Valley’s recent sub-zero temps show patterns
Published: Tuesday, January 15, 2013
Updated: Tuesday, January 15, 2013 15:01
Biting, bleak, numbing and frigid.
All are words used by some members of the USU student body to describe recent Cache Valley weather conditions.
“People are probably thinking, ‘Why was this winter so cold?’” said Dr. Robert Gillies, state climatologist and director of the Utah Climate Center. “Well yes, it was cold, but it’s been a lot colder in the past too.”
Despite record-high temperatures for Utah in 2012 and ever-progressing studies of global warming, students have been questioning why Logan has been so cold since the semester’s start. Some representatives for the Utah Climate Center have been willing to address those questions.
“It’s winter. The global warming piece of climate change doesn’t mean that the seasons go away,” said Dr. Robert Davies, a research associate for the Utah Climate Center. “When you look at the variability in temperature between seasons in any place on the planet, except maybe the tropics, it’s a big range, typically tens of degrees.”
“For example, the average temperature in Utah last July was 70-something degrees,” Davies said. “The average temperature in January will likely be in the 20s or 30s, but that’s a difference of 30 or 40 degrees. That’s what we would call ‘natural variability’ in a range of temperatures due to the seasons.”
The Earth is tilted on its axis as it orbits the sun, and different amounts of sunlight raise and lower seasonal temperatures, Davies said. This is one mechanism that creates change in temperature, but it differs from global warming.
“Global warming is caused principally by greenhouse gases building up in the atmosphere and that is producing an effect,” Davies said. “On an absolute scale, it is much smaller. The temperature has gone up about two degrees Fahrenheit globally in the last 150 years. Compare that two-degree-average rise in global annual temperature to a 30 or 40 degree seasonal spread and what you find is a small trend on a much larger amplitude oscillation.”
Davies likened climate change to waves fueled by an ocean tide.
“A tide might be six feet,” he said. “At the end of the day they might go six feet further up the beach than they did before, but the interval between any two given waves might be 20 feet. The notion with climate change is this very long-term trend. Embedded in that trend is this variability — in this case a seasonal variability — and that doesn’t go away because the mechanism is something totally different.”
Davies said the general winter temperature trend is rising. The average rise in the winter temperature would also be different than the average rise in summer temperature.
“Often it comes to people’s memories of temperatures,” Gillies said. “Last year we had no significant temperature inversions in the valley but we just had one this year.”
Gillies said the recent amount of snow in Cache Valley hasn’t helped the temperature inversion, an event in which air temperatures increase with altitude instead of decreasing.
“Because we have a lot of snow on the ground, we had a big ridge sit over us for nine days,” he said. “It allowed a lot of emission of energy from the surface, and then cold air pooled into the valley. If you were down in the valley, it was a lot colder than if you were up in the mountains.”
Although 2012 was the warmest year in recorded U.S. history, Gillies said people often forget it wasn’t the warmest year for every place in the country. For Utah and Salt Lake City it was the warmest year on record, but it wasn’t the warmest on record for Cache Valley.
“We’ve looked back at the last 50 years of Utah temperatures and done studies that use climate diagnostics,” Gillies said. “We can show the troposphere — the surface up to about 12 kilometers — has warmed up in a long-term trend. When it comes to this variability from year to year, we don’t fully understand those mechanisms. We’re doing a lot here to better understand these things.”
Gillies and Davies said they urge people to obtain a better understanding of the differences between climate change and year-to-year temperature variations.
“We’ve got global warming and yet it’s still cold outside,” Davies said. “But global warming in the arctic is four times the global average and it’s still plenty cold up there. It’s not as cold as it once was, but within that average there’s a lot of fluctuation.”
“Global warming doesn’t mean the seasons go away,” Davies said. “They’re two different things entirely. Winter will still be cold.”