Need quick public buy-in on climate action? Think urban heat islands

As a strategy, it’s local, less controversial and far more manageable, with actionable steps that give quick, tangible feedback while simultaneously addressing climate change.
Hydra Viridis/Shutterstock

Climate change is arguably the biggest challenge facing humanity. It is categorically and qualitatively different from the long list of chronic troubles that civilization has always faced, from poverty and disease to crime and war. Importantly, cities are no longer seen as the problem, as they were a half century ago, before their robust renewal and explosive growth. Today we are in the midst of a golden age for cities — and their resurgence offers some timely optimism for our ability to respond positively to climate change.

But a perennial problem remains: How can we motivate and inspire people to act on a long-term, abstract and seemingly hopeless problem like climate change? How can we negotiate and address such an unwieldy, complex, amorphous and seemingly slow-moving challenge? Part of the issue is that humans are hardwired to deal with more-pressing problems, especially those with palpable and personal immediacy. Objectively presenting the facts, while essential, is never enough.

Each of three basic ways to modify human behaviour — pleasure, fear and guilt — has a role to play. As do other concerns that move us to act, too, such as comfort, health and security, as well as the most fundamental needs of survival and safety. Love of one’s home, community and city can be particularly potent incentives to act in our highest interests, both altruistic and selfish. And the right economic incentives can push us to allow self-interest to be in the best collective interest of society, the environment and our thermal commons.

One key strategy to tap into these intrinsic motivators could be to strengthen awareness of the “urban heat island”, a relatively unknown and misunderstood local phenomenon that is heating up many cities twice as quickly as their surrounding countryside. The issue has been surprisingly underplayed in the literature and public discourse about climate, and it remains unclaimed as the clarion call of any environmental group.

[See: Can Melbourne lower its temperature by 4 degrees?]

So what exactly is an urban heat island? The term describes the higher air and surface temperatures in cities compared to their surrounding territory. The phenomenon is easily confused with global climate change, which has been long and widely agreed by the scientific community to result from changes in the composition of the Earth’s atmosphere.

Unlike climate change, which is a global phenomenon, the urban heat island is a local phenomenon — an important distinction, because climatologists tend to discount local effects in their global models. The physics is also different: the increase in local temperatures is not from greenhouse gases trapping more heat in the atmosphere but from local waste heat. This typically comes from three sources: hot gases emitted from tailpipes and chimneys, hot air discharged by air conditioners, and heat from dark surfaces, such as dark-coloured rooftops, streets and parking lots.

Each of these heat sources raises urban temperatures higher than the surrounding suburbs and rural countryside, which have fewer tailpipes, chimneys and dark surfaces. The rural-to-urban temperature gradient can be 5 to 7 degrees Fahrenheit or more, with heatwaves that may double this differential. Further, such extra heat often induces more use of air conditioners, which consume electricity from power plants whose emissions in turn add to climate change. It’s a self-reinforcing negative cycle.

Immediate and understandable

Many issues around the world are precipitated by thermal and environmental problems — from urban air pollution and congestion to health problems and infrastructure failure, not to mention the profound challenges of sea-level rise, extreme weather, storm-water flooding, drought, famine and more.

“Because it’s more like a 5- to 10-year challenge than a 50- to 100-year challenge, the issue of urban heat islands can more immediately and more urgently rally individuals and communities to change their behaviour.”

The particular cocktail of concerns varies from place to place. For many urbanized areas, especially those in hot and in temperate climates, rising urban temperatures are stirring up trouble sooner than climate change. The loss of air conditioning in a city in southern Iraq during a heatwave in the summer of 2015 triggered civil unrest as intense as the civil war in area.

Indeed, heatwaves kill more people than all other natural disasters combined. The poverty-stricken usually suffer the most in heatwaves, but hotter urban temperatures and heatwaves impact wealthy areas of the metropolis as well. Climate change and urban heat islands are too pervasive for the wealthy to easily escape — they’re social levellers.

