I think most nuclear winter scenarios also have less than a 90% food reduction impact
The Open Philanthropy funded nuclear winter project will soon have an estimate of global agricultural impact, but I think without relocation of crops, 90% production loss is plausible. How that translates into mortality is complicated. It may be possible to relocate crops towards the equator, but the likelihood of that happening would depend on preparation ahead of time for coordination, etc. On the positive side, we have some food storage, which has the potential to take ~10% of the population through a nuclear winter with complete agricultural collapse if perfectly protected. However, on the other extreme, if food were distributed equally, then perhaps a 70% food supply reduction would mean everyone starves. The reality is likely to be between these extremes of perfect protection and equal distribution. Of course the situation changes dramatically if we can produce alternative foods.
The Open Philanthropy funded nuclear winter project will soon have an estimate of global agricultural impact, but I think without relocation of crops, 90% production loss is plausible. How that translates into mortality is complicated. It may be possible to relocate crops towards the equator, but the likelihood of that happening would depend on preparation ahead of time for coordination, etc. On the positive side, we have some food storage, which has the potential to take ~10% of the population through a nuclear winter with complete agricultural collapse if perfectly protected. However, on the other extreme, if food were distributed equally, then perhaps a 70% food supply reduction would mean everyone starves. The reality is likely to be between these extremes of perfect protection and equal distribution. Of course the situation changes dramatically if we can produce alternative foods.