Jan 6, 2021 - Energy & Environment

"Shifting baselines" are changing what normal means

Illustration of a weathervane with a globe on top
Illustration: Sarah Grillo/Axios

Scientists this year will update how they calculate average temperatures, altering our reference point of a "normal climate."

Why it matters: What we think of as normal in life — whether in climate, politics or society — is always changing due to what's known as the "shifting baselines syndrome." Because we often miss those changes, we end up with a warped image of the present that shapes our policies and our future.

What's happening: This spring the National Oceanic and Atmospheric Administration will update its calculation of average temperatures and precipitation.

  • "Normal" high and low temperatures and precipitation — the figures you might see on a daily weather report — are drawn from weather data over a 30-year period, a practice that has been maintained for over a century.
  • Every decade forecasters shift to a newer 30-year data set. Over the past decade that meant 1981–2010, but beginning this year averages will be calculated from 1991–2020.

Because 1991–2020 was warmer than 1981–2010 in nearly every part of the U.S., the update means what we classify as normal temperatures now will actually be higher than just a year ago, because the baseline for what's considered normal has shifted.

Background: The term "shifting baselines" was coined in 1995 by fisheries scientist Daniel Pauly in what became a landmark paper.

  • Pauly was writing about the efforts of fisheries science to determine what was a sustainable catch level for commercial fish.
  • The problem, as Pauly wrote, was that "each generation of fisheries scientists accepts as a baseline the stock size and species composition that occurred at the beginning of their careers, and uses this to evaluate changes."
  • By the time the next generation of scientists began their career, those stocks had declined because of overfishing. But instead of including that decline in their measurements, the new generation of scientists treats the reduced stocks as the new baseline.

Once you've awakened to the concept of shifting baselines, you begin to see it everywhere, from the effects of climate change to our gradual accommodation to COVID-19's once unthinkably high death count.

  • Shifting baselines syndrome is an example of amnesia in action, whether taking place over the course of generations, as Pauly described with fisheries scientists, or even within an individual's lifetime.
  • A 2009 study found evidence of generational amnesia among hunters perceptions of prey species populations in Gabon to perceptions of bird population trends in the U.K. In each case, the researchers found people weren't able to fully perceive the decline that was happening because "younger generations are not aware of past biological conditions."
  • A study published last year looked at Twitter to see how people reacted to unusually hot or cold days. Researchers found the baseline for "normal" was weather that had been experienced just two to eight years before — hardly long enough to accurately perceive the changes wrought by global warming.

Be smart: In essence, shifting baselines syndrome results from one of the fundamental aspects of human psychology: our remarkable ability to adjust to circumstances, whether good or bad.

Of note: Some climate scientists have urged weather agencies to fight shifting baselines by sticking with a static 30-year time period when calculating weather averages, rather than updating the reference period every decade.

The bottom line: If we lose our way among shifting baselines, we lose our ability to value what we've accomplished in the past and fight for what we want to save in the future.

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