Vienna under heat stress: Researchers warn of urban heat islands!

Vienna under heat stress: Researchers warn of urban heat islands!

How hot is it in your local cities? A question that is more relevant than ever in times of extreme heat waves. According to the University of Natural Resources and Life Sciences (Boku), Vienna is particularly affected because the city is one of the heat hotspots. MeinBezirk reports that heat waves with temperatures over 35 degrees are no longer uncommon in Vienna. Urban heat islands, which consist of dense development, sealed areas and the absence of vegetation, make the city particularly vulnerable to heat.

It's not just daytime temperatures that are worrying; nighttime cooling is severely limited in urban areas. While the summer days are getting hotter, the temperatures at night remain high, which further increases the stress on residents. An interdisciplinary research project led by Philipp Weihs at Boku is intensively studying the effects of longer heat waves and possible cooling measures.

Research and solutions

As part of the “Imp-DroP” project, several measures to reduce temperatures are being investigated. This includes evaporative cooling, which is to be achieved through targeted irrigation of green roofs, parks and agricultural areas. In Marchfeld in particular, targeted irrigation shows that the temperature can be reduced locally by up to 3 degrees, while in the urban area the effect remains manageable at around 0.2 degrees.

A comprehensive approach is necessary because even with maximum measures, the cooling effect is not sufficient to compensate for the expected warming. As DW notes, greening and irrigation alone do not solve the problems of climate change. A mix of heat-resilient agriculture, sustainable irrigation concepts and the expansion of solar energy is required to achieve long-term cooling in cities.

Heat islands and their consequences

Urban heat islands are not just a problem in Vienna, but now affect more than 50% of the world's population, with a forecast of almost 70% by 2050. These heat islands can increase temperatures in cities by 10 to 15 degrees Celsius, which has a negative impact on the health of city residents. [LMU]. Inland cities in particular are hit harder than coastal cities.

The challenges in cities are complex and innovative solutions are needed. In countries like Japan, things have gone a step further: water is sprayed onto sidewalks to lower the ambient temperature. Cities like Phoenix and Tokyo have used light-reflecting materials to reduce the heat island effect.

Vienna in focus

The concept of green roofs and the use of photovoltaics on these areas could also become more important in Vienna. According to the Boku research team, urban cooling from such measures could be up to 1.5 degrees. However, it would require enormous amounts of water to cool all green spaces during extreme heatwaves. Currently, Vienna's spring pipelines can only supply 375,000 cubic meters of water, whereas theoretically 630,000 cubic meters would be necessary.

These data make it clear: the city administration and citizens are facing major challenges. Climate change is no longer a distant problem, but is already influencing daily life in Vienna. This makes it all the more important to work together on solutions and develop innovative approaches for a heat-resilient city.