New US climate normals show the fingerprints of global warming

NOAA has released their latest 30-year climate normals for the United States, which now covers the period from 1991 to 2020. This replaces the previous period, which was 1981-2010.

Measuring against the 20th century climate averages, we can clearly see the impacts of climate change on these latest sets of 30-year normals.

Image courtesy NOAA.

As you can see, the latest 30-year temperature departures are the highest since the start of the 20th century. The warming trend is striking, especially over the past 40 years or so.

Clearly, the greatest warming has taken place across the northern and western third of the country.

Image courtesy NOAA.

In terms of precipitation, the most recent 30-year climate averages indicate that the Plains, Midwest and Northeast have been trending wetter. This is especially true across the Upper Midwest, which as also seen an uptick in snowfall.

Unfortunately, earlier predictions that drier climates would trend even drier due to climate change appear to be correct, at least in the southwestern U.S.

As the Southwest gets even drier, there is less moisture to evaporate, which allows more of the sun's energy to go directly into heating the surface, which also helps to explain the rapid warming in this region.

We have not seen the latest 1991-2020 planting zone update, but based on the latest temperature data we can be pretty confident that there will be another shift northward with the zones, especially in the northern half of the country, just like we saw from the 1971-2000 period to the 1981-2010 period (see below).

1971-2000 planting zones

1981-2010 planting zones. Images courtesy NOAA.