The recently released draft report of the Intergovernmental Panel on Climate Change (IPCC) lays out in no uncertain terms that we face an insurmountable challenge in addressing climate change and its impacts. One shocking takeaway is that sea-level rise is now thought to be irreversible. Indeed, rising temperatures and changing weather patterns threaten to send some cities under water, while causing others to dry up. These opposing challenges increasingly threaten the lives and livelihoods of people in many countries as rapid urbanization is making cities even more densely populated. Floods and droughts threatening the world’s cities will force governments of the world to reevaluate the quality of their infrastructure, their disaster management strategies, and of course, their environmental footprints.

Urbanization exacerbates worrying climate change trends

In a newly published chapter in A Research Agenda for Political Demography, we identify a strong reciprocal relationship between patterns of urbanization and the negative consequences of climate change, of which the problem of rising sea levels is a clear example. Simply stated: Cities intensify human-induced warming locally. And data show that urbanization is trending positively, with ever more people (forcibly or voluntarily) moving into cities and natural growth in cities outstripping the pace of population growth in rural areas. For instance, analyses of the 2020 U.S. Census clearly indicate that the United States’ most notable population growth is predominantly in urban areas, with the population of climate-stressed Phoenix, AZ, for example, growing by 9.4 percent in the past decade. In some countries, climate change itself is a driver of urbanization. For example, one study found that between 2005 and 2012, 8 percent of India’s rural-urban migration was at least partially driven by climate change, especially as rainwater shortfalls harmed the livelihoods of people from agricultural communities.

While shocking, the IPCC report’s main conclusions are not surprising. Indeed, New Security Beat has featured articles for years about the implications of climate change for human security. Scientists have long anticipated that sea-level would rise by an average of approximately 1.5ft by 2100. But today, evidence suggests that this is likely to be closer to 2ft—the recent rate of rise has more than tripled from that of 1901 to 1971.

There are currently 250 million people worldwide living in coastal areas highly vulnerable to flood damage. This number is projected to increase to 630 million by the end of the century. A shortlist of coastal megacities vulnerable to climate-related flood damage includes Kolkata, Mumbai, Dhaka, and Guangzhou, with many other large cities at risk, especially in South and Southeast Asia. This is made all the more disturbing given sea level rise. Jakarta, one of the world’s fastest growing cities, could be entirely underwater by 2050, and Shanghai and Hong Kong are also under threat. The developing world’s large cities are not the only ones threatened by sea level rise.  Recent research shows that Miami, Florida is perhaps the city most vulnerable to climate-related flooding, at least in terms of the value of likely property damage.    

In addition to being exposed to conditions of too much water, many of the world’s major cities are also at risk of water scarcity and drought conditions. Indeed, the number of major cities with average maximum temperatures above 95 degrees Fahrenheit is expected to more than double from 354 to 970 by 2050, 14 out of the 20 biggest cities globally experience frequent water scarcity or drought conditions. Accordingly, scenarios such as the taps running dry in Cape Town in the springs of 2018 and 2019 will only become more familiar. Research shows that climate-exacerbated water scarcity is already a problem for numerous cities across the Middle East, North Africa, and South Asia, as well as U.S. cities like Phoenix, Denver, and Los Angeles. The problem is likely to worsen significantly as changing conditions are projected to reduce rainfall in many areas of the world, especially in Latin America and sub-Saharan Africa, where infrastructure and resource distribution are ill-equipped to handle such shocks. 

What, then, can be done about these worrisome dual trends?

First, more research is needed to address the relationship between urbanization and climate change. For instance, climate change exacerbates natural disasters, which, in turn, forcibly displaces populations that often head towards urban destinations. More research could help us to better understand the triggers of sudden (e.g., storm-related) versus slow (e.g., drought-related) migration processes, as well as those that are more likely to involve permanent or temporary/seasonal resettlements. Furthermore, while scholars and policymakers alike are increasingly paying attention to questions about climate-related migration and its effects on receiving (typically, urban) areas, fewer are questioning whether migration helps individuals avoid the catastrophic effects of climate change—i.e., whether it is a sustainable form of adaptation to the climate change risks that we face.

Second, climate change is already increasing the need for disaster risk reduction and response planning by governments, including the need to evacuate cities during extreme weather events. We’ve seen how droughts and increased temperatures are increasing the risk of wildfires, which have severely damaged homes on the outskirts of major cities like Perth, Australia, Athens, Greece, and Tucson, Arizona. Risk of severe flooding in coastal cities will likewise require authorities to improve plans for evacuation, damage mitigation, and other emergency procedures.

Third, we need to identify methods of making urbanization more sustainable. In coastal cities, infrastructure upgrades are especially important since the growing threat of climate change requires not only reducing emissions, but also making coastal floods less severe and more survivable. Amsterdam, with its levees, dykes, designated flood areas, and flood-resistant housing, is sometimes cited as a model city for using infrastructure and urban design to reduce vulnerability to catastrophic floods. In drought-affected areas, this also means developing policies and infrastructure to more effectively obtain and manage water. Given the diverse nature of most cities and the relative vulnerability of underprivileged communities, governments will also need to think about how to equitably implement such responses. It remains to be seen if or how well the world’s major cities can implement similar measures.

Finally, it is important to remember that cities are not just passive victims of climate change, they are also heavy contributors to the problem. As cities are hubs of human activity—industrial and otherwise—they tend to have much larger carbon footprints compared to rural spaces. The presence of factories, the consumption of electricity, and transportation of people from one place to another all generate carbon emissions and can contribute to climate change. Efforts to reduce global carbon emissions will likely require significant improvements to energy efficiency and the quality of infrastructure.