Global long-term mapping of surface temperature shows intensified intra-city urban heat island extremes

Mentaschi, Lorenzo; Duveiller, Grégory; Zulian, Grazia; Corbane, Christina; Pesaresi, Martino; Maes, Joachim; Stocchino, Alessandro; Feyen, Luc

doi:10.21203/rs.3.rs-251967/v1

Cited by 6 publications

(8 citation statements)

References 42 publications

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“…Although the compensating effects of T a and RH on HI 0 makes conceptual sense, what is surprising is that the urban‐rural differences in HI 0 is so close to zero for cities during a heatwave period, with less than a third showing statistically significant differences between the urban area and its rural reference. These results weaken a common premise in many previous studies where increased urban T s is expected to indicate adverse urban impact on overall heat vulnerability (Hsu et al., 2021; L. Zhao et al., 2017; Manoli et al., 2019; Mentaschi et al., 2022).…”

Section: Resultscontrasting

confidence: 64%

“…Coarse to medium‐resolution T s from satellites have been used for hotspot analysis within cities (Hulley et al., 2019; Maimaitiyiming et al., 2014; Mentaschi et al., 2022). Several studies have taken advantage of the spatial continuity of satellite observations to map intra‐urban variability of T s across cities with implications for environmental disparities (Benz & Burney, 2021; Chakraborty et al., 2019; Hsu et al., 2021).…”

Section: Discussionmentioning

confidence: 99%

“…Traditionally, the UHI intensity was quantified using in situ air temperature ( T a ) measurements (Howard, 1833). However, many recent large‐scale observational and modeling studies on the UHI, and urban climate in general, have focused on radiative skin or surface temperature ( T s ) (Chakraborty & Lee, 2019; Chakraborty et al., 2019; Clinton & Gong, 2013; Hoffman et al., 2020; Hsu et al., 2021; L. Zhao et al., 2014, 2017; Manoli et al., 2019; Mentaschi et al., 2022; Schwaab et al., 2021), with many of these studies commenting on heat exposure in cities, their public health consequences, and potential mitigation strategies. Similarly, maps made from satellite‐derived T s are often used as a guide for planning heat mitigation strategies by decision makers (Keith et al., 2019).…”

Section: Introductionmentioning

confidence: 99%

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Lower Urban Humidity Moderates Outdoor Heat Stress

et al. 2022

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Surface temperature is often used to examine heat exposure in multi‐city studies and for informing urban heat mitigation efforts due to scarcity of urban air temperature measurements. Cities also have lower relative humidity, traditionally not accounted for in large‐scale observational urban heat risk assessments. Here, using crowdsourced measurements from over 40,000 weather stations in ≈600 urban clusters in Europe, we show the moderating effect of this urbanization‐induced humidity reduction on outdoor heat stress during the 2019 heatwave. We demonstrate that daytime differences in heat index between urban clusters and their surroundings are weak, and associations of this urban‐rural difference with background climate, generally examined from the surface temperature perspective, are diminished due to moisture feedbacks. We also examine the spatial variability of surface temperature, air temperature, and heat index within these clusters—relevant for detecting hotspots and potential disparities in heat exposure—and find that surface temperature is a poor proxy for the intra‐urban distribution of heat index during daytime. Finally, urban vegetation shows much weaker (∼1/6th as strong) associations with heat index than with surface temperature, which has broad implications for optimizing urban heat stress mitigation strategies. These findings are valid for operational metrics of heat stress for shaded conditions (apparent temperature and humidex), thermodynamic proxies (wet‐bulb temperature), and empirical heat indices. Based on this large‐scale empirical evidence, surface temperature, used due to the lack of better alternatives, may not be suitable for accurately informing heat mitigation strategies within and across cities, necessitating more urban‐scale observations and better urban‐resolving models.

