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In recent weeks,\u00a0catastrophic floods<\/a>\u00a0overwhelmed towns in Germany, Belgium and the Netherlands,\u00a0inundated subway tunnels<\/a>\u00a0in China, swept through northwestern Africa and triggered deadly landslides in\u00a0India<\/a>\u00a0and\u00a0Japan<\/a>. Heat and drought fanned wildfires in the North American West and\u00a0Siberia<\/a>, contributed to\u00a0water shortages<\/a>\u00a0in Iran, and\u00a0worsened famines<\/a>\u00a0in Ethiopia, Somalia and Kenya.<\/p>\n Extremes like these are increasingly\u00a0caused or worsened by human activities heating up<\/a>\u00a0Earth\u2019s climate. For thousands of years, Earth\u2019s climate has not changed\u00a0anywhere near as quickly<\/a>\u00a0or profoundly as it\u2019s changing today.<\/p>\n Yet on a smaller scale, humans have seen waves of extreme weather events coincide with temperature changes before. It happened during what\u2019s known as the Little Ice Age, a period between the 14th and 19th centuries that was marked by large volcanic eruptions and bitter cold spells in parts of the world.<\/p>\n The global average temperature is believed to have\u00a0cooled<\/a>\u00a0by less than a half-degree Celsius (less than 0.9 F) during even the chilliest decades of the Little Ice Age, but locally, extremes were common.<\/p>\n In diaries and letters from that period, people wrote about \u201cyears without a summer<\/a>,\u201d when wintry weather persisted long after spring.\u00a0In one such summer<\/a>, in 1816, cold that followed a massive volcanic eruption in Indonesia ruined crops across parts of Europe and North America. Less well known are the unusually cold European summers of 1587, 1628 and 1675, when unseasonal frost provoked fear and, in some places, hunger.<\/p>\n \u201cIt is horribly cold,\u201d author Marie de Rabutin-Chantal\u00a0wrote<\/a>\u00a0from Paris during the last of these years; \u201cthe behavior of the sun and of the seasons has changed.\u201d<\/p>\n Winters could be equally terrifying. People reported 17th-century\u00a0blizzards as far south as Florida<\/a>\u00a0and the Chinese province of Fujian.\u00a0Sea ice trapped<\/a>\u00a0ships, repeatedly enclosed the Chesapeake Bay and\u00a0froze over rivers<\/a>\u00a0from the Bosporus to the Meuse. In early 1658, ice so completely covered the Baltic Sea that a Swedish army marched across the water separating Sweden and Denmark to besiege Copenhagen. Poems and songs suggest people simply froze to death while huddling in their homes.<\/p>\n These were cold snaps, not heat waves, but the overall story should seem familiar: A small global change in climate dramatically altered the likelihood of extreme local weather. Scholars who study the history of climate and society,\u00a0like me<\/a>, identify these changes in the past and find out how human populations responded.<\/p>\n We know about the Little Ice Age because the natural world is full of things like trees, stalagmites and ice sheets that\u00a0respond to weather<\/a>\u00a0while growing or accumulating gradually over time. Specialists can use past fluctuations in their growth or chemistry as indicators of fluctuations in climate and thereby create\u00a0graphs or maps \u2013 reconstructions<\/a>\u00a0\u2013 that show historical climate changes.<\/p>\n These reconstructions reveal that\u00a0waves of cooling<\/a>\u00a0swept across much of the world. They also suggest likely causes \u2013 including a series of explosive\u00a0volcanic<\/a>\u00a0eruptions<\/a>\u00a0that abruptly released sunlight-scattering dust into the stratosphere; and slow,\u00a0internal variability<\/a>\u00a0in regional patterns of atmospheric and oceanic circulation.<\/p>\n These causes could only\u00a0cool the Earth<\/a>\u00a0by a few tenths of a degree Celsius during the chilliest waves of the Little Ice Age, however. And the cooling was\u00a0not nearly as consistent<\/a>\u00a0as present-day warming.<\/p>\n Small global trends can mask far bigger local changes. Studies have suggested that modest cooling created by volcanic eruptions can\u00a0reduce the usual contrast<\/a>\u00a0between temperatures over land and sea, because land heats and cools faster than oceans. Since that contrast powers the monsoons, the African and East Asian summer monsoons\u00a0can weaken<\/a>\u00a0after big eruptions. That likely disturbed atmospheric circulation all the way into the North Atlantic, reducing the flow of warm air into Europe. This is why parts of Western Europe, for example, may have cooled by more than 3 C (5.4 F) even as the rest of the world cooled far less during the 1816 year without a summer.