I suggest you read up on the Medieval War Spell, AKA the Medieval Optimum, and the Little Ice Age that followed it.
In the Medieval Optimum wine grapes were grown in England, something that's only become possible again in the last few years.
In the Little Ice Age millions died from the cold and famine, including all the Norse settlers in Greenland. Glaciers in the Alps overran towns and some Eskimo hunters paddled their kayaks as far south as Scotland. In addition to the cold weather the change in the climate of the North Atlantic caused violent storms in Europe.
That scene of Washington crossing the Delaware occured near the end of that period, and the recurrent cold weather caused poor harvests and high food prices in France, where conservative peasants refused to switch from wheat to cold resistant crops like potatoes, and helped start the French Revolution.
Having spent too much time with my feet and hindquarters frozen on a deer stand after a zero degree night, I eagerly await a warmer world. The critters have lived through it before, a lot better than I can live through the cold.
Those who cannot remember the past are condemned to repeat it.
-- George Santayana
