, even lower is the remaning heat since earth formation.

So we can ignore it, In venus might be a bit higher due heavy elements, but I guess it can be ignored too.

Now we establish our inputs and sources, we can see that oceans and grounds only act as capacitors, they absorb heat and then release it at night. But you dont gain or lose heat due this, unless your greenhouse gases increase, so oceans trap more heat for a time (inputs are higher than outputs) until it reach equlibrium, if we make co2 values to go back to normal from one day to the other, it may take 30 years to cool again to normal temperatures, because the ocean will provide that heat (outputs higher than input) until reach equilibrium.

Carbon dioxide is a different process. It absorbs infrared in two pretty specific frequency bands, warming the gas (which, like all heated objects, re-radiates the energy at a lower frequency). But like the sweater example I posted earlier, carbon dioxide doesn't care which way is up and which is down. In the same way it keeps some of Earth's heat from escaping, it also prevents some of the Sun's energy from reaching the ground--absorbing it higher up where it more easily radiates back into space. But carbon dioxide is a red-headed stepchild greenhouse gas. Time to meet the Big Bully:

Water vapor is yet another different process. Water (in vapor and liquid form) has a high specific heat. It takes a lot more heat to produce an actual temperature change in water than, say, concrete. This effect cools the air during the day (because energy is converted into a smaller temperature change than if the energy was in the ground). Then, at night, the water vapor cools down more slowly (again, because of its high specific heat) keeping the nighttime warm. That's why the California coast is so nice and the Mojave Desert is a scorcher followed by an ice cube. Lack of water vapor allows the Sun to incinerate desert ground--and then lack of water vapor allows all that heat to radiate out at night.

Summarizing all that in easiest ways to understand:

Both are greenhouse gases, they let more heat pass, but they reflect the heat that tries to escape from earth, so the temperature rise (earth absorbs more heat) until it reach a new equilibrium between energy receive and radiated to space.

Bad example. Car windows are darn near blackbody absorbers; they reflect very little (look at an ordinary car with non-tinted windows and notice how dark it actually is). And then the car interior only heats up to dangerous levels if the windows are closed. Earth's albedo is much higher than a car window, and the figurative windows are always open. Once the sunlight hits the ground, the air circulates upwards, contacting colder air in the upper atmosphere--which obviously can't happen in a car. Circulation is a big factor.

But planets are also close systems from the convection point of view, atmosphere does not escape to space.. (when it does, is negligible) They only transfer heat by radiation to space.

In the car example is similar, you have the Sun as input, and the car outputs are conductive (this is a extra output that should not be there if we want a good comparison, so it should be even hotter) and radiating heat.

So yeah, the car example works perfect.. Why you think is called the greenhouse effect?

Greenhouses can keep tropical plants in cold places, but once it reach the equilibrium, then energy input is equal to output, the only difference is that inside the greenhouse temperature is higher.

Pardon me if I sound like I'm nitpicking.....but you did say the plastic sheets were partially transparent. Meaning lots of them stacked on top of each other are very close to zero transparency. End result: your body heat becomes the primary heat source. Same result as further up: the real reason things warm up under a plastic sheet is because the air under it isn't allowed to circulate. Car windows and plastic sheets (and the glass walls of an actual greenhouse) interfere with air circulation; greenhouse gases do not.

Yeah.. that is the same that happens in venus, it only reach a 10% of sunlight to the surface.. This does not prevent to reach 450 celcius degree, because heat can not escape.

Just make the experiment that I told you, try to leave some air between each layer of plastic so you dont lose all the heat by conduction.

It needs to be sealed.

Check out the Kelvin-Helmholtz mechanism: https://en.wikipedia.org/wiki/Kelvin%E2%80%93Helmholtz_mechanism

Surprise! Jupiter is producing heat via compression alone.

You're right--the heating from pressure is temporary. And you're wrong--Venus' gases have no reason why they "should have cooled already". All the planets (including Earth!) are cooling down. But the process is far from done.

But gravity by it self is not given energy in jupiter.. Is potential energy the source of that heat.

As I said before, if you compress a gas, you release heat, but once the compression is over, then you dont produce more heat.

