Changes in observed climate extremes in global urban areas

Abstract

Climate extremes have profound implications for urban infrastructure and human society, but studies of observed changes in climate extremes over the global urban areas are few, even though more than half of the global population now resides in urban areas. Here, using observed station data for 217 urban areas across the globe, we show that these urban areas have experienced significant increases (pvalue <0.05) in the number of heat waves during the period 1973-2012, while the frequency of cold waves has declined. Almost half of the urban areas experienced significant increases in the number of extreme hot days, while almost 2/3 showed significant increases in the frequency of extreme hot nights. Extreme windy days declined substantially during the last four decades with statistically significant declines in about 60% in the urban areas. Significant increases (p-value <0.05) in the frequency of daily precipitation extremes and in annual maximum precipitation occurred at smaller fractions (17 and 10% respectively) of the total urban areas, with about half as many urban areas showing statistically significant downtrends as uptrends. Changes in temperature and wind extremes, estimated as the result of a 40 year linear trend, differed for urban and non-urban pairs, while changes in indices of extreme precipitation showed no clear differentiation for urban and selected non-urban stations.

Hot playgrounds and children's health: A multiscale analysis of surface temperatures in Arizona, USA

“…However, we demonstrate that within urban neighborhoods and small playgrounds, these surface temperatures vary significantly-and with implications for human thermal comfort and safety-at spatial scales as fine as 1 cm. Although satellite remote sensing data are more applicable for mesoscale urban climate modeling than mesoscale climate models with ≥ 1 km scale resolutions (e.g., Masson et al, 2003;Mishra et al, 2015), these remote sensing data are critically limited for human-and touchscale design, missing crucial information related to touch-scale extreme T s exposures, mean radiant temperatures, and effects of shade. These limitations are impactful especially for children, but also other people exposed to the outdoor environment during partially shaded daytime conditions, including outdoor workers and those engaged in sports or other recreational activities.…”

“…Microscale urban climate models and remotely sensed data (on the order of 1 m 2 to 1 km 2 ) are often employed for heat stress analysis (e.g., Harlan, Declet-Barreto, Stefanov, & Petitti, 2013;Hondula et al, 2012;Masson, Champeaux, Chauvin, Meriguet, & Lacaze, 2003;Mishra, Ganguly, Nijssen, & Lettenmaier, 2015;Stefanov, Prashad, Eisinger, Brazel, & Harlan, 2004), with airborne remotely sensed data providing surface temperatures at a resolution ranging from 7 to 140 m (Stefanov et al, 2004). These scales may possess insufficient spatial resolution to determine certain personal health impacts based on micro-environmental heat exposure.…”

Spatiotemporal Variations in the Impacts of Urban Land Use Types on Urban Heat Island Effects: The Case of Riyadh, Saudi Arabia

“…A recent study by Li et al (in press) posited that global urban extent could increase by 1.2 million km 2 from 2010 to 2050. The rapid expansion of urban land use has impacts on climate (Seto and Shepherd, 2009;Mishra et al, 2015), flood risk (Muis et al, 2015), biodiversity (Grimm et al, 2008), carbon emissions (Houghton et al, 2012) and energy use (Santamouris et al, 2015;Güneralp et al, 2017). The impacts pose challenges to cities in their drives towards achieving urban sustainability and meeting the sustainable development goals (SDG).…”

Magnitude and frequency of heat and cold waves in recent decades: the case of South America

“…To overcome this problem, the Global Surface Summary of the Day (GSOD) meteorological data set has been employed.duced by the National Climatic Data Center (NCDC), available from 1929 to present, which displays a reasonably dense coverage across South America. GSOD has been recently employed to show an increase in the number of heat waves in urban areas at the global scale (Mishra et al, 2015).…”