Green infrastructure can help cities adapt to climate change by moderating the higher air temperatures thus reducing the heat stress experienced by people But the type of greenery plays an important role To understand the extent of urban heat islands and the relationship between daily and seasonal outdoor thermal stress a research team headed by TUM conducted a three-year empirical study in the city of Würzburg Comparing urban and suburban climate conditions The mean air temperature at inner-city sites was 1.3 degrees Celsius higher than at suburban locations during summer and 5 degrees Celsius higher during winter. “The differences were influenced by the characteristics of the prevailing land uses and especially by the number of buildings,” says Stephan Pauleit, Professor of Strategic Landscape Management at TUM At one of the urban locations – ”Marktplatz” where there was no tree – a total of 97 hot days with air temperatures exceeding 30 degrees Celsius were counted over the three-year period of the study the wet bulb global temperature – an index for understanding thermal stress – exceeded the 35 degrees Celsius threshold which indicate  extreme thermal stress The wet bulb globe temperature (WBGT) is defined as the lowest temperature that can be reached under current ambient conditions by the evaporation of water only It was calculated using meteorological data and other associated variables at seven different stations starting from the city center – “Marktplatz” to sub-urban site Gerbrunn These values demonstrate the influence of the surrounding area including site-specific characteristics such as buildings and greenspaces  “Our study showed that extreme heat stress in summer could be halved with around 40 percent cover of greenspaces in the built environment green roofs and green walls with little compromise in increasing winter cold stress,” says Dr a scientist at the Chair of Strategic Landscape Management at TUM A variety of greenspaces is important for the urban climate trees reduce the input of shortwave radiation to the ground level by up to 90 percent in particular during summer when deciduous trees are in leaf in temperate and cold climates trees cool their immediate vicinity by 1 to 8 degrees Celsius and increase the relative humidity of the air the evaporation of water through the leaves during food production trees can also bring negative effects such as hindering the vertical and horizontal mixing of air within narrow street canyons preventing the polluted air at pedestrian level from being diluted and blown away by breezes grass cover reduces the radiative heat load through higher reflection as compared to the built environment It also allows higher wind speeds to limit the summer heat load and greater solar radiation for reduced winter cold stress Indispensable: strategically planned greenspaces “Our results call into question the inner city densification trends currently seen in growing urban areas adequate urban greening must be ensured,” says Rahman To avoid negative effects of climate change on human health greenspaces must be planned strategically to ensure that they can also effectively reduce heat stresses in high-density urban areas are not responsible for the accuracy of news releases posted to EurekAlert by contributing institutions or for the use of any information through the EurekAlert system Copyright © 2025 by the American Association for the Advancement of Science (AAAS) This website is using a security service to protect itself from online attacks The action you just performed triggered the security solution There are several actions that could trigger this block including submitting a certain word or phrase You can email the site owner to let them know you were blocked Please include what you were doing when this page came up and the Cloudflare Ray ID found at the bottom of this page.