Questions & explanations
1. Describe how the SCC for a ton of CO₂ emitted in 2030 is calculated differently from a ton emitted in 2025.
The SCC for a future year (e.g., 2030) considers that the baseline emissions, concentration, and temperature will be higher by then, so the marginal impact of an extra ton might be larger because the system is already warmer (nonlinear damage). Also, the discount factor is smaller (closer to the emission year if discounting from the future? Actually, for a ton emitted in 2030, the discount period to today is shorter, so the present value of that year's damages is larger? Wait: we discount from the time damages occur. A ton emitted in 2030 causes damages from 2030 onward, so the present value is the discounted sum from 2030. Compared to a ton emitted today, the starting point for discounting is later, so the same future damages have a higher present value because the discount period is shorter. However, the marginal damage itself might be higher due to a warmer baseline. Typically, SCC rises over time at roughly the discount rate, because the future ton is discounted less and the damage per ton increases with background warming.
2. Compare the overall approach to carbon pricing across Mexico, Chile, and Colombia.
All three countries have carbon taxes with rates between 3.5 and 5 US dollars per ton, which are low by global standards. Mexico's tax applies broadly to fossil fuel sales but exempts natural gas. Chile's tax targets only large emitters. Colombia's tax also applies to fossil fuel sales, like Mexico's, but includes natural gas (with some exemptions). Chile and Mexico are exploring emissions trading systems; Mexico has a pilot, Chile is developing one. Colombia does not yet have an ETS. All three taxes cover less than half of national emissions. The revenue goes to general budgets, not specifically to climate projects. The overall impact on emissions is modest so far, but these measures create a foundation for future stronger policies.
3. Give an example of a policy to promote environmental justice.
One policy is to require 'environmental impact assessments' that include looking at how a project will affect poor and minority communities. For instance, in the US, the Environmental Protection Agency has an Office of Environmental Justice that reviews proposed projects. Another policy is to give communities the right to know about toxic releases through public databases. In India, a law called the Environmental Impact Assessment Notification requires public hearings, but in practice, poor communities often cannot participate. Stronger policies would give these communities legal help and funding to participate. Environmental justice also involves prioritizing cleanup of polluted areas in disadvantaged neighborhoods.
4. What is the overall impact of Australia's Safeguard Mechanism on national emissions?
The Safeguard Mechanism has had a limited impact on Australia's total emissions because it only covers large industrial facilities, leaving out transport, agriculture, and electricity generation (which has its own Renewable Energy Target). Emissions from covered facilities have stayed roughly flat or grown slightly, partly because baselines were set high initially. Since the 2023 reforms that tighten baselines every year, the mechanism is expected to drive significant reductions of about 5% per year from those facilities. Overall, Australia's emissions in 2022 were about 20% below 2005 levels, but much of that came from renewable energy in the power sector, not the Safeguard Mechanism.
5. Compare the UAE's mandatory ETS with Saudi Arabia's planned approach for the oil and gas sector.
The UAE's mandatory Emissions Trading Scheme (ETS) currently covers cement and oil & gas in Abu Dhabi, with a cap-and-trade system that started in 2018. Saudi Arabia's planned mandatory scheme for oil and gas is not yet in place but is expected to start around 2025. Both target the energy sector, but the UAE's system is already operational and provides experience. Saudi Arabia is likely to design its system based on lessons from the UAE and other global markets. Both aim to reduce carbon intensity while maintaining competitiveness. The UAE uses allowances based on benchmarks; Saudi Arabia may adopt a similar approach. The main difference is timing: the UAE is ahead in implementation.
6. Compare Hotelling's model with real-world oil price behavior.
Hotelling's model predicts that oil prices should rise steadily at the interest rate, but real oil prices have been very volatile, with ups and downs due to geopolitics, economic cycles, and technical changes. For example, in the 2010s, oil prices fell sharply because of new shale oil technology, not because of depletion. The model assumes perfect competition, no market power, and constant extraction costs, which are not true for global oil markets. Many producers also do not behave as pure profit-maximizers; OPEC countries often restrict output to influence prices. As a result, Hotelling's rule is not accurate for short-term predictions but provides a useful long-term framework.
