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Temperatures records show winter warming across Colorado in the last 50 years. So why not in Denver, too?

By Allen Best

Last week it got to 19 below in Fraser, the Colorado town located northwest of Denver in the valley of the same name. The temperature provoked quite a lot of local talk. How things have changed.

The town, adjacent to Winter Park but the elder in incorporation by 25 years, has a storied tradition of deep cold. In the 1960s, it was often reported by morning radio stations—this was before TV really got into the game of morning broadcasts—as having the deepest overnight cold in the nation. (Other places that stood out in my memory: Truckee, Calif., and International Falls, Minn., and less often, Alamosa, Colo.).

Denver KOA’s Weatherman Bowman—there were no women at the microphones in those days—called it the icebox of the nation.

Those temperatures were the result of the steadfast devotion of a couple, Ron and Edna Tucker. They took turns getting up every two hours in order to get an accurate record of the deep freeze. After he died, she kept it up for awhile, then tried to delegate to somebody else. She was also the town’s postmaster. But sometime in the 70s this tedious, detailed record of deep cold lapsed. Since then, it’s been an anecdotal record.

Kirk Klanke arrived in Fraser in 1971, after playing football for the state college in Pueblo.

The difference between now and then?

“Considerable,” he answered. It was 19 below the other night, he reported, which was enough to spark comment. In the 1970s, it would have been typical. “On a clear night it was 25 to 40 below and it sometimes got to 50 below. Even 40 below was memorable. Your car had flat tires from the cold, and they didn’t thaw until you had driven for a little bit.”

“That,” he added, “hasn’t happened in a long time.”

If Fraser were large enough to have had a continuous record, it might have been teased out by Climate Central in that organization’s recent report about the change in winter temperatures across the nation.  All but 6 of the 242 sites for which it pulled weather records showed warming in the last 50 years.

Colorado Springs has increased 2 degrees on average, and Grand Junction 1.5 degrees.

Albuquerque rose 3.2 degrees, Casper warmed 1.5 degrees, and Salt Lake City 1.9 degrees.

Denver? No, not much.

Becky Bolinger, the assistant state climatologist in Colorado, studied the Climate Central work and found that the same recording station at Stapleton (an airport until 1995, then gradually a residential neighborhood now called Central Park Denver) was used for the study. She ran the numbers herself and came to the same conclusion: a very, very small trend downward. Why?

“I would say that major land surface changes have been happening over the past 50 years that could be impacting measurements,” she said when posed with this conundrum by Big Pivots.

Becky Bolinger

What caught her eye was the apparent decrease in variability.

“The peaks and minimums are not as extreme in the latter part of the chart as it was earlier,” she said.

“My speculation is that the land surface changes (airport until mid-1990s, then suburban in the 21st century) has acted to regulate the winter temperatures a little bit more and reduced the extreme warm and cold winters.”

Climate Central meteorologist Sean Sublette says the precise warming levels vary, but the broader picture is clear across the United States. Most prominent was the heating in the Great Lakes states and the Northeast.

But Colorado has clearly warmed altogether, even if the evidence from the state’s largest city is wobbly. Running a chart for Colorado altogether using data from the National Oceanic and Atmosphere Administration’s Climate at a Glance tool, he produced a chart (previous page) from 1895 forward that shows (see blue line) a clear warming trend across Colorado.

Like Bolinger, he points out the lesser variability of recent decades. “The big variations start to go away in the last 30 to 50 years,” he observed.

Climate Central illustrates how a small change in average can produce a big change with this bell curve animation.

There’s been a national trend for more rain in lieu of snow. This has been true even of Denver, according to a 2016 running of the numbers.

At the State Climatologist’s office in Fort Collins, Bolinger says she is not surprised to see some areas of Colorado with little-to-no warming trend during winter.

“Other areas of the country have seen much more pronounced warming in the winter months. For Colorado (and specifically Denver County), more pronounced warming trends are occurring in the summer and fall months.”

What can be said about Colorado’s higher country? Not all that much, because the long-term temperature records are so scant. But in a general way, climatologists know that those places that are coldest tend to warm at a more rapid rate than those are already warm, says Sublette.

“Alaska is warming twice as fast as the rest of the world because it’s so much colder than the rest of the world.”

It stands to reason, he went on to say, that Colorado’s ski resorts are warming more rapidly than, say, the Front Range urban corridor.

“As a general rule, the colder places and higher elevations are going to be warming a little faster than the lower elevations,” he said, but added: “There are always going to be variations.”

In Fraser, you can still see block heaters used to warm engines on cold nights. That wasn’t enough for Kirk Klanke when he was in the construction business. Getting started in the morning was an ordeal. It wasn’t enough to put a block heater on a pickup or car. The oil would freeze. That means steel-on-steel for the first few minutes of operating a vehicle. “You can wear out a motor pretty quickly that way,” he points out.

Instead, he used a 10-inch culvert under the pickup through which he used a weed burner to blow heat and warm the drive train.

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Last winter it got to 25 below, he says, but that was the coldest it has been in several years.

If formal records have not been continuous, the evidence of warming became profound in the early part of this century with the bark beetle epidemic. Before, points out Klanke, forests lost about 10% of trees during a bark-beetle epidemic. The deep, cold winters kept the beetles in check. But in the early 21st century, with the warm winters, the beetle populations exploded.

Just to the west of Fraser, in the Williams Fork Valley, where the northern Colorado’s bark beetle epidemic first flared in 1996, a fire this year burned 15,000 acres.

(This writer can personally testify to some of that cold. In January 1979, he arose one morning when living in Kremmling to a temperature of 62 below zero on the thermometer of Bob Shay’s Phillips 66. A Colorado record was set that morning, but elsewhere in Colorado).

Allen Best
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