New National Oceanic and Atmospheric Administration (NOAA) climate “normals” set for release in May will reflect weather trends from the past decade. Haines likely won’t see much of a shift, but for Alaska, the new normals will reflect rising temperatures that have characterized the past several decades.
At the start of each new decade, NOAA updates its 30-year weather averages, the baseline for what climate scientists call “normal” in a given region, to include the most recent decade. In 2021, this means the new weather averages will be based on data collected between 1991 and 2020 (instead of 1981 through 2010).
“We often use language like ‘warmer than normal’ or ‘more precipitation than normal,’ and (the 30-year average) is the ‘normal’ we are referring to,” climate expert for the National Weather Service in Juneau Rick Fritsch said.
Scientists are anticipating the new normals will reflect the warmer weather that has characterized the past 10 years. The period 2011-2020 was the hottest decade on record in the U.S.
“At the beginning of a new climate normal period, like what we are about to experience, it is quite common to see monthly conditions close to those new normal averages. By the end of that ten-year period, it is much more common to see monthly values warmer than normal. This is a result of our current, steadily warming climate,” Fritsch said.
In Haines, the climate trends are less pronounced, though data for the area is spotty and inconsistent for decades prior to 2000.
“Haines high temperatures appear to have been holding steady or getting slightly cooler on the hundred-year and the thirty-year time scales,” said local meteorologist Jim Green, who monitors the cooperative climate station in town. “Low temperatures appear to be getting slightly to somewhat warmer.”
Haines experienced a period of anomalously warm winters between 2013 and 2018, according to Haines Avalanche Center director Erik Stevens. He said the trend was associated with a variety of factors including high pressure over the West Coast, a decrease in arctic sea ice and routine oscillation in Pacific Basin temperatures associated with sea surface temperature patterns.
Green said Haines weather trends, which are based on “less than ideal” records, suggest average high temperatures will be a few tenths of a degree cooler than those for the previous 30-year average, and low temperatures will be a few tenths of a degree warmer.
“Since the highs are steady to slightly cooling and the lows are warming, I expect the mean temperature will likely not change much at all with the new normals,” Green said.
He said precipitation data for the area is even more unreliable. “There may be a change in the normals, but it might not be accurate or trustworthy.”
Alaska, as a whole, is one of the fastest warming regions of the globe. Statewide, the average temperature increased by 4.0 degrees between 1949 and 2018, with the greatest increases occurring in winter temperatures and in the arctic, according to the Alaska Climate Research Center. Warming in Southeast has been less pronounced during the same time period with 2.5- to 3.5-degree changes recorded in various communities in the region.