Jupiter is still in shrinking process, so the gas lose potential energy (it was at a higher altitud, then the height is reduce), so that is the source of heat. You can not get energy from nothing, that is why gravity by it self does not produce energy.

Lets analize all energy inputs and outputs from jupiter:

Inputs: Sun radiation, radiactive decay, potential energy shrinking process, gas and asteroids that fall in jupiter from space which add kinetic and potential energy, heat remaning since jupiter formation, tidal energy by their moons (this reduce the kinetic energy of the bodies).

Outputs: heat radiated to the space, tidal energy, magnetic fields absorbed by its moons.

Anyway, if we could get back on topic: is there any particular reason that those famous graphs of CO2 vs Temperature automatically indicate greenhouse effect, rather than just solubility of CO2 in water?

My main point is: if the greenhouse effect didnt exist, the graph would look the same (due to solubility), no? Thus, is it not a bad graph to show?

You mean those graph that show estimations of co2 thousands or millons years ago?

We know very little about other greenhouses gases at those times or earth conditions vs other types of energy sources as sun, or different cycles on earth.

There are thousands or chemical process that might have something to do with that, more in the past we look, more heat remaning from earth formation was, the same for radiactive decay, more asteroids falling to earth, different types of water solubility..

One thing is trying to understand today earth conditions with all accurate data from all sources and make predictions with that, than use just co2 estimations from long long time ago.

Edited August 6, 2015 by AngelLestat

[arkie87]

But planets are also close systems from the convection point of view, atmosphere does not escape to space.. (when it does, is negligible) They only transfer heat by radiation to space.

If i understand WedgeAntilles correctly, he is suggesting that convection undermines the radiation blanket caused by greenhouse gases i.e. while radiation cannot penetrate the atmosphere from the surface, convection can and does (indeed, it does as warm humid air rises to form clouds). Thus, while the upper atmosphere which radiates to space is insulated from surface radiation, it is not insulated from the surface by means of convection. So your example of the car is not apropos, since convection is not blocked here.

You mean those graph that show estimations of co2 thousands or millons years ago?

We know very little about other greenhouses gases at those times or earth conditions vs other types of energy sources as sun, or different cycles on earth.

There are thousands or chemical process that might have something to do with that, more in the past we look, more heat remaning from earth formation was, the same for radiactive decay, more asteroids falling to earth, different types of water solubility..

One thing is trying to understand today earth conditions with all accurate data from all sources and make predictions with that, than use just co2 estimations from long long time ago.

If i understand you correctly, you are saying that the graph is unreliable to draw any conclusions, let alone as evidence of the greenhouse effect?

[AngelLestat]

If i understand WedgeAntilles correctly, he is suggesting that convection undermines the radiation blanket caused by greenhouse gases i.e. while radiation cannot penetrate the atmosphere from the surface, convection can and does (indeed, it does as warm humid air rises to form clouds). Thus, while the upper atmosphere which radiates to space is insulated from surface radiation, it is not insulated from the surface by means of convection. So your example of the car is not apropos, since convection is not blocked here.

First, that is the wrong way to approach the problem, It would be very confusing, because we need to focus in the energy sources, and this might looks like the ground is a high energy source, which is not, it's just trapped heat.

The biggest energy source is the sun, and only reach 10% to the surface, so yeah, you might have convection heat, but what it does tells us?

Not much.. IR frequencies can escape even from surface without touch the atmosphere, of course just a bit amount.. but it can.

Then you add a little amount by convection which in upper stages will provide extra radiation, so instead make that step you just focus in input and output radiation, and thats it. like this graph:

Anual Energy Budget Venus.

Also, atmosphere does not escape from the planet, that is why is insolated from the convection point. Only radiation comes out. Similar to the car.

If i understand you correctly, you are saying that the graph is unreliable to draw any conclusions, let alone as evidence of the greenhouse effect?

Yeah, what can tell us just the co2 data from 3 or 4 locations on earth that might have some measurement errors from long long time ago?

Vs all the data (millons of different sources) that we have today?

Even with all the data we have today is really hard to follow all the energetic process in earth, what amount is kinetic energy on wind and sea, what amount is absorbed by oceans and at which deeps? Plus many other factors.

The best thing that scientist may do now, is try to collect more data and improve our climate models until we get better predictions that match data collected.

