Does the weight of the atmosphere change as more gasses are released into it, regardless of the source of the gas?
One would generally imagine yes.
But we can nit pick.
Weight is the force due to gravity of the atmosphere, which is usefully measured as the surface pressure.
Mass is the aggregate of all the material comprising the atmosphere, and is independent of gravity.
Weight is going to depend very slightly on distribution versus altitude, and other effects (such as the Earth’s rotation). Pressure is dynamic in the short term with changing weather.
But gas gets into the atmosphere from water evaporation, volcanic eruption, and a host of minor effects. But there are cycles. In general the amount of water in the atmosphere is constant. As is carbon dioxide. The gasses cycle with a rough steady overall state. But, as we are all too well aware, the equilibriums can shift.
Depends what the question really is. Time period, weight versus mass, and so on.
What I am actually looking for are things that act as thermostats to one degree or another. I know what I am talking about here would be almost if not imperceptible, but I am wondering if it could be more than zero. The effect that I am referring to is evaporation rates of water based on air temps, humidity and atmospheric pressures. I know it is a long shot but I was just curious about it.
By this I would assume you mean a negative feedback processes - ones that tend to self correct and retain an equilibrium. The atmosphere is replete with such processes. They are what maintain the climate as we know it.
Each of the gross atmospheric cycles runs in equilibrium. But like any feedback process there are nuances. There is lag, and there are ways we can drive the process outside of its bounds, and eventually break it. Previous climate switches, like ice ages, are examples. The system can flip to a new equilibrium and becomes stable in that one.
Water evaporating into the air makes it more likely to rain. Higher concentrations of CO2 tend to result in higher rates of CO2 adsorption (chemical, biological etc). So within bounds, the system is steady. But every one of the processes is controlled by a lot more than just the concentration of gas in the atmosphere. Higher sea surface temperature will result in more evaporation, and whilst it will rain more as a result, the equilibrium point will shift. It may shift to the point where the temperatures settle into a new high. CO2 adsorption processes don’t kick in instantly, and the equilibrium point will shift.
Colder land temperatures may mean snow doesn’t fully melt one spring, and next winter more accumulates, and the climate flips to an ice age. So you can get catastrophic switches.
Sea surface temperatures are one of the key determinants of what the equilibrium points are. We see minor wobbles with oscillations such as the el-Nino la-Nina, or similar oscillations in other oceans. They force changes to the local equilibria for a year or so. They provide a clue about the nature of possible long term changes to global equilibria might bring.
There are equilibrium processes that drive the upper atmospheric as well. The temperature profile with altitude changes, with the atmosphere cooling then heating and cooling with altitude, with the exact profile depending upon solar radiation, CO2 levels, radiation into space, etc, all in complex dance. This is the bit that has climate scientists worried.
The high school level understanding is that there are equilibrium processes that run in isolation and keep things at the level. The reality is that nothing is simple, and the equilibrium systems are interconnected and can shift, and even fail if pushed. Many equilibrium processes are under-damped, so have an intrinsic hunting characteristic and wobble around the mid point to varying degrees. Others are over-damped and take time to slowly move back to the mid point.
Just about every process you see around you is an equilibrium process of some sort. Just not always in stable equilibrium right this moment.
thank You, Great answer.
Agree those are excellent answers; thank you @Francis_Vaughan.
Unrelated to the climate issues he covered so well here’s some other factors.
Gasses at the top of the atmosphere are constantly boiling off into space. Meteors are constantly adding new material to the Earth, some of which are, or can be, in gaseous form. The overall earth / atmosphere / meteor system is mostly in an equilibrium, and the net change over time is very slow.
But atmospheric helium for example is on a pretty much one-way decline. It leaks away into space readily and the supply of rocks undergoing helium-genic radioactive decay is a finite planetary resource that once gone is gone forever.
Helium’s total contribution to the weight (mass really) of the atmosphere is minor. But it isn’t zero. Yet.
Atmospheric pressure is essentially the weight of the total mass of air above us. However, pressure changes more with air ciirculation than with composition. There are basic feedback loops as mentioned - the most obvious is plants creating from oxygen (O2) which animals and chemical processes do their best to turn back into CO2. Planets without life to renew O2 (all the rest that we know about) do not have appreciable free oxygen.
Logic would tell us that the increasing level of CO2 means that the total weight of the atmosphere is increasing, when a molecule of O2 is converted into CO2. however, the amount of CO2 is about 0.042% now, about 50% more than before the industrial revolution. This means that about 0.014% of the atmosphere’s O2 is converted to CO2 due to human activity. If my math is correct, for 14.7psi atmospheric pressure, a molecule of O2 has an atomic weight of 32, and CO2 has 44. 14.7 x 0.00014 = 0.0021 PSI more. But 32/44 of that extra CO2 was existing oxygen I think this works out to a square inch of atmosphere up to the edge of space weights about the same as 1/20 teaspoon of water more than before the industrial revolution, all other things being equal.
