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.

[–] hglman@lemmy.ml 11 points 1 year ago

An excellent write-up of what will unfold.

One note is that the food loss won't just be linear. It will be chaotic within the probabilities you noted. Crop loss is effectively a weather event and, as such, a chaotic one. That means extreme events will be the driving force behind food shortages. Namely, heatwaves will cause extensive loss of crops in specific areas. Over some years, that will average down, but people don't eat long-term averages; they eat daily. So we should expect significant one-time impacts. That is, the severity is not the average but rather the peak.