Tuesday, June 20, 2023

NYC is showing its (warming) stripes

 It’s finally here, the 3rd and final “first day of summer”, otherwise known as the summer solstice. As we discussed a few weeks ago, many people consider Memorial Day to be the unofficial start of the season, and June 1st is the start of meteorological summer. But in climate science, today is also "Show Your Stripes Day". Your favorite TV meteorologist might show a version of the graphic below in their weathercast today, or perhaps it's prominently displayed in one of their social media posts:

The "Warming Stripes" for Central Park.
Graphic courtesy of Climate Central

These stripes represent the changing average temperature, either globally or from a single location, depending on which version is shown. The version above is from Central Park reporting station, which has been active since 1869. It’s a highly visual way to demonstrate a somewhat abstract concept: temperatures in NYC have risen quite a bit since record keeping began here. Each stripe on the graphic above represents a temperature departure from the 20th century average. The deeper blues are much colder than average, whereas the red stripes are much warmer. In this article, we’ll break down the stripes further.

Notice the concentration of red stripes on the right side of the graphic, representing an upward trend in temperatures. In fact, both 2021 and 2022 made Central Park's list of top 10 warmest years on record. Here's the full list:

Warmest Years at Central Park (1869 to present)


Temperature

Year(s)

1

57.3 

2020/2012 

2

57.2 

2016/1991/1990

3

57.1 

1998

4

57.0 

1953

5

56.9 

1949/2021

6

56.8 

2006

7

56.7

2010/2015 

8

56.5 

1999

9

56.4 

2011/2002 

10

56.3 

2017/2022

These temperatures are computed by averaging the high and low temperature for each day of the calendar year, then computing the average of those numbers. The 21st century dominates the list, even though it's only 2023. Let's compare the warmest list to the list of record coldest years in New York: 

Coldest Years at Central Park (1869 to present)


Temperature

Year(s)

1

49.4 

1888/1875

2

50.2 

1883

3

50.6 

1885

4

50.7 

1917/1893 

5

50.8 

1873

6

50.9 

1904/1887 

7

51.2 

1926

8

51.3 

1886/1872/1871 

9

51.4 

1874

10

51.7 

1882

It's basically the opposite of the record warm list, as most of these records were set in the 19th century! And putting the two datasets on the same line graph looks downright weird. See below: 


But it does bear a resemblance to the "Warming Stripes" from the beginning of this post:


2023 is on track to add another red stripe to this image. We've already had the warmest January on record in Central Park, and April will go down in history as the 2nd-warmest (the charts, last updated in 2021, are available here). If you want more information about the warming stripes, visit climate scientist Ed Hawkins' website- and for much more on global average temperature changes, Hawkins' University of Reading in England has a wealth of information on their site

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