<p><strong>No, the atmosphere is not becoming thicker.</strong></p>

<p>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 <a href="https://en.wikipedia.org/wiki/Atmospheric_escape">atmospheric escape</a>, 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 <a href="https://en.wikipedia.org/wiki/Faint_young_Sun_paradox">faint young sun paradox</a>; 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.</p>

<p><strong>The atmosphere is not becoming significantly denser, either.</strong></p>

<p>The concentration of gases that we are adding to the atmosphere is typically measured in <em>parts per million</em> (ppm) or <em>parts per billion</em> (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.</p>

<p>The atmosphere does not act like a lens.</p>

CC BY-SA 3.0
2015-12-20T20:25:06.120Z
Well could a double or triple rainbow in the sky indicate a lot of water droplets in the atmosphere?
201044
CC BY-SA 3.0
2015-12-20T21:35:27.947Z
@201044 Yes, along with rather bright sunlight.
gerrit
CC BY-SA 3.0
2014-09-18T04:23:01.097Z
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)
user128932
CC BY-SA 3.0
2014-09-18T20:26:10.273Z
Could the atmosphere in some situation act like a 'lens'?
user128932
CC BY-SA 3.0
2014-09-18T20:28:36.083Z
If a double or triple rainbow occurs in the sky could that indicate a lot of water vapor in the atmosphere?
user128932
CC BY-SA 3.0
2014-09-19T02:27:12.527Z
No, a rainbow indicates water droplets, not water vapour.
gerrit
CC BY-SA 3.0
2014-09-17T15:16:57.960Z
2014-09-18T13:48:02.597Z
2014-09-18T13:48:02.597Z
gerrit
<p>Gerrit is correct that the atmosphere is not becoming <em>significantly</em> denser, but it is becoming <em>marginally</em> 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. </p>

<p>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.  </p>

CC BY-SA 3.0
2016-09-05T07:16:13.297Z
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.
userLTK
CC BY-SA 3.0
2016-09-05T10:46:50.823Z
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?
Gordon Stanger
CC BY-SA 3.0
2016-09-04T13:01:49.450Z
2016-09-04T13:01:49.450Z
Gordon Stanger
<p>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). </p>

<p>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 <a href="https://sites.google.com/a/apps.district279.org/lightapplicationslucysaidu/refraction" rel="nofollow noreferrer">atmospheric refraction</a></p>

<p><a href="https://i.sstatic.net/q90J5.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/q90J5.png" alt="enter image description here"></a></p>

<p>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 <a href="http://bugs.kerbalspaceprogram.com/issues/7741" rel="nofollow noreferrer">rim around the earth</a></p>

<p><a href="https://i.sstatic.net/Cae4s.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/Cae4s.png" alt="enter image description here"></a></p>

<p>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.</p>

<p>Enough of speculations for today, I suppose. </p>

CC BY-SA 3.0
2016-09-05T12:21:03.827Z
2016-09-05T12:21:03.827Z
Little Alien
<p>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?</p>

CC BY-SA 3.0
2015-12-20T20:27:28.983Z
If the atmosphere was somehow 'thicker' or more dense with water vapour , water droplets, all sorts of green house gases and other gaseous pollution ; could the atmosphere slightly magnify the sun's light?
201044
CC BY-SA 3.0
2016-09-05T11:03:50.247Z
@casey Shape alone does not make the glass coating its optical properties because glass does not focus photons. It just transmits or scatters them. Probably it is important to note that it does so based on the light wavelength. This proves my rebuttal of your 'eye opener' correct.
Little Alien
CC BY-SA 3.0
2014-09-15T11:58:38.773Z
This is too short to qualify as an answer, but the answer is **NO**.
David Hammen
CC BY-SA 3.0
2014-09-16T18:10:37.210Z
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?
user128932
CC BY-SA 3.0
2014-09-17T15:27:02.877Z
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.
casey
CC BY-SA 3.0
2014-09-18T04:14:14.013Z
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.
congusbongus
CC BY-SA 3.0
2014-09-18T04:28:52.280Z
You said the O2 today is 21 %. What was it 10 years ago or 20 years ago? If there are less trees and less of forests , like the rain forests would that mean less trees to absorb CO2 thus increasing some of the green house gases , especially with A LOT MORE CARS?
user128932
CC BY-SA 3.0
2014-09-18T17:34:37.337Z
O2 has decreased around 400 ppm over the past 20 years while CO2 has increased by about 40 ppm over the past 20 years.
casey
<atmosphere>
Is the atmosphere becoming thicker?
user128932
# Is the atmosphere becoming thicker?

(Asked by: username_0 on 2014-09-15)

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?

**Tags:** atmosphere

> **Comments:**
> **username_3**: This is too short to qualify as an answer, but the answer is **NO**.  
> **username_0**: 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?  
> **username_4**: 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.  
> **username_5**: 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.  
> **username_0**: You said the O2 today is 21 %. What was it 10 years ago or 20 years ago? If there are less trees and less of forests , like the rain forests would that mean less trees to absorb CO2 thus increasing some of the green house gases , especially with A LOT MORE CARS?  
> **username_4**: O2 has decreased around 400 ppm over the past 20 years while CO2 has increased by about 40 ppm over the past 20 years.  
> **username_1**: If the atmosphere was somehow 'thicker' or more dense with water vapour , water droplets, all sorts of green house gases and other gaseous pollution ; could the atmosphere slightly magnify the sun's light?  
> **username_2**: @username_4 Shape alone does not make the glass coating its optical properties because glass does not focus photons. It just transmits or scatters them. Probably it is important to note that it does so based on the light wavelength. This proves my rebuttal of your 'eye opener' correct.  

---

## 3 answers

### Answer by username_6 on 2014-09-17. Score: 14

**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](https://en.wikipedia.org/wiki/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](https://en.wikipedia.org/wiki/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.

> **Comments:**
> **username_0**: 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)  
> **username_0**: Could the atmosphere in some situation act like a 'lens'?  
> **username_0**: If a double or triple rainbow occurs in the sky could that indicate a lot of water vapor in the atmosphere?  
> **username_6**: No, a rainbow indicates water droplets, not water vapour.  
> **username_1**: Well could a double or triple rainbow in the sky indicate a lot of water droplets in the atmosphere?  
> **username_6**: @username_1 Yes, along with rather bright sunlight.  

---

### Answer by username_7 on 2016-09-04. Score: 5

username_6 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.

> **Comments:**
> **username_8**: 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 username_2.  
> **username_7**: Re username_8: 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?  

---

### Answer by username_2 on 2016-09-05. Score: 3

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](https://sites.google.com/a/apps.district279.org/lightapplicationslucysaidu/refraction)

[![enter image description here](https://i.sstatic.net/q90J5.png)](https://i.sstatic.net/q90J5.png)

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](http://bugs.kerbalspaceprogram.com/issues/7741)

[![enter image description here](https://i.sstatic.net/Cae4s.png)](https://i.sstatic.net/Cae4s.png)

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.


---

