Expert: 'Normal' climate data lags behind rapid change


ANCHORAGE, Alaska (KTUU) - It's common to hear meteorologists to say temperatures or rainfall are either above or below "normal," but in less than two years what's considered normal will change.

Per international standard, climate normals are created using 30 years of climate data, but new normals are only created once every decade.

However, the environment is warming so fast that the method used to determine normals is lagging behind, one climate researcher says.

"What we're finding right now is even using this small window of 30 years that has ended just a few years ago, that is actually a previous climate regime. We're already in a different climate regime," UAF climate research Brian Brettschneider said.

A data set ranging from 1981 to 2010 has been the basis of normal temperature and precipitation for 100 months. In that time Utqiagvik has seen 82 months with an above normal temperature. Weather observation sites at 10 other areas across the state saw 70 to 79 months with above normal temperatures.

"What we've found globally, at any given location, two-thirds of the months have been above this normal, this 1981 to 2010 period," Brettschneider said.

Climate normals differ slightly from the arithmetic mean average for a specific date. They are meant to give a snapshot of the current state of the climate. The thirty year period was selected to be big enough to capture the current climate state, but not so big as to capture multiple climate states.

"The normal as we like to think of is the current state of the climate, they're behind the curve already. As soon as they come out, they'll be fairly representative, but they'll quickly, assuming things keep warming as they have been and there's no reason to think that they won't, they'll become somewhat obsolete fairly quickly." Brettschneider said. "We're in a new regime by every possible metric. Whether its looking at snow, or temperatures or permafrost melt, whatever. We're in a new climate regime and there's really no way to effectively say this is what normal is by looking at history."

When new normals are computed in early 2021, Brettschneider says communities in Alaska near sea ice will see the largest normal temperature increase.

"Everywhere from Bristol Bay northward through Norton Sound and Kotzebue, and then all the way to the North Slop communities, we're looking at on an annual basis, perhaps four to five degrees warmer. That's just tremendous, a tremendous change in basically taking out the 1980s and adding the 2010s," Brettschneider said. "I wouldn't say unexpected, but really unprecedented change in such a short amount of time."

Brettschneider says a new approach is needed when looking at climate data to make important decisions.

"So a lot of times when we analyze this data, we kind of put an asterisk next to it and say 'this is the normal, but the normal is already not normal anymore," Brettschneider said. "We really need to kind of think about it in terms of what's happening right now, the very recent past and very short term projections."

Copyright 2019 KTUU. All rights reserved.

Comments are posted from viewers like you and do not always reflect the views of this station. powered by Disqus