Warming, the effects of which are already being felt in Spain, can have many impacts on life: increased mortality and morbidity, increased energy demand and reduced productivity at work.
Although cities only occupy about 3% of the total land area, more than half of the world’s population lives in urban settings. For this reason, bear a large part of the effects of the global climate crisis.
Until now, the global climate models have been established for large-scale analysis, which has left urban areas underrepresented. A study published in the journal Nature Climate Change estimates that urban regions around the world could get hotter than 4°C in a scene of global warming with high emissions and experience a decrease in relative humidity by 2100.
“Substantial warming in cities may have many impacts on urban life. For example, heat stress could cause a substantial increase in human mortality and morbidity, in energy demand (such as air conditioning) and a large reduction in productivity at work,” he tells the SINC agency. Lei Zhao, lead author of the work and researcher at the Department of Civil and Environmental Engineering at the University of Illinois (USA).
Cities tend to get hotter than rural or suburban areas because surfaces built of concrete and asphalt absorb more heat and inhibit cooling. They experience more heat stress, water scarcity, air pollution and energy insecurity due to their layout and high population densities. According to the researchers, incorporating these variables into climate change predictions is crucial to understanding future urban climate, but doing so is challenging.
“The vegetation o green infrastructure (such as green roofs, street trees, parks and other green areas) could help reduce urban ambient temperature by evaporative cooling. Trees also provide shade for thermal comfort for pedestrians. However, the feasibility and effectiveness of evaporative cooling of green infrastructure depend on the location of cities”, adds the scientist.
Projections also predict an almost universal decline in humidity relative in cities, making surface evaporation more efficient and indicating that adaptation strategies such as incorporating urban vegetation they could be useful.
“Researchers and engineers from different fields have proposed different solutions. Some of the most common include reflective roofs or pavements, green roofs, street trees, solar panels, smart buildings, etc. Some cities around the world have also implemented some policies to encourage infrastructure-based strategies,” says Zhao.
Average rise of 1.9°C
In the study, researchers have taken a closer look at how the climate crisis affects cities through the use of statistical models based on data, combined with traditional process-focused physical climate models.
The model predicts that by the end of this century, the average warming in the world’s cities will rise 1.9°Cwith intermediate emissions and 4.4 °C with high emissions.
“There is no one-size-fits-all solution.. A measure that works well for one city does not necessarily work for another. For example, greatly increasing greenery in a city might not be feasible in dry cities where the water resource is already very scarce. Therefore, large-scale planning and comparison, as well as decision-making based on local specific urban information, are necessary to determine what measures a city should take for the future”, he stresses.
In this way, the interactions between urban land, the lower atmosphere and climate change on a large scale are reflected in the statistical model.