Environmental and ecological discussion, particularly of things like weather and other natural phenomena (especially if they're not breaking news).
See also our Nature and Gardening community for discussion centered around things like hiking, animals in their natural habitat, and gardening (urban or rural).
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Relatedly, higher co2 levels is increasing the level of co2 of our oceans (surprise) and co2 is acidic, leading to (not only less oxygen) the death of anything that uses calcium carbonate (a base) to create some sort of structure.
So not only are they getting hotter, they're dissolving and asphyxiating - potentially collapsing entire ecosystems.
The Sixth Exctinction is rather morose...