Edited August 7, 2015 by AngelLestat

[arkie87]

First, that is the wrong way to approach the problem, It would be very confusing, because we need to focus in the energy sources, and this might looks like the ground is a high energy source, which is not, it's just trapped heat.

The biggest energy source is the sun, and only reach 10% to the surface, so yeah, you might have convection heat, but what it does tells us?

Not much.. IR frequencies can escape even from surface without touch the atmosphere, of course just a bit amount.. but it can.

Then you add a little amount by convection which in upper stages will provide extra radiation, so instead make that step you just focus in input and output radiation, and thats it. like this graph:

Anual Energy Budget Venus.

https://scienceofdoom.files.wordpress.com/2010/08/venus-k-t-comparison.png

Also, atmosphere does not escape from the planet, that is why is insolated from the convection point. Only radiation comes out. Similar to the car.

Your figure is quite poor. 0 reflected by surface? 0 latent heat? 0 thermals? Where are these numbers even from?

I agree, all that matters in the end of outgoing radiation from upper atmosphere, but the point is, that even if lower atmosphere were completely opaque, upper atmosphere wouldnt cool wayyyy down, since convection from surface and lower atmosphere would keep it warm.

Maybe this example will make sense: it's like the difference between being in a car with energy efficient double-pane (high R-value) windows, and single-pane windows. Yes, both windows will trap nearly all the IR radiation emanating from the hot air and surfaces inside the car. However, the single-pane window car will still be cooler, since hot inner surface of the windows can conduct more effectively to the outside surface, where it can then be radiated.

And while the radiation that the surface abosrbs is only a small portion of total incoming flux from the sun, its effect isnt as small. Convection acts to improve the temprature uniformity between surface and atmospheric layers than what it would be without convection. It is all about thermal resistance. And while the thermal resistance from surface to upper atmosphere might be very large via radiation due to the opacity of the lower atmosphere, the convective thermal resistance is much smaller. That is the point.

Yeah, what can tell us just the co2 data from 3 or 4 locations on earth that might have some measurement errors from long long time ago?

Vs all the data (millons of different sources) that we have today?

Even with all the data we have today is really hard to follow all the energetic process in earth, what amount is kinetic energy on wind and sea, what amount is absorbed by oceans and at which deeps? Plus many other factors.

The best thing that scientist may do now, is try to collect more data and improve our climate models until we get better predictions that match data collected.

Ok, I can agree with that. Though i do think that when assessing climate trends, long term trends (1k, 10k, 100k years) are more important than 100 year trends, so ice core data might still be more useful than all the data we can collect in one lifetime.

Edited August 7, 2015 by arkie87

[AngelLestat]

Your figure is quite poor. 0 reflected by surface? 0 latent heat? 0 thermals? Where are these numbers even from?

I think they have some kind of sense.

It gets 653w/m2

From that, 490 is reflective due So2 clouds, then we have 163 remaning, which 146 is absobed by the atmosphere and 17 by the ground.

Then we have a close loop of 16583 w/m2 (earth close loop is 314w/m2 aprox), which is responsible of the higher temperatures.

The surface does not reflect radiation (maybe it does, but is included in the close loop, or maybe is negligible)

There is not thermals, this has sense because it only reach 17w/m2 to the surface, but again, thermals may be represented as the 16000 loop (just because is easier represent all by radiation).

Evapo transpiration is negligible, because the climate is very dry.

From the loop, only 17 w/m2 escape.. this is obvious because is the amount that reach the surface.

Then the atmosphere radiate 163 w/m2 to the space, which is the result of 17+146, so that is the energy equilibrium.

I agree, all that matters in the end of outgoing radiation from upper atmosphere, but the point is, that even if lower atmosphere were completely opaque, upper atmosphere wouldnt cool wayyyy down, since convection from surface and lower atmosphere would keep it warm.

Yeah, but is more easy to understand all just using 1 type of energy transfer, also they also absorb radiation from the surrounding atmosphere.

Maybe this example will make sense: it's like the difference between being in a car with energy efficient double-pane (high R-value) windows, and single-pane windows. Yes, both windows will trap nearly all the IR radiation emanating from the hot air and surfaces inside the car. However, the single-pane window car will still be cooler, since hot inner surface of the windows can conduct more effectively to the outside surface, where it can then be radiated.

