☰ Year plan · Science

Acid rain damage, scrubbers, monitoring and models

Week 14 · 2-4 The Atmosphere and the Role of Science in Its Sustainability (B): effects of acid rain on plants, soil and buildings, scrubbers, monitoring by satellites and weather stations, climate models, forecasting and examples · 3 lessons
3

Climate models and forecasting in practice

Integrated Science Sec 1 Term 1, Unit 2: pp. 103–108
GoalExplain what climate models do, why their answers are ranges, and how forecasts can help in practice.
New words
climate model · a computer program built from physical, chemical and biological equationsuncertainty · the fact that a forecast gives a range, not an exact valuecoral bleaching · corals losing their algae when the water is too warm
Explanation

Climate models are computer programs built from physical, chemical and biological equations. Fed with data from satellites and stations, such as gas emission levels, they predict ranges. For example, a model run in which CO₂ keeps rising can give a rounded range of about 1.5 to 2 °C of extra warming, with changed rainfall patterns and more extreme weather; the range depends on the emission assumptions and is not a forecast for a given date. A model gives ranges with uncertainty, not exact dates. The Paris Agreement of 2015 aims to hold global warming well below 2 °C above pre-industrial levels. Forecasts matter for health (pollution and UV warnings), agriculture (when to plant and harvest) and ecosystems (protecting sensitive species). A forecast of “30% chance of a heat wave” is a probability, not a certainty. Example: coral bleaching happens when corals expel the symbiotic algae that feed them because the water is too warm, and they lose their main food. Forecasts of marine heat waves can help managers reduce other stresses on a reef, for example by limiting local pollution. They cannot prevent the heat itself, and bleaching can still be severe.

Worked examples
A city has an average of 15 °C. If warming of 1.5 °C to 2 °C came, the average would be 15 + 1.5 = 16.5 °C to 15 + 2 = 17 °C. The answer is a range from 16.5 °C to 17 °C, not one number.
A forecast gives a 30% chance of a heat wave on each of 10 similar days. We expect about 30 ÷ 100 × 10 = 3 of them to have one, but we cannot say which. This is why forecasts speak in probabilities.
Invented scenario: a forecast warns that the sea near a reef will be unusually warm next month. Managers cannot cool the sea, but they can cut local pollution and fishing pressure in that time, to reduce other stresses. Bleaching may still happen, and the reef is still at risk.
Class activity

Forecast reading and model game. Take a one-week forecast from a weather app and write down temperature and rain chance. After the week, compare. Did the forecast match? Where was it off, and by how much? Then draw a flow chart: data in, model, range out, decision. Add one decision for health, one for farming and one for nature. Say why a range is more honest than an exact date.

Practice
1
What goes into a climate model, and what comes out?
2
The average is 20 °C. Warming of 1.5 °C to 2 °C is expected. Give the new range.
3
What does coral bleaching mean?
4
Name one agreement about climate and its aim.