How about this weird weather we've been having? It's a common query around the Pacific Standard office, and for good reason: Abnormalities such as the recent cold and snow in Southern California capture pretty much everyone's attention.
Climate change is significantly increasing the chances of more unsettling weather in the years to come, including longer and more severe heat waves. But if you're hoping the strange conditions will inspire people to realize that something profoundly dangerous is occurring—and will prod politicians into acting—new research suggests you're likely to be disappointed.
An analysis of more than two million Twitter posts finds that people do indeed take note of abnormal temperatures. But it also reports that our definition of "normal" is based on recent history—roughly, the past two to eight years.
These findings suggest that, in less than a decade, climate change-induced conditions cease to seem all that unusual. That lack of historical perspective may make it hard to grasp the enormity of the changes that are already underway, and which promise to accelerate.
"This data provides empirical evidence of the 'boiling frog' effect with respect to the human experience of climate change," writes a research team led by Fran Moore of the University of California–Davis. As with the imaginary amphibian who fails to jump out of a pot of water as the temperature slowly rises, "the negative effects of a gradually changing environment become normalized, so that corrective measures are never adopted."
The researchers analyzed data on 2.18 billion Tweets originating in the continental United States between March of 2014 and November of 2016. They calculated the emotional sentiment of each using two linguistic software programs, and specifically noted those that included weather-related terms.
These findings were then matched with local weather data for the week they were posted. Average temperatures were compared with similar data from past decades.
Not surprisingly, the researchers found that people are more inclined to tweet about the weather when conditions are warmer or cooler than usual for the time of year. But this tendency "decays rapidly with repeated exposure," they write.
If Twitter postings are a good indicator of public sentiment, unusually cold temperatures "in a county that has experienced these anomalies for more than five years in a row are no longer remarkable," the authors write. This decline "occurs even more rapidly" for unusually hot temperatures.
On the surface, these results, published in the Proceedings of the National Academy of Sciences, could be interpreted to suggest that we're highly adaptable creatures who quickly adjust to a new normal. But additional evidence suggests otherwise.
By looking at the emotional content of all tweets (not just weather-related ones), the researchers found that changes in the average temperature over the preceding 10 to 15 years were associated with an increase in negative emotions. The crankiness continued "long after these anomalies have become unremarkable."
That finding suggests we haven't adapted all that well to this new reality; we've simply decided there's no point in complaining about it to our online community. And that, the researchers fret, ultimately means there is less pressure for political action.
The study does offer one piece of hope: Moore and her colleagues looked only at the effect of temperature. "It may well be that more acute extreme events such as storms, droughts, wildfires, or floods may be more consequential, and more salient, and therefore less prone to normalization," they write.
Let's hope so. Adaptability is a big reason for our species' success. It will be sadly ironic if it also facilitates our downfall.