CHAPTER THREE LITERATURE REVIEW
3.2 Climate Change
3.2.1 Global Warming
Fekete et al. (2016) explain that the atmosphere, which is composed of different gases, circulates energy from the equator, where the Sun’s radiation arrives most intensely, to the poles via weather systems such as cyclones, storms and weather fronts. Additionally, one of the most important circulation systems that the atmosphere supports is the hydrologic cycle which regulates precipitation in its various forms across the world. However, Tian et al.
(2016) point out that GHGs that remain in the atmosphere for decades and longer, and which impede the escape of longwave radiation, adversely affects the efficient function of the hydrologic cycle. Hope et al. (2017) are of the view that global warming is caused by the rising levels of GHGs. According to the IPCC (2014), the major GHGs are CO2, methane (CH4), nitrous oxide (N2O), hydrofluorocarbons (HFCs), per fluorocarbons (PFCs) and sulphur hexafluoride (SF6). Seneviratne et al. (2016) explain that one of the most common GHGs is CO2 which is an essential link between plants and animals, and as plant material decomposes, bacteria and other organisms consume the mass, releasing more CO2 back to the atmosphere. Jeffery et al. (2016) explain that in the absence of oxygen, bacteria produce CH4, another common GHG. Upadhyaya (2016) claims that since the beginning of the Industrial Revolution, in the mid-18th century, intense and inefficient burning of wood, charcoal, coal, oil and gas, accompanied by massive land-use change, has resulted in increased concentrations of GHGs in the Earth’s atmosphere. The IPCC (2014) reports that the current CO2 level is higher than it has been in at least 800 000 years and while some volcanic eruptions have released large quantities of CO2 in the distant past, human activities now emit more than 135 times as much CO2 as volcanoes each year. Additionally, human activities currently release over thirty billion tons of CO2 into the atmosphere every year. According to the UNFCCC (2011), the WMO describes the build-up of GHGs in the atmosphere as resulting from the growing use of energy and expansion of the global economy. This is underscored by Bouman et al. (2015) who indicate that the combustion of fossil fuels to generate electricity is the largest single source of CO2 emissions. Industrial processes also use
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electricity and therefore indirectly cause the emissions from this consumption (du Can et al., 2015). Several processes also produce CO2 emissions through chemical reactions that do not involve combustion, for example, the production and consumption of mineral products such as cement, the production of chemicals and metals such as iron and steel (Li et al., 2015).
Dimitriou et al. (2015) and Taptich et al. (2015) further explain that the combustion of fossil fuels such as gasoline and diesel to transport people and goods via road vehicles, air travel, marine transportation, and rail is the second largest source of CO2 in the world.
The IPCC (2014) reported that electricity and heat production, industry and transport sectors contributed 60% of the total global direct GHG emissions of the global forty-nine Gt CO2
equivalent that was released in 2010 (Figure 3.1). Of the total global emissions from electricity and heat production, 23% was from buildings and industry (Figure 3.2).
Figure 3.1: Total global direct GHG emissions by economic sector (adapted from the IPCC, 2014: 44)
Other human-related source of GHG, according to Leip et al. (2015), is from domestic livestock such as cattle, buffalo, sheep, goats and camels who cumulatively produce large amounts of CH4 as part of their normal digestive process. Bhada-Tata and Hoornweg (2016) explain that waste from homes and businesses also generate CH4 emissions in landfills as the waste decomposes. Purohit and Hoglund-Isaksson (2016) comment that F-gases have no
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natural sources and only come from human-related activities such as aluminium and semi- conductor manufacturing. The human sources of N2O include agriculture, fossil fuel combustion, wastewater management and industrial processes (Reay, 2015).
The increased amounts of GHGs from all these anthropogenic activities result in a significant increase in the temperature of the earth, which leads to the warming of the earth that triggers climate change (Upadhyaya, 2016). The IPCC (2014) describes the greenhouse effect (or global warming) as the gradual increase, observed or projected, in global surface temperature, as one of the consequences of increasing anthropogenic emissions of GHGs into the atmosphere.
Figure 3.2: Indirect CO2 emissions by economic sector (adapted from the IPCC, 2014: 44)
Hansen et al. (2016) point out that the rapid warming of the planet triggers off unpredictable and often devastating changes to our climate. This is underscored by the IPCC (2014) who state that climate change is the fluctuation in the state of the climate system over time, due to natural variability or as a result of direct and indirect human activities. The IPCC (2014) further asserts that the continued emission of GHGs will cause further warming and long- lasting changes in all components of the climate system, increasing the likelihood of severe, pervasive and irreversible impacts for people and ecosystems.
69 3.2.2 Contributions of humans to climate change
According to Myers et al. (2015), there is almost global consensus among the scientific community that there exists a causal relationship between human activities and climate change. This is underscored by Bouman et al. (2015) who claim that there is compelling evidence that rapid and unpredictable changes in climate results from the combination of natural variability and human influences, in particular land-use changes and GHGs emitted from the use of fossil fuels. This is further emphasised by Hope et al. (2017) who assert that global warming is caused by anthropogenic release of CO2.
The IPCC (2014) maintains that human influence on the climate system is clear, and recent anthropogenic emissions of GHGs are the highest in history. Human-induced GHG emissions have increased since the pre-industrial era, driven largely by economic and population growth, and are now higher than ever (Taylor et al., 2016). According to Stott (2016), such anthropogenic drivers have been detected throughout the climate system and are extremely likely to have been the dominant cause of the observed warming since the mid-20th century.
Cook et al. (2016) also confirm that human influence has been the dominant cause of the observed warming since the mid-20th century and that it is also likely that more than half of the observed increase in global average surface temperature from 1951 to 2010 was caused by the anthropogenic increase in GHG concentrations. Olivier et al. (2015) explain that North America and Europe have produced around 70% of all the CO2 emissions due to energy production, while developing countries have accounted for less than 25%. However, Geng et al. (2016) assert that most future emissions growth will come from today’s developing countries, including South Africa, because of their rapid growth in population and GDP, and their increasing share of energy-intensive industries. Liu et al. (2016) suggest that limiting climate change, in particular from human-induced sources, will require substantial and sustained reductions of GHG emissions.