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How is it overblown sorry? It's half life is actually 9.1 years, which means after nearly a decade, half of it is still left, and this is methane produced annu

by soperj 6y ago

How is it overblown sorry? It's half life is actually 9.1 years, which means after nearly a decade, half of it is still left, and this is methane produced annually, so it's continually being added to. Add that to the fact that methane is 84 times better at trapping heat within the atmosphere than C02. Most methane production from Hydro isn't even counted because it's considered green.

Retric 6y ago
That 84 is based on 20 years, on a 100 year timeframe it’s 21, and a 1 year timeframe it’s approaching 200. All the methane for the last N years is decaying as you move forward. Say at day 1 you released X methane that’s being directly added to the global total. Now move forward to day X0,000, in some ways your adding X methane but because a little methane is decaying from every prior day the net result is not an increase of X, but an increase of X * 1/2^(some number that keeps increasing). So, sure the hover dam is adding net methane. But after 84 years it’s less than 1/2 ^(84 /9.1) or 0.17% as much as directly measured. Further, the GWP of methane is calculated under the assumption it released from the ground where most sources like cows are releasing Carbon and Hydrogen that used to be in the atmosphere in the first place before photosynthesis etc eventually turned it into methane. Also, unlike CO2 it’s really easy to reduce considerations simply by lowering emissions. PS: I have seen several estimates around 7 years, I used 9.1 because the exact number isn’t that important.
- sergeykish 6y ago
  Have you read article? > Warm climate reservoirs generate methane, a greenhouse gas when the reservoirs are stratified, in which the bottom layers are anoxic (i.e. they lack oxygen), leading to degradation of biomass through anaerobic processes. In warm climate it is methane generator, biomass constantly added with river flow.
  - Retric 6y ago
    Yes, but I don’t think you understand what’s being described. Dam methane production is based on the amount of organic matter being added by the river which is effectively a constant over time. It’s effectively the same process as cow’s methane where decaying plants release methane in a low oxygen environment. The issue is you don’t get an accurate number for the amount of methane in the atmosphere from a dam by multiplying average annual methane release by the number of years it’s in operation. Thus the the rate of doesn’t correlate to future global warming making such statements absolutely meaningless. PS: Also, all of this is assuming the study adjusted for what happens when the dam is not there and nearly the same process occurs when the river dumps into an ocean somewhere.
    - sergeykish 6y ago
      Plant either eaten or decays, closed system. Methane does not return upstream only, river flows into ocean, open system. My argument supported by published article and nice picture, look at sediments [1]. Your argument "calculated yearly is not yearly", maybe you should bring some citations, maybe it is you who do not understand what is described. [1] https://en.wikipedia.org/wiki/Ocean_storage_of_carbon_dioxide#Blue_carbon_capture_in_ocean https://en.wikipedia.org/wiki/Ocean_storage_of_carbon_dioxid...
      - Retric 6y ago
        “First, very shallow coastal waters contribute around 50 percent of the total methane emissions from the ocean, despite making up only 5 percent of the ocean area. That's because methane can seep out of natural gas reservoirs along continental margins and can be produced biologically in anoxic (oxygen-depleted) sediments at the seafloor.” https://phys.org/news/2019-10-global-ocean-methane-emissions-dominated.html https://phys.org/news/2019-10-global-ocean-methane-emissions... Dams are collecting the exact same sediments that would end up in estuaries and as that article points out some of that is then turned into Methane. Natural methane is just part of the carbon cycle. It’s generally ignored in oversimplified explanations like you just linked.
        6y ago

by soperj 6y ago

Retric 6y ago

That 84 is based on 20 years, on a 100 year timeframe it’s 21, and a 1 year timeframe it’s approaching 200. All the methane for the last N years is decaying as you move forward. Say at day 1 you released X methane that’s being directly added to the global total. Now move forward to day X0,000, in some ways your adding X methane but because a little methane is decaying from every prior day the net result is not an increase of X, but an increase of X * 1/2^(some number that keeps increasing). So, sure the hover dam is adding net methane. But after 84 years it’s less than 1/2 ^(84 /9.1) or 0.17% as much as directly measured. Further, the GWP of methane is calculated under the assumption it released from the ground where most sources like cows are releasing Carbon and Hydrogen that used to be in the atmosphere in the first place before photosynthesis etc eventually turned it into methane. Also, unlike CO2 it’s really easy to reduce considerations simply by lowering emissions. PS: I have seen several estimates around 7 years, I used 9.1 because the exact number isn’t that important.

sergeykish 6y ago
Have you read article? > Warm climate reservoirs generate methane, a greenhouse gas when the reservoirs are stratified, in which the bottom layers are anoxic (i.e. they lack oxygen), leading to degradation of biomass through anaerobic processes. In warm climate it is methane generator, biomass constantly added with river flow.
- Retric 6y ago
  Yes, but I don’t think you understand what’s being described. Dam methane production is based on the amount of organic matter being added by the river which is effectively a constant over time. It’s effectively the same process as cow’s methane where decaying plants release methane in a low oxygen environment. The issue is you don’t get an accurate number for the amount of methane in the atmosphere from a dam by multiplying average annual methane release by the number of years it’s in operation. Thus the the rate of doesn’t correlate to future global warming making such statements absolutely meaningless. PS: Also, all of this is assuming the study adjusted for what happens when the dam is not there and nearly the same process occurs when the river dumps into an ocean somewhere.
  - sergeykish 6y ago
    Plant either eaten or decays, closed system. Methane does not return upstream only, river flows into ocean, open system. My argument supported by published article and nice picture, look at sediments [1]. Your argument "calculated yearly is not yearly", maybe you should bring some citations, maybe it is you who do not understand what is described. [1] https://en.wikipedia.org/wiki/Ocean_storage_of_carbon_dioxide#Blue_carbon_capture_in_ocean https://en.wikipedia.org/wiki/Ocean_storage_of_carbon_dioxid...
    - Retric 6y ago
      “First, very shallow coastal waters contribute around 50 percent of the total methane emissions from the ocean, despite making up only 5 percent of the ocean area. That's because methane can seep out of natural gas reservoirs along continental margins and can be produced biologically in anoxic (oxygen-depleted) sediments at the seafloor.” https://phys.org/news/2019-10-global-ocean-methane-emissions-dominated.html https://phys.org/news/2019-10-global-ocean-methane-emissions... Dams are collecting the exact same sediments that would end up in estuaries and as that article points out some of that is then turned into Methane. Natural methane is just part of the carbon cycle. It’s generally ignored in oversimplified explanations like you just linked.
      - 6y ago