The purpose of the downscaled scenarios is to illustrate future emissions for Durban based on global development paths. These scenarios reflect future population, GDP and CO2 emissions if Durban had to follow a global development path as depicted in the IPCC scenarios. These scenarios do not include any future climate change policies that may be implemented, however they do include environmental policies that can impact on GHG emissions (IPCC, 2001). The purpose of downscaling scenarios was
to account for global influences on a local level and to allow for a comparison with the scenarios created in LEAP to ensure consistency in the results (Malone et al., 2004).
5.8.1 A1 Scenario
The A1 Storyline reflects a development path with high economic growth rates, slow population growth and high levels of global integration. As a result the population for Durban peaks at 3.8 million people in 2025 and declines to 3.5 million by 2050. This is comparable to the global A1 Scenario, however whilst population peaks in 2050 and declines thereafter in the global scenario, the population for Durban peaks in 2025. A possible reason for this is the impact of HIV/AIDS (Haw and Hughes, 2007), but also as income per capita increases in the city, population growth declines (IPCC, 2001). GDP during this period increases approximately 500% and CO2e emissions increases between 3.3 and 4.2 times the base year depending on the fuel mix of the scenarios.
The A1 Scenario is comparable to the GWC and the BAU Scenarios. The GDP for the A1 Scenario increases to R704.9 billion by 2050, which is in between the GWC and BAU Scenarios (R736 billion and R660 billion). The GWC scenario is similar to the A1F storyline, in that both scenarios experience high economic growth rates and a dependence on fossil fuels. The main difference in the storylines is that the GWC Scenario experiences high levels of population growth, whilst population declines for the A1F Scenario. The A1B Scenario and BAU Scenario both have high economic growth rates, with a balance between renewable fuels types and slow population growth rates.
As shown in Figure 5.24, the CO2e emissions for the GWC are the highest by 2050, followed by the A1f Scenario. The reason for a significantly higher growth for the GWC Scenario is because the scenario assumes that there is no technological change, which would reduce the energy intensity of the economy from 2005-2050. Emissions for the BAU Scenario are initially lower than the A1 Scenarios, but by 2050, are between the A1B and A1T Scenarios. This comparison illustrates that the high economic growth scenarios developed in LEAP are similar to the high growth IPCC scenarios but they have a wide range, ranging from 124 million tCO2e to 65 million tCO2e.
Figure 5.24: Comparison between CO2e emissions (Million tCO2e) for the A1 Scenarios and the GWC and BAU Scenarios from 2005 to 2050
5.8.2 A2 Scenario
The A2 Storyline represents a future with closed economies, high population growth rates and low levels of technological change. As a result, population increases 40% to 4.7 million people by 2050.
GDP growth is slow, with GDP increasing 260% from 2005. Due to the moderate GDP growth, GHG emissions increase approximately 3.3 times from the base year.
The A2 Scenario is similar to the Natural Transition Scenario in that both scenarios experience high population growth rates, moderate GDP growth and slow technological change. However, the city does not move towards a service economy in the A2 Scenario as it does in the Natural Transition Scenario.
As shown in Figure 5.25, the resulting emissions for both the scenarios follow a similar path. The emissions for the Natural Transition Scenario are lower than the A2 storyline as a result of the structural change in the economy.
5.8.3 B1 and B2 Scenarios
The B1 Storyline illustrates a development path characterised by high levels of environmental awareness, high rates of economic growth towards a service and information economy and low population growth. Population and GDP levels are the same as the A1 Scenario but CO2e emissions are 38% lower than the A1 Scenario by 2050. GHG emissions increase 2.4 times from the base year.
The main difference between the A1 and B1 storylines is the high level of environmental and social awareness and the shift to low carbon industries.
