9.1: Introduction
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The Earth’s climate is changing, and it is changing at a rate that has not been seen in millions of years. The cause of this change is the production of anthropogenic greenhouse gas [1] emissions that can be traced back to the mid-20th century and the Industrial Revolution, that brought with it the invention of technology that allowed humans to burn fossil fuels for energy. Since that time, the rate of fossil fuel use has increased, and has allowed great leaps forward in public health, food production, science, and urbanization, in turn contributing to exponential population growth in countries all over the world. Unfortunately, the greenhouse gases (GHGs) produced from burning fossil fuels are disturbing fragile ecological relationships that have evolved over millennia. Part of the solar energy absorbed by the Earth is normally emitted back into space as infrared radiation; now, GHGs in the atmosphere absorb much of that infrared radiation which causes warming. The resulting climate change disturbs the ecology of the planet in manifold ways.
Climate change, or global warming, is a phenomenon that scientists were studying as far back as 1960, when the first models of global climate supported the theory that increasing greenhouse gases were warming the Earth’s climate (Robinson & Robbins, 1968). The causes and impact of global warming were known to scientists, news reporters, and policymakers alike. However, it wasn’t until 1995 that the global community came together to identify strategies to mitigate and adapt to climate change at the first United Nations Framework Convention on Climate Change (UNFCCC) Conference of Parties (COP). Fast forward 19 years later, the 21st Conference of Parties finally achieved a landmark agreement signed by 195 countries to limit the Earth’s warming to “well below 2 degrees Celsius above pre-industrial levels, and to limit the increase to 1.5 degrees Celsius to substantially reduce the risks and effects of climate change” (Rogelj et al., 2016, p. 631). This prescribed limit to warming is based on extensively peer-reviewed climate science by the Intergovernmental Panel for Climate Change (IPCC).
The IPCC is an intergovernmental branch of the United Nations that is responsible for assessing the science of climate change. Its mandate is to provide periodic updates on the science of climate change to help policymakers tackle this multi-sector issue. In 2018, the IPCC published a special report on the impacts of global warming of 1.5° C above pre-industrial levels. Currently, human activities are estimated to have already increased the temperature of the earth 0.8 to 1.2° C above pre-industrial levels. If humans continue to conduct business as usual, the IPCC estimates that we will reach 1.5° C sometime in the next 11 to 33 years (Hoegh-Guldberg et al., 2018). The report’s sobering bottom line tells us that there is a big difference in limiting global warming to 1.5° C compared to 2° C.
| IMPACT | 1.5° C | 2° C | MAGNITUDE of 2 vs. 1° C |
|---|---|---|---|
| Extreme heat: percentage of global population that will be exposed to severe heat at least once every five years | 14% | 37% | 2.6 times worse |
| Sea-ice-free arctic: the minimum number of ice-free summers | once every 100 years | once every 10 years | 10 times worse |
| Sea-level rise: amount of sea level rise by 2100 | 0.04 metres | 0.46 metres | 11.5 times worse |
| Loss of plants: species that lose at least half their range | 8% | 16% | 2 times worse |
| Loss of insects: insects that lose at least half of their range | 6% | 18% | 3 times worse |
| Ecosystems: amount of Earth’s land area where ecosystems will shift to a new biome | 7% | 13% | 1.86 times worse |
| Permafrost: amount of Arctic permafrost that will thaw | 4.8 million km2 | 6.6 million km2 | 1.38 times worse |
| Crop yields: reduction in maize harvests in the tropics | 3% | 7% | 2.3 times worse |
| Coral reefs: further decline | 70 to 90% | 99% | about 1.2 times worse |
| Fisheries: decline in fish stock | 1.5 million tonnes | 3 million tonnes | 2 times worse |
As Table 9.1 shows, global warming has impacts on everything from nutrient and geological cycles, to oceanic currents and atmospheric jet streams, to biodiversity and food production and supply. These multiple impacts present a great threat to human security.