<\/p>\n Temperatures fell well below normal in parts of Europe in 1816. Dagomar Degroot, CC BY-ND<\/p><\/div>\n Feedback loops also\u00a0amplified and sustained regional cooling<\/a>, similar to how they\u00a0amplify<\/a>\u00a0regional\u00a0warming<\/a>\u00a0today. In the Arctic, for example, cooler temperatures can mean more, longer-lasting sea ice. Ice reflects more sunlight back into space than water does, and that feedback loop leads to more cooling, more ice and so on. As a result, the comparatively modest climate changes of the Little Ice Age likely had profound local impacts.<\/p>\n Changing patterns of atmospheric circulation and pressure also led in many regions to remarkably wet, dry or stormy weather.<\/p>\n Heavy sea ice in the Greenland Sea may have diverted the North Atlantic storm track south, funneling severe gales toward the dikes and dams of what are today the Netherlands and Belgium. Thousands of people succumbed in the\u00a01570 All Saints\u2019 Day Flood<\/a>\u00a0along the German and Dutch coast, and again in the\u00a0Christmas Flood of 1717<\/a>. Heavy precipitation and water pooling behind dams of melting ice repeatedly overwhelmed inadequate flood defenses and inundated central and Western Europe. \u201cWho would not take pity on the city?\u201d\u00a0one chronicler lamented<\/a>\u00a0after seeing his town under water and then on fire in 1602. \u201cOne storm, one flood, one fire destroyed it all.\u201d<\/p>\n Disastrous storms, like one in 1775 in the Netherlands, were documented by engravers and other artists. Noach van der Meer II, after Hendrik Kobell<\/p><\/div>\n Cooling sea surface temperatures in the North Atlantic Ocean probably also\u00a0diverted the rain-giving winds<\/a>\u00a0around the equator\u00a0to the south<\/a>, provoking droughts that\u00a0undermined the water infrastructure<\/a>\u00a0of 15th-century Angkor.<\/p>\n Owing perhaps to the modest cooling of volcanic dust veils, disrupted patterns of atmospheric circulation led in the 16th century to severe droughts that contributed to\u00a0food shortages<\/a>\u00a0across the Ottoman Empire. In 1640, the grand canal that supplied Beijing with food simply\u00a0dried up<\/a>, and a short but\u00a0profound drought<\/a>\u00a0in 1666\u00a0primed the wooden infrastructure<\/a>\u00a0of European cities for a wave of catastrophic urban fires.<\/p>\n Today, the temperature shift is going in the other direction \u2013 with global temperatures already\u00a01 C (1.8 F) higher<\/a>\u00a0than before the industrial era, and local, sometimes devastating, extremes occurring around the world.<\/p>\n New research has found that extreme heat waves, those that don\u2019t just break records but shatter them, become\u00a0more common when temperatures change rapidly<\/a>.<\/p>\n These serve as a warning to governments to redouble their efforts to\u00a0limit warming<\/a>\u00a0to 1.5 C (2.7 F), relative to the 20th-century average, while also investing in the development and\u00a0deployment<\/a>\u00a0of technologies that filter greenhouse gases out of the atmosphere.<\/p>\n Visualizing temperature anomalies over 2,000 years, with colder temperatures in darker blues and hotter temperatures in darker reds, shows the chilly periods of the Little Ice Age and the extreme warming of today. Ed Hawkins<\/p><\/div>\n Restoring the chemistry of the atmosphere will still take many decades after countries bring down their greenhouse gas emissions, and so\u00a0communities must adapt<\/a>\u00a0to a hotter and less habitable planet. Nations and communities might learn from some of the success stories of the Little Ice Age: Populations that\u00a0prospered<\/a>\u00a0were often those that\u00a0provided for their poor<\/a>, established diverse trade networks,\u00a0migrated from vulnerable environments<\/a>, and above all\u00a0adapted proactively to new environmental realities<\/a>.<\/p>\n People who lived through the Little Ice Age lacked perhaps the most important resource available today: the ability to learn from the long global history of human responses to climate change.<\/p>\nWhat\u2019s behind the extremes<\/strong><\/h4>\n
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How does it apply to today?<\/strong><\/h4>\n
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