The greatest climate risks to cities are extreme events and sea level rise. Tropical cyclones, floods and landslides resulting from extreme rainfall, wildfire, and heat waves are examples of extreme climate-related events that could devastate a city. As discussed in the coastal impacts lesson, sea level rise is starting to stress some cities and worry many others. Other important climate risks include health impacts (particularly heat stress) air quality, water-borne illnesses, and disease vectors. Cities with strong urban heat island effects are particularly prone to heat stress and air quality issues.
What makes a city more or less vulnerable to climate change and its impacts? Many, many factors. But, we can think about them in 3 broader categories:
Industry is less central today than it was previously in many developed world cities, but it is still dominant in most less-developed cities. In any case, climate has a major impact on most industries. Like the service sector, industry depends on the integrity of the infrastructure. For instance, most industries can experience considerable losses when extreme climate negatively affects transport networks, such as roads, bridges, and pipelines. Many industries are directly weather-dependent, such as construction, so any change in climate will affect them positively or negatively. Other industries are indirectly influenced by climate, but are nevertheless at the mercy of cascading indirect impacts of a changing climate. An example would be the food processing industry, which can shut down altogether when crops fail because of uncooperative weather or climate. The energy production industry is in large part responsible for climate change and is being affected positively and negatively by it. As temperatures go up, more energy is needed to cool homes and businesses but less is required to heat homes, and the direction of change is dependent on the region under consideration. Moreover, as climate change mitigation efforts take hold, fossil fuel-intensive industries will lose business and alternative industries will gain, resulting in a restructuring of energy production.
The social systems of cities are being affected by climate change. Cities tend to be the microcosms of the global system socially, in that the more-affluent classes tend to be the ones driving greenhouse gas emissions, and the less-affluent classes suffer the impacts. Thus, the more affluent are starting to feel mitigation efforts as they alter their energy use, the technologies they use, the nature of their home and business environments, their transportation patterns, and the products they purchase. These changes essentially influence their lifestyle, but not their well-being. The less affluent feel changes in lifestyle to a lesser degree, and are more likely to experience negative impacts of climate change on their well-being, especially in cities in less-developed countries. The most vulnerable among the lower classes are the least empowered and poorest: elderly, young, handicapped and infirm, recent immigrants, and women. These groups are the most exposed to climate and weather. They are most sensitive and have the least adaptive capacity because they have the least access to safe water, food, health care, shelter, social services, employment, and information. Climate change impacts -- sea level rise, increased severe storms, floods, and droughts, and others -- further decrease these essential facets of quality of life and, indeed, survival.
A city is essentially a network of complex, interacting human systems. It is possible to place the human systems most affected by climate change into four categories: utilities and infrastructure, services, industry, and social systems. Let us take a look at each of these systems.
Utilities and infrastructure are fundamental to the functioning of any city. Health and quality of life depend on a safe, reliable water supply and on sanitation via sewers and storm drainage systems. Projected increases in severe storms, floods, and droughts will place considerable stress on these systems and often compromise them. Also basic to any modern city are transport, power, and telecommunication systems. Climate and weather have a major impact on these networks, so any change in climate will undoubtedly affect them, both positively and negatively. For instance, decreases in snow and ice will ease winter travel in heavily traveled midlatitude transportation networks, but increases in the length and intensity of the severe storm season will adversely influence summer travel. As discussed in the coastal impact lesson, the impact of rising sea level on coastal infrastructure is expected to be devastating without major investment in adaptation.
Services dominate the economies of most cities and include trade and finance, retail and commerce, tourism and hospitality, and insurance. Services need reliable utilities and infrastructure to function –– to get employees to and from work, to provide them with water, food, and sanitation on the job, to supply the energy needed to power their electronic and other tools, and to maintain telecommunication networks. As noted above, climate change will either help or harm utilities and infrastructure by decreasing or increasing disruptions and therefore indirectly help or harm services dependent on them. It is also easy to see how climate change will directly affect such services as tourism and insurance, either affecting them positively or negatively depending on the nature and timing of climate impacts on any particular place.