That whole thing is highly dubious, and reads like a slippery slope argument. Like one, there's a limit on how much water can exist as vapor in our atmosphere,

That whole thing is highly dubious, and reads like a slippery slope argument. Like one, there's a limit on how much water can exist as vapor in our atmosphere, (which is far, far less than what the earth's oceans hold), up until the point of boiling. This is conventionally known known as the saturation point, which is 100% relative humidity. Anytime you try to go above this limit, forces the water to condense and drop down back to the oceans as liquid. So the oceans aren't going to evaporate out to being dry like it predicts unless global temperatures rise by an extreme amount - quite likely requiring boiling temperatures, but in any case, extreme enough that life would likely be dead from the temperature alone. So its subsequent reasoning on how photosynthesis and life ends is not likely how it will play out. Additionally, it ignores that CO2 is made by animals, and O2 is made by plants, and therefore, the entire possibility of having a natural carbon cycle without volcanism. Never mind the fact that we currently have climate change tech that produces CO2 already, and if we survive that long, could easily prevent photosynthesis from ending in such a way.