| A few degrees either way would not change whether or not humans can survive in most places. What it would change for many places is (1) how much effort it requires to live there, and (2) how many people can live there. E.g., if climate change greatly reduces the water supply in a region, that can be address with effort (transporting water in from somewhere else) or by cutting the population in the region down to what the reduced supply can support. The problem is finding a way to fund that effort in such areas or to reduce their populations without it degenerating into wars and terrorism. As an example, consider India and Pakistan. They both greatly depend on water from Himalayan glaciers that are rapidly shrinking. It is not at all hard to imagine them going to war with each other over how to allocate that water between them. They both have nukes. You might think a nuclear war between them would not be a threat to the rest of the world because neither of them have big nukes. But it is not the nukes that would hurt the rest of the world. It is the firestorms. Here's a paper [1] and article [2] that looks at a hypothetical nuclear war between them involving about 100 nukes the size of the Hiroshima bomb from WW II, directed at the major population centers. That's about 1/3 of the nukes they have available. Based on the amount of combustible material in the target areas, they estimate 1.5 Tg of soot aerosol would end up in the upper atmosphere. They then use climate models to predict what that would do to temperature and precipitation, and applied that to crop models. What they get is several years of temperature reduction and precipitation reduction. The strongest effects would be in the temperate regions of the US, Europe, and China, and last 10-15 years. That should result in serious worldwide food shortages for quite a while. Note that the shortages would not just be in the poor, undeveloped countries. This would be food shortages even in the rich, developed world. It is not unlikely that this would lead to more wars. [1] https://www.pnas.org/content/117/13/7071 [2] https://blogs.ei.columbia.edu/2020/03/16/even-limited-india-... |