Yeah, its similar, the glass acts as co2 layer and radiactive emitter to the space, which it gets its energy from convective, conduction and radiation.

Ok, I can agree with that. Though i do think that when assessing climate trends, long term trends (1k, 10k, 100k years) are more important than 100 year trends, so ice core data might still be more useful than all the data we can collect in one lifetime.

Yeah it helps, what I mean is that it is not enough to draw conclusions just from that data, they should be use as complementary info; nothing more.

[arkie87]

I think they have some kind of sense.

It gets 653w/m2

From that, 490 is reflective due So2 clouds, then we have 163 remaning, which 146 is absobed by the atmosphere and 17 by the ground.

Then we have a close loop of 16583 w/m2 (earth close loop is 314w/m2 aprox), which is responsible of the higher temperatures.

The surface does not reflect radiation (maybe it does, but is included in the close loop, or maybe is negligible)

There is not thermals, this has sense because it only reach 17w/m2 to the surface, but again, thermals may be represented as the 16000 loop (just because is easier represent all by radiation).

Evapo transpiration is negligible, because the climate is very dry.

From the loop, only 17 w/m2 escape.. this is obvious because is the amount that reach the surface.

Then the atmosphere radiate 163 w/m2 to the space, which is the result of 17+146, so that is the energy equilibrium.

Sorry. I thought this was for earth, not Venus. My bad.

Yeah, its similar, the glass acts as co2 layer and radiactive emitter to the space, which it gets its energy from convective, conduction and radiation.

No comment regarding single-pane vs. double-pane windows?

[peadar1987]

Ugh, here goes...

Not at all. You spotted something.

Before I start, keep in mind that the source you provided in the original post is heavily biased, and therefore not reliable. It's a web site that's dedicated entirely to squashing global warming skepticism, and the site only appears to collect data that supports that goal. That's not how one is supposed to do science.

Actual climate scientists weren't the ones who started the politicisation of climate change. When there are large sections of the media and society who take a politically-motivated stance against established science, there is a need for websites like this to counter their specious claims.

That said: the first problem here is that the graph showing temperature changes lagging behind CO2 changes is an approximation. We're making educated guesses at what Earth's temperatures and CO2 concentrations were in the past, via indirect methods (frequently ice cores). It's entirely possible our measurements are off.

A fair point, but according to our current scientific knowledge, it's more likely that they are right than wrong.

The second problem is: people are just plain stubborn. Point out a problem with a chart, as you did in the OP, and a large number of people will refuse to listen to you, walk away in a huff, and go right on posting that chart in other threads on other web sites. Happens all the time, and not only in global warming arguments.

Which is far more true of global warming deniers than accepters, in my subjective experience. Case in point: the "Global warming stopped in 1997" brigade.

The third problem is much more insidious. You already snagged a piece of it when you called attention to the possibility that temperature affects CO2 levels, rather than the other way around. The argument of "does CO2 affect temperature, or does temperature affect CO2?" is old hat in global warming arguments. But there are always at least THREE possibilities, and the third possibility has been almost entirely drowned in the vitriol people have been spewing at each other in arguments over climate science for the last forty-odd years. Here's that third possibility: temperature and CO2 could both be caused by something else entirely. The chart does show a correlation--but that correlation doesn't tell you what the cause is. We humans have an automatic tendency to assume it's one or the other--but what if the cause isn't on the chart?

If you can find a cause that correlates so well to both temperature and CO2, submit it to a peer-reviewed journal. Many very well-funded researchers have tried. None have succeeded.

Oh, and it gets better--the fourth possibility is that the chart is simply a flat-out lie. I've seen more than one global warming alarmist say the following in online chat forums: "so what if global warming isn't real? If people think it's real, they'll work harder to clean up the planet!" Gives a whole new meaning to the old snippet about how "the truth hurts".......

Nope nope nope nope nope. Conspiracy rubbish.

I've got a big surprise in store for you, dude. Hang onto your potatoes!

Venus isn't what you think it is. It's not a planet-size warning to Earth about what will happen if we don't all turn into Al Gores. The barbecue-grill temperatures on our sister planet are almost entirely NOT the result of carbon dioxide!

