Cities occupy only about 3% of the entire land surface. Global climate models are designed to analyze the big picture, and as a result, urban areas are poorly represented. Scientists have now looked at how climate change affects cities, using data-driven statistical models combined with traditional physical climate models.
A new study by engineer Lei Zhao of the University of Illinois at Urbana highlights that cities, home to more than 50% of the world’s population, are subject to tremendous heat stress, water scarcity, air pollution, and energy insecurity due to their layout and high-density population. In suburban and rural areas, the situation is not so critical.
“In cities, there are concrete and asphalt surfaces that absorb and retain more heat than natural surfaces. This and other factors disrupt other biophysical processes on a local scale, explaining Zhao, a civil and environmental engineer. Incorporating these types of fine-scale variables into climate modeling is critical to understanding the future of urban climate. However, it is not that easy.”
Global climate models predict future scenarios by simulating larger-scale processes such as greenhouse gas emissions and climate change. By combining this method with a statistical model that simulates a complex and detailed climate model for urban landscapes, Zhao’s team bridged the information gap between urban and global areas.
According to Zhao, the model predicts that average warming in global cities will increase by 1.9°C by the end of this century, with intermediate temperature rises and 4.4°C.
Projections also predict an almost universal decline in urban relative humidity.
The scientist noted that the forecasts do not take into account the impact of future urban development.