Does earth's atmosphere grow?

[Grok]

This occurred to me while discussing global warming in Free Space. Does the earth's atmosphere grow and if so by how much? Conversely, does it shrink, or does it stay static? Could global warming be attributable to a period where the atmosphere grows. For example, gas expands under heat, correct? If the sun is heating up, then earth's atmosphere would heat up, and therefore grow, making it thinner and allowing more energy in. If CO2 is being added to our atmosphere by autos, is the atmosphere growing to compensate for this extra gas? So, the molecules are spaced further apart, and the supposed greenhouse energy is not trapped because it has more room to escape. Instead, it's just letting more energy in, or is the atmosphere not growing and therefore trapping more energy and causing it to heat up? Why would energy be able to easily come into the atmosphere in one direction, but not get back out? Could someone explain this portion of the greenhouse effect to me?

 

[silylene old]

The atmosphere grows in volume sometimes, as a result of solar radiation and magnetic field interactions. When these volume increase occur, the frictional drag on the ISS increases, causing accelerated orbital decay (a bad thing). <br /><br />The atmosphere loses mass into space due to the pressure of the solar winds continuously. Lighter elements such as hydrogen are preferentially lost. However, at the same time, the atmosphere gains mass as a result of volcanoes, acidification of carbonates, burning of fossil fuels and decaying of organic matter. I am not sure of the net mass balance however. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[Grok]

silylene,<br /><br />I see, but why would the same energy that comes into the earth be suddenly trapped by greenhouse gases? I mean, the greenhouse gases were there when it came in. Why would the energy penetrate the greenhouse gases and then not be able to escape. What feature of greenhouse gases cause this? Reflectivity?

 

[Grok]

eburacum,<br /><br />Thanks for the succinct explanation. So, has the greenhouse effect ever been recreated in a laboratory? Do we know for a fact that there's enough of it in the atmosphere to trap the gases and cause the heating we've seen over the last century?

 

[silylene old]

eburacum45: I think you have generalized too much.<br /><br />Earth has lost 18% of its oxygen in the last 3B years<br />http://thayer.dartmouth.edu/spacescience/wl/misc/Outflow/Seki%2001.pdf<br /><br />Earth lost hydrogen at a rate of 5.6E10 kg/yr in the Archean age when the atmosphere was CH4 rich; nowdays it loses hydrogen at a significantly lower rate of 3.2E8 kg/yr. (taken from Table 1 in this excellent reference) http://thayer.dartmouth.edu/spacescience/wl/misc/Outflow/Seki%2001.pdf )<br /><br /><br />This reference tries to estimate the amount of N2 released into the atmosphere from the mantle, and the amount lost into the mantle. The nitorgon fluxes they discuss are huge from these mechanisms, and it's a gain: http://geosci.uchicago.edu/~dauphas/RefereedArticles/dauphas_marty_EPSL04.pdf<br /><br />Overall the Earth is currently gaining atmosphere, primarily due to mantle degassing.<br />http://www.huxley.ic.ac.uk/Local/EarthSciUG/ESFirstYr/EarthMaterials/mrpalmer/EarthMaterials/earth/earth1/l1.html <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>

 

[silylene old]

<font color="yellow">Very little of the Earth's atmosphere is lost; hydrogen is the only gas which is very likely to escape readily, and most of that oxidises back into H20 almost as soon as it is formed. <br /></font><br /><br />actually the O2 levels over the past 3B years have fluctuated significantly.<br /><br />18% was lost to space. Point is, that's a lot. Probably a similar % of nitrogen was lost, it's nearly the same atomic weight as atomic oxygen. I couldn't find a good source on this.<br /><br />Luckily mantle outgassing and other sources have replaced it.<br /><br />BTW mantle outgassing is by far the largest source of atmospheric gain. <div class="Discussion_UserSignature"> <div class="Discussion_UserSignature" align="center"><em><font color="#0000ff">- - - - - - - - - - - - - - - - - - - - - -</font></em> </div><div class="Discussion_UserSignature" align="center"><font color="#0000ff"><em>I really, really, really miss the "first unread post" function.</em></font> </div> </div>