It’s likely at some point you have heard a newscaster or meteorologists say, “temperatures today were 10 degrees above or below normal.”
But what is normal, especially around New England?
Meteorologically, our weather normals come from 30 years of data of high, low, and average temperatures that are compared to the weather of the day. Our normals are updated once a decade and this week we got a new set of data.
Writing about 30-year normals might seem a bit mundane but it’s super important to understand what’s going on with the atmosphere on a long-term basis. When NOAA releases these normals it gives us an opportunity to look at trends and things are definitely trending warmer.
Since we just flipped to the new set of numbers this week it’s likely that there will be fewer days of above-average temperature in the next couple of years. The reason for this is that we’re going to be comparing the daily weather to the new, warmer set of normals so it’ll take a while before we start seeing the average increase again. By the end of the decade, the data from the 1990s will probably statistically be significantly cooler than the first 30 years of this century.
Blue Hill in Milton has the longest continuous weather observations at a single site in the country, providing a long run of data to consider.
The newly released averages for Blue Hill are about a half a degree warmer than those from 1981-2010. Precipitation is virtually the same, although the gaps between rainfall may be increasing as is the amount of rain when it does rain. In other words, the way we receive our annual allotment of rain and snow is different and this has implications for water management, farming, and even home gardeners.
Average temperatures across nearly all areas of the country for most seasons are now warmer than they were a decade ago.
When we look back at the past 100 years, the warming is particularly evident. Pay particular attention to the last three sets of data below and note the warming accelerating.
These new climate normals will be evaluated and expanded for other data sets over the coming months. Already we can use these new numbers to illustrate just how much our climate has changed.
One of the glaring examples is up in Fairbanks, Alaska, categorized as a subarctic region for decades.
Climatologists use the widely accepted Köppen classification for different areas of the globe — Greater Boston is hot summer humid continental, for example.
In Fairbanks they are now categorized as warm summer continental climate, and no longer subarctic, as of this week’s data release.
If that doesn’t illustrate a changing climate to you nothing will.
It's official: just-released @NOAANCEIclimate 1991-2020 normals, Fairbanks Aiport no longer a sub-Arctic climate in the widely used Köppen classification. Now a "warm summer continental" climate. Change because the May normal temp went above 50F (10C). #akwx @Climatologist49 pic.twitter.com/tFPo1fCnUq— Rick Thoman (@AlaskaWx) May 4, 2021