All forms of radiation, including heat, follow the inverse-square law: double the distance from a radiation source, and the radiation received does not get reduced to half--it gets reduced to one-fourth! Radiation received depends on exposed surface area. Hold a playing card in front of your face at varying distances, and you can see it yourself: at twice the distance, the card is half as wide and half as tall--which is one-fourth the surface area. Cut the distance from a radiation source in half, and you get FOUR TIMES as much radiation. This remains true even for radiation that goes right through you (such as gamma radiation). It may seem that your entire body is still being exposed to gamma radiation, but if you double the distance from the source, you now only have one-fourth as many gamma rays going through your body (taking that playing card and sticking pins in it would be a good analogy--at twice the distance, the card gets one-fourth as many pins).

Venus is thirty percent closer to the sun than Earth is. That doesn't mean Venus gets thirty percent more heat from the Sun.....it means Venus gets twice as much. And guess what? Venus is twice as hot as Earth. The high temperatures on Venus are almost entirely the result of Venus being closer to the Sun, and its thick carbon dioxide atmosphere has very little to do with it.

Others have more than adequately covered this. Venus is actually above the blackbody temperature you would expect at its distance from the sun. This part of your post has been completely and utterly debunked by multiple sources using actual science and maths.

Oh, there's more! Here's some more fun for the science wonks in here. It turns out that Venus' night side is just as hot as the day side! It's been verified via satellites landing on the planet. This is particularly impressive when you remember that a Venus day is longer than a Venus year. That's what carbon dioxide actually does. It buffers and slows temperature changes.

This is because supercritical CO2 is a good conductor and convector of heat, with very high thermal inertia, which means that the rate of heat loss into space on the night side is slowed. CO2 buffers and slows temperature changes in response to increased or decreased insolation, simply because it is thermal mass, but this has pretty much nothing to do with global warming. We are not significantly changing the thermal mass of our atmosphere by burning fossil fuels, but we are changing its absorption and reemission characteristics, which is the main issue.

In visible light, to be sure. In the infrared range? Not so sure. I've seen a lot of sites describing the surface of Venus being photographed in infrared, which suggests its atmosphere is at least partially transparent to infrared.

The majority of the sun's output is in the visible range. This is not surprising when you think of what "visible" actually means. It's the range of wavelengths we have evolved to be able to see. It wouldn't make much sense if we evolved to see best in wavelengths not commonly emitted by our major source of lighting.

Actually, in terms of received radiation, Mercury is colder than it "should" be.

The daytime side of the Moon tops out at the boiling point of water. Mercury? About twice that. Except Mercury gets FIVE TIMES as much incident radiation as the Moon. Probably due to different compositions.

Even though solar irradiation scales with the square of distance, radiative heat transfer (and therefore reemission of heat) scales with the fourth power of temperature. Even though Mercury would absorb 5 times more heat from the sun than the moon would, all other things being equal, as it increases in temperature, it also emits much more energy into space, so the temperature will stabilise at a temperature that is still higher, but not 5 times as high.

Stuff about pressure

As others have pointed out, pressure doesn't produce heat. Compression produces heat. The Kelvin-Helmholz mechanism isn't relevant for something as small as the atmosphere of a terrestrial planet, which will have long ago reached an equilibrium point in terms of pressure.

The most significant negative effect is this: as something gets warmer, it radiates heat faster.

But there's something else going on that hardly anybody ever notices: the principle of diminishing returns. Most people assume "X amount of CO2 produces Y degrees of warming". And it doesn't work that way. If you start with a planet that's a CO2-free ice cube, the first kilogram of CO2 you add to the atmosphere will produce considerable warming. The second kilogram, much less. The third kilogram, even less than the second. Why? Because you've got more CO2 molecules competing for the same amount of heat. And the molecules don't play nice; they circulate around and on top of each other, jostle each other, steal heat from each other, and occasionally insult each others' mamas.

Only over short timescales, and with limited amounts of heat available. In the solar system, over many years, and with practically unlimited energy available from the sun, the atmosphere will reach an equilibrium temperature, no matter how much of it there is. This is, of course, complicated by the emission and absorption spectra of the component gases.

