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Is the atmosphere getting more dense with various gases, car pollution (200 million cars just in North America), factory pollution, more water vapor and denser cloud cover? If so could a "thicker" atmosphere act like a lens and magnify the Sun's rays to an intensity a higher than what it should be?

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    $\begingroup$ This is too short to qualify as an answer, but the answer is NO. $\endgroup$ – David Hammen Sep 15 '14 at 11:58
  • $\begingroup$ gaseous emissions don't increase the density of the atmosphere around you. The only thing that can increase the density of air is lowering the temperature or increasing the particulate/aerosol content (e.g. smoke, water content, etc) $\endgroup$ – farrenthorpe Sep 16 '14 at 6:00
  • $\begingroup$ The Atmosphere is 'shaped' like a 'convex' lens 'pointing' towards the Sun ( that is one hemisphere of Earth). This couldn't act like a real lens? $\endgroup$ – user128932 Sep 16 '14 at 18:10
  • $\begingroup$ Shape alone does not make a lens, optical properties such as diffraction and refraction do. The atmosphere is not focusing photons but rather transmitting, absorbing or scattering them based on their wavelengths. $\endgroup$ – casey Sep 17 '14 at 15:27
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    $\begingroup$ Do you mean physically thicker, or more dense? The percentage of O2 during the Carboniferous was 35% (compared to 21% today), and since O2 is slightly more dense than dry air, it would have made for a somewhat denser atmosphere. $\endgroup$ – congusbongus Sep 18 '14 at 4:14
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No, the atmosphere is not becoming thicker.

If anything at all, the atmosphere is getting thinner, but only on very long time scales. Planet Earth very slowly loses parts of it atmosphere due to atmospheric escape, either to space or to the solid Earth. Historical atmospheric pressure is hard to determine, but billions of years ago, it might have been much thicker than it is now, in particular with a lot more greenhouse gases. One clue is the faint young sun paradox; we know there was liquid water at a time the solar output was 20% less, which would require so much greenhouse effect that the total atmospheric pressure must have been much higher. But the jury is still out on that one.

The atmosphere is not becoming significantly denser, either.

The concentration of gases that we are adding to the atmosphere is typically measured in parts per million (ppm) or parts per billion (ppb). The effect of adding to this is small compared to the natural variability in atmospheric surface pressure / density due to weather and other effects.

The atmosphere does not act like a lens.

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  • $\begingroup$ Sorry I just realised I should have said denser. Is the Atmosphere (with all the 'green' house gases and pollution and particles ,dust and water vapor and cloud cover) getting DENSER. And as such could act like a convex lens? ( of course 'thicker' could mean denser) $\endgroup$ – user128932 Sep 18 '14 at 4:23
  • $\begingroup$ Could the atmosphere in some situation act like a 'lens'? $\endgroup$ – user128932 Sep 18 '14 at 20:26
  • $\begingroup$ If a double or triple rainbow occurs in the sky could that indicate a lot of water vapor in the atmosphere? $\endgroup$ – user128932 Sep 18 '14 at 20:28
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    $\begingroup$ No, a rainbow indicates water droplets, not water vapour. $\endgroup$ – gerrit Sep 19 '14 at 2:27
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    $\begingroup$ @201044 Yes, along with rather bright sunlight. $\endgroup$ – gerrit Dec 20 '15 at 21:35
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Gerrit is correct that the atmosphere is not becoming significantly denser, but it is becoming marginally denser, actually by about 0.02%, because CO2 is about 1.5 x denser than air, and we have increased it by about 120 ppm since the start of the industrial revolution. In the short term this is a worry, but in the long term, geologically speaking, it is a mere blip in the Earth's evolving atmosphere - like major volcanic eruptions. Out-gassing of radiogenic helium is insignificant, as is incoming gaseous debris from space.

Refracted solar insolation doesn't significantly vary with changing atmospheric density, and even if it did, it would only be an imperceptible and trivial influence upon where the sunlight was absorbed - merely a local thermal anomaly, very rapidly redistributed by the weather.

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  • $\begingroup$ Don't you have to look at what goes into the CO2 though? CH4 + 2O2 > CO2 + 2 H2O. We lose 2 molecules of O2 for 1 molecule of CO2, a net loss. But each additional carbon in the chain adds 1C and 2 H, so for each chain CH2 + (1.5)O2 > CO2 + H20, where 3 oxygens become 1 CO2, so with oil and methane. On average, I think burning fossil fuels reduces the mass of the atmosphere, but it depends somewhat on the carbon to hydrogen ratio. The effect is pretty small though. More dense because of CO2, Yes, also lighter - a little. $\endgroup$ – userLTK Sep 5 '16 at 7:16
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    $\begingroup$ Re userLTK: Agreed, the carbon comes from the ground, the oxygen from the atmosphere, but it's not quite that simple, because much of the atmospheric CO2 is recycled through the biosphere, which tends to maintain its own equilibrium with atmospheric oxygen. Burning the hydrogen in oil and gas would create more vwater, so would make the atmosphere lighter, but burning coal, with a higher C:H ratio would cause the reverse. On balance I would have expected a slightly heavier atmosphere - but as you say, it depends on the global aggregate C:H ratio. Does anyone know what this is? $\endgroup$ – Gordon Stanger Sep 5 '16 at 10:46
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Regarding the last part of your question. The atmosphere keeps temperature of the Earth warmer than it would be without it not because of lensing but because of the greenhouse effect. The light from the sun hits the ground, heats it up and hot ground emits the thermal radiation, like your back burner. The greenhouse gases capture it. The thicker is the atmosphere, the higher is the probability that low-freq thermal radiation will be turned back to Earth (Sun is much hotter, it emits much higher-freq light, the atmosphere is transparent for it).

You say that there can be another effect, the photons which fly tangent to the earth surface can be captured by the atmopsphere (lens) and deflected to the ground, like if you capture a fly that passes near you with your hand, and sent it into your mouth. It seems that the effect is real and known as atmospheric refraction

enter image description here

You can feel it on the sunraises and sunsets, when the sun is behind the horizon, the atmosphere is still light, which means that it captures some light, the photons that go tangent to the earth surface and would pass by if atmosphere did not capture it. That is, the lens cannot produce more photons than Earth receives from the sun. It cannot raise the Earth temperature. It can only collect all the light and send it into one dot or grow bigger, collecting some light from outside the Earth and send it to the Earth, like capturing the flies near your body with long hands. Let's suppose that refraction is real and atmosphere can capture the tangent photons. So, the question is: which effect is stronger: greenhouse warming or lensing warming? The thicker atmosphere increases both of them. But, the diagram is misleading. It says that the atmosphere is very fat, almost like the Earth diameter or larger, which is far from truth. In fact, the atmosphere is only a couple of kilometers in thickness whereas the Earth is 6000 km. Morevover, refraction operates only on the perimeter area, the rim around the earth

enter image description here

whereas greenhouse gases reflect the Earth heat back to the surface over the whole earth surface, which makes the effect not 1000 times smaller but 1000x1000 times smaller. So, I would account your lensing as important only when atmosphere sichness would reach the size of the Earth and beyond. There is however one negative feedback that I cannot estimate but it would be important for a very large atmosphere. It is that surface of heat irradiation would also be much larger if your planet is much larger. Probably your lensing gives less warm than increased irradiation takes away.

Enough of speculations for today, I suppose.

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