At present population levels a repeat of the Little Ice Age a mere 400 years ago will cause mass starvation worldwide. (newclimatemodel.com)
However, you can't make a plausible prediction of future survival without an estimate of present population size: not even today's worst journalists would buy it, nor should they. (polarbearscience.com)
But a sudden reduction in present population (the most likely result of another abrupt cooling) via war, famine, and disease would leave a world of small despotic governments that all hated their neighbors because of genocidal warfare during the crash. (WilliamCalvin.com)