Research says planting trees could reduce growing temperatures in urban areas
Half of the world’s population resides in urban areas, but cities account for just around 3% of the world’s land area, which suggests that recent climate studies have found building green infrastructure and growing urban vegetation to be a safe option for cities trying to shield themselves from rising temperatures.
Lei Zhao, a University of Illinois scientist and lead author of the study published in Nature Climate Change, says this has indicated that city-specific data has not been generated by previous climate models. “Almost all models have no urban representation,” Zhao says. “Although such a small region is populated by cities, it is where a lot of the human influence [of global warming]takes place.
So by presenting multi-model climate forecasts unique to urban areas, we filled the void. “Scientists and urban planners have long known that temperatures in cities are higher than in rural areas.”
Infrastructure such as dark asphalt and concrete surfaces absorb more solar radiation, while decreased tree cover contributes to the so-called “urban heat island effect.” This means that temperatures can be up to 5C (9F) warmer in cities than in rural areas around them. However, Zhao explains that urban and rural climates vary in other ways. “The urban heat island is one of the reasons why the urban warming signal is different from that of other landscapes,” Zhao said. But it’s not just the temperature, but the humidity as well.
“Many of the urban climate variables differ from other landscapes. “The model predicts that for almost all cities, green infrastructure will be a successful investment. By releasing water into the atmosphere, which cools the air, trees and plants help to lower temperatures. The new model, however, predicts that the air will become drier over the next century in most cities outside of coastal regions, making surface evaporation more efficient, which means that higher levels of urban vegetation will be more effective in combating global warming. Zhao hopes the data will enable urban planners and policymakers to make more informed decisions on mitigating rising temperatures. “If you look at large-scale projections, you can see if the warming signal is different from other places and how the humidity varies, so it can help you design your strategy differently.”