Overview

• Grade Level: AP World History / AP European History / AP Environmental Science / AP Chemistry / English (grades 9-12)

• Time Required: Single class (45 minutes); bell-ringer option (10 minutes); extension (2 additional class periods)

• Historical Period: Romantic-era Europe and the Indonesian eruption of 1815 to 1816

• Modern Connection: The May 2026 Nature Communications paper by Maarten van Herpen and Matthew Johnson showing that the 2022 Hunga Tonga underwater eruption generated reactive-chlorine chemistry that scavenged methane in the stratosphere at roughly 900 tonnes per day

Learning Objectives

Students will be able to:

1. Describe the mechanism by which a large volcanic eruption can inject sulphur dioxide into the stratosphere and produce sulphuric-acid aerosols that cool the planet for one to three years afterwards.

1. Trace the cause-and-effect chain from the 10 April 1815 eruption of Mount Tambora to the 1816 'year without a summer' to the rainy June at Villa Diodati to the conception of Frankenstein.

1. Explain the difference in atmospheric chemistry between Tambora (a land eruption that injected sulphur dioxide) and Hunga Tonga (an underwater eruption that injected seawater and generated reactive chlorine), and identify why one produced cooling and the other produced methane oxidation.

1. Construct an argument, using both historical and modern evidence, about the limits of our ability to predict complex-system responses to large chemical perturbations.

Before Reading

Anticipation Questions

1. If a volcano on the other side of the world erupted next month, what effects, if any, would you expect to feel in your own region within a year? List three predictions.

1. Mary Shelley wrote Frankenstein in a summer that was unusually cold and stormy. How much of an author's work do you think depends on the weather she happens to be writing in? Defend your answer.

1. When scientists run climate models, they make predictions about what the atmosphere will do. How surprised should we be when the atmosphere does something the models did not predict?

Key Vocabulary

• Stratosphere: The layer of Earth's atmosphere above the troposphere, roughly 10 to 50 kilometres in altitude, where weather does not happen and where aerosols injected by major volcanic eruptions can remain suspended for years.

• Pyroclastic flow: A fast-moving current of hot gas, ash, and rock that flows down the flank of an erupting volcano at hundreds of kilometres per hour and is the immediate cause of most volcanic-eruption fatalities.

• Sulphur dioxide (SO₂): The volcanic gas whose stratospheric oxidation produces sulphuric-acid aerosols. These aerosols reflect a small fraction of incoming sunlight back into space and produce post-eruption cooling.

• Aerosol: A suspension of fine solid particles or liquid droplets in a gas. Stratospheric sulphuric-acid droplets formed after Tambora are the classic example.

• Methane (CH₄): A potent greenhouse gas, the second-most significant driver of human-caused warming after CO₂, with a 100-year global-warming-potential (GWP100) approximately 28 to 30 times higher than CO₂ on a per-mass basis.

• Reactive chlorine: Free-radical chlorine species (Cl•, ClO•) that can attack methane and other organic molecules in the atmosphere. In the Hunga Tonga plume, reactive chlorine appears to have been generated by interactions among volcanic ash, salty seawater and stratospheric ultraviolet light.

• Formaldehyde (CH₂O): A short-lived intermediate produced when methane is oxidised in the atmosphere. The Hunga Tonga plume contained the highest stratospheric formaldehyde concentration ever recorded, providing the signature that allowed van Herpen and Johnson to estimate the methane-oxidation rate.

• Year without a summer: The popular name for the unusually cold northern-hemisphere summer of 1816 that followed Tambora.

During Reading

Guided Questions

1. Identify the chain of cause and effect linking the 10 April 1815 Tambora eruption to the wet summer at Lake Geneva in June 1816. What were the intermediate steps?

1. Note the precise date and place of the ghost-story challenge that produced Frankenstein. Who proposed it?

1. Identify three differences between the Tambora eruption and the Hunga Tonga eruption that the story emphasises. Why do those differences matter?

1. List the specific atmospheric-chemistry chain by which reactive chlorine destroys methane in the Hunga Tonga plume.

After Reading

Discussion Questions

1. The story argues that the connection between Tambora and the cold summer of 1816 was not made by scientists until the 1920s, more than a century after the event. Why might it have taken so long? What kinds of evidence had to accumulate first?

1. Mary Shelley believed she was simply having unusually bad weather, not weather caused by a volcano on the other side of the world. To what extent do you think modern observers correctly attribute today's weather and climate events to their underlying drivers? Defend your answer.

1. The Hunga Tonga plume removed methane at roughly 900 tonnes a day. The atmosphere contains roughly 5.4 billion tonnes of methane. Calculate (roughly) how long the Hunga Tonga rate of removal would have to continue to halve atmospheric methane. What does that calculation say about the practical climate significance of the finding?

1. The story closes by saying "the atmosphere is the largest unintentional chemistry experiment on Earth, and it is still surprising the chemists who watch it." What is the rhetorical work that sentence is doing? Do you accept it?

1. (Genuinely debatable.) The story claims that "we live inside a chemistry experiment we did not design" and that "it is wise to be humble about the answers it is going to give us next." Is that an argument for caution about climate intervention, for confidence in natural systems, or for something else entirely?

The Parallel

1. List the structural features that are similar between the Tambora and Hunga Tonga eruptions. List the features that are different. Which list is longer, and which is more important?

