Some wisdom on these questions may be found in an important new work of history, “Global Crisis.” It’s Geoffrey Parker’s examination of the last great climate shock experienced by human beings: the Little Ice Age.

After a half millennium of very benign temperatures, the Northern Hemisphere began gradually to cool after about 1550. Slow cooling plunged into deep freeze in about 1620. Over the next half-century, the peoples of the Northern Hemisphere suffered climate catastrophe after climate catastrophe:

-Over the winter of 1620-21, the Bosporus dividing Europe from Asia (in modern-day Turkey) froze for the one and only time in recorded history.

-The summer of 1627 was the wettest recorded in Europe for 500 years, followed in 1628 by one of the coldest summers recorded.

-In 1641, the Great Canal that connected Beijing — the planet’s greatest city — to its food supply in southern China dried up for lack of rain, again for the only time in recorded history. China suffered repeated crop failures through the 1640s because of patterns of drought and excessive rain.