We are scientists who study how humanity is adapting to the effects of climate change. While some effects are characterized by sudden and catastrophic events — recent hurricanes, wildfires, floods — most of the change is happening gradually via a steady deterioration of conditions year-over-year, decade-over-decade. This pace of change helps us adapt by providing at least some time for our economic, political and social systems to respond.
However, the pace of our changing climate may also come with a downside. It may be easy for humans to normalize a climate that is, at least on geological-time scales, rapidly and dramatically changing.
The metaphor of the boiling frog has long been used to describe this potential risk. If a frog is placed into an already heated pot, the fable goes, it will immediately jump out. If, however, the frog is placed into a cool pot that is slowly heated, the gradually climbing temperature will fool the frog into thinking conditions are not changing, and it will eventually be cooked.
Science tells us that this story is false, at least for frogs. But might it apply to humans? Along with our co-authors, Flavio Lehner and Patrick Baylis, we recently found evidence that humans may in fact be strikingly similar to the fabled boiling frog. Our work was published Monday afternoon in the Proceedings of the National Academy of Sciences.
Using billions of U.S. Twitter posts, we were able to measure the remarkability of different weather. Commenting on the weather is an age-old and ubiquitous characteristic of human society, but the type of weather that gets talked about varies from place to place and over time. One-hundred-degree temperatures are expected in Phoenix in June. The same temperatures, however, would excite considerable discussion if they occurred in January instead of June, or in Seattle instead of Phoenix.
Discussions on Twitter clearly reflect that people comment more on the weather when it is different from normal. But disturbingly, people seem to have short memories when it comes to determining what kind of weather is “normal.” While people do tweet about unusual temperatures (a particularly warm March in New England, for example), this effect quickly disappears if the same weather persists year after year.
We estimate that it takes five years for changes in temperature to become completely unremarkable. In other words, on average, people in the United States are basing their idea of normal weather on what has happened in the last handful of years.
Worse yet, we find that the effects of temperature on emotional states persist — hot temperatures make us grumpy — even while we remark less about these unusual temperatures. We’re not fully adapting to the costs of unusual temperatures; we’re just becoming accustomed to them.
The implications for climate change are clear and alarming. If emissions are not rapidly cut, warming over the next century will exceed that of the last half-million years. But if we ignore weather and climate events that happened more than five years ago, even the changes we notice will seem small. As with the apocryphal frog, the gradual pace of change combined with our rapid adaptation of expectations could deceive us into thinking that our changing climates are not changing much at all, that they are normal. They are not.
Devoting sustained attention to changing bad habits can be difficult, but people can and do change from couch potatoes to marathon runners. Let’s be aware of how we collectively become accustomed to our new climates. Let’s act to check our own perceptions against the raw facts of climate change. Let’s be vigilant against the normalization of worsening environmental conditions. And, most important, let’s jump out of the pot.