4 ms·

The other big difference is that methane stays only around 12 years in the atmosphere compared to centuries for CO2.

KAMSPioneer 3y ago
My understanding is that the methane decomposes into CO2 and water, so it ends up doing the same damage as CO2 in addition, anyway.
Nasrudith 3y ago
It converts to CO2 if I recall correctly, only 19x of it expires effectively.
orwin 3y ago
Half life is 12 year. It also rise rapidly in the high troposphere (where the magic happen), so the methane we emit today will have an effect in 2-3 year, whereas the carbon we emit today will have an effect in roughly 20 year. Today's climate is caused by 2003 emissions.
throwawaymaths 3y ago
This is so confusing to me. Iirc decades ago the rationale for methane being worse is that it stayed along longer. Now we know better from isotope studies (there's probably atmospheric bacteria breaking it down). The IR absorption spectrum of methane is way way weaker than CO2. (I have taken one myself in advanced pchem lab. This also makes sense b/c CO2 has a higher interatomic dipole moment and c-infinity symmetry so symmetry breaking rovibrational absorb more). So I don't understand how methane has a stronger forcing function, and I can never get a straight answer from anyone.
- BlueTemplar 3y ago
  Like TFA says : it doesn't end up in the same place in the atmosphere ? (A little bit like Ozone is bad to have around us, but extremely important in ~high (?) atmosphere?) IIRC (but I am way less certain of this) there's also extra issue with methane degrading into not only CO2, but also water, and in a place where they increase the greenhouse effect rather than reducing it ? P.S.: Also water vapor is an extremely powerful greenhouse gas... but I have no idea which fraction of water ends up in this phase under these conditions, nor how long water lasts there... P.P.S.: Oh, also, I just remembered : CH4 (+X O2) => CO2 + H2O, is just one of many reactions that happen... IIRC this is also where the ozone layer is and all of these ingredients and products all have an effect. But in the end it's all oversimplified into CO2 has this greenhouse effect, and CH4 that one - by the climatologists ? (All of this from climatology 101 that I had to take a decade ago, because there was no other option for a remote physics degree...)

My understanding is that the methane decomposes into CO2 and water, so it ends up doing the same damage as CO2 in addition, anyway.

Nasrudith 3y ago

It converts to CO2 if I recall correctly, only 19x of it expires effectively.

orwin 3y ago

Half life is 12 year. It also rise rapidly in the high troposphere (where the magic happen), so the methane we emit today will have an effect in 2-3 year, whereas the carbon we emit today will have an effect in roughly 20 year. Today's climate is caused by 2003 emissions.

throwawaymaths 3y ago

This is so confusing to me. Iirc decades ago the rationale for methane being worse is that it stayed along longer. Now we know better from isotope studies (there's probably atmospheric bacteria breaking it down). The IR absorption spectrum of methane is way way weaker than CO2. (I have taken one myself in advanced pchem lab. This also makes sense b/c CO2 has a higher interatomic dipole moment and c-infinity symmetry so symmetry breaking rovibrational absorb more). So I don't understand how methane has a stronger forcing function, and I can never get a straight answer from anyone.

BlueTemplar 3y ago
Like TFA says : it doesn't end up in the same place in the atmosphere ? (A little bit like Ozone is bad to have around us, but extremely important in ~high (?) atmosphere?) IIRC (but I am way less certain of this) there's also extra issue with methane degrading into not only CO2, but also water, and in a place where they increase the greenhouse effect rather than reducing it ? P.S.: Also water vapor is an extremely powerful greenhouse gas... but I have no idea which fraction of water ends up in this phase under these conditions, nor how long water lasts there... P.P.S.: Oh, also, I just remembered : CH4 (+X O2) => CO2 + H2O, is just one of many reactions that happen... IIRC this is also where the ozone layer is and all of these ingredients and products all have an effect. But in the end it's all oversimplified into CO2 has this greenhouse effect, and CH4 that one - by the climatologists ? (All of this from climatology 101 that I had to take a decade ago, because there was no other option for a remote physics degree...)