And the sun plays a key role, as mentioned above. Not just hot seas creating moe water vapour - also, hot land causes hotter air which rises. Colder polar climates, colder seas, etc. cool the air which flows to push out lighter hot air. The changes in atmospheric pressure due to this circulation by convection far outweigh any pressure differences due to changes in composition. Also note the chief result of massive forest fires is not so much a rise on CO2 as an increase in particulate which heats the atmosphere by absorbing sunlight. Or, particulate from volcanoes reflects light back into space, reducing overall earth temperatures. Clouds reflect the sun back into space, cooling that area of the earth. Air pressure depends on whether you are near an upward convection cell (sucking in all the water vapour around and condensing and raining as it goes) or a downward convection (dry air pushing away all the clouds). Also, thanks to coriolis force, these motions create vortices that can maifest as anything from small loccal effects - tornadoes - to massive storm systems.
There’s also an effect that impacts satellites. Solar activity during peak sunspot cycle (like now) heats the outler layer of the atmosphere, so it expands. This doesn’t really affect earth level (altough there is some debate about solar particles, cosmic rays, and cloud formation) but slightly denser atmosphere in Low Earth Orbit causes satellites there to slow faster than anticipated.
(Musk lost a bunch of Starlink satellites this way. They are launched quite low so the failed ones will re-enter quickly; then very slow thrusters on each will slowly raise them to their planned orbits. Some did not have enough oomph to overcome the drag, could not escape to a higher level and were expected to re-enter within a few weeks of launch.)
Thanks for a great answer. I am curious as to your thoughts on a couple of things. I like the concept of developing a model for the optimum levels of co2. This would naturally involve discovering and evaluating all the benefits we might be getting from the added carbon as well as the detriments.
Well, if you live in Canada, you benefit from a warmer globe. The downside appears (this year) to be messed up criculation patterns resulting in a much drier climate here, so existing forests are turning into CO2 at an accelerated rate.
There’s also the apparent downside, from what I’ve read, too much CO2 dissolved in the ocean turns it acidic, which is not good for overall life.
But presumably there’s a feedback, assuming other conditions for plants are good - that plants will grow faster, sucking the CO2 out of the atmosphere faster. A lot of the CO2 is also dissolved in the oceans, where the algae etc. will convert it into O2. Obviously this process is not fast enough to match the rate at which we are releasing and burning carbon locked underground for geological time. The other problem is unless something sequesters new plant life as it dies, it simply decays releasing that CO2 all over again. Coal is layers of plants from the carboniferous (!) era that got covered up before it could burn. Oil is sea life that sank to the sea bottom and became covered up by layers of silt eons ago. We’ve disturbed all that.
At this point there are no easy solutions, other than “stop making things worse…”
Congratulations. You’ve now decided to re-invent the existing field of study called “climate science”. We already know the “optimal level”. The one the whole rest of the ecosystem and sea level and the human built environment and agriculture were used to. The one we just wrecked and are continuing to wreck further.
There are dozens of shelf-feet of studies cataloging exactly the tradeoffs you discuss. The result, net of a few crackpots, is it was just about perfect back in 1850. But not anymore. And it’s now driving away from optimal at an ever increasing rate.
I was reading recently where a few billion years ago all the water on earth was frozen. Over millions of years co2 built up to about 155,000 parts per million. This was enough to warm the atmosphere up to about 30 degrees and allow the water to melt. If you compare today’s levels with ancient levels it works out to be about 1/9 of the greenhouse effect, assuming it is linear with no feedback effects from water vapor. So that would mean a bit over 3 degrees Fahrenheit is coming from CO2. That works out fairly linear using rough numbers, as about 3 degrees is what we are currently getting.
In the age of the dinosaurs, there were forests in the arctic regions and a sea ran up the center of nNorth America connecting the gulf and the arctic sea. Dinosaurs migrated up nd down the coast. (Without grass, erosion was worse so the foothills of the Rockies, of the old sea coastline, is now full of dinosaur bones where dead were buried in mud that has turned to rock, and their bones preserved.) Obviously, this indicates total global temperature was a lot higher.
However, this means the giant creatures we associate with the dinosaur age lived in what are now the temperate zones. In the tropics, there was a lot less of the bigger creatures, and many were like the Dimetrodon, large sail-back fins to help shed heat.
We are currently in a warm spell between ice ages (assuming we haven’t actually cancelled them with CO2 emmmissions). 40,000 years ago (or from 100K to 15K years ago) there were glaciers coming down from the arctic, sea levels were much lower due to volumes of water tied up in glaciers, etc. (The cycle of ice ages appears to have started about 1M years ago.)
Climate varies over eons. Bigly.
Another point to ponder - there’s another feedback mechanism. Oxygen is very reactive. If plants produce too much oxygen, forest fires would be easier to start and burn faster. To little oxygen and the forests can get much thicker without burning. This is a sort of optimal level feedback mechanism. We have “just the right amount” at about 21% oxygen, enough to sustain the processes which turn it into CO2 but not too much.
If you want to get a basic understanding of weather and what the atmosphere circulation is doing - the best thing I found was the weather section in the private pilot ground school textbook. Not sure what the latest version of this book is, esp. for USA.