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Researchers at University of the State of Arizona (ASU) have used sophisticated climate modeling techniques to study the magnitude of rising temperatures, urban sprawl and greenhouse gas emissions intensifying the effects of climate change. In the United States, temperatures are expected to increase by seven degrees Celsius by 2099.
The ASU team examined various heat mitigation strategies including street level trees and technical solutions to combat the urban heat phenomenon. The researchers found that many of the proposed solutions would provide only a fraction of the projected heat relief.
"Previous studies have shown that conventional warming reduction strategies act primarily by lowering diurnal rather than nocturnal temperatures," said co-author of the study, Professor Matei Georgescu. "However, cities tend to have their greatest impacts on the regional thermal environment in the evening and at night."
"We have simulated the effects of conventional heat attenuation approaches with more widely accepted cooling strategies, but we have also simulated the impacts associated with near surface temperature materials. We found moderate attenuation of overnight temperatures with low thermal admittance materials. "
While previous studies assumed that the effects of urbanization and greenhouse gases could be determined by simply summing the effects of both factors, the current study found a nonlinear interaction between the two factors. urban expansion and greenhouse gas emissions across the country.
"The effects of urban development and greenhouse gas emissions are less than the sum of individual components," said Professor Georgescu. "This is obvious only during the night. The magnitude of the non-linearity reduces the total warming of 1 C (1.8 F) locally. "
However, "we have to remember that this is considerably less than total warming itself (from 4 to 8 ° C, from 7.2 to 14.4 ° F) depending on the simulated GHG scenario," he said. Professor Georgescu.
Regardless of the extent of warming, the models predicted persistent heat, especially in the country's regional urban centers. Overall, the simulations predicted that urban warming in the afternoon would be more pronounced in the eastern United States and that night warming would be more pronounced in the Appalachian Valley and Great Lakes regions. and central California, mainly due to urban expansion.
The researchers also analyzed the performance of various heat-attenuation technologies, such as cold roofs and green roofs, given the higher regional temperatures predicted.
"Using dynamic interactive simulations, we have examined several adaptation strategies in order to offset the projected urban warmth of the 21st century," explained the study's co-author, E Scott Krayenhoff. "We combined the high-intensity implementation of cold roofs, green roofs and street trees (ie, a full adaptation scenario) and found that this led to an average cooling 1.3 to 2.0 C 1 C (1.8 F) night cooling. In the afternoon, the local cooling in many planned metropolitan areas in the United States was slightly higher, notably in California, Texas and the Northeast. "
The study is published in the journal Nature Climate change.
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By Chrissy Sexton, Earth.com Editor
Payed by Earth.com
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