Earth has experienced at least five Ice Ages: the Huronian, the Cryogenian, the Andean-Saharan, the Karoo, and the Quaternary. The latest of these is the Quaternary Ice Age, which began 2.6 million years ago and is still ongoing. That might sound off given that the popular conception of an ice age is of a world blanketed in snow and roaming with wooly mammoths, but the scientific definition only requires that a substantial ice sheet be present on the Earth’s surface, and Antarctica fits the bill. While their causes vary, ice ages are typified by periods of sustained global cooling and glacial expansion. Going by this, the Little Ice Age qualifies, though it is also an ice age within an ice age, making it a sort of matryoshka doll climate event. The Little Ice Age is not the only lesser ice age, though it is the best known as it occurred the most recently and within recorded history. After having touched on similarities, our next logical step is to examine what makes the Little Ice Age different.
Defining the Little Ice Age
True to its name, the Little Ice Age only lasted a few hundred years, as compared to the major Ice Ages, each of which lasted millions of years. The most common chronology for our topic sees it beginning in the early fourteenth century and ending by the middle of the nineteenth century. Some climate scientists, or climatologists, use a narrower definition that places the Little Ice Age’s starting date in the early sixteenth century.
During the Little Ice Age the average temperature across the Northern Hemisphere dropped by about 1.1 °F (0.6 °C). This downward trend led to the growth of mountain glaciers in several places across both hemispheres, though most of the Little Ice Age’s effects were concentrated in the Northern Hemisphere (for reasons we will get into later). Glaciers expanded in Alaska, the Andes, the Alps, and elsewhere. These expansions were greatest in Northern Europe and North America as these regions saw the lowest temperature dips throughout the Little Ice Age. As anyone who has read or watched the news in the past decade can attest, seemingly small changes in the average global temperature can have and have had profound effects on people’s day-to-day lives.
In the more general definition of the Little Ice Age, it follows directly after (or put another way, ends) the Medieval Warming Period. Some evidence of the Little Ice Age can be found in contemporary records, such as in tax accounts where grain tithes in certain areas fell considerably, though the bulk of proof comes from proxy data. In the climate sciences a proxy is an object that once examined can tell a researcher something about the past it experienced. Proxies include ice cores, lake sediment, corals, and tree rings (all of which can contain evidence of past climate conditions). However, one should not be too quick to shortchange non-proxy records. Long before the Little Ice Age was coined as a term in 1939, oral histories containing details of the period were being solidified and passed down generationally. One example of this is the Tlingit peoples of the Pacific Northwest Coast of North America with some of their stories of this time persisting over eight hundred years.
All of these records indicate that different regions experienced different levels of cooling, and that some even remained stable or warmed. Meteorological effects also varied drastically between regions. Much of Northern Europe was subjected to harsher winters and shorter summers, while Southern Europe faced prolonged droughts some years and unparalleled rainfall in others. Proxy data also indicates that parts of Africa as well as Central and Southern Asia also experienced severe droughts over the course of the Little Ice Age. Whereas major Ice Ages see worldwide cooling, the Little Ice Age did not impose a universal experience.
Living Through the Little Ice Age
As previously mentioned, some of the most severe and well-documented effects of the Little Ice Age took place in Northern Europe. Glaciers in the Alps crept down the mountains and swallowed entire villages in France and Switzerland. Harsher winters and wetter summers led to widespread crop failures across Northern and Central Europe. This caused famines and inflated the price of staple grains and wine. Some less remote areas were able to cope via trade networks, relying on neighbors experiencing less severe conditions than themselves to make up for their agricultural losses, but Iceland and parts of Switzerland and Scotland were isolated by the creeping glaciers and thus unable to access outside sources for relief.
One the topic of Iceland, the North Atlantic was also highly impacted by the sustained colder temperatures. In addition to the Baltic Sea and rivers across Europe freezing over, ocean routes between continental Europe and Iceland became choked with ice. Being cut off from outside help there was no relief when crops in Iceland failed, which lead to half the fifteenth century population dying as a result. Other food sources were also affected. Cod fishing in the North Atlantic ground to a halt in the seventeenth century as the fish migrated south to warmer waters.
