Will not completely go extinct is not the same as fine. Even ignoring climate refugees and all that, let’s look at a simple thing: food supply.

The mathematics of global famine are quite simple. Add all the calories that earth produces in one day on average and divide it by 1500. That’s the amount of people that can exist.

Now, like 70% off all calories come from just 3 crops: rice, corn and wheat. As a good approximation, all of those lose about 10% harvest yield for each 1 degree C in temperature rise. It’s not really linear and is better at the beginning (so like 5% for the first degree), and much worse further on. But in general the approximation works.

Humanity now produces about 1.5x of the food supply we need, and even with super-optimized logistics we’re not going to get it lower than 1.2–1.3x population, since a lot of food gets wasted by cafes/restaurants and people themselves. Some just gets bad because it’s not consumed in time or takes too long to deliver or sell.

And with the current temperature rise estimations we’re looking at losing caloric supply for about 20% of the entire population in the next 20 or so years.

And that’s just one example. Have you seen rivers of dead fish in Australia and the states? For each species there is a point when the water gets too hot to hold enough oxygen or to cool down their bodies, and then bam — the whole species dies in a day. Right now, some algae, corals and plankton are like 1.5 degrees away from mass death.

It’s not really that “fine”.

Sorry for the rant.