Fig. 10. Change in outdoor days with different definitions. Normalized change in annual outdoor days in 1991–2020 with respect to 1961-1990. Various definitions considered in this study are indicated in each plot. The changes are normalized by the 1961-1990 mean. These global maps are derived from ERA5.
5. Conclusions
Here, we used the state-of-the-art reanalysis data and projections from 60 GCMs (31 CMIP5 and 29 CMIP6) to propose that the climate hazard associated with the change in outdoor days (i.e., the number of days with pleasant weather that allows for outdoor activities by most people) could contribute to the north-south disparity that sustains inequality and injustice of climate change. We project that this disparity is expected to increase considerably in the future, assuming the high emissions scenarios.
Our results have important implications for the injustice of climate change. That is, the negative impacts of climate change accompanied by the decreased outdoor days will significantly affect tropical countries, including Colombia, Brazil, Ivory Coast, Nigeria, Sudan, Indonesia, Bangladesh, and India, which are developing countries with large populations but relatively minor emitters of carbon dioxide (Figs. S3 and S9). Meanwhile, some of the historically largest emitters of carbon dioxide, including the United States, Canada, the European Union, Russia, and Japan may benefit to varying degrees from the increased outdoor days. It is important to note that climate risk inferred from the existing literature may be substantially underestimated, especially in tropical regions since they do not consider risk caused by the climate hazard related to outdoor days, as evident from our analysis.
The findings reported here are not only important from the point of view of climate risk and how it varies spatially and temporally, but they also contribute to informing the ongoing discussions regarding compensations for loss and damage imposed by climate change.
Acknowledgments.
We acknowledge support from the Abdul Latif Jameel Water and Food Systems Lab (J-WAFS) at MIT, and the MIT Climate Grand Challenges project: Jameel Observatory- Climate Resilience Early Warning System Network (CREWSnet).
Data Availability Statement.
All original CMIP5 GCMs, CMIP6 GCMs, and the ERA5 reanalysis used in this study are publicly available at https://esgf-node.llnl.gov/projects/cmip5/, https://esgf-node.llnl.gov/projects/cmip6/, https://doi.org/10.24381/cds.adbb2d47, respectively. CMIP5 and CMIP6 models used in this study are listed in Table S1. The gridded population density of the world is from the Center for International Earth Science Information Network (CIESIN 2018). The gridded global datasets for GDP are available from Kummu et al. (2018). GDP per capita and CO2 emissions per capita are from https://ourworldindata.org/grapher/gdp-per-capita-maddison-2020 and https://ourworldindata.org/grapher/co-emissions-per-capita, respectively.
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