c. 1500

The Little Ice Age

Weather is the day-to-day and place-to-place variation in temperature, humidity, wind, and other environmental parameters. Climate, in contrast, is the long-term average of the weather, typically measured over decades to centuries and potentially described on a global scale. Evidence for climate excursions such as ice ages comes from a variety of sources, including the fossil record, ice cores, tree rings, or—in the last few centuries—records of direct temperature measurements and other meteorological data. Indeed, such direct measurements, supplemented by anecdotal historical accounts, reveal that much of the Northern Hemisphere experienced a significant drop in average annual temperatures, and a significant increase in glaciation, during much of the fourteenth to nineteenth centuries, compared to mid-twentieth century averages. The cause is uncertain, but probably related to slight variations in the Sun’s energy output and the cooling effects of atmospheric ash and dust from volcanic eruptions.

This span of time is often informally called “The Little Ice Age.” Historical accounts tell of significantly colder winters in Europe and North America during this time period, including unusual (compared to previous centuries) freezing-over of rivers, damage to mountain villages due to advancing glaciers, and widespread closure of ports and normal sailing routes because of extensive sea ice. Climate data spanning this time period show a decrease of only about 0.5°C to 1.0°C in average global temperature—
a small change, to be sure, but large enough to cause major climatic, economic, and human impacts. Colder, longer winters led to shorter growing seasons and widespread famine, drought, and loss of life across Europe, for example. European explorers and early settlers reported similar extreme conditions and food shortages in North America as well.

The end of The Little Ice Age in the climate data corresponds approximately (and probably coincidentally) to the beginning of the Industrial Revolution in the mid-nineteenth century. Since that time, global average temperatures have increased by about 1°C (to about 0.5°C above mid-twentieth century averages) and mountain glaciers and polar ice sheets have retreated dramatically. As the climate continues to warm over the coming decades and perhaps centuries, we should be prepared for a very different environment than that experienced by our pre–Industrial-Revolution ancestors.

Spanish artist Francisco de Goya’s The Snowstorm was painted in the late 1780s, during a colder-than-average span of several centuries informally known as the Little Ice Age.