Global warming is making summers hotter—dangerously so, and at an unprecedented rate. Heat waves, which recently shattered heat records in Europe and the U.S., are becoming more frequent, as are flash floods and wildfires.
Continuing along this path would seem to threaten summer’s reputation as a time for being outside, affecting peoples’ favorite summertime leisure activities like riding bikes, attending festivals, or taking hiking trips.
Already, less predictable fluctuations in daily temperatures and precipitation are changing how people play outside, says Casey Wichman, an environmental economist at the research organization Resources for the Future. In 2017, he and another environmental economist, Nathan Chan at the University of Massachusetts Amherst, studied how weather might affect our demand for leisure activities outdoors—things like running, hiking, or even visiting a local park. They started by looking at recreational cycling, using bike-share data from over 27 million weekend trips across North America.
Some of the results were expected: Rain and extreme cold kept people off bikes. To their surprise, though, people were overall just as willing to bike on extremely hot days. In fact, the pair did further analysis of how Americans spend their time and found that rising temperatures could actually add $20.7 billion per year to the outdoor recreation industry (today valued at nearly $900 billion) by 2060.
Is that a silver lining to climate change?
Not quite, says Wichman, who spoke with CityLab on how outdoor recreation might change as global temperatures get warmer. This interview has been edited for length and clarity.
During the mid-July heat wave in the U.S., cities had to cancel outdoor events that had been planned months in advance. New York City, for example, canceled two really big ones: the celebrity-filled OZY festival and, for the first time ever, the New York City Triathlon. Are we going to start seeing fewer outdoor events in the summer—for the sake of public safety?
I would probably anticipate that these that these festivals and these outdoor activities shift to different times of the year. This is one way that we will adapt to hotter temperatures. If you look at music festivals across the U.S., my sense is that there are a lot more in the summer in the northeast than there are in Arizona and Texas. We can learn a lot about how regions within our own country have already adapted to to extremes, and that will give us a blueprint for what we would expect for other areas.
We as humans are very good at adapting to new things, but that adaptation comes with a cost. One challenge that we economists have is to measure what the costs of climate adaptation are, and get a sense for what that means to the average person, because there are a lot of intangible things, like bringing people together in a city.
And how are we adapting, according to your 2017 study?
I don’t want to overstate what our research can say, but using the  American Time Use Survey, we looked at the aggregate level of participation in warm-weather activities. So that kind of gets rid of winter sports. But based on some aggregate data, we have evidence that warm-weather recreation will increase with warmer temperatures.
That doesn’t mean we’re hiking more in 100-degree weather, right?
Where we’re seeing a lot of action is on the “shoulder” seasons, as March and October become relatively more pleasant to go outside. That kind of induced recreation in shoulder seasons swamps any negative effect that we see during the peak summer months.
Just last weekend [during the heat wave] my partner and I rode our bikes from the southern tip of D.C. to the northern tip, and it was 95 degrees out and miserable. We didn’t go outside in the hottest part of the day; we started our ride early when it was cooler. So there’s both this kind of within-day substitution, as well as across-day substitution.
Ultimately, your study looks largely at recreational biking. How much does your study apply to other types of outdoor activities?
What we see with cycling is sort of a rosy picture. We might be able to ride our bikes more as the climate warms, but for other activities like hiking, hunting, snow sports, or potentially fishing, there are more mixed and negative outcomes.
There are also regional differences. In the hottest locations in our data set, in the southern United States, increases in extreme temperature are bad for outside activity rates. So when it gets marginally hotter in Austin, Texas, people go outside less. That’s moving from a 90-degree day to 100-degree day.
Another aspect that I’m exploring with my co-author Nathan Chan is looking at substitution among destinations. We’re looking at visitation to national monuments and memorials, as well as museums. The idea here is that, on really hot days, people substitute trips to the National Mall and the Lincoln Memorial for indoor cultural amenities.
What does all this mean for local and public health officials, especially in urban areas where the heat island effect is making cities hotter?
The research I’ve done suggests that people are still going to go outside when it’s hot out, they’re going to be exposed to extreme temperatures, and that could have an impact on their health. So I think there are a few low-cost things such as providing reminders to hydrate and to stay out of the sun, or to encourage organizers to shift their recreational activities toward the early mornings or evenings.
Secondly, there’s a lot we can think about with infrastructure to mitigate those extreme effects, whether that’s providing splash pads and water fountains in public parks or investing in more trees to provide shaded paths.
There are a lot of benefits from being outside and in nature, and I would hate to live in a world where climate change prevents that, and where we all sit inside in our air conditioned bubbles. So there are additional benefits from investing in green space in cities. You know that reduces overall temperature—it reduces the heat island effect, which makes cities better places to recreate.