Although most of climate change's social impacts are likely to be negative, a paper published online this week in Nature Human Behaviour reports a possible beneficial impact of climate change for the United States. The study suggests that warming over the course of this century may increase net recreational physical activity, in turn magnifying many of the physiological and psychological benefits of exercise.

Nick Obradovich and James Fowler use data on reported participation in recreational physical activity from over 1.9 million Americans between 2002 and 2012, coupled with daily weather data, to show that cold or very hot temperatures, as well as rain, reduce physical activity. They then combine their historical estimates with output from climate models and project the possible impacts on physical activity of future climatic changes by 2050 and 2099. They find that warming is likely to increase overall exercise rates across the United States. They suggest that these increases will occur primarily during the cooler months of the year, particularly in northern states, whereas it is likely to decline during summer months, especially in southern states.

However, the effects of warming on physical activity are unlikely to be uniformly beneficial worldwide, note the authors. Countries with warmer average climates and lower prevalence of air conditioning may see net reductions in physical activity due to climate change.