• 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 is the main cause of the recent rise in global temperatures? (human activities adding greenhouse gases, especially by burning fossil fuels / the Sun getting much hotter / volcanoes only / the Moon moving closer) → human activities adding greenhouse gases, especially by burning fossil fuelsPrompt: What has changed most since the 1800s?
2. Study: Cooling coffee. Time (min) → Temperature (°C) 0 → 82 5 → 72 10 → 62 15 → 52 20 → 42 Estimate the value at 2.5, assuming the pattern between neighbouring points is a straight line. → 77Prompt: 2.5 lies halfway between 0 and 5.
3. Before 1800, carbon dioxide in the air was about 280 ppm. Recently it was about 420 ppm. By how many ppm has it risen? → 140 ppmPrompt: Subtract the old value from the new value.

• 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 326 ppm in 1970 and about 390 ppm in 2010. What was the mean rate of increase, in ppm per year? Give 1 decimal place. → 1.6Prompt: 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? (People burn no fuel in summer / The instruments are faulty / Volcanoes erupt every winter / Northern Hemisphere plants absorb CO₂ in spring and summer and release it in autumn and winter) → 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 8 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. Annual mean CO₂ at the Mauna Loa observatory was about 326 ppm in 1970 and about 390 ppm in 2010. What was the mean rate of increase, in ppm per year? Give 1 decimal place. → 1.6Prompt: rate = change in CO₂ ÷ change in time
2. How do scientists know CO₂ levels from hundreds of thousands of years ago? (from old newspapers / they guess / from air bubbles trapped in ice cores from Antarctica / from satellite photos of the past) → from air bubbles trapped in ice cores from AntarcticaPrompt: Snow traps tiny samples of air as it turns into ice.

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