There’s a new definition of "normal” for weather and climate in the US – and it tells us a fair amount about how the climate crisis is changing our planet.
The new normal was announced by the National Oceanic and Atmospheric Administration (NOAA) earlier this month to reflect the recent changes seen in weather and climate data seen over the course of the past 30 years. The US Climate Normals collection has 10 versions based on 30 year periods: 1901-1930, 1911-1940, 1921-1950, 1931-1960, and so on. The latest denotes the “normal” conditions seen from 1991-2020.
The new normals are used as a basis for judging how daily, monthly, and annual climate conditions compare to what’s "normal" for a specific geographic area. In other words, when the daily weather report on the news says “it’s 2 degrees above a typical June day for Chicago,” for example, their idea of normal will be different from the previous normal, which was 1981-2010.
The changing face of the new normal can be best seen in the image below. The sharp rise in temperatures has become increasingly obvious in the latter half of the 20th century. Since the 1970s, we’ve increasingly seen more above-average annual temperatures in the US. This trend continued between 1981-2010, but above average annual temperatures now dominate the map of the US. This is the general picture across the US, but the reality is a lot more complex as these changes were not seen uniformly across the country. For instance, parts of Montana, the Dakotas, and Minnesota have seen temperatures are somewhat cooler than those based on 1981–2010, especially in the late winter and spring seasons.
While these leaps in temperature might not sound vast, they have had some profound effects in regards to extreme weather events like heatwaves, droughts, wildfires, floods, and hurricanes, all of which have hit the US in recent years.
The US has also seen a startling rise in rain and snow in recent decades. The last four 30 year periods – the 1961-1990, 1971-2000, 1981-2010, and 1991-2020 Normals – were the four wettest three-decade periods seen in the NOAA data. Once again, these changes are not uniform across the US. For example, the Southwest has generally become drier unlike the rest of the country.
However, the word “normal” may be a tad misleading since all of these trends are far from normal. Instead of being produced by achingly slow natural processes, the trend is being driven by human activity, primarily the release of greenhouse gases and their warming effect on Earth.
“It seems odd to still call them normals because 1991-2020 was anything but normal climate-wise,” North Carolina’s state climatologist Kathie Dello told the Associated Press.
For this reason, some climate scientists do not like this system of reporting “new normals” as it downplays the severity of the situation at hand and normalizes climate change. Nevertheless, when the past decade’s idea of normal looks distinctly different from the normal of 50 years ago, it’s clear the planet has undergone some serious and rapid changes.