In North America, the other area hardest hit by cooling temperatures, the Native American tribes living across the prairies and the upper Mississippi valley who relied on farming had to shift much of their subsistence to hunting as climate change reduced arable land in those regions from the thirteenth to sixteenth centuries.
Yet despite all this death and destruction, it would be misleading to only focus on these effects. In some places there was a silver lining to the Little Ice Age, that or the people found one. One instance of such activity was in the repurposing of frozen rivers and lakes. While they were no longer navigable in the same fashion as before, Europeans (especially in Scandinavia) made do with ice skates, or turned their frozen waterways into playing fields for games and amusements like colf (a predecessor to golf). Examples of these types of scenes can be found in the works of painters like Hendrick Avercamp, a Dutchman whose legacy shows us that the Little Ice Age did not only produce pain and suffering.
What Caused the Little Ice Age?
Climatologists are not exactly sure what caused the Little Ice Age but are fairly certain that the period resulted from a combination of factors, these being: a reduction in solar output, an increase in the atmosphere of volcanic gas and ash, and changes in certain atmospheric currents.
At two separate points during the Little Ice Age the Sun’s output, or irradiance, dropped considerably. These events are known as the Spörer Minimum (1450–1540) and the Maunder Minimum (1645–1715). The discovery of these Minimums is credited to astronomer John Allen Eddy, who named them after astronomers that came before him and contributed pioneering work to the field regarding observations of sunspots. Sunspot activity and solar output can generally be correlated, and so a decline and one tends to coincide with a decline in the other. Almost all of Earth’s energy begins as electromagnetic radiation output by the Sun, thus even a slight dip in its irradiance leads to a noticeable cooling of the Earth.
Increases of volcanic gas and ash in the atmosphere are another contributing factor to the Little Ice Age. Similar to the conditions that wiped out the dinosaurs, when particulate matter and other substances create a reflective blockade in the stratosphere not as much solar radiation is able to make it to the Earth’s surface, which consequently cools the planet. The most notable volcanic eruptions during the Little Ice Age were from the volcanic fissure Laki in Iceland (1783) and from Mount Tambora on the Indonesian island of Sumbawa (1815).
The third major cause of the Little Ice Age’s causes was changes in atmospheric circulation, specifically over the North Atlantic. Most of these changes involved the weather system known as the North Atlantic Oscillation, a cyclical phenomenon of pressure and wind strongly associated with two neighboring pressures systems: the Icelandic Low and the Azores High. The North Atlantic Oscillation cycles wind and moisture around parts of Europe due to its varying pressure differentials that increase and decrease. During portions of the Little Ice Age the North Atlantic Oscillation experienced prolonged decreases in pressure due to atmospheric depressions in Iceland and the Azores. This allowed more cold wind into the system and brought about irregular distributions of moisture. These colder temperatures created harsher winters and the irregular rain patterns contributed to droughts and deluges.
The combination of all three of these phenomena created an additive, and as speculated by some, multiplicative effect, that dropped regional temperatures and caused drastic variances in rainfall that any one of these factors alone might not have produced.
What Ended the Little Ice Age?
As with what started the Little Ice Age, its end can be traced to a combination of factors. Volcanic gases and ash eventually dispersed, the North Atlantic Oscillation returned to a more neutral pressure, and solar output rebounded from centuries long lows. The other major trend causing the climate pendulum to swing from cold to hot is global warming. Britain’s Industrial Revolution was the first, beginning in the 1760s, though other countries followed suit and began to ramp of the scale of their productive industries via coal powered machinery and other new technologies. Burning coal releases carbon dioxide (CO2) into the air, and proxies show that by the 1830s the world’s oceans were starting to warm due to the increased greenhouse effect brought on by the byproducts of coal-powered manufacturing. Of course, this trend continues to this day with the extraction, refinement, and burning of hydrocarbons. Another Little Ice Age might be too drastic a corrective, but hopefully we will be able to swing the pendulum back the other way, and soon.
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