Fireflies are turning on earlier than they used to

François Villon ended each stanza of a particular poem with “Mais où sont les neiges d’antan?” (“But where are the snows of yesteryear?”) The plaintive line has proven so resonant that its fame exceeds the poem’s.

Knowing only the famous refrain, I’d always presumed that the poem was about past winters. I’d also wondered whether Villon lived during the Medieval Warm Period , a three-century span of elevated temperatures in Europe that began in 950 AD.

In fact, the poem, which bears the title “Ballade des dames du temps jadis” (“Ballad of the Ladies of Times Past”), laments past women, real and mythological. Their finite, virtuous lives had long ended but remained in Villon’s mind like a long-remembered snowfall.

Villon himself was born in Paris around 1431, the year when one of his “snows,” Joan of Arc, was executed in Rouen. The photo shows actor Ronald Colman, on the right, as Villon in the 1938 movie, If I Were King.

By 1431 a period of lower than normal temperatures had Europe in the grip of what has been called the Little Ice Age . If Villon had chosen to write literally, not metaphorically, about past winters, he would likely have lamented their lost mildness, not their lost snowfalls.

Villon’s poem—or rather my erroneous extrapolation it—had me thinking about how I and other people perceive the effects of climate change. I was born in 1962, four years after Charles Keeling began monitoring atmospheric carbon dioxide from the summit of Hawaii’s Mauna Kea. In 1958 the concentration was 315 parts per million by volume. Now, it’s 385 ppmv.

My longest string of memories tied to one place corresponds to my 20 years in Washington, DC. In that time, the summers have seemed to become hotter and the winters have seemed to become milder. Indeed, this past summer was the hottest on record, but the winter that preceded it was the snowiest.

My strongest personal perception of climate change concerns fireflies. They now start to appear in the city’s residential streets in late May, a month earlier than I seem to recall when I first arrived in DC in 1990. Maybe I should write a poem.

Poetry aside, such personal perceptions matter. Mitigating the effects of climate change will require people to use fossil fuels far more sparingly. They might be more willing to pay for those mitigations if they knew, from their personal experience, that Earth is getting worryingly warmer.