Trees and shrubs are starting to turn green in much of Alaska. But Fairbanks is the only community in the state with an historical record tracking the green up date.
Jim Anderson, a University of Alaska Fairbanks professor, started collecting the data in the 1970s. He also came up with a lovely definition: “Birch and aspen leaves open just enough to produce a faint but distinct green flush through the forest canopy.”
These days the National Weather Service makes the call on the official green up date. And this year it was Monday, May 8th.
Alaska’s Energy Desk is checking in with climatologist Brian Brettschneider each week as part of the segment, Ask a Climatologist.
Interview Transcript:
Brian: They look at the same ridge line and the same direction and they have the same methodology every year. So it’s a really consistent record that now stretches over four decades and it’s not replicated anywhere else in the state.
Annie: Is May 8 typical?
Brian: May 8 is almost right on schedule. May 9 is the long term average. And it’s been earlier than normal for the last couple years, but the trend line is heading back toward that average date. But it can vary quite a bit. It can be as early as say April 26 and as late as May 26, so a 30 day period.
Annie: And why should we care about when green up happens?
Brian: Apart from how it changes the look of the landscape, it actually has important climate considerations. Most notably, once the leaves come out, they can transpire moisture to the atmosphere. So the amount of moisture available in the atmosphere for precipitation really goes up dramatically once those birch and aspen trees are fully leafed out. Also, if you’re an allergy sufferer, the pollen in the birch and the aspen follows quickly behind leaf out. Fairbanks has some of the worst birch pollen anywhere in the entire world and last year was a record.
Annie: And even though you don’t have records for the rest of the state, can we say anything about green up in the rest of Alaska?
Brian: It’s highly dependent on temperatures and starting in late April, the interior becomes the warmest part of the state. So they’re warming up faster than we are here in Anchorage, Juneau or in other parts of the state. So it does vary based on exposure, aspect and a few other considerations, but generally its going to occur in the central part of the state before most other places.
Annie Feidt is the broadcast managing editor at Alaska Public Media. Reach her at afeidt@alaskapublic.org. Read more about Annie here.
