16 votes
Accepted

How did CO₂ originate on Earth before there was life?

The answer is Volcanos. There might be other inorganic processes capable to produce $\text{CO}_2$, but on Earth, the main inorganic source of $\text{CO}_2$ are volcanoes. In some period of Earth's ...
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15 votes

What keeps the different gases mixed in the atmosphere?

It's because gases also diffuse. If you separate two gases of different densities by a horizontal membrane, and then slowly remove the membrane, then the interface will diffuse. You can try this with ...
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14 votes

Why is it colder in the mountains than at sea level?

The traditional answer basically comes down to the physics concept of adiabatic cooling, a description of which is: There is less pressure as you go up in the atmosphere (basically due to less air ...
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11 votes

Why have "ozone-depleting substances" led to a third of all global warming and half of arctic sea ice loss?

The Global warming potential (GWP) describes how much global warming a particular gas may induce in a particular time period. It is often expressed in terms of CO₂-equivalent. The best known ...
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11 votes

Why are atmospheric BrO and ClO important to measure by satellite?

BrO and ClO significantly deplete ozone from the atmosphere. Researchers at Harvard University state: It is a remarkable fact that perhaps the most important observation coupling climate forcing ...
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10 votes

Can I use diamonds as fossil fuel?

Diamonds are expensive. Really expensive. Even "cheap" synthetic diamonds are orders of magnitude more expensive than conventional fossil fuel. By using them as fuel, you will increase ...
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8 votes
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What "g" would be needed to keep helium on Earth?

Atmospheric escape is the loss of planetary atmospheric gases to outer space. You'd never be able to contain ALL of any gas forever by gravity. Ultimately you end up in the rarefied atmosphere where ...
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  • 511
8 votes

The free oxygen (O$_2$) in the atmosphere is largely a result of what process?

You are correct in thinking that oxygen comes from photosynthesis. In fact it is so much associated with photosynthesis, as opposed to any inorganic process, that the presence of oxygen in the ...
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8 votes
Accepted

How is the equilibrium of 21% oxygen in Earth's atmosphere established?

I'm not sure I can give a good technical answer. I don't think the amount of oxygen in the Earth's atmosphere is due to equilibrium but more of a consequence of the formation of the solar system, ...
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  • 5,707
8 votes
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ppmV versus μmol/mol for atmospheric CO2 - how to convert?

According to the US Carbon Dioxide Information Analysis Center : Though in their data table they use the term "ppmv", they explain: The CO2 mixing ratios are reported as micromoles per mole ...
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  • 5,892
8 votes

Why is the Earth's shadow blue?

To my eyes, the belt of Venus looks purple, which didn't makes sense to me, as the very short wavelength of purple light should have been scattered long before arriving back there. Then all made sense ...
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8 votes
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Convert NO2 concentration in Sentinel-5P data from mol/m2 to μg/m3 on the ground level

...measured in mol/m² within the total or tropospheric column. Is it possible to deduce concentrations for a specific slice of the troposphere? Not really, since you have a crucial bit of information ...
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7 votes

What is the difference between a carbon sink and a carbon reservoir?

The difference is that a carbon sink accumulates carbon, whereas a carbon reservoir has accumulated carbon. That is to say: A carbon sink is an ongoing process which is increasing the amount of ...
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  • 4,080
7 votes

What causes smog to clear up on some days?

My guess would be a combination of boundary layer, cloud cover, and emissions (though that isn't terribly specific). Smog is a combination of nitrogen oxides (which cause smog's brown color), ozone, ...
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  • 1,361
7 votes

Does natural plant decomposition release more greenhouse gases than burning

Another way of looking at the question: I take 2 standard wheelbarrows of bits of plants from my garden. One wheelbarrow is used to fill the compost bin. The other goes to the bonfire. How much ash ...
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  • 540
7 votes
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Why is the Earth's shadow blue?

How can the air in the Earth's shadow scatter blue light if it doesn't get any direct illumination, and any indirect illumination getting back there should be VERY depleted in blue (i.e. mostly red ...
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  • 406
7 votes

Have the oceans dissolved water vapour?

The answer is no, yes and then, perhaps, no. No: water vapour is not "dissolved" in the oceans, rather it becomes part of the oceans through a phase change from vapour to liquid (possibly via an ...
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7 votes

How to convert mol/m^2 to total mass ( e.g gram, kg etc )?

$\rm \frac{mol}{m^2}$ shows the amount of $\rm{NO_2}$ in the atmosphere over a square meter of surface area - in mols. The molar mass of the $\rm{NO_2}$ is $14+2\cdot 16=46$. It means, the mass of 1 ...
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  • 642
6 votes

How to understand the bizarre high level for both PM2.5 and Ozone

I think it is important to keep in mind the mechanisms that form PM$_{2.5}$ are different than the mechanisms that form O$_3$. From the data your provided you can draw some simple conclusions: ...
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6 votes
Accepted

What denotes a parameterization in a model? (semantics )

As defined in the AMS glossary, a parameterization is a simplification of one or several processes in a model. I add that a parameterization commonly adds an error and increases the uncertainty in the ...
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6 votes
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The difference of vertical advection and convection process for chemistry species

The difference between advection and convection in Chemistry Transport models (CTMs) is a question of scale: Advection is driven by winds that are provided by the meteorological input dataset. Thus, ...
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6 votes
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What's the background concentration of trace gas/pollutants?

Background pollution is what would be measured if no anthropogenic emissions existed. In other words, if you shut off human activity (or avoid the emissions from it), you can measure the background. ...
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6 votes

What would a planet's sky look like with different chemical compositions, such as low nitrogen, high methane etc?

Except for Rayleigh scattering (Is the color of the sky the same everywhere on earth?) gases typically do not add any color to atmospheres, they are usually transparent in visible light. The Halogen ...
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6 votes
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What is brown carbon?

Carbonaceous aerosols are formed by a mixture of substances with different chemical, physical, and optical properties. Certain organic substances are mostly transparent to sunlight and therefore do ...
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6 votes
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If methane decays to $\small\sf{CO_2}$ in the atmosphere, shouldn't there be much more $\small\sf{CO_2}$?

So what am I missing in this analysis? The linked data says 2017 CH4 was about 1850 ppb, not 1850 ppm. Dividing parts per billion (ppb) by 1000 results in parts per million (ppm). In other words, ...
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  • 20.2k
5 votes

What is the ratio of infra-red light absorbed by green house gases?

There is no simple relationship since it all depends on the frequency (IR spectral lines for most species of molecules are a mess). The most direct and precise way of calculation is through line-by-...
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  • 2,083
5 votes
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Persistence time of ozone

Let's first consider the scenario in the absence of free radicals that can act as catalysts of $O_3$ destruction. In such scenario, added to the absence of UV radiation, the photolysis of ozone ($O_3 +...
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5 votes

How can scientists measure chemical composition on other planets?

Scientists can measure the chemical composition of the atmosphere of other planets using spectroscopy. Each molecule in the atmosphere absorbs and re-radiates at specific frequencies of light that ...
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