The B2 Scenario is similar to the A2 Storyline, but is characterised by an increase in environmental awareness and an emphasis on providing local solutions for sustainability. Therefore, population and GDP is similar to the A2 Scenario, however CO2e emissions are about 40% less than A2 emissions by 2050. CO2e emissions increase approximately 2.3 times from the base year, from 19.57 million tCO2e in 2005 to 44.66 million tCO2e in 2050.
The emissions for the B1 and B2 Scenarios can be compared with the Natural Transition and Slow Go City Scenarios (Fig. 5.26). However there are not many similarities between the drivers of emissions for these scenarios. The main similarity between the Natural Transition and the B1 Scenario, is that both scenarios assume a shift towards a service and information economy. The Slow Go City is similar to the B1 Scenario as both scenarios enhance the implementation of cleaner and more efficient technologies. By 2050, emissions for the Natural Transition Scenario are the highest, followed by the Slow Go City and the B1 development path, which follow a similar emissions path to the Slow Go City. The emissions for the B2 Scenario are slightly lower than the other scenarios, which is due to moderate economic growth and local concerns for environmental protection. The Low Carbon City emission curve is also illustrated in Figure 5.26, to show the difference in emissions of the moderate GHG emissions pathways and the low carbon emissions path. The Low Carbon City also has some similarities with the B1 Scenario, in that both scenarios assume structural change in the economy towards services and both scenarios adopt cleaner technologies. However, by 2050, emissions for the
Figure 5.25: Comparison of CO2e emissions (Million tCO2e) for the A2 and Natural Transition Scenarios from 2005 to 2050
Low Carbon City are approximately 60% lower than the moderate emissions scenarios. This is because the Low Carbon City assumes direct climate change mitigation occurs, whilst the B1 Storyline only includes environmental policies that can have an impact on emissions (Nakicenovic et al., 2000).
5.8.4 Conclusion
The different development paths had a range of impacts on emissions. Rapid economic growth, with no climate change mitigation in the GWC Scenario, results in a 6.3 times increase in emissions from the base year to 2050. In the BAU Scenario, emissions will increase 3.5 times from the base year. If there is a transition to a post-industrial society, with no climate change mitigation, emissions will increase 3 fold from 2005 to 2050. The National Transition Scenario illustrated that if Durban moves towards a service sector economy, which are predominantly low carbon sectors, with no climate change mitigation, emissions will increase 3.15 times the 2005 levels. If the city is slow to respond to climate change as in the Slow Go City, emissions will increase 2.5 times from the base year. The Low Carbon City Scenario a results in reduction in emissions of 1% from 2005. These were compared to the IPCC downscaled scenarios, which followed a similar pattern. The scenarios are comparable to developing city scenarios, but illustrate that the city is lagging behind developed cities. The IPCC downscaled scenarios fall within the range of the scenarios created in LEAP. However, whilst some of the LEAP scenarios include climate change mitigation assumptions, the IPCC scenarios only include environmental concerns that impact on a reduction in emissions. As a result the Low Carbon City emissions are much lower than the IPCC Scenarios. Furthermore, emissions for the GWC Scenario are greater than the A1F Scenario because the GWC Scenario assumes that there is no technological change in the economy that would improve efficiency. Therefore, while the IPCC Scenarios do provide a range of possible future emissions, it is also possible for emissions to be higher than the IPCC range. This is similar to a model developed for the USA, which found that the range of the IPCC scenarios is too narrow .
Figure 5.26: Comparison between moderate emission paths (Natural Transition, Slow Go City and the B1 and B2 Scenarios and the Low Carbon City, from 2005 to 2050
In order to make an impact in the reduction of emissions, it is essential for the city to target the commercial and industrial sector, which is the sector that emits the highest GHG emissions. However all these scenarios are still insufficient for achieving the RBS emissions target of a 60-80% reduction from 1990 levels. Achieving this reduction would require more than a 50% improvement in energy efficiency, structural change in the economy to low energy intensive sectors and a 20% contribution of renewable energy to total energy supply.
6 CONCLUSION