This lesson is a bit unique in that we are tackling two separate but decidedly related issues - impacts of climate change on our coasts and impacts of climate change on our cities. Not all cities are near water, but many of our largest, busiest, most populated cities are. Therefore, it makes sense to think about these issues in tandem while also recognizing their unique attributes. And then, let's add extreme weather events to the mix because while they don't happen exclusively on the coasts or in the cities, the nexus of these produces some of the biggest concerns related to human impacts of a changing climate.
By the end of this lesson, you should be able to:
This lesson will take us one week to complete. Please refer to the corresponding module in Canvas for specific assignments, deliverables, and due dates.
If you have questions, please feel free to post them to the "Have a question about the lesson?" discussion forum in Canvas. While you are there, feel free to post your own responses if you, too, are able to help a classmate.
For this lesson, we'll explore two of the most vulnerable environments to climate change impacts - the coasts and cities with particular emphasis on their vulnerabilty to extreme weather events.
Scientists have little doubt that the impacts and costs of climate change will be unavoidable –– and most likely the greatest –– in coastal environs. More people and more infrastructure will suffer harm in coastal zones than in any other place on Earth. Most other aspects of climate change are only now starting to be felt, but impacts in coastal zones are readily apparent today and accelerating. In response to this unfolding disaster, many of the world’s great coastal cities are already developing adaptation strategies and hoping to avoid the human and financial tragedy that awaits them.
About half the world’s population currently lives in cities. An increasingly larger proportion of the population will live in cities at the same time that climate change intensifies. About 85 percent of the Western Hemisphere’s population will be living in cities by 2030, up from somewhere near 50 percent in the middle of the 20th century. Even more shocking urban growth has taken place in Asia and Africa, going from 17 and 15 percent urban in 1950 to a projected 54 and 51 percent in 2030, respectively. Estimates are that more than 37 percent of the world’s population will live in cities with populations larger than 1 million people in 2030. Against this backdrop of unprecedented urban growth, this lesson will explore relationships between cities and climate change.
Many people mistakenly think that cities have no connection with climate because urban dwellers’ homes and vehicles insulate them from direct contact with it. Climate, however, is intimately linked to cities and their inhabitants. Many urban activities are climate sensitive, including such diverse activities as basic water use, transportation, construction, and sport and recreation. Climate also affects the costs of climate control, causing urbanites in tropical and subtropical climates to expend huge amounts of energy and money on air conditioning, whereas city dwellers in extratropical climates spend vast sums on heating in winter. Climate and weather also interact with socioeconomic and other natural stresses to increase or decrease overall stress on urban inhabitants.
Climate-city relationships therefore significantly influence the way that cities function, so if these interactions change because climate changes, cities must adapt to accommodate the new climate. Consequently, understanding the likely impacts of climate change on cities, the vulnerability of cities to those impacts, and the potential of cities for adaptation to climate change is a vital area of study because of the enormous number of people who live in cities.
Year | Percentage Urban | Percent of the world's urban population living in the region | Percent of urban population in different size-class of urban centre, 2000 | ||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1950 | 1975 | 2000 | 2030* | 1950 | 1975 | 2000 | 2030* | Under 0.5 m | 0.5 - 1 m | 1 - 5 m | 5 - 10 m | 10 m+ | |
Northern America | 63.9 | 73.9 | 79.1 | 86.7 | 15.0 | 11.9 | 8.8 | 7.1 | 37.4 | 11.0 | 34.3 | 5.4 | 11.9 |
Latin America and the Caribbean | 42.0 | 61.2 | 75.4 | 84.3 | 9.6 | 13.0 | 13.9 | 12.4 | 49.8 | 9.0 | 21.7 | 4.9 | 14.7 |
Oceania | 62.0 | 71.5 | 70.5 | 73.8 | 1.1 | 1.0 | 0.8 | 0.6 | 41.9 | 0.0 | 58.1 | 0.0 | 0.0 |
Asia | 16.8 | 24.0 | 37.1 | 54.1 | 32.0 | 37.9; | 47.9 | 53.7 | 49.0 | 10.0 | 22.6 | 8.8 | 9.7 |
Africa | 14.7 | 25.4 | 36.2 | 50.7 | 4.5 | 7.0 | 10.3 | 15.1 | 60.2 | 9.6 | 22.1 | 4.6 | 3.5 |
WORLD | 29.0 | 37.2 | 46.8 | 59.9 | 100.0 | 100.0 | 100.0 | 100.0 | 52.6 | 9.8 | 22.4 | 6.8 | 8.4 |
We hear a lot about sea level rise in the context of climate change. But what are the mechanisms by which the water is rising? There are three factors:
To further complicate an already complex matter, these changes in ice volume aren't happening in a vacuum. NASA has this nice visualization [14](I couldn't figure out how to embed it here, but please go review it, it's only 1:08 minutes long) of the snowfall Antarctica experienced over the 20th century. As it turns out, because many parts of Antarctica saw increased snowfall, this helped mitigate the sea level rise we would have otherwise expected (by their estimates, this amounted to about 0.4 inches).
