Cascade Tuholske is a postdoctoral research scientist at Columbia University’s Center for International Earth Science Information Network (CIESIN); Chris Funk is the director of the University of California Santa Barbara’s Climate Hazards Center; and Kathryn Grace is an associate professor of Geography, Environment, and Society at the University of Minnesota. This article first appeared on The Conversation.
Since the early 1980s, extreme urban heat exposure has increased considerably, with overall exposure more than tripling in the last 35 years.
According to a new report issued on October 4, 2021, about 1.7 billion people, or almost one-quarter of the global population, now reside in metropolitan regions where extreme heat exposure has increased.
The majority of reports on urban heat exposure are based on broad estimations that ignore millions of people who are at risk.
We took a deeper look. We counted the number of days per year that people in over 13,000 urban locations were exposed to excessive heat using satellite estimates of where everyone on the planet lived from 1983 to 2016.
The picture that emerges is one of dramatically growing heat exposure, particularly among the poor and disenfranchised.
Sub-Saharan Africa and southern Asia accounted for over two-thirds of the global rise in urban exposure to high heat.
This is due in part to climate change and the urban heat island effect, which occurs when temperatures in metropolitan areas rise due to the materials used to construct roads and buildings.
However, it is also due to the rapid increase in the number of people living in congested metropolitan areas.
The number of people living in cities and towns has increased dramatically, from 2 billion in 1985 to 4.4 billion now.
While patterns vary by city, the fastest urban population increase has occurred in African cities where governments have failed to plan or build infrastructure to meet the requirements of additional urban people.
THE HEAT RISK IS INCREASING DUE TO CLIMATE CHANGE.
In already warm countries, it is evident that the combination of rising temperatures and high urban population expansion is harmful.
How bad will it get, and who will be the hardest hit? In his latest Cambridge University Press book “Drought Flood Fire,” Chris Funk examines these heat exposure forecasts for 2030 and 2050.
Urban population growth is likely to continue, and if greenhouse gas levels continue to rise at their current rate, urban people will face significant increases in heat exposure.
Since pre-industrial times, the earth has warmed by slightly over 1 degree Celsius (1.8 degrees Fahrenheit),
and research reveals that this warming is leading to more catastrophic weather and climate extremes.
By 2050, we will very certainly have experienced another degree of warming, if not more.
By 2050, this level of warming, when combined with urban population growth, could result in a 400% increase in intense heat exposure.
The vast majority of those affected will live in river basins such as the Ganges, Indus, Nile, and Niger in South Asia and Africa.
The cradles of civilization are becoming epicenters of heat danger because they are hot, humid, crowded, and poor.
At the same time, research suggests that individuals on the margins—the poor, women, children, and the elderly—may lack access to services that could help them stay safe in excessive heat, such as air conditioning, rest during the warmest times of the day, and health care.
IDENTIFYING WHO IS AT RISK
We used data and algorithms that include breakthroughs in both social and physical sciences to count the number of urban dwellers exposed to excessive heat.
More than 3 billion people live in cities that are 25 kilometers or more away from a reliable weather station.
Climate model simulations used to forecast historical weather were not intended to assess a particular person’s risk; rather, they were meant to assess general trends.
This means that the consequences of excessive heat on hundreds of millions of underprivileged city dwellers around the world have gone undocumented.
In reality, just two extreme heat events have had a substantial impact on Sub-Saharan Africa since the 1900s, according to official records. Our findings reveal that this official record is false.
REASONS TO DO SOMETHING
The problem is not urban population expansion in and of itself. The confluence of high heat and big urban populations,
however, calls into doubt the traditional assumption that urbanization decreases poverty uniformly.
Historically, urbanization was linked to a change in labor from farming to industry and services, as well as increased agricultural efficiency due to industrialization.
However, urbanization has occurred in portions of Sub-Saharan Africa without accompanying economic expansion.
This could be attributable to health-improving post-colonial technical advancements.
Medical improvements have allowed people to live longer and more children to survive past infancy,
but post-colonial administrations frequently lack or fail to organize the resources needed to support large numbers of people moving to cities.
What concerns us is that, because urban excessive heat exposure has been largely ignored by development policy, impoverished urban inhabitants would find it more difficult to escape poverty.
Extreme heat has been found in numerous studies to affect labor productivity and economic output.
Low-wage workers have fewer safeguards than higher-wage workers.
They are additionally plagued by expensive food and shelter expenditures, as well as a shortage of air conditioning.
ACTIONS THAT CITIES CAN TAKE
The pandemic of the coronavirus and the Black Lives Matter movement has heightened calls for more political and scientific attention to inequity and injustice.
A fundamental characteristic of more integrated and socially relevant climate-health science is better data that helps to reflect the genuine lived experiences of persons.
Governments and businesses can benefit from cross-disciplinary collaborations like ours to accommodate new urban residents and prevent heat-related suffering.
If early warning systems are combined with activities such as the opening of cooling centers, for example, hazards can be reduced.
Governments might also set occupational heat regulations to protect marginalized people from heat and empower them to avoid it.
However, these initiatives must reach the most vulnerable populations.
Our findings provide a road map for policies and solutions to lessen the harm caused by urban excessive heat, not only in the future but now.