Climate change or just the winter? Experts sound off on what they think

SALEM, Ohio — Another polar vortex is set to invade the northeastern part of the United States at the end of the week Feb. 24.

Some meteorologists say it will be the last one. That is, for the winter season of 2014…

Not uncommon

Brett Anderson, a senior meteorologist for Accuweather.com, says polar vortex reach as far south as they have this year about every four years.

However, this winter season has been a little different because of high pressure over the eastern Pacific Ocean and the Alaska region, which is forcing the vortex south.

After the polar vortex invades one more time, odds are getting smaller that they will return in March, Anderson said.

“If I was a betting man, I would say this is the last one for this particular winter,” said Anderson.

Climate change?

Although the 2013-2014 has been one of the roughest winters in many years, Anderson doesn’t feel there is enough evidence to say climate change is triggering the extreme weather.

However, three climate scientists said otherwise Feb. 18 during a conference call, saying that recent record-setting snowfalls and persistent cold temperatures are consistent with climate change, likely due to changes in the jet stream.

Major cities in Michigan, Ohio, Kansas and Indiana saw record-setting snowfall in December and January, while Missouri, Minnesota, North Dakota and South Dakota experienced single-day record snowfall events, sometimes accompanied by high winds. Cities like Detroit and Columbus, are on pace to set records for their snowiest winters ever.

“The number of extreme precipitation events in the Midwest has been increasing over the last 20 years, which is consistent with what we would expect from climate change, which has caused increased amounts of water vapor in the atmosphere,” said Dr. Kenneth E. Kunkel, research professor with the Department of Marine, Earth, and Atmospheric Sciences at North Carolina State University, and at NOAA’s National Climatic Data Center.

Kunkel said the Midwest has experienced greater than 40 percent increase in extreme events in the last 20 years, compared to the norm during 1900 to 1960 period.

“While the heavy snow of this winter is primarily a consequence of the persistent storm track, it may have been enhanced by the increasing amounts of water vapor in the atmosphere.”

National Climate Assessment

The scientists said the increased extreme precipitation events are consistent with data in the draft National Climate Assessment, an analysis of climate change in the U.S. prepared by the federal government and hundreds of climate scientists from across the country every four years.

The scientists also stressed that average U.S. temperatures are not falling, and are actually rising overall — decreasing the frequency of extreme cold.

In January, the average U.S. temperature was just 0.07 degrees below the 1981-2010 average, according to the National Climatic Data Center.

“While we are definitely seeing cold days in the Midwest, days like this used to be far more common and last for much longer,” said Dr. Michael Wehner, senior scientist with the Computational Research Division at Lawrence Berkeley National Laboratory. “For example, Chicago’s 11-day stretch of days below freezing in December and January was much shorter than in past years, as the city has twice experienced more than 40 days in a row of freezing temperatures since 1976. It is likely that these temperature extremes would have been far colder if not for the impact of climate change.”

The experts also discussed a link between melting Arctic ice, the jet stream and the “polar vortex” that has helped drive recent cold temperatures.

“Some science suggests that the extended cold snap experienced in the Midwest in December and January is consistent with expected shifts in the jet stream driven by the rapidly warming Arctic,” said Dr. Jennifer Francis, research professor, Institute of Marine and Coastal Sciences, Rutgers University.

“Weakened west-to-east jet stream winds can allow the polar vortex to plunge southward, trapping cold temperatures in some areas and warmer-than-normal temperatures where the jet stream surges northward.

“This will require more study, but it provides further potential evidence of climate’s connection to extreme temperatures and precipitation.”

Global average warmer

According to the National Oceanic and Atmospheric Administration, the combined average temperature over land and ocean surfaces for January was the warmest since 2007 and the fourth warmest on record at 54.8 degrees, or 1.17 degrees above the 20th century average of 53.6 degrees.

During January 2014, most of the world’s land areas experienced warmer-than-average temperatures, with the most notable departures from the 1981–2010 average across Alaska, western Canada, Greenland, Mongolia, southern Russia, and northern China, where the departure from average was +5.4 degrees or greater.