As sea level rises, it pushes inland. How far it penetrates depends on the interplay of several factors.
Along the Mid-Atlantic coastline from about New York City to Cape Hatteras, North Carolina, the combination of climate change-induced sea level rise, a rapidly sinking coastline, coastal currents that reinforce sea level rise, and a very broad, flat coastal shelf results in relative sea level rise that is about twice the global average.
While sea level rise might feel like a more direct threat to some human settlements, increasing ocean temperatures themselves carry important consequences to understand, too. The rising ocean temperature is having dramatic effects in some areas. Along polar coastlines, sea ice is thinning and melting altogether, opening the coastlines for modern human development, but causing traditional societies and wildlife that depend on the presence of sea ice to move or die. Coastal permafrost is melting quickly, causing shoreline collapse and rapid coastal retreat, damaging ecosystems and human structures –– indeed, entire Native Alaskan settlements are moving as the villages literally collapse. In tropical areas, rising ocean temperatures are contributing to coral bleaching and death, destroying these rich ecosystems worldwide and wrecking tourism industries in many locations.
Perhaps an even greater threat associated with climate change is ocean acidification. The global ocean absorbs a major proportion of the atmospheric carbon dioxide emitted by fossil fuel burning and other human activities. The absorption of CO2 is acidifying ocean water. Scientists estimate that since the beginning of the Industrial Revolution, ocean acidity (in terms of H+ ion concentration) has increased 30 percent and will increase much more in the future. The main concern is that increasing acidification could affect major oceanic carbonate-based species and ecosystems–– from plankton, to corals, to shellfish.
All these impacts are happening today and will certainly increase in the future. Sea level rise will continue to accelerate from glacial melt and especially from thermal expansion; it could become catastrophic if the Greenland or West Antarctic ice sheets were to collapse. Ocean storms such as hurricanes are expected to intensify, and some scientists think that ocean storm frequencies could increase in the future. Accelerating sea level rise and more intense storms will mean that storm surge and wave damage will be much greater, as will be coastal erosion. Coastal ecosystems will come under even more stress than they are feeling today. Ever-increasing ocean temperatures and acidification could mean the end of corals, and a worst-case scenario could see the collapse of major ocean food chains.
Sea level responds to two elements of climate change. First, as the lower portions of the atmosphere warm, freezing levels rise and move poleward, causing glaciers to melt in mountain and polar regions. The resulting meltwater drains to the oceans and increases their volume, thereby raising sea level. Scientists have understood the relationship between sea level and glaciers for more than a century: when ice sheets build on the continents, sea level goes down by 100 meters as the water from the oceans goes into these glaciers; when the ice sheets melt, water rushes back to the oceans and sea level rises, pushing coastlines miles inland from their positions during glacial maxima. Human-induced global warming is therefore augmenting this natural process.
Sea level also responds to climate change through the thermal expansion of water. When water heats, it expands; as the ocean heats with global warming, it expands. As long as ocean temperatures continue to increase, the global ocean will continue to expand.
To understand the human risks of climate change in the coastal zone, it is useful to examine the vulnerability of coastal people and places to climate change impacts. Recall that there are three dimensions of vulnerability: exposure, sensitivity, and adaptive capacity. Exposure usually relates to physical vulnerability, whereas sensitivity and adaptive capacity relate to social vulnerability.
As described in the account of physical impacts above, exposure of coastal people and places is increasing. Climate change is exposing billions of people and their built environments to rising sea levels, more intense storms, enhanced storm surge, and worse coastal erosion. These people are exposed to degrading and reduced ecosystems, upon which many people depend for their livelihoods.
How much this increased exposure harms people and places depends on their sensitivity. In underdeveloped and developing countries, hundreds of millions of people residing in the coastal zone live in poverty, and their livelihoods are at risk of harm by climate change. Many of these people are very young or very old, which makes them even more sensitive. In addition, these impoverished people tend to live in substandard housing, without running water or adequate sanitation, nutrition, and health care; burgeoning poverty, corruption, and overcrowding mean that many of these areas are getting worse, rather than better over time. Coastal hazards associated with climate change exacerbate these infrastructural challenges, sometimes greatly.
