echoesof.science · Ages 15–16
Climate change: the evidence and the numbers
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the game and the quiz
echoesof.science/school/climate/ages-15-16/
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Climate is the statistics of weather over a long period, usually 30 years. Köppen climate zones are defined by thresholds: in a polar climate no month averages above 10 °C; in a temperate climate the coldest month averages between 0 °C and 18 °C and at least one month averages above 10 °C.
The greenhouse effect is the warming that results when the atmosphere traps heat radiating from Earth toward space. The key greenhouse gases are carbon dioxide, methane, nitrous oxide, chlorofluorocarbons and water vapour. Water vapour acts as a feedback: a warmer climate holds more of it, which amplifies the warming.
Carbon dioxide at Mauna Loa was 313 ppm when Charles David Keeling began measuring in March 1958. In May 2026 it peaked at 432.00 ppm, 1.8 ppm higher than in May 2025. It peaks every May and falls during the northern growing season as plants take up CO₂. The IPCC states that the 2019 value (410 ppm) was higher than at any time in at least 2 million years.
Experiment: Data investigation: how fast is CO₂ rising?
- Plot CO₂ (ppm) against year for the four values given.
- Calculate the mean rate of rise from 1958 to 2026 in ppm per year.
- Calculate the rate from 2019 to 2026 and compare it with the 1958–2026 mean and with the 1.8 ppm rise between May 2025 and May 2026. Is the rise speeding up?
- The 1958 value is from March and the 2025 and 2026 values are May peaks. Explain how the seasonal cycle could affect your calculated rates.
- Optional: plot one full year of monthly data and measure the size of the seasonal cycle (highest minus lowest month).
- Write a conclusion with the evidence and the main uncertainties.
| Date | CO₂ (ppm) | Years since previous | Rise (ppm) | Rate (ppm/yr) |
|---|---|---|---|---|
| March 1958 | ||||
| 2019 | ||||
| May 2025 | ||||
| May 2026 |
Questions
Sketch the Keeling curve from 1958 to 2026: show the long-term rise and the yearly seasonal wiggle. Label the axes with units.
🍎Calculate the mean rate of CO₂ rise between 2019 (410 ppm) and May 2026 (432 ppm). Compare it with the 1958–2026 mean.
A friend says: 'Last winter was very cold, so the climate is not warming.' Write a short scientific reply.
Explain why melting Arctic sea ice does not raise sea level much, but melting of the Greenland ice sheet does.
Sources for every fact on this sheet: echoesof.science/school/climate/sources/