5 May 2021   Leave a comment

The National Oceanic and Atmospheric Administration (NOAA) has released a report on new “normals” for temperature and precipitation in the US. NOAA determines these normals for thirty-year periods and assesses current conditions with those periods. NOAA explains:

“U.S. Climate Normals are designed—and best-suited for—better understanding what is happening today. Rather than assess long-term climate trends, Normals reflect the impacts of the changing climate on our day-to-day weather experience. Normals are not merely averages of raw data. Thirty years of U.S. weather station observations are compiled, checked for quality, compared to surrounding stations, filled in for missing periods, and used to calculate not only averages, but many other measures. These then provide a basis for comparisons of temperature, precipitation, and other variables to today’s observations.”

The procedure is designed to help us make the distinction between weather and climate. We experience weather on a daily basis but climate is far less observable except over a long period of time. I have little difficulty in asserting that the climate today is different from when I was 12 years old (in 1961): spring comes earlier for me and winter starts a little later. I am pleased that NOAA agrees with my clearly unscientific assessment:

“The 1981–2010 average temperature for the contiguous U.S. was 52.8°F while the new average temperature for the contiguous U.S. for 1991-2020 is 53.3°F. The new normals period, 1991-2020, is the warmest on record for the country. But warming is not ubiquitous across the contiguous U.S. in either geographic space or time of year. Changes vary from season-to-season and month-to-month.

“For instance, the north-central U.S. Temperature Normals—for those in the Northern Plains and Upper Midwest—have cooled from 1981–2010 to 1991–2020, especially in the spring. The South and Southwest are considerably warmer. Normals were also generally warmer across the West and along the East Coast. Precipitation-wise, the Southwest was drier; wetter averages emerged in the U.S. east of the Rocky Mountains, especially the Southeast in the spring.

NOAA presents its data graphically

The distinction between weather and climate is important. Europe experienced the coldest April in decades this year. Nonetheless, the trend toward warmer climate continues. European temperatures were the highest ever recorded in 2020:

“2020 was Europe’s warmest year to date, as temperatures rose by almost half a degree above previous records. Across the entire continent, mean temperatures exceeded the 1981-2010 average, with parts of northern and eastern Europe being more than 2°C warmer. The same regions had higher than average daily minimum temperatures, while France and Benelux countries saw higher daily maximum temperatures.

“’We’ve had some periods of exceptionally high temperatures, heatwaves in summer and a warm spell in autumn, though they were not as intense, widespread and long-lived as in recent years,’ says Dr. Francesca Guglielmo, senior scientist at the Copernicus Climate Change Service (C3S) and one of ESOTC report’s co-authors.

“The most striking temperature anomaly was last winter. Cold season temperatures rose on average about 1.9°C above the previous record and 3.4°C above the average for 1981-2010, in what C3S scientists deem ‘an exceptionally warm’ winter. ‘The number of days in which the temperature stayed below zero throughout the day illustrates this warming,’ says Dr. Freja Vamborg, senior scientist at C3S and lead author of the report. ‘Whether you have a freezing or non-freezing situation in a certain location, it makes a big difference.’”

Posted May 5, 2021 by vferraro1971 in World Politics

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