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This winter has certainly been a wild ride with the Midwest suffering from record setting cold and unprecedented flooding, Washington experiencing unparalleled amounts of snow, and an usually wet winter pulling much of California out of a years-long drought. No corner of the country was left untouched by some sort of extreme winter weather, even North Carolina, which experienced a record-setting snowstorm back in December.

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Perhaps the most notable ‘extreme’ event this winter was the ‘polar vortex’ in late January, which drove the Midwest into a deep freeze and caused at least twenty-one deaths. Illinois experienced its coldest recorded temperature in history, at minus thirty-eight degrees, while one town in Minnesota experienced a wind chill of negative sixty-six. By the end of January, at least 340 daily cold records had been broken or tied.

The media was abuzz with catchy headlines like ‘Chicago Colder than Antarctica!’ leaving many readers asking whether ‘so-called’ global warming was really a problem. And as he does anytime the temperature drops, President Trump took to Twitter, exclaiming “Wouldn’t be bad to have a little of that good old-fashioned Global Warming right now!”

What everyone seemed to forget was that January is the middle of the Antarctic summer. Temperatures at McMurdo Station, along the continent’s icy margins, are regularly above zero during the summer. What people should have been more concerned about was that, at the same time, temperatures in Siberia were up to ninety degrees above historical averages. Meanwhile, large swaths of Australia were experiencing record-setting heat, sparking destructive wildfires and power outages across the country. And as the Midwest was bracing for bitter cold, Alaska experienced an extraordinary heat wave during which, one-third of the ice covering the Bering Sea vanished in just over a week.

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Photo 1: At the end of January, while Chicago (left) was caught in a deep, life-threatening freeze, Australia (right) was experiencing destructive wildfires and record setting heat (Photo Credit – New York Times)

Trump may be the most prominent politician who readily mocks climate science the moment the temperature drops or rain falls in the arid West, but he is certainly not the only one. In 2015, Senator Inhofe of Oklahoma brought a snowball into Congress as ‘proof’ against climate change. In addition to illustrating a problematic distrust of science more generally, what their rhetoric reflects is a fundamental misunderstanding of the relationship between weather and climate. That misunderstanding is why people dismiss global warming when they experience an unusually cold month or question the validity of climate science when a drought-prone area gets heavy rain. And it is why extreme weather has become one of the fiercest battlefields in the war over climate action.

To put it simply, weather is a short-term phenomenon. It is the day-to-day state of the atmosphere on a time scale of days to weeks. Climate, though, is the aggregation of many years of weather. A heat wave is weather. But it is the climate that makes the southeast so unbearable in the summer. The National Centers for Environmental Information perhaps says it best: weather tells you what to wear on a given day, but climate tells you what to keep in your closet.

The intense cold in January was a classic example of an extreme weather event. But it was the global climate pattern driving that extreme event that we should be worried about. The polar vortex is a stream of very cold, upper atmosphere air that circulates around the North Pole in the winter. When the vortex is strong, it traps the extreme cold of the Arctic in the far north, keeping temperatures in the lower forty-eight and Northern Eurasia relatively mild. But, decades of warming in the Arctic region – and the resulting loss of sea ice and change to the jet stream – is weakening that force. Rather than deflecting warm air from the south and trapping cold air in the north, a weaker polar vortex fluctuates and shifts, allowing for a heat wave in Alaska and bone chilling cold in the Midwest.

So, paradoxically, this winter’s regional extreme cold events were driven fundamentally by global-scale warming, as concentrations of atmospheric carbon dioxide reach levels not experienced in 800,000 years. According to the World Meteorological Organization, the last four years have been the hottest on record, while the twenty warmest years ever recorded have all occurred in the past twenty-two years. One recent study projected a fivefold increase in heat-related deaths in the United States, and up to a twelvefold increase in some less developed countries like the Philippines, by 2080.

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Photo 2: An example of extreme regional cold at the same time as overall global warming. In December 2017, parts of the US were fifteen to thirty degrees colder than average, but the world as a whole was almost one degree warmer than the long-term average (Photo credit – Karsten Haustein via New York Times)

The increasing likelihood of more severe cold snaps due to global warming is just one of the surprising, and oft misunderstood, consequences of climate change. For example, scientists suspect that climate change will lead to more intense hurricanes, which the last few hurricane seasons seems to support. In fact, models project an increase up to 87% in the frequency of Category 4 and 5 storms on the East Coast, even as those models suggest a possible decrease in the overall frequency of storms. This is likely due to how warmer ocean temperatures lead to more intense wind speeds and greater potential for precipitation. Meanwhile higher sea levels will exacerbate the impacts of storms on coastal communities.

In addition, climate change is expected to increase the likelihood of both droughts and extreme rain events. Increasing temperatures mean more rain rather than snow, earlier snow melt, and increased evaporation, all recipes of a drought disaster as the California experience illustrates. Global climate models actually suggest the American Southwest is one of the regions in the world most vulnerable to climate change-driven drought. At the same time, warmer temperatures mean the atmosphere can hold more moisture, leading to more extreme, massive rain and snow storms when there finally is precipitation. However, the increasing increment of time between rainfall means that soils tend to dry out and harden. As a result, farmers need more water to grow the same crops and rain events tend to result in more flooding as the water fails to infiltrate into the dried-out soils.

The relationship between extreme weather and climate is complicated and rarely intuitive. As a result, both opponents and supporters of climate action readily use extreme events as ‘evidence’ for their position. Trump provides a perfect example of the weaponization of science and the proliferation of misinformation meant to stymie climate action efforts. But as our scientific understanding of the impacts of climate change on specific extreme weather events improves, so does scientists’ confidence in using science as a weapon themselves. Unfortunately, though, the most effective mechanism for changing hearts and minds on climate change seems to be devastating disasters themselves, illustrating the need to build resilience and improve disaster preparedness no matter what the President says.

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Featured Image: The frozen shoreline of Chicago during January 2019’s record-setting cold wave (Photo Credit – National Geographic)

About the Author: Leah Campbell is a first-year Ph.D. student in the Department of City and Regional Planning, where she focuses on integrating equity and resilience into climate adaptation to address urban flooding. Prior to UNC, she worked in the environmental nonprofit sector in California after receiving her B.S. in Geophysics and Environmental Science from Yale in 2015. Outside of academics, Leah enjoys folk music, long road trips, and anything that gets her outside.

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