This chapter first explores the primary impacts of climate change on the natural world. Next, the chapter explores the continuous drivers of climate change and frames climate change, in both its causes and its impacts, as an issue of social injustice and inequity. Further, this chapter will look at the climate justice social movement and its aims, and how the various climate justice campaigns around the world are at once targeting the reduction of greenhouse gas emissions as well as the underlying political systems that enable fossil fuel extraction and use and championing the just representation and consideration of those underrepresented communities on the front lines of climate disasters. We will end the chapter by drawing on the connections between the need for climate justice in reducing present and future risks to human security, in upholding democracy, a secure food supply and maintaining public health.
Climate Change Impacts on Natural Systems
The effects of climate change on natural systems include major changes in regional weather patterns, ocean acidification, sea level rise, and melting of glaciers and polar ice caps. Within and besides these major categories of impacts, there are many other effects on our natural world and the organisms that live in it. This section will look at the major climate change effects on Earth, and give brief examples of the impacts seen on humans and ‘nature.’ The next section will delve deeper into climate change impacts on ecosystems, giving an example of how one climate change impact can cause a domino effect that will be felt by the intimately interconnected species, nutrients, and habitats in a biome. Following this, detailed examples of impacts on human society will be discussed.
Climate change has major effects on the Earth’s overall temperature, the ocean, Earth’s biogeochemical cycles, and cloud formation. These effects translate further into major changes in weather such as increased variability and unpredictability of rainfall, increased intensity and frequency of heat waves, droughts, and extreme events such as hurricanes. Further, the increased overall temperature of the Earth induces accelerated melting of the polar ice caps and other large bodies of ice, creating sea level rise and threatening fresh water supplies. Finally, the increased levels of carbon dioxide in Earth’s atmosphere and oceans mean that there are greater levels of hydrogen ions in the ocean, causing ocean acidification.
Sometimes climate change can reinforce itself, which manifests as accelerating change. This is dangerous as it reduces our response time. For example, the albedo effect describes the accelerating warming of polar regions; as their cover of snow and ice disappears those regions no longer reflect sunlight but absorb more of it, warming up even more. To accelerate the process even more, the warming of arctic climates causes the melting and breakdown of permafrost soil, which liberates methane (a very potent GHG), and causes even more warming.
Heat Waves and Droughts
The rising temperature caused by climate change increases evaporation in some areas, which results in more storms and higher precipitation in other areas. This intensified water cycle means certain parts of the world are experiencing greater than average rainfall while other areas are experiencing greater than average periods of drought. On average, dry areas will become drier, while wet areas will become wetter (Field, 2014).
In those areas that are already dry, heat waves and droughts are occurring more frequently and with greater intensity. Seasonal temperature averages are breaking records in cities, states, and countries all over the world. Along with the increase in average temperature, prolonged periods of heat are impacting ecosystems and humans. Sustained levels of heat waves in the ocean can have negative consequences such as loss of kelp forests, coral reef decimation, and loss of marine invertebrates (Smale et. al., 2019). In cities, the consequences of increased intensity and frequency of heat waves include greater number of hospitalizations due to heat stress, and a greater number of deaths due to heat exhaustion and heat stroke. The IPCC Special Report on an increase of 1.5° C states that there are “lower risks projected at 1.5 degrees Celsius than at 2 degrees Celsius for heat-related morbidity and mortality.” (Hoegh-Guldberg et al., 2018, p. 11) Heat waves are particularly hard on the senior population, and the effects of heat waves are exacerbated in urban centers, where average temperatures are several degrees higher than in the rural areas surrounding cities (Hoegh-Guldberg et al., 2018).
An increase in global temperature can disturb fragile biological relationships that are much older than the human species. Studies showed that the mountain pine beetle’s range in the Pacific Northwest of Canada has grown considerably as temperatures warm, as the beetle can now survive in a hospitable environment that was previously inhabitable (Sambaraju et al., 2019). In addition, a longer summer season in the Pacific Northwest has made it easier for the mountain pine beetle to cause damage to larger swaths of forest. Making matters worse, the frequency and intensity of droughts are a stressor to trees’ defensive mechanisms, allowing the pine beetle to be more successful in its attack, decreasing the tree’s chances at survival. Further, greater swaths of damaged trees can act as kindling to wildfires, adding dangerous fodder to a dry, hot environment that is already ideal for the spread of fires.
