US winter one month shorter

Straws Lane, Macedon Ranges (Victoria) this July

You can clearly see how the world is warming using average temperatures or the temperature anomaly, as calculated by NASA, NOAA, Berkeley Earth, of the 3 or 4 other organisations which make the effort.  But you can also see global warming in how much later the winter begins and how much earlier summer starts. 

In the southern hemisphere, mid-winter is in the middle of the year.  Autumn is in March and spring in September.  When we first moved here 25 years, the first frosts came in the last week of April, the first warm day in mid-October.  Now the first frosts don't come till early June and the first warm day comes in early September.  But that isn't very scientific: we need to know the average and we need to properly measure the data.  This winter for example was a lot like it was 25 years ago: we got snow down to 600 metres.  We haven't had that for a long time.  Does it mean global warming is over? Prolly not.

Somewhat more scientific than my impressions:  using records from 700 weather stations, NOAA has calculated that winter in the USA is on average 1 month shorter than it was 100 years ago.

The trend of ever later first freezes appears to have started around 1980, according to data from 700 weather stations across the US going back to 1895 and compiled by Ken Kunkel, a meteorologist at the National Oceanic and Atmospheric Administration’s National Centers for Environmental Information.

Kunkel compared the first freeze from each of the 700 stations to the station’s average for the 20th Century. Some parts of the country experience earlier or later freezes every year, but on average freezes are coming later.

The average first freeze over the last 10 years, from 2007 to 2016, is a week later than the average from 1971 to 1980.

This year, about 40% of the Lower 48 states have had a freeze as of 23 October, compared to 65% in a normal year, according to Jeff Masters, meteorology director of the private service Weather Underground.

In Ottawa, Illinois, the average first freeze for the 20th century was 15 October. The normal from 1981 to 2010 based on NOAA computer simulations was 19 October. Since 2010, the average first freeze is on 26 October. Last year, the first freeze in Ottawa came on 12 November.

Last year was “way off the charts” nationwide, Kunkel said. The average first freeze was two weeks later than the 20th century average, and the last frost of spring was nine days earlier than normal.

Overall the United States freeze season of 2016 was more than a month shorter than the freeze season of 1916. It was most extreme in the Pacific Northwest. Oregon’s freeze season was 61 days – two months – shorter than normal.

[Read more here]