19 Degrees · classroom sheet · ages 16 and up

Testing a climate claim with real data

The claim: warming seas are giving bull sharks more time and more coastline, and bites have followed. Your job is to test it like a scientist, using the data from 19 Degrees (Researchers tab, then Download the data and images).

Bull shark bites below 19°C: 0 of 170. Coastal share: 4% (1900–59) to 68% (since 2015). WA: 10 since 2020 against 9 in 1900–2019.

Months a year the sea off Sydney is 19°C or warmer

1900s		6.4
1910s		6.5
1920s		6.2
1930s		6.8
1940s		6.9
1950s		7.0
1960s		6.6
1970s		7.1
1980s		7.8
1990s		8.1
2000s		8.6
2010s		9.1
2020s		9.3

Dashed line = 6 months, half the year

Tasks

Rate, not count. WA had 9 bull shark bites in 120 years and 10 in 6.5 years. Work out both yearly rates and how many times larger the recent rate is. Why compare rates rather than totals?
Chance or change? The page reports p = 0.002 for the WA bull shark share of all shark bites. In one sentence, explain what that p-value means, and one thing it does not tell you.
Other explanations. List three things besides warming that could explain bites moving into coastal waters (see "Could something else explain it?" in the page's Researchers tab). For each, describe evidence that would rule it in or out.
Design a test. Pick one of the fifteen testable claims (C1–C15) in the page's Researchers tab. State the claim, the data you would need, who holds it, what result would support it and what would prove it wrong.
Communicate. Write a 40-word social post that is accurate, not scary, and includes one number and one safety action.

Teacher notes

Ages 16 and up (Australia Years 10–12, US Grades 10–12, UK Years 11–13) · one 60–90 minute lesson, or two lessons with the data · individual or small groups

Learning intentions

Claims about climate and wildlife can be tested with real data.
Rates, p-values and alternative explanations all matter when judging evidence.
A good test says in advance what result would prove the claim wrong.

Success criteria

I can calculate and compare rates over different time periods.
I can explain what a p-value does and does not tell us.
I can evaluate alternative explanations and design a falsifiable test.

Big ideas

Testing a claim with real data. Rates versus counts, statistical significance and its limits, correlation versus cause, and what would prove a claim wrong.

Curriculum links

Australia (v9)	AC9S10U04 (models of energy flow between Earth's spheres to explain patterns of global climate change); AC9S10I05, AC9S10I06, AC9S10I07 (analysing data, assessing validity and reproducibility, constructing evidence-based arguments). Senior secondary: suits depth studies or research investigations in Biology, Earth and Environmental Science, and General or Standard Mathematics (statistics).
United States (NGSS)	HS-ESS3-5 (analyse geoscience data to make an evidence-based forecast of the rate of climate change and its impacts); HS-LS2-6 (evaluate claims about how changing conditions affect ecosystems).
England (National Curriculum)	GCSE Biology: ecology (abiotic factors, adaptation, distribution of organisms). GCSE Geography: climate change. A-level Biology and Geography independent investigations; GCSE and A-level maths statistics.
International Baccalaureate	DP Biology (ecology) and Environmental Systems and Societies (climate change, biodiversity); the Extended Essay and internal assessment (independent investigation).
Other curricula	Cambridge IGCSE and A Level Biology and Environmental Management. New Zealand NCEA: Science and Biology investigations, Statistics. Canada (Ontario): Grade 12 Biology, Population dynamics; Grade 11 Environmental science.
Global goals	UN Sustainable Development Goals 13 (Climate action) and 14 (Life below water); UNESCO Education for Sustainable Development.

Mapped by topic. Check your own syllabus for local codes.

Lesson sequence

Phase	Time	What happens
Engage	10 min	Present the claim. Ask students to predict what evidence would convince them, and what would not.
Explore	20 min	Tasks 1–2: rates and the p-value.
Explain	10 min	Class discussion: what does a p-value not tell us? Correlation versus cause.
Elaborate	25 min	Tasks 3–4: alternative explanations and designing a test from the Researchers tab (C1–C15).
Evaluate	10 min	Task 5, then peer review of the test designs against the rubric.

Materials

Printed sheet; calculators. For two lessons: computers with the downloadable CSVs or the starter notebook (Python) from the Researchers tab.

Differentiation

Support: Model task 1 together; provide a worked example of interpreting a p-value.
Extension: Run the starter notebook, change the threshold from 19°C to 18.5°C and 19.5°C, and report how sensitive the rule is. Strong designs can be sent to 19 Degrees as a contribution.

Assessment

Rubric for task 4 (design a test). Excellent: falsifiable claim, appropriate data and holder named, a clear result that would disprove it, and a confounder addressed. Sound: testable claim and data named, disproof stated loosely. Developing: claim restated without a clear test.

Wellbeing

This topic involves injuries and deaths. Some students may know someone affected by a shark bite or a drowning. Keep the focus on patterns and staying safe, avoid graphic images and news footage, let students step out if they need to, and follow your school's wellbeing procedures. Sharks hold cultural significance for many Indigenous peoples, including Aboriginal and Torres Strait Islander, Māori, Native Hawaiian and other Pacific peoples; if you explore this, use resources developed with or approved by local communities.

Answer guide. 1: 9/120 ≈ 0.07 a year against 10/6.5 ≈ 1.54 a year, about 21 times higher; rates allow for periods of different length. 2: if nothing had really changed, a difference this big would turn up by chance only about 2 times in 1,000; it does not say why the change happened or how big it matters. 3: identification (early river bites were labeled bull sharks partly by place), beach nets since the 1930s, rain and runoff plumes, more people surfing and spearfishing; test with confirmed-species bites, net locations, rainfall and river-mouth distance. 4: any claim with a measurable, falsifiable outcome. 5: for example, "Bull sharks never bite in water below 19°C, and that water now lasts 3 months longer off Sydney. Stay out of murky water after heavy rain and swim between the flags."

Data: Australian Shark-Incident Database (Taronga Conservation Society Australia and Flinders University); HadISST sea temperature (UK Met Office); Pacoureau et al. 2021; Surf Life Saving Australia. From 19 Degrees, free and open source. © 2026 Blake Erickson.