Snow. That white substance that makes our lives miserable (if you’re shoveling) or enjoyable (if you’re sledding) seems like something foreign to central Illinois this winter.

Indeed, it appears that winter forgot to come this year in many parts of the country; mild temperatures have been recorded throughout most of the United States, with most of the nation experiencing at least 5 degrees above average.

So this begs the question: Is this the result of global warming?

Not quite. Eric Snodgrass, professor in atmospheric sciences, clarifies that there is a distinction between weather and climate, particularly that climate is the average of weather over long periods of time.

“When you talk about climate change, you have to keep weather separate,” Snodgrass said.

Of course, one season or incident does not in itself make a trend, and the warm temperatures during most of winter break weren’t solely driven by climate change.

Jeff Frame, professor of atmospheric sciences, argues that isolated events might lead people to make conclusions about global warming and climate change, but that idea is incorrect.

“This winter has been incredibly warm (10 degrees higher than average in central Illinois), while in Alaska it has been 7 degrees below average,” Frame said. “So you can’t just look at one area, you can’t just look at one event, you can’t just concentrate on certain cities.”

If this pleasant winter weather is not due to global warming, then what’s going on?

Sara Strey, Ph.D. student in atmospheric sciences, explained that the year-to-year differences in weather are due to weather cycles related to wind patterns, ocean currents and other variables related to what is going on in the Arctic Circle.

“Last winter was extremely cold because of La Nina,” Strey said. “This winter we … have La Nina again, coupled with an interesting phase in the arctic oscillation.”

Snodgrass explained La Nina as a phenomenon where the equatorial Pacific waters are colder than their average value, which leads to more snow and cold in central Illinois.

“Preventing La Nina from making it a cold winter, however, is something called the arctic oscillation (AO),” Snodgrass said. “When it is in the positive phase, it means that the cold air stays locked up in Canada.“

The last two winters however, saw an AO in its negative phase. Frame explained that when the arctic oscillation is in its negative phase, cold air gets displaced southward from the pole, which makes the winters in the northern United States much colder and leads to heavier snow fall.

All these explanations, however, don’t shed light on what global warming is all about. To understand it, one has to look at the greenhouse gases and their affect on long-term climate changes.

Snodgrass explains that greenhouse gases include carbon dioxide, water vapor, methane and nitrous oxide. They trap the heat that wants to escape the Earth’s surface into the atmosphere, leading to a warming effect. These gases are found in trace amounts in the atmosphere, yet a minuscule change in their concentration can lead to dramatic effects.

Carbon dioxide is the main contributor to the recent increase of about 1 degree Celsius over the past 130 years in the global average temperature, Frame said.

“All else being equal, increasing CO2 levels will increase temperatures,” Frame said. “CO2 levels are not the only governor, since global temperatures are fairly complicated.”

Though it is not the sole factor in these recent increases, it is one of the primary causes.

Snodgrass explained that natural events may also lead to temperature changes, like volcanoes, changes in the sun and weather cycles. But their contributions are so small that they are ruled out, and carbon dioxide is the main factor scientists are concerned about.

Although this season’s mild temperatures are not specifically tied to global warming, Don Wuebbles, professor in atmospheric sciences, says there is still a clear consensus in the scientific community that climate change is an important concern.

“In the scientific community, there is no real debate,” Wuebbles said. “There’s just no question it’s happening. The data is clear.”

Strey said the climate science community is in agreement that the global temperature has increased, and that change was likely caused by people.

“We as scientist don’t sit around and debate whether the climate is changing. We worry about how it’s changing and what patterns are changing and how that will impact other weather patterns,” Strey said.

As the winter here in Central Illinois continues with its irregular temperature swings, however, one should keep a critical mind when thinking about the weather and climate change.

“Global warming can’t explain yearly variation in temperatures,” Frame said. “One drought here, a heat wave there doesn’t prove or disprove anything.”