Last month, Hurricane Harvey dumped more rain on the Texas coast in a week than most states see all year. As I write, Florida is engulfed in a hurricane expected to cause tens of billions more in damage. We know rising sea levels mean higher storm surges. We know hotter air means potentially larger hurricanes with more rain and winds. What’s harder to say is whether we should blame these particular storms—or any other weather event—on global warming. This issue first came to the attention of most Americans in the wake of hurricanes Katrina and Rita, when the fate of New Orleans was in doubt. In a way, however, the question of bad luck versus climate change has been with us at least since the first Europeans arrived in America. And as it turns out, we’ve often gotten the answer wrong.
Climatically speaking, America has always been a land of variability and extremes. Early explorers and colonists arrived expecting climates in America to resemble those at the same latitudes in Europe, so that orange trees would grow in Maine and sugar and spices in Virginia. Instead they encountered America’s stronger continental seasons, with storms, frosts, and heat waves of a kind rarely felt in Western Europe.
Worse still, they arrived at the nadir of the so-called Little Ice Age. The mid-1500s to early 1600s—roughly the time from the Coronado expedition to the founding of colonies at Jamestown, Santa Fe, and Quebec—brought probably the fast cooling and lowest global temperatures of at least the past two millennia. Early colonial accounts include some remarkable extremes, including winters with heavy snows across the Gulf states, and when the James River froze halfway across at Jamestown and the Rio Grande all the way across around present-day Albuquerque. Much of today’s eastern US suffered exceptional droughts, and the Gulf of Mexico and Atlantic were unusually cold and stormy.