There are probably several reasons, but I've got a theory for you which you've probably never heard:

Right now, Earth's global mean temperature is about 288 degrees Kelvin. Which is above freezing, but kinda chilly. Obviously, Earth isn't the same temperature everywhere......but what if it was? What would happen? Well, then the ENTIRE planet would be above freezing, both polar ice caps (and all other ice everywhere else!) would melt completely, and there would not be much rejoicing. A completely different result than we actually have today--yet the global mean temperature is the SAME.

In order for the planet to get out of an Ice Age (or to start one!) it's not enough to add heat. It matters where the heat goes. If it stays near the equator and the poles get colder, that would allow the ice caps to advance. If it's more evenly circulated for whatever reason, more heat would reach the poles, and it would be bye-bye Ice Age.

Bottom line: when people worry about global warming and note the planet's mean or average temperature going up, that doesn't tell you what's actually going to happen. You need to ask more questions.

This is pretty much true. For example, increased temperature can result in more precipitation. This means more clouds, and in areas that are still below freezing, increased snowfall, meaning greater albedo in these areas, reducing their temperature, even though temperatures elsewhere may be higher.

Plus, its atmosphere is partially transparent at infrared and ultraviolet wavelengths (and UV delivers more energy than infrared or visible light!), there's constant lightning, there's exothermic chemical reactions involving the sulfuric acid in the planet's atmosphere, and also the planet has no magnetic field and is constantly getting bombarded with high-energy solar wind (which is not only heating Venus more than Earth, but also slowly stripping Venus of its atmosphere!) There's actually lots of things that could do it. I've never been able to find exact values for most of them (because nobody knows), but it's enough to make me think twice about the real reasons our sister planet is such a hothead........

Take another look at the graph I linked earlier. UV is higher-energy, sure, but most of the sun's output is still in the visible range. Even though Venus' atmosphere is partially transparent in UV and IR, that doesn't mean wholly transparent.

Disagree. Temperature is the cause of pressure. The reason a gas has pressure is because the molecules are moving around and bouncing off each other. Increase the temperature? The molecules bounce faster and harder, causing the pressure to go up.

Increasing the pressure increases the temperature, increasing the density increases the pressure and temperature. The factors are all interactive. But when Venus' atmosphere formed (or changed, or whatever caused it to turn into pea soup) the increase in pressure was definitely at least partially responsible for the increase in temperature.

Incorrect. Containment is the cause of pressure. An uncontained gas has zero pressure, no matter what its temperature. On a planetary surface, the "containment" is the force of gravity.

The mass of Venus' atmosphere compressing under gravity as it formed would certainly have increased its temperature, but there has been billions of years since then for it to reach equilibrium, and its temperature today has nothing to do with any temperature rise during its formation.

Not true. When the atmosphere absorbs heat and warms up? The atmosphere itself becomes the radiator. More so when high-altitude winds are constantly circulating heat from the surface to the cooler upper atmosphere and to the dark side of the planet.

Ooh, hey--here's something interesting for you to chew on. You're familiar with the fact that water vapor is a greenhouse gas? One of the strongest ones, too. So then, why is it that areas with moist air (i.e. coastlines) are warmer at night.....and COOLER during the day? As opposed to deserts, which in general are blazing hot during the day and FREEZING COLD at night? Most people forget that about deserts. And this isn't just true about deserts; most areas of the Earth with dry air have wider temperature swings.

Edit: Actually wrong.

That's what greenhouse gases actually do. Your sweater doesn't know which is inside and which is outside; it insulates equally in all directions. Greenhouse gases don't only keep heat in--they also keep it out

Greenhouse gases don't work like sweaters. They absorb unidirectional radiation and reemit it omnidirectionally, and they do this more effectively for the wavelengths of radiation reemitted from the earth than for those in the incident solar radiation.

Gravity = constant application of work.

Nope, work is only done when energy is expended. An apple sitting on a table is having no work done to it by gravity, even if there is a force applied.

The above effect does happen, but it's minor; the effect of ALL atmospheric gases, greenhouse or not, absorbing heat from the ground via direct contact is more significant.

