Pre-requisites: These lectures assume that undergraduates are familiar with the essential mechanisms of global warming, including how the greenhouse effect actually works and the origin of the logarithmic relationship between carbon dioxide concentrations and global temperatures; how the climate system responds to rising greenhouse gas emissions, including the difference between equilibrium and transient response; and the evidence for human influence on global climate, including the role of observations and simple and complex climate models, climate variability and how we quantify human influence on extreme weather events. Anyone unsure of these topics can look at the first three lectures of the Oxford Climate Society and Oxford Geography Society course “Climate Change, a summary for policy-makers”, available at Global Climate Change: A Summary for Policymakers .
Lecture 1: Costing the Earth - what is the true price of fossil carbon?
This lecture will explain how we assign a present monetary value to the future climate impacts of today’s greenhouse gas emissions, emphasising the importance of scenarios; equity and welfare; the notion of discounting future harms and benefits; bottom-up versus top-down, and model-based versus empirical, approaches to quantifying global economic impact; the concepts of risk, hazard and vulnerability and implications of adaptation; and different classes of uncertainty, including both physical and social responses. We’ll discuss the challenge of monetising irreversible impacts such as species extinction, including the (special?) case in which the species in question is Homo sapiens.
Lecture 2: Bending the curve - how to start reducing carbon dioxide emissions?
This lecture focuses on the challenge of reducing emissions in the next decade or two, starting down the path to net zero. We begin from the economic benefits of burning fossil carbon, and the consequent challenges of reducing emissions. We will look at global drivers of carbon dioxide emissions in the “shared socio-economic pathways” used in the IPCC 6th Assessment Report; compare marginal and total costs of different approaches to reducing CO2 emissions; and introduce you to cost-benefit and cost-effectiveness analysis and the importance of non-monetary barriers and incentives.
In his review of Stern et al (2006), William Nordhaus says “The Review takes the lofty vantage point of the world social planner, perhaps stoking the dying embers of the British Empire, in determining the way the world should combat the dangers of global warming.” Explain the concepts of the Social Cost of Carbon Dioxide (SC-CO2) emissions and the Marginal Abatement Cost (MAC) and how they are used to determine an “optimal” level of emission reduction in conventional climate policy. Can a global SC-CO2 be determined empirically? If not, how can it be determined, and is it a useful concept at all? How should we assess the true cost of fossil carbon?
- https://www.carbonbrief.org/qa-social-cost-carbon for an introductory overview of the classical approach to quantifying the SC-CO2 using Integrated Assessment Models (IAMs).
- Stern, N. et al (2006), The Stern Review: The Economics of Climate Change, summary available on https://webarchive.nationalarchives.gov.uk/20100407163608/http://www.hm-treasury.gov.uk/d/Summary_of_Conclusions.pdf. A landmark report that motivated the UK 2008 Climate Change Act, notable for its very high estimates of the SC-CO2.
- Nordhaus, W. D. (2007), A Review of the Stern Review on the Economics of Climate Change, Journal of Economic Literature, Vol. XLV, pp. 686–702 http://piketty.pse.ens.fr/fichiers/Nordhaus2007b.pdf
- Burke, M. et al (2015) “Global non-linear effect of temperature on economic production”, Nature, 527:235-239, https://www.nature.com/articles/nature15725. See also Pretis et al (2017), summarised on http://www.climateeconometrics.org/paris-impacts/
Lecture 3: Short-lived promises and cumulative risks - setting climate priorities
Is it true that planting trees is “the most effective climate change solution available to the world right now”, or that adopting “a vegan diet is probably the single biggest way to reduce your impact on planet Earth”? This lecture explains why net anthropogenic CO2 emissions need to be reduced to zero to halt the rise in global temperature, putting paid to myths of a “fair and sustainable” per-capita CO2 emission rate and “Nature-Based Solutions” to ongoing fossil fuel use. We’ll also discuss how other climate pollutants behave, including methane, nitrous oxide and aerosols, and how the concept of “CO2-equivalent emissions” has led to widespread confusion about the relative effectiveness of different climate policies.
Lecture 4: Achieving net zero - what will it take to stop climate change?
The scientific answer is very simple: we need to reduce net global carbon dioxide emissions to zero. We may well have to do other things as well, but we know we have to do at least that. This lecture focusses on the second half of the transition, where we go beyond just reducing emissions to ending the practice of dumping carbon dioxide into the atmosphere altogether. We will see how this is a very different challenge, and discuss the formidable practical, political and ethical challenges of trying to do this using conventional measures such as carbon pricing, cap-and-trade and cap-and-dividend regimes. Finally, your lecturer will introduce you to the critical importance of “upstream” measures that are generally ignored by environmentalists but (he argues) represent the only effective and ethically defensible way of ultimately dealing with this problem.
The UK Parliament has declared “climate emergency” and committed the UK to net zero greenhouse gas emissions by 2050, while the 2019 Labour Party Conference passed a motion calling on the Party to “work towards a path to net zero carbon emissions by 2030”. What does net zero greenhouse gas emissions mean in the context of “ending our contribution to global warming”? Using the Excel spreadsheet model provided, or the simple equation relating emissions to warming provided in the lectures, assess and explain what our options are for meeting the goals of the Paris Climate Agreement for a central estimate of the climate response. You will notice this model/equation does not predict runaway climate change, even at 3 to 4°C of warming, yet Steffen et al (2018) argue “even if the Paris Accord target of a 1.5 °C to 2.0 °C rise in temperature is met, we cannot exclude the risk that a cascade of feedbacks could push the Earth System irreversibly onto a “Hothouse Earth” pathway.” How should current policies respond to that argument?
- IPCC (2018) “Global warming of 1.5°C” [V. Masson-Delmotte, et al (eds.)]. World Meteorological Organization, Geneva, Switzerland. https://www.ipcc.ch/sr15/ for the IPCC’s latest assessment of the risks of a warming of 1.5°C and 2°C and associated global emission pathways. Focus on the SPM and chapter 2 on “Mitigation pathways compatible with 1.5°C.”
- Steffen, W. et al (2018) “Trajectories of the Earth System in the Anthropocene”, PNAS August 14, 2018 115 (33) 8252-8259; first published August 6, 2018 https://doi.org/10.1073/pnas.1810141115 for a much more pessimistic view that has done much to inspire the rhetoric of Greta Thunberg and Extinction Rebellion.
- Committee on Climate Change (2019) “Net Zero: the UK’s contribution to stopping global warming”, available on https://www.theccc.org.uk/publication/net-zero-the-uks-contribution-to-stopping-global-warming/, for the UK’s current plans.
- Allen et al (2009) “The Case for Mandatory Sequestration”, Nature Geoscience, 2:813-815, available on https://www.nature.com/articles/ngeo709 for a very different (and rather more optimistic) scenario.