In developed countries, socioeconomic safety nets are much greater and far fewer people are directly sensitive to the impacts of climate change. Instead, the sensitivities relate to the built environment and can still be great. Inundation from sea level rise and storm surge are the greatest threats. Consider the case of New York City, where trillions of dollars in sophisticated infrastructure -- subways, telecommunications, sewers, and water systems -- exist below ground and could easily be submerged by storm surge in the short run and permanent inundation in the long run. If such flooding occurred, the impacts would cascade around the world. For instance, if workers in the financial district could not get to work because the subways were closed, and if the telecommunications connecting to the New York Stock Exchange were to go down, financial chaos and crisis would spread worldwide. Given that the world’s three major financial centers (New York, London, and Tokyo) are coastal cities, it is clear that in the long term even more affluent countries are sensitive to coastal zone impacts of climate change.
We're sensitive to different things. In sum, it is possible to say that sensitivity to climate change is increasing in the coastal zones of undeveloped, developing, and developed countries. In less affluent countries, sensitivities tend to involve direct impacts on people, but in more wealthy countries, sensitivities are to infrastructure and therefore are felt by individuals and households indirectly. The interconnectedness of the global society means that coastal zone sensitivities and impacts propagate throughout the world. This sensitivity to climate change is mounting in coastal areas because of growing populations and their associated infrastructure.
Adaptive capacity provides the means to decrease vulnerability by either reducing exposure or lessening sensitivity. In the coastal zone, adaptive capacity varies greatly at all scales, from person to person, household to household, neighborhood to neighborhood, settlement to settlement, and country to country. Many factors affect adaptive capacity -- financial resources, technological resources, political resources, and many more. All things being equal, people and places with greater financial resources have greater adaptive capacity. For instance, a rich city might be able to afford to build a sea wall around the city, but a poorer city might not. The rich city is more likely to have a strong intellectual and educational heritage and the technological means to design the sea wall, whereas the poorer city might still possess these characteristics, but it cannot apply them without access to funding. However, even the rich city might not be able to build the sea wall if the political elite are ideologically opposed to doing so; if the poorer city does not follow that ideology and has strong political connections to the nation’s rulers and access to national funds, then they might, in the end, be able to build the sea wall.
The physical impacts of climate change on coastlines are bad, but the human impacts could be even worse. Humans put more pressures on coasts than any other area, which should be no surprise to you now that you've seen how reliant on the coasts are settlements are.
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.
The impacts of climate change on cities and the coastal zone will be significant and are compounded by the fact that coasts double as population centers for almost half of the world's people.This growing density of population in the coastal zone is exposing more people and infrastructure to climate change, greatly intensifying the impacts.
Ocean warming, sea level rise, and ocean acidification are clearly observable today and their impacts are unavoidable. Even with strong, concerted efforts to mitigate climate change, and even if the polar ice sheets do not collapse and cause catastrophic sea level rise, ocean warming and sea level rise will accelerate during the 21st century because of the climate system’s inherent lags and the thermal inertia of the ocean. Sea level rise will continue for centuries, again because of the ocean’s thermal inertia. Ocean acidification mirrors carbon emissions to the atmosphere, so the oceans will continue to acidify for as long as carbon emissions rise, but will fall when emissions eventually fall. In this lesson, you also learned that cities are already feeling the impacts of climate change, but that those impacts are going to get much worse as cities continue to grow and as climate change continues to intensify. You found out that the human systems most affected by climate change are utilities and infrastructure, industry, services, and social systems. You discovered that the overall vulnerability of any city is a function of its location, size, and type of economy. Finally, you learned that although the capacity for adaptation is generally high in cities, four factors complicate adaptation: adaptation depends on the rate and magnitude of climate change; adaptation links to economic, political, technical, and social systems at scales ranging from local to global; climate change is only one of many risks that cities manage; and adaptation sometimes has unanticipated consequences.