Another ecological effect of increased surface temperatures in world oceans is the bleaching of coral reefs. Australia’s Great Barrier Reef, purported as the largest living organism in the world, (2,2500 km long) is dying from the effects of climate change and industrial sediments. [2]
Precipitation and Storms
As noted above, recent years have seen a major increase in frequency and intensity of rainfall and storms in certain parts of the world (Hoegh-Guldberg et al., 2018). The warmer temperatures caused by climate change increased the intensity of the water cycle, and generally, rainfall will increase in areas that are already experiencing higher than average levels of rainfall, but precipitation will generally decline in subtropical regions.
The melting of ice caps and the warming of surface water are likely to affect the major ocean currents that determine regional weather cycles. All of the major currents are connected into a coherent global system (the ‘Global Conveyor Belt’), which means that changes to currents in one region could affect other regions far away (World Ocean Review, 2010). Evidence is mounting that such changes are imminent (Editor, 2018)). Examples that raise particular concerns are:
- The climate of Europe is determined by the Gulf Stream delivering warm waters from the Caribbean. Increased input of freshwater from the melting of the Greenland Ice Shelf could disrupt this mechanism which would change the climate of Europe to resemble that of Labrador.
- Agriculture in the Indian subcontinent and parts of South East Asia depends largely on the annual Monsoon rains. Those depend in turn on ocean currents and prevailing winds, which are interdependent. A failure of the Monsoon would amount to a catastrophe of unprecedented proportions.
- Of similar importance to the climate of Mesoamerica is the El Ninjo-La Ninja system.
In addition, most climate models predict increased intensity of rainfall nearly everywhere when it does occur (Pfahl et al., 2017). Scientists are still in the process of analyzing the complicated relationship between climate change and precipitation in order to better understand patterns and gather forecasts, but there is consensus that “risks from heavy precipitation events are projected to be higher at 2 degrees Celsius compared to 1.5 degrees Celsius of global warming … in regions including several northern hemisphere high-latitude and high-elevation regions, eastern Asia, and eastern North America” (Hoegh-Guldberg et al., 2018). Table 9.1 showed the overall extent of the differences.
Recent modeled projections show a likely increase in occurrence of high intensity tropical storm hurricanes, with a possible decrease in overall frequency of storms (Pachauri et al., 2014). These more intense storms are very likely to be accompanied by higher than usual volumes of rain. In addition, climate models predict an increase of 2-11% in wind speed by the year 2100 (Knutson et al., 2010). In 2017, Hurricane Harvey broke the record for most rainfall in any tropical hurricane system, with some areas receiving 91 or more centimetres of rain, totalling over 152 centimetres of rain over the duration of the storm. Its highest wind intensity on land was 177 km per hour. At least 68 people died from the direct effect of the storm, and the economic devastation to homes and infrastructure was second only to Hurricane Katrina (National Oceanic and Atmospheric Centre, 2018).
Sea Level Rise
Another major impact of the increased global temperature of climate change is sea level rise. It is caused by a combination of the melting of the polar ice caps, the warming of the ocean causing thermal expansion, and a reduced amount of liquid water storage on land (Hoegh-Guldberg et al., 2018). Global mean sea level rise (GMSLR) has occurred naturally in the past but it was slower. The rate of GMSLR has more than doubled from the period of 1901-1990, to 1993-2010 (Church et al., 2013) from 1.5 mm per year to 3.2 mm per year. The GMSLR rate of increase in the 21st century is projected to exceed that of 3.2 mm, in all Representative Concentration Pathways (RCP). RCPs represent possible future scenarios of anthropogenic greenhouse gas emissions of varying concentrations in the atmosphere (Van Vurren et al., 2011). The pathways show different rates and magnitudes of climate change, and is a standard set of scenarios that allows scientists to assess risks associated with each. “The goal of working with scenarios is not to predict the future but to better understand uncertainties and alternative futures, in order to consider how robust different decisions or options may be under a wide range of possible futures.” (IPCC, 2019).
