Fig. 2. Global distribution of outdoor days. Climatology of (a) annual, (b) spring, (c) summer, (d) autumn, and (e) winter outdoor days for the period 1959-2021. These global maps and time series are derived from ERA5.
Here, we show that the recent global warming due to climate change has disproportionately affected outdoor days in the global north and south (Fig. 3 and Fig. S2b). Based on the modern climate record, annual outdoor days show a decreasing trend in the global land areas while exhibiting an asymmetric pattern between developing countries in the south and developed countries in the north (Fig. 3). The enhanced risk of a climate hazard, in the form of reduced outdoor days, is particularly significant in the tropical regions. Outdoor days in these regions have decreased by about 13% in the last three decades compared to the period 1961-1990, showing a significant downward trend (p-value < 0.01). Meanwhile, high-latitude countries have benefited from recent global warming, with a 16% increase in the number of outdoor days. Furthermore, on a seasonal time scale, outdoor days in the tropical regions show sharp reductions of outdoor days in the relatively warm season (Fig. 4). Meanwhile, the net change of outdoor days in middle-latitude countries is mostly positive but small because of cancellation between increasing and decreasing trends during the winter and summer, respectively (Fig. 4).