On a side note about methane, scientists have speculated that some unexplained shipping losses (new ships in good weather) could be explained by methane "burps". We know these burps happen and if a ship happened to be above one it would lose buoyancy and sink immediately or if partially over one, its back would break...and sink.
We crossed another threshold a couple of years ago - we can no longer plant enough trees to save us from rising CO2.
https://www.businessinsider.com/so-m...save-us-2017-5
Most climate scientist think that reducing CO2 output is no longer sufficient, we need to start capturing it although the technology to do that (economically) is in its infancy.
In all the 650+ SciFi books I've read, not one of them predicted that we would actually put a value on our continued existence, like we are doing right now, and worse still - decide it's too expensive to save ourselves.