For RCP 2.6, considered the world’s best case scenario for limiting greenhouse gas emissions, projected GMSLR is between 0.28 to 0.61 meters by 2100. For RCP 8.5, the “worst case” scenario for limiting anthropogenic climate change, GMSLR could be between 0.53 meters to 0.98 meters by 2100 (Church et al., 2013). Almost all major coastal cities would be affected, with over 570 low-lying coastal cities inundated by at least half a meter in sea level rise by 2050 (C40 Network, 2019). The impact on megacities will be discussed in section 9.1.3. If crucial ‘tipping points’ in emissions are transgressed, a self-reinforcing ‘runaway’ greenhouse effect might ensue. The consequence would be a scenario called Hothouse Earth, which involves all ice disappearing and sea levels rising by 10-60 metres (Steffen et al., 2018).
Ocean Acidification
The increased concentration of carbon dioxide in our atmosphere translates to an increase in carbon dioxide concentration in our oceans (as approximately a third of atmospheric \(\ce{CO2}\) is absorbed by the ocean) (Gruber et al., 2019), leading to a lower pH of the ocean. Ocean acidity as expressed by hydrogen ion concentration, has increased by 26% since 1850, a rate of change that is tenfold the rate of change from any time in the last 55 million years (Doney et al., 2009). As the oceans become more acidic, carbonate ions are not as freely available, making it difficult for organisms to produce calcium carbonate that make up shells and skeletons. This can have a cascading effect of other unwanted impacts on marine ecosystems, fisheries, aquaculture, and tourism. There is also a possibility that higher levels of carbon dioxide in the oceans may benefit photosynthetic organisms like algae and kelp (Britton et al., 2016), which could be desirable with kelp forests but disastrous with algal blooms. The impacts of ocean acidification are explained in closer detail in the next section.
Delving Deeper: Climate Change Impacts on Ecosystems
The primary driver of climate change is the emission of greenhouse gases, which can have many unintended impacts on the Earth’s natural processes, as detailed in the previous section. This section will delve deeper into climate change impacts, and look at how the changes in Earth’s natural processes can impact an ecosystem by threatening the species that call it home, and interrupting fragile ecosystem services.
Ecosystems encompass all living organisms within a particular area, and the non-living things with which they interact. For example, a forest ecosystem includes the living trees, mosses, microbes, deer, birds, and insects that call it home, as well as the air, soil, lakes, rocks, and sunlight within it. Together, each organism and non-living substance are part of a coexisting community that is itself made of countless interdependent relationships. Many of these relationships are developed over such long periods of time, that they have come to rely on the specific habits of species, or the specific timeline and pattern of a nutrient cycle.
For example, the Pacific Northwest coastal ecosystem is home to oysters of many different species. Each species has adapted to thrive in the cold waters off the western coast of North America, which welcome a periodic upwelling of nutrient-dense waters from the deep ocean (Kämpf & Chapman, 2016). However, ocean acidification due to climate change is threatening the continued survival of oyster species. The increased acidity of the ocean affects the Pacific Northwest oyster species in two major ways. First, the lower pH wears at a young oyster’s shell, which is made up of calcium carbonate. Calcium carbonate, when interacting with a low pH solution, slowly dissolves as free hydrogen ions work to break calcium carbonate molecules apart. Another way a low pH ocean can interfere with oyster shells is by binding with free carbonate ions in the ocean, and making them less abundant in the environment for an oyster to use to build its shell. This is particularly stressful for young oysters, as their life cycle requires them to build up 90% of their body weight as shell within the first few days of life. Further, more carbon dioxide in the oceans can spell trouble for oyster reproduction. A recent study on Sydney rock oysters found the ratio of females to males in oyster populations could be affected by increased levels of carbon dioxide in the ocean (Boulais et al., 2017), where ocean acidification was found to increase the ratio of females to males by 16%. This could have negative implications for successful reproduction of oyster populations in light of an increasingly acidic ocean.
