• Quick retrieval from earlier learning (The greenhouse effect and climate change; Interpreting data from tables and graphs). Students answer on mini whiteboards.
• Show answers together and note who needs support in the main task.

1. What does the greenhouse effect do? (Greenhouse gases trap some heat, keeping Earth warm enough for life / It makes oxygen / It makes holes in the atmosphere / It reflects all sunlight back to space) → Greenhouse gases trap some heat, keeping Earth warm enough for lifePrompt: Without it, Earth would be much colder.
2. Study: Cooling coffee. Time (min) → Temperature (°C) 0 → 88 5 → 78 10 → 68 15 → 58 20 → 48 Estimate the value at 7.5, assuming the pattern between neighbouring points is a straight line. → 73Prompt: 7.5 lies halfway between 5 and 10.
3. Before 1800, carbon dioxide in the air was about 280 parts per million (ppm). Recently it was about 410 ppm. By what percentage has it increased? Give a whole number. → 46 %Prompt: First find the increase.

• Show today's forecast and ask what it means for the class and how forecasters know.
• Share the objective: Analyse climate data: CO₂ records and temperature trends. Read the success criteria together.

• Work through the example out loud, saying why you do each step, not just what you do.
• Example: Annual mean CO₂ at the Mauna Loa observatory was about 317 ppm in 1960 and about 414 ppm in 2020. What was the mean rate of increase, in ppm per year? Give 1 decimal place.
• Step 1: (414 − 317) ÷ (2020 − 1960) = 97 ÷ 60 = 1.62
• Step 2: So the answer is: 1.6
• Answer: 1.6
• Pause after each step and ask a student to say what comes next.

• Do these together. Students try each step on whiteboards before you reveal it.
• Use the hints as prompts rather than giving the answer.

1. Annual mean CO₂ at the Mauna Loa observatory was about 369 ppm in 2000 and about 414 ppm in 2020. What was the mean rate of increase, in ppm per year? Give 1 decimal place. → 2.3Prompt: rate = change in CO₂ ÷ change in time
2. The CO₂ record from Mauna Loa rises every year but also goes up and down within each year. Why the yearly wiggle? (Northern Hemisphere plants absorb CO₂ in spring and summer and release it in autumn and winter / Volcanoes erupt every winter / The instruments are faulty / People burn no fuel in summer) → Northern Hemisphere plants absorb CO₂ in spring and summer and release it in autumn and winterPrompt: Most land, and so most plants, is in the Northern Hemisphere.

• Students work on the student sheet. Circulate and check the first two answers of every student early.
• Students who finish: write a question of their own for a partner, with the answer.

The 6 questions are on the student sheet below, with answers in the key.

• Two questions on their own. Sort answers into got it / nearly / not yet to plan the next lesson.

1. How do scientists know CO₂ levels from hundreds of thousands of years ago? (they guess / from old newspapers / from satellite photos of the past / from air bubbles trapped in ice cores from Antarctica) → from air bubbles trapped in ice cores from AntarcticaPrompt: Snow traps tiny samples of air as it turns into ice.
2. Climate evidence: which statement is NOT true? (Global average surface temperature has risen by more than 1 °C since the late 1800s. / Sea level is rising as oceans warm and land ice melts. / Most of the extra CO₂ comes from volcanoes. / Burning fossil fuels is the main cause of the recent rise in atmospheric CO₂.) → Most of the extra CO₂ comes from volcanoes.Prompt: What is the difference between weather and climate?

Free online practice with hints and printable worksheets for this skill: eurekami.com/science/grade-11.