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Is Global Warming Responsible for the Amount of Snow We are Getting?

UMass Lowell Image

Boston Globe
03/07/2015


YES

Juliette Rooney-Varga
Associate professor at UMass Lowell, director of the UMass Lowell Climate Change Initiative

The science is very clear: While no individual weather event can be attributed solely to global warming, all the weather we are experiencing is affected by it. We know that global average temperature is increasing, causing rising sea levels, increased moisture in the atmosphere, and extreme weather events that are becoming more common and more extreme.

Here in the Northeast, intense precipitation events have increased by more than 70 percent since the 1950s. And despite the wild fluctuations in New England temperatures, globally, 2014 was the warmest year on record and even here average winter temperatures have increased by about 4.5 degrees Fahrenheit since 1970.

The conditions that have generated this winter’s historic snowfall are consistent with global warming: record high sea-surface temperatures off the coast have provided moisture and energy to fuel these storms. Ironically, it is also possible that the rapid decline in Arctic sea ice over the past several decades is causing the Polar Vortex to wander further south, bringing frigid Arctic air into our region.

The causes of these ongoing changes are explained by basic physics. While the sky seems limitless, our atmosphere is actually very thin: if the Earth were the size of an apple, the atmosphere would be about the thickness of its skin. As long as we emit carbon dioxide and other heat-trapping gases into that thin atmosphere, they accumulate, and so too does the energy in our climate system.

As a result of our emissions so far, we know that some further change is now inevitable, and that a swift and ambitious shift away from fossil fuels is necessary to avoid a future with untenable impacts.

What can we do to tackle the causes of climate change and to prepare for the impacts that we can no longer avoid?

For example, building a reliable, effective rapid-transit system would reduce our reliance on cars while cutting costs associated with snow removal, road repair, and parking. Building a more distributed, renewable energy grid would reduce our vulnerability to outages when extreme events hit. Better insulation for our homes would cut energy costs, while also reducing the damage from ice dams and our vulnerability in the event of power outages.

With more extreme weather in the forecast, it is time to take a longer view.

NO

Richard Lindzen
of Newton; Alfred P. Sloan Professor of Atmospheric Sciences, Emeritus, at MIT

There is a big difference between the claim that global warming is responsible for the amount of snow we are getting and the statement that global warming might have some effect.

The answer to the first question is certainly no, while there is no way to answer the second question.

Large snowfalls are hardly unheard of in our region. Moreover, the amount can vary sharply over relatively small distances. Predictions are difficult and frequently wrong. The important point is that snowfall and most other seasonal features depend on many factors, generally much bigger than the very small changes in global mean temperature anomaly (mean temperature for brevity) that is the basis for claims of global warming.

For example, this mean temperature has been statistically trend free for about 17 years. Claims that we were at record-breaking warmth last year are based on an increase of about .03 degrees centigrade, which is statistically insignificant.

The temperature simply showed that the trendlessness continued through last year. Despite this, the last 17 years have seen both warm and cold winters, and snowy and relatively snow-free winters. Obviously, factors other than this global anomaly must have been in play.

Snow requires temperatures below freezing, but high enough for the atmosphere to hold significant amounts of moisture. In the extreme cold of Antarctica, for example, snowfall amounts are very low.

The UN’s Intergovernmental Panel on Climate Change claims that manmade global warming is associated with the temperature increase from about 1978 until about 1998. The period since 1998 has remained warm but steady despite predictions of rapid increase in temperature. Yet, both 1978 and this year have been heavy snow years with a variety of conditions in between.

The reason for the variability is fairly clear from a look at a weather map. We see disturbances in the form of eddies traveling east with irregular speeds and paths. These eddies are essentially turbulence on a continental scale. When the winds associated with these eddies blow from the north, we get cold; when they blow from the south, we get warmth; when they blow strongly over long distances, we get record-breaking temperatures; and when they blow from the northeast, they can bring cold, moist air that can produce severe snow.

A major source of both the strength of these eddies and the range of temperature variability is the temperature difference between high and low latitudes. Interestingly, this is expected to decrease in a warmer world. Under the circumstances, it would appear that associating extreme cold and heavy snow with global warming is more than a bit of a stretch.