4 ms·
It bears repeating, the carbon dioxide/methane doesn't have any impact on global warming (troposphere warming?) until it reaches sufficient height. It takes 2-
by orwin 3y ago
It bears repeating, the carbon dioxide/methane doesn't have any impact on global warming (troposphere warming?) until it reaches sufficient height.
It takes 2-3 years for the methane to reach those heights, and 20+ for the carbon dioxide. The average increase in temperature we have now is caused by 2003's emissions.
Other informations about how all this work (basic, incomplete, but better than what I usually hear):
Greenhouse effect doesn't really work like a greenhouse.
Basically, to be in a balanced system, earth has to re-radiate all the energy it gets from the sun. The energy a body radiate depends on its temperature (plank's law). Earth need to reach 255K (-18 basically) to radiate all it gets from the sun. The nitrogen, dioxygen and argon in the atmosphere do not prevent that radiation, but water (especially) and Co2 do.
This basically make that earth cannot radiate the energy it gets at ground level (that's the greenhouse effect) and has to radiate the energy where the atmosphere is thinner, a few kilometers up, where the concentration of both Co2 and h2o is lower (concentration here as particle per m3). So the earth has to heat all the atmosphere until that altitude (where GHGs do not block radiation anymore) reach 255K.
So, when the Co2 concentration above that point rises, the altitude the radiation occurs rises too. But that altitude is colder, it cannot radiate as much energy as it gets from the sun. So the atmosphere heat up a bit, until that new altitude reach 255k.
Obviously it's a lot more complex, with reflection, absorption spectrum of molecules... There is also more than one GHG, there is stratosphere effect, but this explain way better than 'we live in a big greenhouse'.
Does that make sense? First time I do this in writing and in English?
I'll take every correction that will not make the explanation too hard (unless I'm flatly wrong and lying instead of vulgarising).
- rich_sasha 3y agoVery interesting. Please can you suggest a reference?
- orwin 3y agoIn French (I don't know if the English words I used were correct, so I can't search English sources): Article from a vulgarisation paper: https://www.futura-sciences.com/planete/dossiers/climatologie-tout-savoir-effet-serre-1954/page/4/ https://www.futura-sciences.com/planete/dossiers/climatologi... And a pdf from my previous university (way drier, lot of math and inference, nice graphs though): https://web.lmd.jussieu.fr/~jldufres/IUFM_Creteil/Dufresne_bil_serre_terre.pdf https://web.lmd.jussieu.fr/~jldufres/IUFM_Creteil/Dufresne_b...
- jbotz 3y agoI can't find a date on either of these, but they look a bit dated. The newest reference in the presenetation is from 2007 and uses graphs from 2001. I know that I heard something aout CO2 taking 20 years to get to the upper atmosphere around then, too, but not since, and I remember being curious about that and researching it a bit about a decade ago and finding that this is not what most atmospheric scientists believed (anymore?).
- orwin 3y agoI stopped learning physics circa 2011, so I might be dated too tbh. I'll look into it tomorrow.
- philipkglass 3y agoCarbon dioxide takes 20+ years to reach the stratosphere? Gases with higher molecular weights like halogenated ozone depleting substances reach the stratosphere in no more than 5 years: https://www.epa.gov/ozone-layer-protection/basic-ozone-layer-science https://www.epa.gov/ozone-layer-protection/basic-ozone-layer... Ozone depleting substances that release chlorine include chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), carbon tetrachloride, and methyl chloroform. ODS that release bromine include halons and methyl bromide. Although ODS are emitted at the Earth’s surface, they are eventually carried into the stratosphere in a process that can take as long as two to five years. I would expect gases with a lower molecular weight to blend into the homosphere even faster.
- reaperman 3y agoProbably depends on the % threshold you set, as it asymptotically approaches some equilibrium.
- NovaDudely 3y agoIm don't have enough knowledge to know how accurate that is, but if true that is both fascinating and worrying. I say this simply because I figured warming at any level would be an issue but what you say sounds plausible. I have some reading to do.
- dbsights 3y agoAbout that negative 18 degrees for equilibrium, does that take into account the heat radiating from within the earth as well? Radioactive decay, the core is quite hot.