Oysters also provide important ecosystem services to their surrounding environment and the organisms living in it. Oysters feed by filtering their surrounding water and taking up phytoplankton or algae biomass through their gills. Inadvertently, this process helps improve the water quality by removing organic and inorganic particles. The inorganic particles that the oysters are unable to absorb are packaged into bundles and released as pseudofeces, which are then deposited into the lowest level of the ocean substrate, where it poses little to no harm to the ocean ecosystem. The loss of oyster reefs from ocean acidification could impact the quality of water in these coastal marine ecosystems, the effects of which are not yet fully understood.
Oyster reefs also provide a habitat for other organisms such as barnacles, mussels, and anemones. The hard reefs formed by oysters’ shells and the surrounding substrate allows these animals to attach to a secure and sheltered structure. Oyster reefs also provide hiding spots for prey seeking refuge, which in turn draw larger predators to reefs, creating a dynamic, thriving environment. Other oyster reef ecosystem services include the provision of a spawning area for species of fish such as oyster gobies and blennies, who lay their eggs in dead oyster shells. A reduction in oyster reef substrate would pose a problem to species that rely on reefs for habitat, reproduction, and shelter. As a keystone species, fluctuation in oyster populations will have a substantial effect on a large number of other organisms.
Finally, oyster reefs serve as breakwaters that can protect nearby shorelines from erosion, and are being used and considered as a tool in adapting to sea level rise. New York City’s Billion Oyster Project is an oyster reef restoration project, that aims to educate the public on the importance of oysters as a keystone species, an “ecosystem engineer,” and collects oyster shells from restaurants to return to the ocean as a building block of new oyster shells, and reefs (Billion Oyster Project, 2019).
We have used the example of the coastal marine ecosystem of oyster reefs as an example of how the impacts climate change can wreak havoc on ecology, and, in turn, the disrupt the role that ecology plays in bolstering resilience to climate impacts. This is only one example, and there are many other climate change impacts that can have trickle down effects through Earth’s ecosystems.
Impacts on Human Society
Climate change impacts, including the impacts on ecosystems, threaten human society in many ways. This section will broadly review the effects of climate change on human society. Human societies are deeply embedded into natural ecosystems and are dependent on them for sources of food, potable water, shelter, waste processing, raw materials and more. Humans are undeniably reliant on these ‘ecosystem services’ provided by nature, but for the greater part of modern society’s existence, there has been little to no thought on ensuring these ecosystem services can be sustained for future generations. Our rate of resource extraction has exacted an insurmountable cost to the planet (further discussed in Chapter 12).
We will use the example of Mumbai, India, as a case study of climate change impact on human society, and how one climate change impact can create another unexpected, and often undesired, consequence. (See Figure 9.1.)
Climate change is expected to wreak havoc on human society in many ways. Major costs are associated with the displacement of communities, building degradation, flood damage, loss of tourism, and increased mortality. Table 9.2 below depicts estimated costs of various impacts on human society from climate change in Mumbai.
| TYPE OF IMPACT | TYPE OF COSTS/PERIOD OF IMPACT | COST (millions of US$) |
|---|---|---|
| Dislocation due to extreme events of flooding of low-lying areas every five years until 2050[3] | Cumulative costs from 2005-2050 | 0.57 |
| Material damage to low-lying areas due to extreme evemts every five years until 2050[4] | Cumulative costs from 2005-2050 | 8.962 |
| Mortality costs due to extreme events of flooding every five years until 2020[5] | Cumulative costs from 2005-2050 | 4.263 |
| Disability-adjusted life years (DALYs) lost due to diseases like marlaria, diarrhoea and leptospirosis[6] | Cumulative costs from 2005-2050 | 4.406 |
| Building foundation damages due to sea-level rise for 2050[7] | Cost estimate for the year 2050 | 2,097.917 |
| Tourism loss resulting from fewer tourists visiting Mumbai[8] | Cost estimate for the year 2050, as compared with the base year 2005 | 2,743.101 |
The impacts of global warming will cause great disruptions to society, and some foreseeable consequences of these impacts include forced migrations and displacement of populations. Though the UNHCR does not formally recognize environmental refugees, the number of persons that are forcibly displaced due to climate change impacts will soon become too great to ignore, and will exert effects on states and human security.