Cities Are Heating Up Fast — But Don't Have To

The average temperature in cities is going up more than twice as fast as the temperatures on the rest of the planet.

Brian Stone, director of the Urban Climate Lab at Georgia Tech, says city governments alone can't do much to affect global warming trends, but there are steps they can take to make their own neighborhoods cooler.

"Planting just trees here and there is really not going to be sufficient. Large cities need to be planting really probably hundreds of thousands of trees," Stone told Here & Now.

Stone is author of "The City and the Coming Climate: Climate Change in the Places We Live," an excerpt of which you'll find below.

The unseasonably warm weather throughout Great Britain in the spring of 2003 was embraced by a population accustomed to the persistently overcast and damp conditions of a Northern European winter. Although still cold, February and March of that year had yielded an unusual number of sunny days, with relatively few rainstorms and periods of overcast skies. In April, Britons flocked to beach communities for the Easter holiday, taking advantage of temperatures reaching into the 70s, a generous 10 degrees above normal for that month. As one media report noted at the time, “An unexpected glimpse of sunshine could brighten the weekend for millions of people in southern England.” Another concluded that not even Miami, Florida, could muster the same tropical conditions experienced in Northern Europe at times that year. Mother Nature, it seemed, was smiling on the island kingdom.

The explanation for Britain’s good fortune was to be found in the presence of a stationary high-pressure weather system centered over Scandinavia, which was drawing in warmer air from farther afield and elevating temperatures across Europe. The warm weather that Easter weekend was enjoyed in several European capitals, where long-shut windows were opened to blue skies and winter layers removed. In the spring of most years, momentary glimpses of the Sun over Northern Europe are to be celebrated; this year, however, the Sun was here to stay.

Although no one recognized it at the time, Europe was experiencing the early stages of a heat wave so extreme it would far surpass any comparable weather event in more than three centuries of record keeping. Since temperature observations were first maintained in 1659, a period when Louis XIV ruled France and the Pilgrims occupied Plymouth, not a single summer had produced temperatures so intense and over such an extended period of time. Maintained by a succession of stationary weather systems over the Northern Atlantic and Central Europe, conditions of excessive heat and drought would persist for almost eight months. By summer’s end, the heat wave had reduced ancient rivers to non-navigable streams, consumed in fire an area larger than some European nations, and claimed more lives than the United States lost in a decade of warfare in Vietnam.

The heat wave of 2003 would constitute the single most catastrophic weather event to be visited on Europe – and, arguably, any modern nation – during the period in which weather observations have been recorded. Less than a decade since its occurrence, however, many [outside of Europe] will not recall having heard of the event.

This perhaps was the central lesson of the crisis: heat kills quietly.

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In the months following the heat wave, postevent assessments would document massive social, economic, and environmental impacts. By the end of the summer, more than 25,000 fires had consumed a total of 647,069 hectares across Portugal, Spain, France, Italy, Austria, Finland, Denmark, and Ireland – an area roughly equivalent to that of Luxembourg. Portugal alone would lose an estimated 10% of its total forestland. Agricultural losses were unprecedented. The excessive heat and drought reduced fodder harvests in France by an estimated 60% and by at least 30% in neighboring countries. One of the most productive agricultural regions in Italy reported a 40 to 50% drop in olive production and a 40 to 100% reduction of the peach, apricot, and grape yields, with the costs of produce on the shelf in Britain rising by 40%. The limited evidence available suggests the impact of the heat on livestock was substantial: it was reported that 80,000 chickens perished on a single farm in England. Overall, economic losses from the heat wave across Europe were estimated to be about $13 billion, a figure that is certain to underestimate the true costs.

The most consequential statistics, however, concerned the loss of human life. European governments were astounded to discover the true number of their citizens who had perished from the heat over the course of a few weeks in a single summer. A joint study commissioned by the European Union (EU) would show through comparisons of fatality rates in June through September 2003 with previous months, or with the same months in previous years, that tens of thousands of excess fatalities had resulted from the extreme heat.

The epicenter of the disaster was in the countries of France and Italy. Initially estimated in the immediate aftermath of the heat wave to have suffered 5,000 fatalities, French officials would later discover this number to underestimate the actual death toll by about 300%. During the period spanning June through September 2003, France suffered a staggering 19,490 excess deaths from the heat wave – almost 12 times greater than the number of deaths typically experienced during these months. Italy was found to closely match this grim total, with 20,089 citizens having died from the heat. What is most remarkable about these numbers – and perhaps most foreboding – is that almost 40,000 citizens had died from hot weather in two of the most affluent and medically advanced societies in the world.

