Humans have been urbanizing in earnest since the beginning of the Industrial Revolution. Worldwide, 55% of humans live in urban areas, and the ratio is much higher in the Americas. This trend is only accelerating, with automation of agriculture and resource extraction reducing rural labor needs, while the information and service economies of cities continue to increase labor needs.
As an example, the Appalachias of 1910 had close to 800,000 people employed in the coal industry, and that number is around 60,000 today. For comparison, New York City had under 5 million residents in 1910 vs 8.6 million today.
Global warming caused by humans since the beginning of the Industrial Revolution has a correlation with urbanization. Automation allowed and required the work force to leave rural areas and congregate in much more efficient cities which produced much more value. Urbanization is one of the factors which allowed more humans to survive and hence the population to grow. Cities were integral to the success of the Industrial Revolution, and without them humanity wouldn’t have changed the climate as much. But there are dozens of other factors, so it can’t be stated that cities are the cause of global warming, just a factor in the system which led to global warming.
Now that we are moving into a new energy economy, cities remain the most efficient way to produce value, house the vast majority of the populace, and create information. Contra-urbanization would not aid in decreasing global warming but would in fact increase energy demand substantially, and until the energy supply is completely decarbonized, would lead to increased global warming.
Since WWII in North America, there is a causative factor related to urbanization and global warming. The rise of the car suburb and related sprawl has led to vast increases in distances traveled by mostly individuals in large automobiles and SUVs to work, shopping, and entertainment. Those large automobiles all have been gasoline- and diesel-fueled until very recently, and even now the vast majority still are. And roads and distant suburbs are much more energy expensive to build and service per capita than dense urban buildings. Suburban sprawl is causative of global warming. Outer suburbs with single-family detached homes and often one or more vehicles per adult are one of the most energy intensive and carbon-emitting forms of living, as long as the primary energy sources for transportation, services, and heating are fossil fuels. As soon as the outer suburbs are transformed with electric transportation, electric heat pumps, electric service vehicles, and the electricity comes from carbon-neutral sources, the suburbs will merely be inefficient and causes of regional congestion of little value. They’ll still be a poor urban pattern for other reasons, but it won’t matter nearly as much.
That’s the warming side of things. Climate change, defined as the rapid changes to historical weather patterns, sea level rise, and related impacts of rapid global warming, has correlations to urbanization, mostly in the form of economic impacts.
Cities are both the most resilient form of living humans have created for masses of people, and most dependent on extended supply chains and automated rural resource extraction and agriculture. Cities have also been built in places where trade distribution forms came together, often sea ports. Their physical infrastructure, layout, and zoning assumes one set of climate conditions, frequency of severe weather events, and severity of those events.
But climate change means that for many major cities, those conditions have altered already and are expected to alter much more over the coming decades.
In North America, the canary-in-the-coal mine cities are New York and Miami. Superstorm Sandy was a deeply unusual storm. It was massively wide and came ashore relatively slowly across a huge area of New York and New Jersey. Lower New York was inundated and subways flooded. Entire seaside neighborhoods in the surrounding area were wiped out, and in some cases have been abandoned. Miami is built on tourism and agriculture dollars, along with port trade. But it’s flat, at sea level and built on porous limestone. And it’s exposed to both Atlantic and Gulf of Mexico hurricanes, which are becoming more severe. It gets its water from the Biscayne Aquifer, which has long had a salinity problem, but with sea level rise, the aquifer is getting more and more brackish. New York is easier to protect from climate impacts, but it’s incredibly hard to protect Miami and it will likely diminish substantially over the coming decades. It only exists at its scale because of electric air conditioning, and extreme weather interrupts electrical supplies. It only takes a few days of no electricity in humid and hot days and nights for mortality rates to spike.
So some cities are poorly sited and built for the reality of a rapidly changing climate. Others are better situated. Before a NASCO conference I was speaking at recently in Vancouver I had breakfast with the regional development executives for the Columbus, Ohio, region. That city has reinvented itself as a massive distribution hub for a large portion of the USA, with rail yards, trans-shipment yards and freight trucking bustling, and major warehouse distribution centers for the major retail and wholesale organizations. They have also been very successful at attracting data warehouses based in part on Amazon’s presence, and now are an AI hub and autonomous driving hub. One aspect of the conversation dealt with regional resilience and shifting of opportunity related to climate change. They had already seen a Japanese firm shift from planning an east coast distribution center to a Columbus-area DC simply because it wouldn’t be disrupted by sea level rise and hurricanes.
It’s expected that climate change will have three impacts in the Columbus area, only two of which it’s somewhat prepared for. The first is simply climbing temperatures with a relatively impoverished subset of the populace who can’t afford air conditioning. They are the warehouse workers of the distribution centers. They are the security guards and drivers and janitors. And they are at risk of increased temperatures causing increased ill health for them and their families. The second is flooding from thunderstorms, a traditional problem for Columbus. Unlike southeastern US cities, Columbus has abundant water supplies, although its increasingly difficult to find clean fresh water for its needs due to agricultural effluents, but that abundance turns into point excesses quite regularly. And climate change fuels changes and likely increased rainfall and frequency and severity of thunderstorms. Are the DCs set for 1000-year floods every 5 to 10 years? Probably not. Finally, Columbus is subject to tornadoes, and while studies are mixed about causes so far, tornadoes have been changing their patterns, frequency, and severity and are expected to definitely increase in frequency and severity in the future due to climate change.
And warehouses are lovely targets for tornadoes, and tornadoes come with thunderstorms. Is Columbus set up to accommodate both 1000-year flooding and tornado swarms? Can it be? Is its building zoning up to date? Are its flood control systems set up for regular 1000-year flooding events? For 10,000-year flooding events? Probably not, and zoning and regulations needs to work through the implications of both of these things.
But these are more solvable problems than hurricanes and sea level rise, and Columbus is arguably more attractive than coastal cities for forward looking development. Similarly, I assessed sea level threats to major growth cities based on McKinsey’s study of future economic megacities and found a shift, especially in China, to inland cities.
So there are relationships, but they vary substantially. What urban areas don’t do is cause any illusion of warming due to the heat island effect as global warming ‘skeptics’ like to claim. That’s adjusted for, and there is strong consilience on historical and changing temperatures.