Earth’s vital signs: carbon, warming and the energy turning point
Students work with the Keeling curve, real electricity data and the 2026 State of the Climate report to calculate change, link cause and effect, and weigh up whether the world is making progress.
Learning objectives
- Explain the seasonal cycle and long-term rise in atmospheric carbon dioxide.
- Calculate percentage change and compare rates of change from real data.
- Evaluate evidence of progress and problems in the global energy system.
Key words
Starter 5 minutes
Scientists check 16 “vital signs” of the planet each year, like a doctor checking a patient. Seven are now at record extremes. In pairs, list three things you would measure to check the planet’s health, and say why.
Task 1: The Keeling curve 15 minutes
68 years of carbon dioxide at Mauna Loa
Monthly CO₂ in parts per million, March 1958 to September 2026. The darker line removes the seasonal cycle.
- CO₂ was 315.7 ppm in March 1958 and 432.3 ppm in May 2026. Calculate the percentage increase. Show your working. [3](432.3 − 315.7) ÷ 315.7 × 100 = 36.9%. (1 mark for the difference, 116.6 ppm; 1 for dividing by the starting value; 1 for the answer.)
- The light line zigzags up and down every year. Explain why. [2]Plants in the Northern Hemisphere, which has most of the world’s land, absorb CO₂ as they grow in spring and summer, lowering levels; they release it in autumn and winter as leaves fall and decay, raising levels.
- The yearly rise averaged 0.86 ppm in the 1960s and 2.64 ppm in 2015–2024. How many times faster is CO₂ rising now? [2]2.64 ÷ 0.86 ≈ 3.1 times faster.
Task 2: The energy turning point 15 minutes
Renewables overtook coal in 2025
World electricity generation by source, terawatt-hours, 2000–2025.
- By how much did renewables exceed coal in 2025? [1]10,726 − 10,472 = 254 TWh.
- Calculate the percentage change from 2015 to 2025 for coal and for solar + wind. What do your answers show? [4]Coal: (10,472 − 9,284) ÷ 9,284 × 100 = +12.8%. Solar + wind: (5,492 − 1,086) ÷ 1,086 × 100 = +406%, about five times larger. Solar and wind grew very fast, but coal still grew too, so clean power was added alongside coal rather than replacing it.
- Coal generation in 2025 was still higher than in 2015. Suggest two reasons why, even though renewables grew so much. [2]Any two, e.g.: total electricity demand grew (more people, air conditioning, industry, data centres); some countries still build or rely on coal plants; renewables started from a small base. The State of the Climate report says renewable growth “was insufficient to displace fossil fuel consumption”.
Task 3: Is the world making progress? 15 minutes
- Extended answer. “The world is winning the fight against climate change.” How far do you agree? Use evidence from this pack. [6]See the mark scheme in the teacher notes.
Extension
Open Earth’s Vital Signs. Pick one indicator that updates live from NOAA (CO₂, methane, nitrous oxide or sea level). Record its latest value and explain whether it has improved or worsened since this pack was written.
Teacher notes
Key facts. The 2026 State of the Climate report (Ripple, Wolf et al., BioScience, 14 October 2026) found seven record extremes: carbon dioxide, methane, nitrous oxide, ocean heat content, sea level, glacier thickness and Greenland’s ice mass. The report recommends three fast-track measures: mangrove restoration, shifting towards plant-based diets and distributed solar.
| Level | Mark scheme for question 7 (6 marks) |
|---|---|
| Level 3 (5–6) | A balanced judgement supported by data on both sides: progress (renewables overtaking coal, 42.6% low-carbon power, solar and wind up about 400% since 2015) against problems (record CO₂ at 432.3 ppm, warming rate doubling, fossil fuel use at a record). Reaches a clear conclusion, e.g. progress in technology but not yet in outcomes. |
| Level 2 (3–4) | Uses some data on both sides, or develops one side well; conclusion may be implied. |
| Level 1 (1–2) | Simple agreement or disagreement with little evidence. |
Common misconception. “Renewables overtaking coal means emissions are falling.” Not yet: total fossil fuel use and energy CO₂ emissions reached new highs in 2025, because demand grew faster than clean power could replace fossil fuels.
Link to students’ lives. Ask students to use ClimateIQ Personal at home with a real electricity bill, then compare which of the report’s three fast-track measures they could act on.