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).