In short, the impacts of climate change on the coastal zone will be momentous. Significant coastal adaptation is unavoidable and will be costly. To minimize these impacts and costs, climate change mitigation is critical and should start at once. In this lesson, you learned about the physical impacts of climate change on coastal zones, especially sea level rise and the two factors –– glacier melt and thermal expansion of sea water –– driving that rise. You read that sea level rise causes many problems such as coastal erosion, enhanced storm surge, and salt water intrusion. You also learned that climate change melts coastal permafrost, kills corals, and acidifies seas. These and other physical impacts have tremendous impacts on humans and the built environment, which are best understood by examining vulnerability's three dimensions: exposure, sensitivity, and adaptive capacity. The lesson compared the costs of adaptation to the costs of failing to adapt. It concluded that the impacts of climate change are unavoidable in the coastal zone, so adaptation should start at once.
In this lesson, you have learned that cities are already feeling the impacts of climate change, but that those impacts are going to get much worse as cities continue to grow and as climate change continues to intensify. You found out that the human systems most affected by climate change are utilities and infrastructure, industry, services, and social systems. You discovered that the overall vulnerability of any city is a function of its location, size, and type of economy. Finally, you learned that although the capacity for adaptation is generally high in cities, four factors complicate adaptation: adaptation depends on the rate and magnitude of climate change; adaptation links to economic, political, technical, and social systems at scales ranging from local to global; climate change is only one of many risks that cities manage; and adaptation sometimes has unanticipated consequences.
We've explored the challenges coastal environments - both build and natural - face in a changing climate. We've also learned about the challenges for cities. When we tie these challenges together and look at the compounded dangers for coastal cities, the urgency of the problem emerges. With so much of the world's population relying on coastal cities for their homes, livelihoods, and global economy, there is much to be lost to adverse impacts from climate change.
Obviously not all extreme weather risk happens at the coasts or within cities, but we've explored them together, recognizing that when these factors overlap - coastal cities experiencing extreme weather events - the climate impacts for people and our environment are high. While the connections between some weather events and climate change are not as clearly understood as others, people are increasingly vulnerable to these events as they become more severe and frequent. We'll spend some time in Unit 3 talking about how we can respond to these events to increase our adaptive capacity.
You have reached the end of Lesson 5! Double-check the lesson assignments in the corresponding lesson module in Canvas to make sure you have completed all of the tasks listed there.
Links
[1] https://www.flickr.com/photos/33707373@N03/4552301841/
[2] https://www.flickr.com/photos/33707373@N03/
[3] https://creativecommons.org/licenses/by/2.0/
[4] http://www.flickr.com/photos/bradjacobson1/4132574746/#/photos/bradjacobson1/4132574746/lightbox/
[5] http://www.flickr.com/photos/bradjacobson1/
[6] http://creativecommons.org/licenses/by-nc-nd/2.0/
[7] https://www.ipcc.ch/
[8] https://www.noaa.gov/education/resource-collections/climate-education-resources/climate-change-impacts
[9] https://climate.nasa.gov/news/2680/new-study-finds-sea-level-rise-accelerating/
[10] https://www.nationalgeographic.com/environment/global-warming/big-thaw/
[11] https://www.nationalgeographic.com/magazine/2017/07/antarctica-sea-level-rise-climate-change/
[12] https://www.nature.com/articles/s41586-018-0179-y
[13] https://www.pnas.org/content/116/4/1095
[14] https://svs.gsfc.nasa.gov/13117
[15] https://www.nature.com/articles/ncomms7346
[16] http://www.flickr.com/photos/usarmyafrica/5157191333/
[17] http://www.flickr.com/photos/usarmyafrica/
[18] http://creativecommons.org/licenses/by/2.0/
[19] https://www.grida.no/resources/7332
[20] https://creativecommons.org/licenses/by-nc-sa/2.0/
[21] http://climate.nasa.gov/evidence/index.cfm
[22] https://www.ipcc.ch/report/ar4/wg1/observations-ocean-climate-change-and-sea-level/
[23] https://www.grida.no/resources/5638
[24] http://onesharedocean.org/public_store/lmes_socioeco/population/lmes_socio_eco_coastal_population_2010_100km.png
[25] https://www.washingtonpost.com/news/wonk/wp/2015/09/03/how-so-many-of-the-worlds-people-live-in-so-little-of-its-space/
[26] http://www.oceansatlas.org/subtopic/en/c/114/
[27] https://www.flickr.com/
[28] http://www.flickr.com/photos/bear_in_va/
[29] http://creativecommons.org/licenses/by-nc-sa/2.0/
[30] https://www.123rf.com/profile_kwest19
[31] https://www.bbc.com/news/science-environment-46384067
[32] http://www.desktopdress.com/desktop-wallpapers/natural-pictures/beautiful-sydney_australia#1280x960