南京大学生命科学学院滕潄清、徐驰课题组与国内外多个研究团队合作，通过遥感数据对全球约500个特大城市绿色基础设施的热缓解能力进行量化。研究发现，在高温季节，绿地可平均降低城市地表温度约3°C，这对于缓解极端高温至关重要。降温能力（cooling capacity）在全球南北方城市存在显著差异：平均而言，南方城市的降温能力只有北方城市的约70%；考虑人口密度和空间分布后，南北方城市居民获得的平均降温收益（cooling benefit）也表现出类似差异。这种降温不平等源于全球南北方城市绿地数量和质量的差异，受自然和社会经济因素的共同影响。研究进一步表明，提高城市绿色基础设施的数量和质量，在增加降温能力和减少全球不平等方面潜力巨大。
该研究于2024年9月2日以“Green infrastructure provides substantial but unequal urban cooling globally (https://doi.org/10.1038/s41467-024-51355-0)”为题在线发表于Nature Communications。生命科学学院博士生李宇翔为论文第一作者，徐驰教授、滕漱清助理教授和北卡罗莱纳州立大学Robert Dunn教授为论文共同通讯作者，奥胡斯大学Jens-Christian Svenning教授、中国科学院生态环境研究中心周伟奇研究员、密歇根大学朱凯副教授、埃克塞特大学Jesse Abrams博士与Tim Lenton教授、俄勒冈州立大学William Ripple教授、复旦大学余兆武研究员共同参与本项研究。
本文还考虑城市绿地基础设施和人口的空间分布，以量化每个城市平均城市居民根据其位置所获得的冷却缓解效益。这种冷却效益是人们实现冷却的更直接的度量，考虑了城市绿地基础设施和人口密度的城市内地理因素。我们关注冷却能力和冷却效益作为评估单个城市冷却能力的指标，以评估它们的全球不平等。我们特别感兴趣的是将冷却适应不平等与收入不平等联系起来。虽然这可以通过使用现有的国家收入指标进行分类来实现，但在这里我们使用传统的全球北方/南方分类，因为它与地理学的历史联系在气候研究中具有影响力。
Here, we assess the global inequalities in the cooling capability of existing urban green infrastructure across urban areas worldwide. To this end, we use remotely sensed data to quantify three key variables, i.e., (1) cooling efficiency, (2) cooling capacity, and (3) cooling benefit of existing urban green infrastructure for ~500 major cities across the world. Urban green infrastructure and temperature are generally negatively and relatively linearly correlated at landscape scales, i.e., higher quantities of urban green infrastructure yield lower temperatures42,43. Cooling efficiency is widely used as a measure of the extent to which a given proportional increase in the area of urban green infrastructure leads to a decrease in temperature, i.e., the slope of the urban green infrastructure-temperature relationship42,44,45 (see Methods for details). This simple metric allows quantifying the quality of urban green infrastructure in terms of ameliorating the urban heat island effect. Meanwhile, the extent to which existing urban green infrastructure cools down an entire city’s surface temperatures (compared to the non-vegetated built-up areas) is referred to as cooling capacity. Hence, cooling capacity is a function of the total quantity of urban green infrastructure and its cooling efficiency (see Methods).
As a third step, we account for the spatial distributions of urban green infrastructure and populations to quantify the benefit of cooling mitigation received by an average urban inhabitant in each city given their location. This cooling benefit is a more direct measure of the cooling realized by people, after accounting for the within-city geography of urban green infrastructure and population density. We focus on cooling capacity and cooling benefit as the measures of the cooling capability of individual cities for assessing their global inequalities. We are particularly interested in linking cooling adaptation inequality with income inequality40,46. While this can be achieved using existing income metrics for country classifications47, here we use the traditional Global North/South classification due to its historical ties to geography which is influential in climate research.