7. How does regulatory impact assessment differ from cost-benefit analysis?
Regulatory impact assessment is a broader process that includes cost-benefit analysis as one of its parts. Cost-benefit analysis is the specific method of calculating net benefits in monetary terms. However, regulatory impact assessment also looks at other factors like distributional effects (who gains and loses), administrative feasibility, and whether the regulation fits with existing laws. It may also consider qualitative impacts that cannot be easily monetized. So, cost-benefit analysis is a tool used within the larger framework of regulatory impact assessment. Not all regulatory impact assessments do a full cost-benefit analysis; some use simpler cost-effectiveness analysis.
8. How are environmental externalities linked to distributional effects?
Environmental externalities are costs that affect third parties, but these costs are not spread evenly. For example, a factory's air pollution creates health costs, but the people who live near the factory – often poorer – suffer more than distant rich suburbs. So the externality has a distributional effect: it harms some groups more than others. Even if the total social cost is the same, how it is shared matters for fairness. The Coase theorem says bargaining can solve externalities, but if one party is poor, they cannot pay to stop pollution. So distributional effects show that efficiency alone is not enough; we must also consider who bears the costs and who gets the benefits.
9. Compare South Africa's carbon tax with pilot programs in other African countries.
South Africa's carbon tax is the most advanced in Africa: it is a national, mandatory tax covering about 80% of emissions, with a clear rate and plan to increase over time. In contrast, other African countries have pilot programs that are either voluntary, limited to certain sectors, or still in draft stages. For example, Côte d'Ivoire's pilot is a voluntary carbon credit market, not a tax. Kenya's proposed tax is still under debate. Nigeria's draft carbon tax focuses on oil and gas. South Africa's tax has been in operation since 2019 and includes many allowances, while other countries are still in early learning phases. The scale and enforcement in South Africa are much larger.
10. How do uncertainty and technological change affect the optimal depletion path?
Uncertainty about future demand or new discoveries can make resource owners extract faster or slower. If there's a risk of a new technology (like renewable energy) replacing the resource, owners may extract more quickly before the price falls. Similarly, if extraction technology improves, costs drop, which encourages more extraction today relative to the future. Hotelling's rule becomes more complex with uncertainty: the expected growth rate of net price should still equal the interest rate, but actual paths can vary. Technological change that reduces costs or creates substitutes can cause prices to depart from the simple Hotelling path, often leading to lower prices over time.
11. Compare Australia's former carbon pricing mechanism with the current Safeguard Mechanism.
The former carbon pricing mechanism applied a fixed price or ETS to a broad set of emitters, including fuel suppliers, covering about 60% of national emissions. The current Safeguard Mechanism targets only large industrial facilities that emit over 100,000 tons per year, covering about 30% of national emissions. The former had a clear, uniform price on carbon, while the Safeguard uses baselines and allows trading of ACCUs, which sets an implicit price that varies. The former was designed to reduce emissions broadly; the Safeguard focuses on the biggest industrial emitters with gradually tightening limits. The former was short-lived; the Safeguard has been in place since 2016.
12. What is the Environmental Kuznets Curve for CO2?
The Environmental Kuznets Curve (EKC) for CO2 is an idea that as a country's income per person grows, its carbon emissions first rise and then eventually fall. It looks like an upside-down U shape on a graph. Low-income countries emit little because they are mostly agricultural. As they industrialize, they burn more coal and oil, so emissions increase. After a certain income level, people start demanding cleaner air, governments pass stricter rules, and services replace heavy industry. Then emissions decline even as income keeps rising. However, some studies show that CO2 emissions never really fall; they just increase more slowly. The EKC is debated and not a certainty.