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Section: Resultscontrasting

confidence: 64%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Lower Urban Humidity Moderates Outdoor Heat Stress

et al. 2022

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“…It is typically thought that UHIs increase in magnitude as a city increases in size and population (Li et al 2017;Zhou et al 2017;Mentaschi et al 2022), though this effect is smaller in tropical cities (Manoli et al 2019). We found that UHIs in long-urbanised areas in Makassar have remained stable since at least the 1990s, in line well-researched cities such as London (Jones & Lister 2009), but have expanded into recently urbanised areas, following patterns observed across Europe (Trusilova et al 2009) and Africa (Li et al 2021).…”

Section: Discussionsupporting

confidence: 62%

“…2017; Zhou et al . 2017; Mentaschi et al . 2022), though this effect is smaller in tropical cities (Manoli et al .…”

Section: Discussionmentioning

confidence: 99%

Spatio-temporal development of the urban heat island in a socioeconomically diverse tropical city

Ramsay

Duffy

Burge

et al. 2022

Preprint

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Urban heat islands, where temperatures are elevated relative to non-urban surrounds, are near-ubiquitous in cities globally. Yet, the magnitude and form of urban heat islands in the tropics, where heat has a large morbidity and mortality burden, is less well understood, especially for socioeconomically diverse communities such as those living in urban informal settlements. We utilised 29 years of Landsat satellite-derived surface temperature, corroborated by in situ measurements, to provide a detailed spatial and temporal assessment of urban heat islands in Makassar, Indonesia, a city that is representative of rapidly growing urban settlements across the tropics. We did so with explicit consideration of vulnerable communities living informally. Our analysis identified surface urban heat islands of up to 9.2 C in long-urbanised parts of the city and 6.3 C in informal settlements, the seasonal patterns of which were driven by change in non-urban areas rather than in urban areas themselves. In recently urbanised areas, the majority of urban heat island increase occurred before areas became 50% urbanised. As tropical cities continue to expand we expect that urban heat islands will develop quickly as land is urbanised, whereas the established heat island in long-urbanised areas will remain stable in response to city expansion. Green and blue space protect some informal settlements from the worst urban heat islands and maintenance of such space will be essential to mitigate the growing heat burden from urban expansion and anthropogenic climate change. We advocate for green space to be prioritised in urban planning, redevelopment and informal settlement upgrading programs, with consideration of the unique environmental and socioeconomic context of tropical cities.

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Responses in thermal tolerance and daily activity rhythm to urban stress in Drosophila suzukii

Sato

Takahashi

2022

Ecology and Evolution

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Cities experience changes in abiotic factors, such as warming, increases in noise and light. These changes can lead to phenotypic changes. Several studies have revealed that altered environments change phenotypes in plants and animals in cities. However, limited studies have isolated evolutionary from nongenetic changes. Here, we analyzed the evolution of thermal tolerance and diurnal activity patterns in the urban population of the fruit pest, Drosophila suzukii . Urban and rural isofemale lines were reared under constant conditions. We compared the lower and upper thermal limits (CT min and CT max , respectively), and effects of temperature exposure on the thermal limits of urban and rural populations. Common garden experiments showed that urban populations exhibit a lower CT min than rural populations, suggesting genetic difference in CT min among populations. On the other hand, the difference in CT max between urban and rural populations was not significant. Exposure to cold temperature did not affect CT min in both urban and rural populations. In contrast, exposure to hot temperature increased CT max especially in urban population, suggesting that urban populations evolved in response to urban heat. We also investigated the daily activity patterns of urban and rural populations and the effect of lifelong artificial light at night on daily activity. We found that night‐time light (dim light) reduced the total amount of activity compared to dark night condition. In addition, dim light at night altered the daily rhythm of activity and increased the activity rate at night. The effect of night light on total activity was less in urban than that in rural populations, suggesting that populations in cities evolved to mitigate decreased activity under night light. Our results showed that environmental temperature and artificial light at night evolutionarily and plastically influence ecologically important traits, such as temperature tolerance and diurnal activity.

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Global long-term mapping of surface temperature shows intensified intra-city urban heat island extremes

Cited by 6 publications

References 42 publications

Lower Urban Humidity Moderates Outdoor Heat Stress

Lower Urban Humidity Moderates Outdoor Heat Stress

Spatio-temporal development of the urban heat island in a socioeconomically diverse tropical city

Responses in thermal tolerance and daily activity rhythm to urban stress in Drosophila suzukii

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