Carbon dioxide is a different process. It absorbs infrared in two pretty specific frequency bands, warming the gas (which, like all heated objects, re-radiates the energy at a lower frequency). But like the sweater example I posted earlier, carbon dioxide doesn't care which way is up and which is down. In the same way it keeps some of Earth's heat from escaping, it also prevents some of the Sun's energy from reaching the ground--absorbing it higher up where it more easily radiates back into space. But carbon dioxide is a red-headed stepchild greenhouse gas. Time to meet the Big Bully:

Water vapor is yet another different process. Water (in vapor and liquid form) has a high specific heat. It takes a lot more heat to produce an actual temperature change in water than, say, concrete. This effect cools the air during the day (because energy is converted into a smaller temperature change than if the energy was in the ground). Then, at night, the water vapor cools down more slowly (again, because of its high specific heat) keeping the nighttime warm. That's why the California coast is so nice and the Mojave Desert is a scorcher followed by an ice cube. Lack of water vapor allows the Sun to incinerate desert ground--and then lack of water vapor allows all that heat to radiate out at night.

Referring to my previous comment, water vapour has only a small effect on the specific heat of air.

Moreover, earth's ecosystem is pretty much saturated with water. If you emit water into the atmosphere, it will quickly condense and rain out, giving it a very short atmospheric lifetime, and not having a huge effect on the overall water content of the air. The same is not true of CO2. If you emit CO2, it stays in the atmosphere far longer.

Water has an atmospheric lifetime of about 9 days. CO2 an atmospheric lifetime of over 30 years.

Edited August 7, 2015 by peadar1987

[YNM]

I am confused by your response: solubility of water goes down with temperature, making CO2 come out of the ocean and enter the atmosphere, thereby raising CO2 ppm with temperature. Thus, the graph would still look as is, no?

This effect occurs according to everyone, and global warming in the past actually depended on this effect according to the original paper to create a positive feedback loop, so i dont see how an informed person can dispute it...

I urge you, to look at this two data :

V NOTE : read this right to left V

Yeah, it becomes a problem once the levels of CO2, as recovered from recent past (read : less than 0.1% of a billion year, least are few tens of generations) carbonate data, and the current data, are far different. Earth did have a higher temperature in the long past, but humans aren't used to this, I suppose. AFAIK, one thing that a human is good at, is changing their surrounding environment to suit their needs - why not on this one as well ?

[arkie87]

If you can find a cause that correlates so well to both temperature and CO2, submit it to a peer-reviewed journal. Many very well-funded researchers have tried. None have succeeded.

They dont have to find a source that effects temperature and CO2. Temperature change by itself effects CO2! As mentioned above, this is a requirement of the theory of how CO2 affects global temperature via its positive feedback mechanism.

As you have correctly pointed out, radiative heat transfer scales with the fourth power of temperature. This applies not only to absorption of solar radiation, but also to reemission of heat. Mercury would absorb 5 times more heat from the sun than the moon would, all other things being equal, but as it increases in temperature, it also emits much more energy into space, so the temperature will stabilise at a temperature that is still higher, but not 5 times as high.

Please explain this effect. Why should objects which are hotter absorb more radiative heat?

Only partially true. At 30 celsius, as air goes from 0% to 100% humidity, its specific heat capacity increases from 1.007 J/kgK to 1.04 J/kgK, which is an increase of 3%, more or less, so not particularly significant. The main driver of greater temperature swings in drier climates is the absence of the moderating effect of large amounts of water on the ground, not in the air.

This isnt how it would work. Cp does not change significantly. What causes the thermal inertia is the latent heat of the water vapor. Going from 30C air at 80% relative humidity down to 20C at 100% humidity, requires removal of water vapor thereby releasing latent heat in addition to sensible heat. The effective "Cp" over this range is about 2.8 J/kg-K

Moreover, earth's ecosystem is pretty much saturated with water. If you emit water into the atmosphere, it will quickly condense and rain out, giving it a very short atmospheric lifetime, and not having a huge effect on the overall water content of the air. The same is not true of CO2. If you emit CO2, it stays in the atmosphere far longer.

Water has an atmospheric lifetime of about 9 days. CO2 an atmospheric lifetime of over 30 years.