[See: Three questions for cities as the Paris Agreement on climate change turns one]

Still, it’s important to recognize that from a climate perspective, it is beneficial for more people to live in cities, especially in developed countries. Compared to their suburban and rural counterparts, urban residents in richer countries tend to have smaller ecological footprints, which is roughly equivalent to their energy or carbon footprint. Urbanites walk, bike and use mass transit more than auto-dependent suburban and rural residents, and their more compact, multi-floor housing takes less energy to mechanically heat and cool.

This rarely applies to developing countries, where rural residents who migrate to the city typically sprout larger footprints as their income rises. But they also tend to have fewer children, because there is less need for their free labour in farming, making large families an economic liability rather than an asset. And urban homes tend to be smaller than in rural areas. This dampening of birth rates decreases the total carbon footprint of the nation.

Importantly, the ways to mitigate and adapt to urban heat islands are essentially identical to strategies to address longer-term global climate change. Because it’s more like a 5- to 10-year challenge than a 50- to 100-year challenge, this issue can more immediately and more urgently rally individuals and communities to change their behaviour. Urban heat islands are local and more manageable, with actionable steps that give quicker feedback from successful outcomes.

Because it begets quick, visible results, the urban heat island also tends to emphasize mitigation less than adaptation, which feels more proactive and satisfying than trying to deal with longer term, more uncertain climatic impacts. Urban heat islands also threaten an individual’s personal health and life expectancy, acting as a private stimulant to act.

[See: What effect could President Trump have on U. S. cities’ climate action?]

This issue is not only more immediate and understandable, but as a result it’s also less controversial. Directly focusing on local overheating and heatwaves can defuse partisan or religious scepticism about both the human-centric causes and the urgency of global climate change. Everyone can sense the heat radiating off hot, dark surfaces; they can feel the hot air coming out of tailpipes and air conditioners; they appreciate the shade from trees and cooling breezes. There’s no obtuse scientific narrative about invisible gases trapping infrared heat in the upper atmosphere.

If we want cities to play the positive, synergistic role that they can naturally assume in the ongoing battle against climate change, we have no choice but to retrofit them to keep them cool enough for human comfort and civility. And in the developing world, new cities must be planned to mitigate and adapt to the urban heat island from the outset.

Stealth tool

Because urban cooling emphasizes adaptation over mitigation, it appeals to the human proclivity for short-term thinking and prompt action, especially reacting to immediate crises. Its concrete steps provide a proactive sense of progress against the uncertainties of the slowly unfurling disruption of the Earth’s weather and climate.

It is about managing public perception, as well as dealing with a costly and accelerating physical imperative. Cooling the urban and global thermal commons sits on the right side of multiple equations. As reason and motivator to address both global and local climate change, the urban heat island can help inform and shape urbanism in the coming years.

[See: Eleven cities that are showing the way on fighting climate change]

Reducing the heat spewing from tailpipes with more walkable, bikeable and transit-oriented communities is an obvious strategy to reduce heat islands. Perhaps the lowest-hanging fruit is to lighten the colours of roofs and pavements. And the age-old practice of planting trees for cool microclimates has a wonderfully long list of other benefits.

Indeed, these antidotes have collateral benefits beyond cooling the urban environment and addressing climate change. They also reduce pollution and congestion, not to mention enhance safety, value and beauty. The other good news is that cities usually offer economic and social opportunity, while fostering creativity, productivity, commerce, community, women’s rights, arts and culture.

Municipal and metropolitan government are not only on the thermal front line, but they also seem to be more proactive and agile than national governments in their commitment and initiatives. Indeed, over 500 cities worldwide now measure greenhouse gas emissions, often with reduction targets, including some that have declared a goal of zero emissions by mid-century. Cities such as Louisville, in the United States, are actively putting new initiatives in place, while Hong Kong has been doing so for years.

[See: How to globalize the sustainable city]

Cities have long played a central role in our survival and evolution, and they will continue to do so as we combat climate change. If the populous city is the infantry, the urban heat island is the Trojan Horse — stealthily changing behaviour and winning immediate battles in the longer war against climate change.

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Doug Kelbaugh

Doug Kelbaugh is professor of architecture and urban planning and former dean of the Taubman College of Architecture & Urban Planning at the University of Michigan, and author of several books and numerous articles.