Climate vs. Weather: How Anecdotal Evidence and Confirmation Bias Influence Our Perception of Climate Change

By: Dan Conant

In the midst of another mild winter in the Northeast U.S., the news reports of “warmest ______ on record” are starting to emerge after our planet experienced its warmest January on record.[i]  This blog entry considers how a person might evaluate their personal experience of changing weather patterns, and whether those experiences may be indicative of a changing climate.

Following the warmest January ever recorded, articles are being published proclaiming the arrival of anthropocentric-influenced climate change.[ii]  Climate change skeptics will quickly counter this narrative by pointing to the fact that anecdotal[iii] weather evidence, such as a single warm month, is not sufficient scientific evidence to support claims of climate change because local weather phenomena cannot be equated with climatic changes.[iv]  However, both skeptics and believers in anthropocentric-driven climate change are quick to point to weather fluctuations to support their positions,[v] resulting in counterclaims of confirmation bias.[vi]

The difference between weather and climate is substantial, but long-lasting weather patterns play an important role when evaluating climate.  Weather is categorized as short-term (minutes to months) atmospheric changes and commonly includes conditions and measurements of temperature, humidity, precipitation, cloudiness/brightness, and wind.[vii]  On the other hand, climate is a description of the long-term pattern of average weather over time and space in a particular area.[viii] More generally, climate refers to the type of weather that a person might expect for that location at that time of year.[ix]  When considering climate conditions of an area, scientists will evaluate average precipitation, temperature, humidity, wind, and other measures of weather.[x]  Some scientists define climate as the average weather as taken over a 30-year span.  With the aforementioned in mind, one might wonder whether their own anecdotal evidence of changing weather patterns might be corroborated by scientific evidence, and therefore be able to refute counterclaims of confirmation bias from the skeptics.

Born in 1989, the author grew up in the Northeast United States and was accustomed to long and cold winters made bearable by the activities that the weather brought, and summers that were generally hot and sweaty.  The author has no vivid memories of significant change during the summer months; the author remembers it being hot and sweaty from June through September.  On the other hand, in the author’s early years (circa 1993-2006), ponds and lakes would freeze as early as mid-December, and in January bodies of water were typically safe for ice skating and pond hockey.  The snow levels varied year to year but the local ski hills in New York, Connecticut, and Massachusetts seemed to always have coverage by mid-January as well.  Last month, the author was home and noticed those same ponds and lakes were not frozen, and a quick trip to the Catskills (in Massachusetts) for a day of skiing showed that the local ski mountains had poor snow coverage.  Although the author is a firm believer in maintaining objectivity and approaching everything with a healthy dose of skepticism, he sides with the majority that anthropogenic climate change is real.[xi]  The question remains; is there any data to support the author’s perceptions of changing weather patterns over his 30-year existence, and if so, are they indicative of a changing climate?

Although data and analysis perfectly corresponding to the author’s lifetime is not readily available, data and analysis from a recent 30-year period has been analyzed.  From the period of 1986-2016, the annual average temperature in the Northeast United States increased by 1.43 degrees Fahrenheit relative to 1901-1960.[xii]  The author’s anecdotal evidence of warmer winters may also have some merit; as of 2016 the five warmest winters have all occurred in his lifetime, with 2016 being the warmest.[xiii]  Since the 2016 Climate Report, the 2016-17 winter (Dec.-Feb.) was the 5th warmest for the Northeast, 2017-2018 was the 34th warmest, and 2018-2019 was the 30th warmest.[xiv]  If the 2019-2020 winter continues with its record-setting warmth, it could find itself among the ranks of the warmest winters.  Regarding the author’s observations of reduced snow coverage during his period of existence, researchers who mapped changes in snow mass from 1982 to 2016 found very little decrease in snow mass in the Eastern U.S., but did find that the snow season shrank by 34 days.[xv]  The researchers found that the reduction in snow season was primarily driven by a late beginning to the snow season.[xvi]  This somewhat corroborates the author’s observations that there has been less snow coverage in January.  Ultimately the author’s memories of changing weather patterns are not strongly supported by scientific data to confirm suspicions of rapidly changing climate due to anthropogenic activities.  Going forward the author will remain diligent in observing the world around him and wondering whether he is experiencing any perceptible change, and whether that observed change is supported by scientific evidence.

Image from CBC

Image: Kate Letterick, People in Moncton Warned Not to be Fooled by Apparently Frozen Ponds, Lake, CBC News (Dec. 24, 2019, 3:54 PM).

[i] Matthew Cappucci, ‘The Warmth is Really Unheard of’: Europe Just Posted its Warmest January on Record, Washington Post (Feb. 4, 2020), https://www.washingtonpost.com/weather/2020/02/03/warmth-is-really-unheard-much-eastern-europe-including-helsinki-moscow-saw-warmest-january-record/.

[ii] Id.

[iii] Anecdotal Evidence,  Rationalwiki.org (Feb. 3, 2019), https://rationalwiki.org/wiki/Anecdotal_evidence.  For the purposes of this blog entry, anecdotal evidence is primarily references personal testimony and experiences that persons have had due to weather-related events.

[iv] Tom Zeller, Is It Hot in Here? Must be Global Warming, The New York TImes (July 31, 2010), https://www.nytimes.com/2010/0801/weekinreview/01zeller.html

[v] Id.

[vi] Center for Research on Environmental Decisions, Columbia University, The PsyChology of CLimate Change Communication 4 (Andria Cimino, Oct. 2009), https://coast.noaa.gov/data/digitalcoast/pdf/psychology-climate-change-communication.pdf. Confirmation bias “makes people look for information that is consistent with what they already think.”

[vii] Brian Dunbar, NASA – What’s the Difference Between Weather and Climate?, NASA.gov (last updated Aug. 7, 2017), https://www.nasa.gov/mission_pages/noaa-n/climate/climate_weather.html.

[viii] Id.

[ix] Id.

[x] Id.

[xi] Earth Science Communications Team, NASA’s Jet Propoulsion Laboratory, Scientific Consensus: Earth’s Climate is Warming, Climate.NASA.gov, (last updated Jan. 28, 2020), https://climate.nasa.gov/scientific-consensus/.

[xii] U.S. Global Change Research Program, 2017: Climate Science Special Report: Fourth National Climate Assessment, Volume I 187 (Wuebble et. al. (eds.)), https://science2017.globalchange.gov/downloads/CSSR2017_FullReport.pdf

[xiii] NOAA National Centers for Environmental Information, State of the Climate: National Climate Report for February 2016 (March 2016), https://www.ncdc.noaa.gov/sotc/national/201602.

[xiv] Climate At a Glance: Regional Rankings, NOAA.gov, (last updated Jan. 2020), https://www.ncdc.noaa.gov/cag/regional/rankings/.

[xv] Xubin Zeng et. al., Snowpack Change From 1982 to 2016 Over Conterminous United States. Geophysical Research Letters (Dec. 2018), https://www.sciencedaily.com/releases/2018/12/181212093320.htm

[xvi] Id.

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