On April 1st it snowed in Connecticut. Some got the joke, some didn’t. If I had a dollar for every complaint I’ve heard about our unpredictable, unreliable, unbearable spring weather…uh, I might be able to buy a tank of gas.
We had some serious snowfall in New England this winter, so I am not unsympathetic. But no one who lives here should be surprised.
That’s weather, not climate. However…this might be a surprise:
In the United States, spring now arrives an average of ten days to two weeks earlier than it did twenty years ago. Many migratory bird species are arriving earlier…. Snow cover is melting earlier. Plants are blooming almost two weeks earlier in spring.
—The Weather of the Future by Heidi Cullen
That’s climate, not weather.
Last fall, I found an isotherm map printed in a 1986 “Backyard Gardener Calendar.” I became curious about the dates of the first frost/last frost. Have planting zones migrated? Is spring coming earlier?
Pick Stamford. Twenty-five years ago the map pegged the last frost for April 15, and the first frost for October 25–about 28 weeks between them. Frost is defined as temps below 28 degrees Fahrenheit, “destructive to most vegetation.” But the probability is not given: are those dates 10%, 50% or 90% likely?
I contacted the CT State Climate Center at UConn to ask about comparable figures for this year. Would they show a two-week difference since 1986?
A climate scientist named Zhao Xue, very helpful on the phone, emailed me a raft of information, including a NOAA link for isotherm maps with data from 1951 to 1980.
The comparison with 25 years ago hinges entirely on probability.
Zhao sent me a NOAA link with freeze/frost dates for this year (U.S. Climate Normals). The “freeze free period” this year is highly likely (90% probability) to be longer than 25 weeks. And it is highly unlikely (10% probability) to be as long as 30 weeks.
Do my 1986 “Backyard Gardener” dates fall within that range? Yes they do–smack dab in the middle–50% probability.
Which is why the term “exact science” is a misnomer. Science always deals in probabilities and ranges, and is always subject to later revision.
Indeed, Zhao emphasized: “I believe the dates are based on probability calculation (from previous experience)–not on real observation.”
Whose frost first?
For some real observation, I called Ted Mankovich: computer scientist, horticulturist, photographer and mainstay of the Guilford Land Conservation Trust. Ted created a program that’s been recording the temperatures at his house every 10 minutes for the last 5 years. Who else does that?
But translating temperatures into frosts is not as simple as it sounds. We exchanged ideas, and Ted followed up with a blog post titled ‘Frost & Textures.’ Very entertaining—you can read it and see his great pictures here—but I will skip ahead to his conclusion:
We started with a question of whether I recorded the day of the first and last frost. We end with two new questions. What is your definition of first and last frost? How can you go from temperature readings to determining first and last frost? And we haven’t mentioned that frost is very territorial. My first frost isn’t your first frost even if we agree on what that is.
Groundhog Day in January!
The Union of Concerned Scientists and the town of Punxsutawney, Pennsylvania announced today that Groundhog Day will be pushed forward eight days to January 25 in 2012 in recognition of the impact climate change has had in the region.
The change is based on analysis by UCS scientists who found that, since 1997, spring has come an average of eight days earlier to western Pennsylvania.
But when I clicked through….
You just fell for an April Fool’s Day joke from the Union of Concerned Scientists! We hope you got a good chuckle out of it. But while these jokes may be funny, some people are trying to fool the public about climate change science every day of the year…
The UCS (of which I’ve been a member for some years) didn’t say whether they’ve actually documented a change in the arrival of spring in Western Pennsylvania.
I’ll give the last word to , head of the Climate Analysis Section at the : “It’s not the right question to ask if this storm or that storm is due to global warming, or is it natural variability. Nowadays, there’s always an element of both.”
Note: All photos and captions (‘cept Punxsutawney) in this post are taken from Ted Mankovich’s excellent blog Olmsted Irregulars, and used with his permission. They were taken at Olmsted Outlook: a special one-half acre parcel located on the West River that was given to the Guilford Land Conservation Trust in 1981 by Howard and Deborah Weaver. The park and other GLCT lands are cared for by the Olmsted Irregulars with Ted’s enthusiastic and knowledgeable leadership.