But if CO2 by itself isnt enough to cause a significant greenhouse (everyone suggests it works via positive feedback loop with water), then the stability and quick residence time of water vapor matters. Adding more CO2 might increase the amount of water vapor. But the water vapor cycle is so stable and self-correcting (negative feedback) that it might not matter.

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I urge you, to look at this two data :

V NOTE : read this right to left V

http://www.globalwarmingart.com/images/7/76/Phanerozoic_Carbon_Dioxide.png

http://www.globalwarmingart.com/images/d/d3/Carbon_Dioxide_400kyr_Rev.png

Yeah, it becomes a problem once the levels of CO2, as recovered from recent past (read : less than 0.1% of a billion year, least are few tens of generations) carbonate data, and the current data, are far different. Earth did have a higher temperature in the long past, but humans aren't used to this, I suppose. AFAIK, one thing that a human is good at, is changing their surrounding environment to suit their needs - why not on this one as well ?

I'm not sure what your point is? You didnt address my comment at all.

These data are over two different time scales, so of course they dont have to agree. And they have no bearing on our discussion of whether or not as temperature goes up, CO2 concentration in atmosphere should go up or down.

[peadar1987]

They dont have to find a source that effects temperature and CO2. Temperature change by itself effects CO2! As mentioned above, this is a requirement of the theory of how CO2 affects global temperature via its positive feedback mechanism.

You're dead right, but unless I have misunderstood Wedge, he is saying that there could be a factor that was affecting both temperature and CO2 without them affecting each other. It was to him that my point was addressed.

Please explain this effect. Why should objects which are hotter absorb more radiative heat?

Sorry, that's my sloppy posting. I'll tidy it up a little to make it more understandable.

What I was trying to say (badly) was that although Mercury gets ~7x the solar radiation of earth due to being ~0.38x the distance from the sun, the rate at which it radiates heat to space will scale with the fourth power of temperature, meaning it will not be ~7x as hot.

This isnt how it would work. Cp does not change significantly. What causes the thermal inertia is the latent heat of the water vapor. Going from 30C air at 80% relative humidity down to 20C at 100% humidity, requires removal of water vapor thereby releasing latent heat in addition to sensible heat. The effective "Cp" over this range is about 2.8 J/kg-K

True, my mistake.

But if CO2 by itself isnt enough to cause a significant greenhouse (everyone suggests it works via positive feedback loop with water), then the stability and quick residence time of water vapor matters. Adding more CO2 might increase the amount of water vapor. But the water vapor cycle is so stable and self-correcting (negative feedback) that it might not matter.

Not really. It's not the CO2 that affects the water-carrying ability of the air, it's purely the temperature. Higher temperature=higher carrying capacity, and there is enough water around that the carrying capacity is filled pretty quickly, there's no real significant lag, as there is with some positive feedback loops, like releasing methane from permafrost.

edit: Although this is only true of low-altitude humidity. Humidity at higher altitudes is governed by the dynamic behaviour of convection cells like the tropical convergence zone, and the El Nino cycle, which are still quite poorly understood. This is one of the posited reasons for the slowdown in warming over the last decade, the current status quo isn't allowing an increase in humidity at sea level to be translated into an increase in the stratosphere, dampening the feedback loop to some extend.

Edited August 7, 2015 by peadar1987

[arkie87]

I appreciate your ability to admit you are wrong (rather than what others seem to do, which is confuse the issue until it is unclear what we are debating anymore )

and there is enough water around that the carrying capacity is filled pretty quickly, there's no real significant lag, as there is with some positive feedback loops, like releasing methane from permafrost.

Relative humidity is rarely 100% (indicating saturated water vapor content in the air for a given temperature), so the air could usually acquire more water vapor. The only time relative humidity approaches 100% is at night when the air is cooling. When the air is warming, the water vapor content does not keep up with saturation levels.

edit: Although this is only true of low-altitude humidity. Humidity at higher altitudes is governed by the dynamic behaviour of convection cells like the tropical convergence zone, and the El Nino cycle, which are still quite poorly understood. This is one of the posited reasons for the slowdown in warming over the last decade, the current status quo isn't allowing an increase in humidity at sea level to be translated into an increase in the stratosphere, dampening the feedback loop to some extend.

I can agree with that