14 May Urban Heat Islands can modify temperatures thousands of kilometres away
The Urban Heat Island (UHI) effect is a phenomenon that has been studied for a number of decades, however a newly discovered relationship between meteorology and an UHI has been found to result in weather altering temperature changes thousands of kilometres away. Researchers from the Scripps Institute of Oceanography and the National Centre for Atmospheric Research (both in the United States) examined the excess heat generated by buildings and vehicles moving through cities in the Northern Hemisphere.
The research led by Guang Zhang of the Scripps Institute found that a significant portion of that heat is lifted into the jet stream (a region of very fast moving air currents) and is transported with the jet stream, which disrupts traditional energy flows and causes surface temperatures to change in locations that are subject to the same wind current circulation patterns large distances away. The average temperature difference during the winter in most of North America and Asia was a 2 degree Farenheit increase and a 2 degree Farenheit decrease in the fall in Europe.
While the research team stated that the effect on the climate is negligible compared to the effect of greenhouse gases that trap heat and contribute to long term climate change, the relationship between UHIs and the jet stream can account for differences between higher concentrations predicted using computer modelling and actual temperature observations. In order to more accurately simulate the regional scale impacts of climate change, future models will need to account for this newly discovered phenomenon.
In previous blogs I discussed the local scale impacts of UHIs, and the results of this research in combination with the local scale impacts illustrate that planning decisions both within a city region and beyond will need to address UHIs and assess the risks for the immediate area and major nearby cities. In the short to medium term when a number of cities in developing countries will commence (and some will continue) dramatic transformations of their skylines with the addition of many more office and residential buildings, UHIs and increased vehicular and public transport emissions will need to be scrutinised and given adequate coverage in planning models, policy frameworks and ultimately planning decisions.
Cities in developed countries that are undergoing renewal also need to consider UHIs and emissions in combination. It is only when UHIs and associated issues such as air emissions are integrated into planning models, policies and decisions that meaningful, appropriate and robust management and mitigation strategies can be chosen and applied.
As a climate change futurist I can see that Governments at the Local and State level and their urban and city planning and development/construction partners will be required to take a multidisciplinary approach to addressing UHIs as a part of resource/energy management and climate change due diligence in the urban and city areas under their jurisdiction, and to ensure the long term sustainability of these areas as far as is practicable.
Governments of all political persuasions and levels (e.g. regional, provincial, local and State) are starting to investigate such approaches, and this will only become more important as the resources available to urban and city areas (e.g. water and energy amongst others) will become critical elements of climate change risk assessments.
If you would me to deliver a keynote presentation on integrating UHI risks, mitigation and management into decision making at your company’s annual conference, or you are an Urban Design/Development Industry body/group looking for a keynote on this topic at your annual conference, please don’t hesitate to get in touch.
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