Deep freezes, massive snowfalls, and a devastating ice storm forming to the east of the Rocky Mountains create a picture of seasons that are usually associated with climate change. Yet under the right conditions such phenomena can still be extremely destructive.

Global cold spells are becoming less common and not as severe due to overall warming, but millions of people are bracing for prolonged cold snaps. Winter in the United States remains one of the fastest-warming seasons, and even this year the number of warm records exceeds the number of cold records in the Lower 48 states.

The Western states are already recording one of the warmest winters on record, while ski regions, particularly in Colorado and other snow-rich centers, are facing snow deficits.

Climate Central researchers analyzed the trend of annual minimum temperatures in U.S. cities, and the data show that these values are rising along with climate change. For example, in Minneapolis the annual minimum temperature has risen by about 12°F since 1970 (about 7°C). In Cleveland, the annual minimum temperature has increased by 11.2°F (about 6.2°C).

Arctic Dynamics and Implications

Although global warming generally leads to warmer winter seasons, harsh winter phenomena are still possible – and perhaps even more likely – because warming is not the sole consequence of human-caused climate change,

– Jennifer Francis, researcher at the Woodwell Climate Research Center

The cold air that storms into from the Arctic comes from the polar vortex – a massive wall of cold air that usually keeps cold within the polar latitudes. However, when the vortex becomes stretched, it can dip southward and bring cold beyond its usual range.

There is a clearly defined link between stretched vortex events and extreme winter weather specifically in the United States,

– Judah Cohen, MIT scientist

According to Cohen, during periods of rapid Arctic climate shift the polar vortex becomes more stretched and unstable, increasing the risk of waves of severe winter weather in mid-latitudes, including the United States, Europe, and parts of Asia. On the southern flanks of the vortex over the United States and Asia there is a rising incidence of heavy winter events, and while a single event cannot be unambiguously linked to climate changes, experts believe such a combination creates a more risky and unpredictable winter.