URI professor discusses this season’s winter weather, climate change

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KINGSTON, R.I. – February 26, 2014 – From Atlas to Zephyr, the Northeast has endured quite a few storms during the 2013-2014 winter season. And with this week’s forecast calling for more snow and another possible polar vortex, it doesn’t look like the winter weather is going to loosen its icy grip anytime soon.

In this Q&A, we asked URI Oceanography Professor John Merrill to describe the science behind this season’s wintry weather and its relationship with climate change. An atmospheric scientist, Merrill uses meteorological techniques to study the long range transport of substances in the atmosphere and the impacts of meteorological processes on the environment. He teaches a graduate-level course in climate and radiation, and an undergraduate course in oceanography and global change at URI’s Graduate School of Oceanography.

URI: Between the snowstorms and polar vortexes, how does the 2013-2014 winter season compare to past winters?

John Merrill: In the Northeast, it has been a cold, snowy winter. I have not looked

at variations elsewhere with any care, but we know that it’s been warm and

dry in the West, particularly the Southwest. Such variations tend to balance

out, as if there’s a Conservation of Trouble, only so much to go around.

URI: What causes some winter seasons to be better or worse than others?

JM: Several factors that vary contribute to the severity of conditions in

any season. The circulation of the atmosphere is inherently variable, and other

environmental factors cause changes that vary from year to year. Also, there’s

a big difference between the impact of snow and cold on a trucking company

that wants to get fresh goods to a remote place than on a utility providing

power to a densely-populated city.

URI: Why are we seeing more snow and ice storms in the South this year, and is this type of weather behavior unusual?

JM: For quite a while in January and early February the track of the jet

stream extended deeper into the south than it often does. This left New

England and the Midwest in colder air than usual, and brought cold and snow

to places where these are not common. It was simply a change in the pattern of

flow. Such changes can be forced by variations like El Niño, but in this

case I don’t believe that’s what’s going on.

URI: What is the relationship between “weather” and “climate”?

JM: Climate is the aggregate of many weather situations, the distribution

and variability of conditions ‘on average’ for an area. A summary

by a colleague may be helpful: climate is what you expect, but weather is

what you get.

In some applications the specifics can be important. For climate analysis, a typical averaging period is 30 years. Tables of average temperature at

various cities are available, showing the average and range for each day

of a year, based on 30-year averages. Fine. But river flow statistics were

used in a similar way in negotiating a water-rights treaty with Mexico, for

Colorado River water. We later realized that the 30 years used in the average

were the wettest 30 years in over 100 years. So we promised more water to

Mexico than we can manage to deliver.

URI: Does snow and cold weather disprove climate change?

JM: Cold weather and snow occur every year, and their occurrence has

nothing to do with climate change. The character of the climate change we

are experiencing is such that an increase in the occurrence of extreme

events is anticipated, including extremes in temperature and precipitation.

This has been documented very clearly in temperature, and the data on precipitation extremes are quite good in a number of areas. Quick summary: considering how much rain falls each day, there will be fewer days with average precipitation and more with very low or very high amounts. So droughts and floods will both become more common. This result is not easy to understand or explain, however, and lots of people find it hard to believe.

URI: Do you like or dislike winters in Rhode Island – why or why not?

JM: I admit I’ve tired of the effort in shoveling, the disruptions in

travel and other impacts of winter weather. My wife and I have decided to

retire to a spot where snow does not fall.