A number of unusually severe blizzards have hit the northeastern United States in recent years, making headline news. In February of 2010, the U.S. East Coast was hit by a winter storm dubbed “Snowmageddon” or “Snowpocalypse.” The storm caused blizzard conditions that brought the Washington, D.C., area to a standstill and broke snowfall records for the mid-Atlantic region. In January 2016, another historic and deadly blizzard, nicknamed “Snowzilla,” struck the mid-Atlantic region. Snowfall totals reached 0.3–0.9 meters (one–three feet), breaking records in Baltimore, Maryland; Washington, D.C.; New York City, New York; and Philadelphia, Pennsylvania. In January 2019, a polar vortex plunged the U.S. Midwest into Arctic conditions.

Extreme weather events like these are predicted to become more intense thanks to climate change, despite the fact that winters are getting shorter, and global temperatures are on the rise.

Blizzards are a dangerous type of winter storm characterized by strong winds, snow, and reduced visibility. The National Oceanic and Atmospheric Administration (NOAA) defines blizzard conditions as winds over 56 kilometers per hour (35 miles per hour) with either falling or blowing snow that reduces visibility to 0.4 kilometers (0.25 miles) or less for at least three hours. Blizzards form when snow falls in windy conditions or when snow is lifted from the ground by strong winds. Some blizzards can cause whiteout conditions where it is impossible to tell the sky from the ground.

The World is Getting Warmer

In an analysis of all studies published between 1991–2011 expressing a position on human-caused global warming, 97 percent of research studies published agreed that climate change is real, and it is caused by human activities—primarily the burning of fossil fuels. When fossil fuels—such as gas, coal, and oil—are burned, large amounts of carbon dioxide (CO2) are released into the atmosphere. Carbon dioxide is an example of a group of compounds known as greenhouse gases that allow the sun’s heat to reach Earth and then trap it in the atmosphere. When greenhouse gases are present in appropriate amounts, they help keep Earth warm enough to support life. However, the addition of human-contributed greenhouse gases to the atmosphere causes global temperatures to rise—a phenomenon known as global warming. Average global temperatures have already risen by about 0.8°C (1.4°F) in the last century, and they are expected to continue to rise should no actions take place to reduce the amount of greenhouse gases in the atmosphere. Although Earth’s climate has had warmer and cooler periods throughout history, the current rate of warming has far exceeded that of past millennia.

Why All the Snow?

First, it is important to remember weather and climate are two different things. Weather refers to short-term conditions in the atmosphere and describes these conditions in terms of humidity, precipitation, temperature, wind velocity, and atmospheric pressure. It could be rainy, sunny, windy, or snowing, for example. Climate, on the other hand, is a long-term average of weather patterns, usually measured over a period of 30 years or more.

A blizzard such as 2016’s “Snowzilla” is an example of short-term weather event. On the other hand, the recent warming temperature trends over the past two decades suggest a change in climate. Twenty of the hottest years on record have happened in the last 22 years, with the 2015–18 taking the top four spots.

Scientists predict climate change could make blizzards more intense. A warmer atmosphere holds more moisture. This moisture eventually falls as precipitation—either as rain (when temperatures are warm) or snow (when temperatures are below freezing)—which results in more frequent and intense storms. Sea temperatures are also on the rise, which increases the amount of energy and moisture available to storms, thus amplifying their severity.

On average, winters are getting warmer and shorter, with fewer places experiencing extremely cold temperatures. However, because the warmer atmosphere holds more moisture, blizzards are more likely to occur and be more severe in places where temperatures are still cold enough for snow.

It is difficult to look at a specific storm and say it was caused by climate change, but scientists are getting closer to doing so with a developing area of research called “extreme event attribution.” For example, the Snowmageddon blizzards of 2010 have been linked to higher-than-usual surface temperatures in the Atlantic Ocean. Part of this temperature increase can be directly attributed to global warming. Nevertheless, scientists are confident that global warming is making extreme weather events more likely.

How Can Climate Change Affect Blizzards?

The extent of sea ice in the Arctic has been steadily declining since record keeping began in the 1970s. Melting sea ice enhances the effects of global warming in the Arctic because it causes a positive feedback loop. The loop begins when sunlight, which would have been reflected by the ice, gets absorbed by the newly exposed, dark ocean water instead. The sunlight warms the sea surface, which melts more sea ice, and so on. As a result, the Arctic is warming about twice as fast as the rest of the world—a phenomenon known as Arctic amplification. This influences weather patterns in other parts of the world. Arctic warming could increase the likelihood of extreme winter weather in parts of the United States, Europe, and Asia.

The effects of global warming are also felt in the atmosphere, particularly the jet stream. The jet stream is a fast-moving current of air that circulates in the troposphere and has a significant effect on weather in Europe and North America. It is driven by the difference between air temperatures to the north and south of its path: The bigger the temperature difference, the faster the jet stream. As the Arctic warms, the temperature difference between the polar regions and the tropical regions decreases, which slows the jet stream and causes its path to weave farther north and south. As it dips farther south than usual, it pulls Arctic air down from the north, causing a persistent spell of unusually cold weather in that region. Disturbances to the jet stream have been linked to an increase in extreme cold weather events, including blizzards.