1. Both halves of the story end with the observation that the atmosphere did something the models had not predicted. In one case the effect was harmful, in the other helpful. Should we treat the two cases symmetrically? Defend your answer.

1. Could there be a similar parallel in another field, where a large natural perturbation produced an effect that the underlying theory had not predicted? Suggest one example and defend it.

Activities

Bell-Ringer (10 minutes)

Project a side-by-side image: J. M. W. Turner's "The Burning of the Houses of Lords and Commons" (1834) with its dramatic red-orange sky next to a NASA satellite photograph of the Hunga Tonga umbrella cloud (2022). Ask students: "What do these two images have in common, scientifically?" Have them write two sentences identifying a chemical or physical similarity. Use the responses to introduce the lesson.

Single Class (45 minutes)

• 0 to 5 minutes: Bell-ringer recap. Establish the connection between volcanic eruptions and atmospheric optics.

• 5 to 18 minutes: Read the historical half of the story aloud or play the audio narration. Students fill out a guided-reading organiser with three columns: "What Tambora did," "What 1816 was like," "How the connection was eventually traced."

• 18 to 30 minutes: Read the modern half aloud or play the audio. Students extend the organiser with parallel columns: "What Hunga Tonga did," "What van Herpen and Johnson found," "What it might mean for climate policy."

• 30 to 42 minutes: Whole-class discussion of After Reading question 5 (the humility-about-complex-systems argument). Structured as a four-corners activity. Students physically move to a corner of the room marked "Argument for caution about geoengineering," "Argument for confidence in self-correction," "Argument for more research," or "Argument for none of these."

• 42 to 45 minutes: Exit ticket. One sentence: "The most important thing the year-without-a-summer story can teach us about today's climate science is: ___."

Extension Activity

Quantitative climate-modelling essay (3 to 5 pages, two class periods): students choose either the Tambora cooling response (from the historical climate record) or the Hunga Tonga methane-oxidation effect (from the van Herpen and Johnson paper) and write a short essay estimating, with sources, the magnitude of the effect, comparing it to a relevant baseline (the total stratospheric sulphate budget for Tambora, or the annual anthropogenic methane budget for Hunga Tonga), and proposing one experiment or observation that would refine the estimate. Cite at least three primary or near-primary sources.

Primary Source Connections

• Maarten van Herpen, Matthew Johnson et al., "Satellite quantification of enhanced methane oxidation applied to the stratospheric plume following Hunga Tonga-Hunga Ha'apai eruption," Nature Communications (May 2026). The paper at the centre of the modern half. Type: peer-reviewed scientific paper. Available open access at nature.com.

• Mary Wollstonecraft Shelley, Frankenstein, or The Modern Prometheus (first edition 1818). The novel begun at the Villa Diodati during the rainy summer of 1816. Type: novel. Available through the British Library digital archive.

• John William Polidori, The Vampyre: A Tale (1819). The vampire novella also begun at Villa Diodati. Type: novella. Available at Project Gutenberg.

• Mary Shelley's "Author's Introduction to the Standard Novels Edition of Frankenstein" (1831). Shelley's own retrospective account of the ghost-story challenge at Villa Diodati. Type: autobiographical preface.

• William Jackson Humphreys, Physics of the Air (1920 and revised editions). The first systematic treatment of volcanic dust as a climate forcing. Type: scientific monograph. Available through HathiTrust.

• J. M. W. Turner, The Lake of Lucerne (1810s-1820s landscapes). Type: oil paintings. The post-Tambora red sunsets visible in much of Turner's work from 1816 to 1818. Available through the Tate Britain digital collection.

Standards Alignment

C3 Framework

• Dimension 1 (Developing Questions): Compelling question: "What is the proper humility for a species that lives inside an atmosphere whose chemistry it does not fully understand?" Supporting questions about cause and effect across continental distances, about the role of scientific instruments in revealing previously invisible connections, and about the limits of predictive modelling.

• Dimension 2 (Applying Concepts): Chemistry (atmospheric oxidation, free-radical chemistry, aerosols). Environmental science (climate forcings, greenhouse-gas budgets). History (Romanticism, the Napoleonic-era European economy, the great Indonesian eruptions of the 19th century). Literature (Frankenstein, The Vampyre, Romantic poetry).

• Dimension 3 (Evaluating Sources): The story is accompanied by a populated evidence manifest with eighteen verified claims and direct source URLs. Students can interrogate each claim by clicking through.

• Dimension 4 (Communicating Conclusions): The structured four-corners discussion (Single Class, 30 to 42 minutes) and the extension essay both require sustained argumentation.

AP Alignment

• AP World History: Key Concept 5.4 (Global Migration) and Key Concept 5.3 (Nationalism, Revolution, and Reform). The 1816 famine years and their effect on European emigration to North America.

• AP European History: Romanticism unit. Frankenstein, The Vampyre, and the Romantic response to industrialisation and natural disaster.

• AP Environmental Science: Unit 7 (Atmospheric Pollution) and Unit 9 (Global Change). Greenhouse-gas budgets, aerosol forcing, and the difference between short-lived and long-lived climate forcings.

• AP Chemistry: Unit 5 (Kinetics) and Unit 6 (Thermodynamics). Free-radical reaction mechanisms, the chlorine chain in atmospheric methane oxidation.