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Comment by DavidKarlas | Hacker News Reader

Isn't this just cycling carbon in ecosystem? Same as planting tree on 100 year scale is pointless... I would imagine that hydro is ~neutral on 100 year scale, while coal is not, since we introduce carbon into ecosystem. What am I missing?

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Produces methane, not CO2 because the plants decompose in an oxygen free environment. Because of the cycling of water throughout the year, during the dry seasons plants grow along the shoreline (which varies considerably because of the use of hydro), and then are covered up during the rainy season. This can be hundreds of kms every year.

Methane isn't great, but unlike CO2 is has a pretty short lifetime in the atmosphere (just 12 years). So the impact of the methane release from hydro is basically static rather than an ever increasing problem.

This is not true! Methane is not only 84x more warming than CO2, it is at a record high at <1900ppb and rising, the current level is higher than the RCP 4.5 warming scenario by the IPCC (which is in the middle level of a warming scenario), and there is evidence that the atmospheric lifespan might be increasing

This is what my quick google turned up [1].

> A molecule of methane traps more heat than a molecule of CO2, but methane has a relatively short lifespan of 7 to 12 years in the atmosphere, while CO2 can persist for hundreds of years or more.

Doesn't mean it's correct though so I'd be happy to see different thinking on this.

That being said, IIRC, isn't one of the models for the increasing methane the melting permafrost [2]? So the levels are somewhat expected to be increasing pretty rapidly as a result of global warming in general.

[1] https://climate.nasa.gov/vital-signs/methane/

[2] https://earth.org/data_visualization/what-is-permafrost/

https://climate.mit.edu/ask-mit/why-do-we-compare-methane-ca... "Over 20 years, the methane would trap about 80 times as much heat as the CO2. Over 100 years, that original ton of methane would trap about 28 times as much heat as the ton of CO2."

So converting a bunch of atmospheric CO2 to methane evey year is not good.

Well, shoot, that's awful.

It's continuously releasing methane, and methane degrades into.... CO2.

> So the impact of the methane release from hydro is basically static rather than an ever increasing problem.

You can also say the same thing about the coal plant.

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