Significant contribution to urban climate change research by our own Dr. Scott Krayenhoff

Posted on Wednesday, February 24th, 2021

Written by Dr. Simone Haerri

Chicago during summer heat on the left, and our own Dr. Scott Krayenhoff on the right

SES researcher Dr. Scott Krayenhoff recently published results from his urban climate research in high impact journals contributing significantly to this important aspect of environmental science.

Cities tend to be hotter than surrounding environments, and with climate change, urban areas are expected to have even higher temperatures. Together with a worldwide tendency of urbanization, overheating in cities is an increasing challenge, and not only for human health. There are a variety of ways the urban environment can be modified to help reduce the heat. In an article recently published in Environmental Research Letters, led by Dr. Scott Krayenhoff, 146 studies performed over a 30-year period that looked at various urban mitigation strategies were reviewed. The group of researchers from various countries assessed each strategy for its benefits in mitigating hot temperatures in those urban environments.

The mitigation strategies ranged from increasing the reflectivity of building roofs, to planting green roofs, increasing street tree cover and adding rooftop photovoltaic panels. What they found was a surprisingly large variation in cooling effectiveness of the different strategies across different studies, and a lack of studies that directly research the impacts of one single strategy on cooling. In addition, many of those strategies are highly dependent on the type of neighbourhood and local climate. This led to recommendations for improved design of urban heat mitigation studies.

Dr. Scott Krayenhoff also recently co-authored an article in Nature Climate Change that provides the first multi-model projections of future overheating across global cities, which the aforementioned heat mitigation strategies seek to offset. That article highlights the importance of building robust climate projections by relying on a suite of global climate models to ensure effective future urban planning. Climate models historically tend to ignore cities, because their direct climate impacts do not strongly affect global climate. However, urban areas modulate and modifty how global climate change will affect climates in cities. In this high-impact paper, the researchers including our own Dr. Scott Krayenhoff use an emulator to include the local climate effects of urban areas in the CMIP5 suite of global climate models. Urban areas, despite covering about 3% of Earth’s surface, harbor more than 50% of the global population with that percentage projected to increase substantially in the future. With that in mind, it is critical to understand how climate change will affect our cities worldwide.

Applying that combined climate model, they found consistent results that, under a high-emission scenario, cities across the world are expected to experience an increase in temperatures of about 4C by the end of this century. Designing and re-designing urban environments to help mitigate that warming is one crucial aspect of climate change adaptation.

To learn more about Dr. Scott Krayenhoff’s research, check out his personal profile here:

Original articles:

Krayenhoff, E. S., Broadbent, A. M., Zhao, L., Georgescu, M., Middel, A., Voogt, J. A., ... & Erell, E. (2021). Cooling hot cities: A systematic and critical review of the numerical modelling literature. Environmental Research Letters

Zhao, L., Oleson, K., Bou-Zeid, E., Krayenhoff, E. S., Bray, A., Zhu, Q., ... & Oppenheimer, M. (2021). Global multi-model projections of local urban climates. Nature Climate Change, 1-6.

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