The National Oceanic and Atmospheric Administration published the new U.S. Climate Normals in July, and data shows that warming temperatures in Southern Southeast Alaska have reduced annual snowfalls and increased annual rainfalls.
In a phone interview Friday, National Weather Service Juneau meteorologist Cody Moore explained that “Our climate normals are calculated for a 30-year period, and so, every decade they are updated.”
He noted that the old normals were calculated for the period from 1981 to 2010. The new normals are calculated from 1991 to 2020.
Data from the National Weather Service in Juneau show cumulative precipitation normals in the pre-2021 period as noticeably lower than the new normals calculated for Southeast Alaska.
Data found at www.ncei.noaa.gov/news/noaa-delivers-new-us-climate-normals shows that the new normals are set at an 8.29-inch annual increase in precipitation at the Ketchikan International Airport for the 1991 to 2020 period, in contrast to the 1981 to 2010 period.
Moore discussed the phenomenon.
“This is a trend that we’ve been noticing over the past few decades, that the average precipitation across Southeast Alaska is increasing — mainly with rainfall,” he said, adding that “snowfall — average snowfall — has been decreasing while rainfall has been increasing, especially in the December timeframe, obviously, winter time.”
When asked if this is a phenomenon meteorologists expect to see related to climate change, he answered that yes, temperatures also have been increasing slightly.
“With warmer temperatures, it is expected that precipitation events will be heavier as well,” he said. “You have more energy in the atmosphere, they’re stronger, so it just makes sense that your normal precipitation will be going up as well.”
Moore pointed out that in Southeast Alaska, however, temperatures haven’t been rising as fast as they are in Interior Alaska or in the Arctic.
“We have a very marine environment here, so we’re influenced heavily by the ocean, so our temperatures don’t rise nearly as drastic as other portions of Alaska,” he said, but added, “however, there is a noticeable difference, when you have temperature rises of upwards of one degree” within the 30-year window of when normals are calculated.
“We’re seeing a lot more record highs in the summer, warmer temperatures in the winter, more rain rather than snow in the winter, so even though it’s small increases in temperature, they do make a big difference,” Moore said.
He said that around Southeast Alaska, areas have warmed from about one-half degree to about 1.5 degrees since 1981.