Millions Under Blizzard Warning: Is It Climate Connected?

Winter Storm Stella is headed to the Northeast and states from Maryland to Maine are expected to witness more than a foot of snow, hurricane force winds and coastal flooding through March 14.

The massive snowstorm has multiple climate connections helping to fuel its destructive power. Elevated sea levels will amplify and extend the reach of Stella’s storm surge. A warmer atmosphere can hold more water vapor for Stella, increasing blizzard risk as the storm can collect and dump that moisture as extreme snowfall, sleet and rainfall. Sea surface temperatures are record warm in the Atlantic Gulf Stream, pumping more heat energy and moisture into the storm, further increasing the risk of blizzard.

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The amplification of these physical mechanisms can be seen in the long-term trends. Between 1961 and 2010, there have been twice as many extreme regional snowstorms in the U.S. compared to 1900 to 1960. In New York City, which is forecast to receive between 12 to 18 inches of snow over the course of one day, six of the 10 all-time biggest snowstorms on record have occurred since 2000. An extreme event driven by natural variability and amplified by climate change is consistent with what science projects for a warming world.

Climate Science At-a-Glance

• The storm is driven by classic Nor’easter conditions, aided by other regional weather patterns and amplified by climate change. This combination is consistent with what science projects for a warming world over the short-term.

• Extreme winter snowfall is increasing in many colder regions as the warming atmosphere is holding more water vapor and dumping more snowfall where temperatures are still below freezing.

• The storm is pulling moisture from the Gulf Stream where sea surface temperatures are record warm, increasing the risk of blizzard. Snowfall and sleet can increase where temperatures are still below freezing while rain can increase where temperatures rise above freezing. The profile of Stella matches the Goldilocks profiles of recent nor’easters in which a sharp contrast between cold continental air and a relatively warm ocean permitted the storms to tap moisture fed by high sea surface temperatures and convert it into exceptional snowfall.

• There have been twice as many extreme regional snowstorms in the U.S. between 1961 and 2010 compared to 1900 to 1960.

• In New York City’s Central Park, of top 10 all-time snowfall events since 1869, six have occurred since 2000.

• Coastal flooding driven by storms is now significantly worse due to storm surge riding on higher sea levels.

Warmer Seas are Helping to Fuel Winter Storm Stella’s Destructive Power

The storm is pulling heat and moisture from the Gulf Stream, where sea surface temperatures are record warm at more than 7.2°F (4°C) above the 1961 to 1990 average. Global warming raises sea surface temperatures.

The additional water vapor fed into the storm can increase snowfall where temperatures are still below freezing and increase rain and sleet where temperatures rise above freezing. The water vapor can also provide additional latent heat to power the storm. This is expected to help fuel hurricane-force winds that have the potential to whip up dangerous storm surge.

Warmer, Saturated Air Holds and Dumps More Snow, Giving Rise to More Extreme Storms

Extreme precipitation is linked to the global warming of the atmosphere. A warmer atmosphere that is fully saturated holds and dumps more precipitation. Storms passing through a warmer atmosphere can pick up more moisture, resulting in extreme precipitation: such as blizzard when temperatures are below freezing and sleet or heavy rain when they are not.

Temperatures in the Goldilocks range of between about 28°F and 32°F, accompanied by moisture, mean more snow. The profile of Stella matches the Goldilocks profiles of recent nor’easters in which a sharp contrast between cold continental air and a relatively warm ocean permitted the storms to tap moisture fed by high sea surface temperatures and convert it into exceptional snowfall.

There were twice as many extreme regional snowstorms in the U.S. between 1961 and 2010, compared to 1900 to 1960. In New York City, six of the top 10 snowfall events since 1869 for Central Park have occurred since 2000.

These events and trends are in-line with a consistent set of findings delivered by numerous leading science reports. The U.S. National Climate Assessment reports that there has already been an increase in extreme precipitation in the Northeast, with precipitation rising by 71 percent between 1958 to 2012. Extremely heavy snowstorms have increased in number during the last century in northern and eastern parts of the U.S.

Should global warming continue unabated, local temperatures in the U.S. northeast would eventually warm to the point of converting extreme snow fall to extreme rainfall. However that signal has not yet been detected and is not expected to emerge for perhaps another 20 years.

Climate Change Contribution to Sea Level Rise Can Top Coastal Defenses

The storm’s exceptionally strong winds are expected to drive a peak storm surge of 1 – 3 feet on Tuesday along much of the coast of Delaware, New Jersey, New York, Connecticut and Massachusetts, including Cape Cod and the islands.

Coastal flooding driven by storms is amplified by storm surge riding on higher sea levels. Due to climate change, the global ocean has already risen 8 to 10 inches over the last century as warmer ocean waters expand and ice sheets and glaciers melt. In addition, the intense winds that produce storm surge can gain strength from warmer than average sea surface temperatures. Warming seas and elevated sea levels are both driven by global warming.

In low-lying areas, a small increase in sea levels translates into much greater inundation as storm surge travels much further inland. In addition, even a small increase in surge can top coastal defenses and disaster often strikes when thresholds are crossed. Twenty-four percent of the property damage in New York City during Superstorm Sandy has been attributed to elevated seal levels that extended the reach of the storm’s surge. While climate change may be responsible for only part of any particular climate event, that change may be largely responsible for most of the damage in that event, such as when flooding defenses are breached.

New, more intense extremes can overwhelm and collapse existing human systems and structures.

Reposted with permission from our media associate Climate Signals.