Table_1_Urban Growth and Heat in Tropical Climates.DOCX

This research describes the change in temperatures across approximately 270 tropical cities from 1960 to 2020 with a focus on urban warming. It associates urban growth indicators with temperature variations in tropical climate zones (tropical rainforest, tropical monsoon, and tropical wet-dry savanna). Our findings demonstrate that over time while temperatures have increased across the tropics, urban residents have experienced higher temperatures (minimum and maximum) than those living outside of cities. Moreover, in certain tropical zones, over the study period, temperatures have risen faster in urban areas than the background (non-urban) temperatures. The results also suggest that with continuing climate change and urban growth, temperatures will continue to rise at higher than background levels in tropical cities unless mitigation measures are implemented. Several fundamental characteristics of urban growth including population size, population density, infrastructure and urban land use patterns are factors associated with variations in temperatures. We find evidence that dense urban forms (compact residential and industrial developments) are associated with higher temperatures and population density is a better predictor of variation in temperatures than either urban population size or infrastructure in most tropic climate zones. Infrastructure, however, is a better predictor of temperature increases in wet-dry savanna tropical climates than population density. There are a number of potential mitigation measures available to urban managers to address heat. We focus on ecological services, but whether these services can address the projected increasing heat levels is unclear. More local research is necessary to untangle the various contributions to increasing heat in cities and evaluate whether these applications can be effective to cool tropical cities as temperature continue to rise. Our methods include combining several different datasets to identify differences in daily, seasonal, and annual maximum and minimum temperatures.

本研究聚焦城市增温现象，分析了1960年至2020年间全球约270座热带城市的气温变化情况。本研究将城市增长指标与热带气候区（热带雨林气候区、热带季风气候区以及热带干湿季稀树草原气候区）的气温波动建立关联。研究结果显示，随着时间推移，全球热带地区气温普遍升高，而城市居民所经历的极端最高、最低气温均高于非城区居民。此外，在部分热带气候区内，本研究周期内城市区域的气温增速高于背景（非城市）气温。研究结果同时表明，若不采取减缓措施，随着气候变化持续与城市扩张推进，热带城市的气温将持续以高于背景区域的速率攀升。城市增长的多项核心特征，包括人口规模、人口密度、基础设施建设以及城市土地利用格局，均与气温波动存在关联。研究证实，高密度城市形态（紧凑布局的居住与工业开发区域）与更高的气温水平相关；在多数热带气候区内，人口密度相较于城市人口规模或基础设施建设，能更好地预测气温波动。但在热带干湿季稀树草原气候区，基础设施建设则比人口密度更能有效预测气温增幅。城市管理者可采用多项潜在的热环境减缓措施，本研究聚焦生态服务手段，但目前尚不清楚此类措施能否应对预测中的气温持续升高态势。未来需开展更多地方性研究，以厘清城市气温升高的各类驱动因素，并评估在气温持续攀升的背景下，此类措施能否有效为热带城市降温。本研究采用的方法整合了多类数据集，以解析日、季、年度尺度下的极端最高与最低气温差异。