That's an incredibly confident statement that very much misses the point. 50% loss of the global human population means we don't come back to the current level of technological development. 80-90% means we go back to the stone age.

Photosynthesis stops working at temperatures very close to our current high temps. Pollen dies at temperatures well within those limits - we're just lucky we haven't had massive heatwaves at those times in the year.

People need to understand that climate change isn't a uniform bumping up of the thermostat - it's extra thermal energy that exists in a closes system. That extra energy does what it wants, when it wants, in ways we can't currently accurately predict. It could be heatwaves that kill off massive swaths of global food production. Or hurricanes that can spin up and hit any coastline at any time of year. Or a polar vortex that gets knocked off the pole and sits over an area of the globe where the plant and animal life has zero ability to survive the frigid temperatures.

It's not a matter of getting to wear shorts more often. We're actively playing russian roulette with the future of humanity.

The Earth was full of plants 65 million years ago when the atmosphere had like 4000PPM of CO2. most of those plants are still around.

The people saying plants will stop photosynthesis are taking you for a ride. Climate Change might certainly have some negative effects but “plants won’t exist” is not one of them.

It's the "arguments as soldiers" pattern. The idea that global warming will make plants incapable of photosynthesis helps the cause of fighting against global warming. You wouldn't betray the cause by refuting the idea ("stabbing your own soldiers in the back"), would you?

> zero chance climate change (1-2 degree increase) would end humanity

“Humanity” is not the same thing as “human civilization”.

But, yes, its unlikely that it will be extinct in a century, even more unlikely that it will be from climate change.

...and yet climate change is still more likely to do it in that time than AI.

This the the difficulty in assigning probability to something that is distinctly possible but not measured.

Your guess on what AI will do in the future is based on how AI has performed in the past. At the end of the day we have no ability to know if the function it will follow or not. But on 1900 and one second I can pretty much promise you that you would not have said that nuclear war or climate change would be your best guess on what would cause the collapse of humanity. Forward looking statements that far in the future don't work well these days.