Green spaces provide substantial but unequal urban cooling globally
Yuxiang Li, Jens-Christian Svenning, Weiqi Zhou, Kai Zhu, Jesse F. Abrams, Timothy M. Lenton, William J. Ripple, Zhaowu Yu, Shuqing N. Teng, Robert R. Dunn & Chi Xu
Nature Communications volume 15, Article number: 7108 (2024) Cite this article
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Abstract
Climate warming disproportionately impacts countries in the Global South by increasing extreme heat exposure. However, geographic disparities in adaptation capacity are unclear. Here, we assess global inequality in green spaces, which urban residents critically rely on to mitigate outdoor heat stress. We use remote sensing data to quantify daytime cooling by urban greenery in the warm seasons across the ~500 largest cities globally. We show a striking contrast, with Global South cities having ~70% of the cooling capacity of cities in the Global North (2.5 ± 1.0 °C vs. 3.6 ± 1.7 °C). A similar gap occurs for the cooling adaptation benefits received by an average resident in these cities (2.2 ± 0.9 °C vs. 3.4 ± 1.7 °C). This cooling adaptation inequality is due to discrepancies in green space quantity and quality between cities in the Global North and South, shaped by socioeconomic and natural factors. Our analyses further suggest a vast potential for enhancing cooling adaptation while reducing global inequality.
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Introduction
Heat extremes are projected to be substantially intensified by global warming1,2, imposing a major threat to human mortality and morbidity in the coming decades3,4,5,6. This threat is particularly concerning as a majority of people now live in cities7, including those cities suffering some of the hottest climate extremes. Cities face two forms of warming: warming due to climate change and warming due to the urban heat island effect8,9,10. These two forms of warming have the potential to be additive, or even multiplicative. Climate change in itself is projected to result in rising maximum temperatures above 50 °C for a considerable fraction of the world if 2 °C global warming is exceeded2; the urban heat island effect will cause up to >10 °C additional (surface) warming11. Exposures to temperatures above 35 °C with high humidity or above 40 °C with low humidity can lead to lethal heat stress for humans12. Even before such lethal temperatures are reached, worker productivity13 and general health and well-being14 can suffer. Heat extremes are especially risky for people living in the Global South15,16 due to warmer climates at low latitudes. Climate models project that the lethal temperature thresholds will be exceeded with increasing frequencies and durations, and such extreme conditions will be concentrated in low-latitude regions17,18,19. These low-latitude regions overlap with the major parts of the Global South where population densities are already high and where population growth rates are also high. Consequently, the number of people exposed to extreme heat will likely increase even further, all things being equal16,20. That population growth will be accompanied by expanded urbanization and intensified urban heat island effects21,22, potentially exacerbating future Global North-Global South heat stress exposure inequalities.
https://www.nature.com/articles/s41467-024-51355-0
