When the temperature drops and the snow falls, it’s not uncommon to hear people question, "How is climate change real if the winter is cold?"
Trends show winters have warmed over the past few decades, so this year’s cold spells in Pennsylvania, much like the one that’s gripping Europe now, makes one wonder what’s happening.
Are we returning to the cold, snowy winters that some Pennsylvanians remember from their youth? Probably not.
While we were shivering through the cold, most of the planet was much warmer than normal. Central Alaska was 18 degrees Fahrenheit above average, and even though we set some record low temperatures here in Pennsylvania this winter, the number of record high temperatures in the U.S. outnumbered record lows by 9:1 over the past year.
The cold snap may just have been normal weather variability, but ironically, climate change could increase the likelihood that we’ll see occasional brief, but intense, bouts of cold.
The Polar Vortex
Lying over the Arctic is a permanent low-pressure system called the polar vortex, which generates winds that circulate around the pole, helping to isolate the coldest air. The colder the arctic, the stronger the winds, and the more contained the cold.
Decreased ice cover in the artic and warmer ocean temperatures, however, have resulted in the Arctic warming twice as fast as the rest of the planet, weakening the winds. Add to this changes in the jet stream due to climate change, and the vortex is now more likely to meander, or form bulges that allow pockets of cold air to temporarily descend south.
That’s likely why snow was falling in Rome and record lows were being set across Europe at the end of February, while it was nearly 50 degrees F above average near the North Pole, and ice cover in the Arctic was the lowest ever recorded for this time of year.
A Really White Christmas in Erie
One area of the commonwealth got more than just cold air during January. When the cold Arctic air began spreading south on Christmas day 2017, it picked up copious amounts of moisture from the relatively warm water of Lake Erie, blanketing Erie with seven feet of snow in six days.
While snowfall has decreased significantly across much of the country due to climate change, it’s also likely to contribute to increased lake-effect snow downwind of the Great Lakes because ice is forming later in the season, melting sooner, and covering less of the lake’s surface.
The Great Lakes have seen below average ice cover for 15 of the past 23 years, and when the cold air invaded in late December, Lake Erie was ice free.
By the time the cold spell ended, Lake Erie was 90 percent ice covered, and the lake effect-machine turned off.
A very warm February has reduced ice cover to only 15 percent, and with several weeks of winter left, could more lake-effect snow be in Erie’s future?
Learn More About Climate Change
As the caretaker of 2.2 million acres of state forest and 121 state parks, and the state’s primary conservation agency, DCNR has a unique role and responsibility in helping the commonwealth reduce and adapt to climate change.
While climate change presents significant challenges, there is much we can do including:
- Managing our forests to sequester an increasing amount of carbon
- Ensuring that our public lands remain resilient
- Helping private landowners and communities reduce their carbon footprint and adapt
When natural areas are healthier, they are more resilient and can better withstand the stresses placed on them by climate change.
For the past year, a team of more than 80 DCNR staff have worked with the Northern Institute of Applied Climate Science to evaluate data on current and projected impacts to identify the department’s top climate change vulnerabilities. They were ranked on the likelihood they would occur and how severe they would be.
The team also developed adaptation strategies and general recommendations to address those vulnerabilities.
DCNR will be releasing its climate change mitigation and adaptation plan this spring.
To learn more about climate change and what DCNR’s plan will include, visit the agency’s Addressing Climate Change on Public Lands web page.