Greenup hit Sunday, going full spring in one day. 

The trees turned green in Fairbanks early Sunday.

Elsewhere in America the change is a good deal more gradual, but here it’s as if someone flipped a light switch. Hillsides of aspen and birch that were brown on Saturday morning underwent a metamorphosis by Sunday. It would be different if we had dozens of varieties of trees, but these two debut in spring all at once.

“It’s green-up day in Fairbanks,” meteorologist Rick Thoman wrote on Twitter Sunday. He said the Fairbanks office of the weather service “has called green-up on Chena Ridge as occurring Sunday May 10.”

It is the proper occasion to write of and remember Jim Anderson and Ted Fathauer. We can thank these two long-departed scientists and Thoman for the unique climate record known locally as Greenup Day. It happens all of a sudden during the 19-hour days, with the carpet of leaves turning more vibrant by the hour.

Anderson, a pollen scientist, worked at the Institute of Arctic Biology on the West Ridge of the University of Alaska Fairbanks and had many interests in life. A man of endless curiosity, he collected 700 sport coats, 7,000 neckties, 12,000 books and 25 typewriters during his 66 years.

He was compulsive about many things, which made him a better scientist.

“One of those compulsions for Anderson was the study of a small airborne irritant that each spring makes life miserable for one in five northern people: pollen. For years, he sampled pollen with a mechanized air-sniffer on the roof of the Arctic Health building on the UAF campus. By being meticulous in counting the pollen grains trapped on the clear film of his samplers, Anderson came up with a pollen calendar for Fairbanks, and later Anchorage. His calendar shows that birch trees in both cities release the most pollen — up to 4,500 grains per square meter of air — from May 10 through the 20th,” writer Ned Rozell said in a brilliant 2007 obituary.

Starting in 1974, Anderson began taking note of the day that Chena Ridge took on a green hue as seen from outside his office at UAF. He wrote down these eyeball estimates on his calendar year after year, often consulting with marine scientist Bob Elsner to see if he agreed.

“I look across at the hillside from West Ridge and look for that day when the first faint flush of green appears in the canopy,” he said when I talked to him 20 years ago. “Often it may be brown in the morning and show faint signs of green by the end of the day.”

“It wasn’t as definite as we’d like to see this year and it’s been somewhat delayed by the cool weather in May,” he told me on May 17, 2000 after the first colors came into view.

Anderson had memorized a quarter-century of exact Greenup Day dates up to that time. I know this only because when I interviewed him he mentioned that in 1983, the leaves popped out on May 11. Impressed by this, he replied, “It’s just a very small data set.”

While Anderson cataloged the landscape from the West Ridge, a few miles away, Fathauer, a meteorologist at the National Weather Service, began doing something similar. He kept track of the scene as viewed from his place on Chena Ridge. His Greenup Day calls were often one or two days behind those of Anderson.

The process of determining this day in advance is a bit like predicting the Nenana Ice Classic or picking the perfect day to take off your snow tires. In 1998, Fathauer and Rick Thoman developed a formula to predict Greenup Day that included spring temperatures and other information. Thoman has continued to work on the formula, with recent assistance from Jan Dawe.

On April 20, the forecast was that the trees would transition from May 9-12. It happened on May 10.

Thoman and Fathauer shared the compulsion for studying climate and weather. Fathauer went back to school for seven years and completed a master’s degree in 2012, writing “The Relation of Spring Pollen Release to Weather in Fairbanks, Alaska.”

When he told me about his idea of getting a doctorate as his retirement project, he could barely contain his excitement. Having just completed a master’s degree within the absolute maximum time allowed, he said he was ready for a new challenge. He died in early 2013, after a lifetime of studying the weather.

I’ll never forget the 40-below afternoon in 2006 I spent with Fathauer, who wasn’t wearing a winter coat, traveling around Fairbanks to find the most accurate and inaccurate bank and store thermometers.

Fathauer said that when he arrived in Fairbanks in 1970, “I thought I had found paradise on earth and I still believe that.”

It’s interesting that Anderson once said something similar about the Goldstream Valley. “It’s heaven out there,” he said.

This piece originally appeared in Dermot Cole’s blog, Reporting From Alaska, at He can be reached at