2 ms·
> then total atmospheric carbon is unchanged but the proportion of methane, and therefore the total GHG effect, is increased at that time. Summing over time, an
by codethief 4y ago
> then total atmospheric carbon is unchanged but the proportion of methane, and therefore the total GHG effect, is increased at that time. Summing over time, and you get an increase in overall heat that has been trapped
This is not correct. We are already in a steady state. Methane levels due to cattle are already at their maximum (given a fixed amount of cattle).
At any point in time, gras will absorb some CO2 from the atmosphere, cattle will convert some gras / carbon into methane and emit the latter into the atmosphere, and some methane in the atmosphere will decompose into CO2. This is a continuous process, that's happening every second, and if the amount of cattle is kept constant, there is a maximum amount of methane that you can reach in the atmosphere as well as a maximum amount of CO2. After all, the total amount of carbon involved in the process is constant – energy conservation dictates that mass doesn't appear out of nowhere.
In fact, since we've been doing agriculture for a time much longer than the time scale in which grass grows, a cow digests grass or methane decomposes into CO2, this whole closed loop has already settled into a steady state: At any point in time, the amounts of methane and CO2 in the atmosphere due to cattle are constant. The resulting radiative forcing will thus stay constant, too.
- ramblenode 4y agoMaybe we were talking past each other. > ...and if the amount of cattle is kept constant... My point (unclear) is that this is not a constant, but a variable (in the sense that it is a societal choice). Animal agriculture shifts more of the distribution of atmospheric carbon at any time toward methane, which accelerates warming. > ...this whole closed loop has already settled into a steady state: At any point in time, the amounts of methane and CO2 in the atmosphere due to cattle are constant. The premise that the amount of animal agriculture is constant is incorrect. It has been increasing year over year for some time as the human population increases. The theoretical concentration of methane has been increasing over that same time. It's also worth noting that industrial animal agriculture is not a closed loop because it currently relies on mined hydrocarbons for feedstock fertilizer and transport.
- codethief 4y agoThanks for your comment! > The premise that the amount of animal agriculture is constant is incorrect. That certainly is true – I just had a look at the exact numbers: Cattle has seen a 15.6% increase between 2000 and 2020[0]. However, even if you double the numbers in my calculation in my other comment[1], you will see that agricultural greenhouse gases in the atmosphere are still basically nothing compared to those caused by fossil emissions. > because it currently relies on mined hydrocarbons for feedstock fertilizer and transport. Many types of food require fertilizer for production and logistics. I'm not trying to say that animal agriculture might not be comparatively bad here but we certainly won't get rid of fertilizer- and logistics-related emissions over night by overcoming animal agriculture. In fact, it could be that we'd just replace one emission source with another. So, before prescribing vegan diets for everyone, I'd really like to see some numbers that suggest that such a move would actually change anything. [0]: https://www.destatis.de/EN/Themes/Countries-Regions/International-Statistics/Data-Topic/AgricultureForestryFisheries/livestock_meat.html https://www.destatis.de/EN/Themes/Countries-Regions/Internat... [1]: https://news.ycombinator.com/item?id=35675049 https://news.ycombinator.com/item?id=35675049