In all, the EU estimated that more than 70,000 citizens of 12 countries died from heat-induced illnesses over a four-month period in the summer of 2003. This number represents more fatalities than have resulted from any EU or American conflict since World War II, or any natural disaster (hurricanes, earthquakes, floods, etc.) to have ever struck a developed nation. It dwarfs the 1,800 deaths attributed to Hurricane Katrina in 2005 and effectively renders trivial the 774 lives lost during the highly publicized SARs epidemic that struck Europe and Asia in the same year as the heat wave, an event giving rise at the time to virtual hysteria. Americans would need to experience more than 25 terrorist attacks equivalent in destruction to 9/11 before such a death toll would be approached. Yet the global response to this climate event, an event that reveals more about the profoundly changing environment in which we now live than any other yet endured, has largely been one of indifference. Although numerous books have been published and movies produced on recent disasters such as Katrina and the SARs outbreak – at the time of this writing, the U.S. Library of Congress held more than 200 books on Hurricane Katrina alone – to date, not a single book has been published on the 2003 heat wave.

Not one.

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[T]he events of summer 2003 highlight a central truth about climate change that is often lost in the global- and future-oriented debate over a warming environment: the impacts of climate change at the urban scale are profoundly greater than the impacts of climate change at the global scale. And a second truth: the impacts are here with us today.

One of the key findings of postevent assessments following the 2003 disaster was that the vast majority of those who perished in the heatwave lived in cities. This fact is not explained by the larger percentage of the national populations residing in cities across Europe, because the rate of heat wave fatalities among residents of large urban areas such as Paris and London was greater than that among residents of smaller towns or rural areas. And this fact is at odds with the general presumption of superior health care in cities, which provide far greater access to emergency medical facilities. The heat wave claimed a disproportionate number of lives in cities simply because the cities were hotter than rural areas – substantially hotter.

Cities do not cause heat waves – they amplify them. Because of the greater prevalence of mineral-based building materials, such as stone, slate, concrete, and asphalt, cities absorb and retain substantially more heat than rural areas characterized by more vegetative cover. Known generally as the “urban heat island effect,” this phenomenon keeps cities warmer by several degrees than surrounding countryside throughout the year. However, during unusually hot days, the divergence between urban and rural temperatures can be much greater, literally tipping the balance between an unpleasantly hot day in one environment and a public health emergency in another.

This observation is illustrated well by data obtained during the 2003 heat wave. As part of an ongoing research study unrelated to the heat wave itself, an extensive network of meteorological instruments was in place in and around Strasbourg, France, throughout the heatwave event. Data from this network showed that the increase in heat index values at the height of the event, a measure that accounts for both temperature and humidity and most closely captures the physiological impacts of heat on the human body, was about 30% greater in the downtown district than in the surrounding countryside. Nighttime heat index values, which provide the most direct indicator of the body’s ability to cool down during a heat wave, were at times measured to be 50% greater in the urban center. What these measurements show is that the effects of the heat wave for urban residents were as much as 50% greater than for rural residents just a few miles away. The significance of these differences
is hard to overemphasize: one’s decision to remain in a city during a heat wave can quite literally mark the difference between life and death.

In the first decade of this century, for the first time in history, the majority of the planet’s humans resided in cities. We are an urban planet. If ongoing changes in climate are to have an impact on the human species, most of these impacts will play out in urban environments. Yet climate science to date has provided very few insights into how cities, in particular, will be influenced by climate change. Continuously framed as a global phenomenon, with implications for the planet as a whole, the climate change of peer-reviewed scientific papers and international accords does not seem to be taking place anywhere people actually live. In fact, the moment a climate-related event with tangible geography occurs, such as a heat wave or hurricane of unprecedented intensity, we are quickly told that no single event can be proven to be an indication of climate change. For the nonscientist attempting to formulate an opinion on the issue, the likely outcome is not surprising: if climate change is not happening in the places we live, it’s not happening.

More problematic for cities than the framing of the issue, however, is the uniform adoption of the global scale as the legitimate basis for scientific inquiry. Preoccupied with measuring the rate of temperature change at the scale of the planet as a whole, we have largely overlooked the rate at which climate is changing in cities. Indeed, as examined in the following pages, temperature data from urban weather stations are statistically adjusted in the global temperature datasets employed by climate scientists to measure global warming. Were these temperature measurements not modified, we would find that the environments in which we live are actually warming at a substantially higher rate than the planet as a whole, with troubling implications for anyone who lives, works, or owns property in cities.

Above all, it is the rate at which climate is changing in cities that most clearly illuminates the lessons of the European heat wave for urban governments and residents. Were such an event to remain a statistical improbability, cities could be forgiven for prioritizing other critical needs above preparations for combating climate change. Studies focused on this question following the heat wave would show that, absent the influence of human-induced warming, an event approaching the intensity and duration of the 2003 heat wave would indeed remain quite rare, occurring, on average, once every thousand years. Yet, assuming global temperatures continue to rise at the rate of recent decades, the frequency of such a heat wave increases substantially – so much so that, by the year 2040, such heat waves may be expected to occur every year. Such a world seems hardly imaginable: temperatures of sufficient intensity and duration to physically warp the steel of railroad tracks and melt the asphalt of streets – every year.

For those of us who give ourselves better than even odds of being here in 30 years, a principal lesson of [the 2003 heat wave] is undeniable: this is not our grandchildren’s problem alone.

Excerpted from the book THE CITY AND THE COMING CLIMATE by Brian Stone. Copyright © 2013 by Brian Stone. Reprinted with permission of Cambridge University Press.