Exercises: The causes of climate change

The diagram represents the greenhouse effect in four numbered steps.

1. a) Explain what happens in each of the steps labelled with the numbers 1 to 4.
2. b) Which number corresponds to the heat returned by the atmosphere towards the surface?
3. c) Name two greenhouse gases.

Explain the difference between weather and climate, and give an example of each.

Name three human activities that increase emissions of greenhouse gases into the atmosphere.

The greenhouse effect is a natural phenomenon necessary for life. Explain why this is so and clarify the current problem (the enhanced greenhouse effect due to human emissions).

How is deforestation linked to climate change? Reason two different mechanisms: the reduced absorption of $\text{CO}_2$ and the emissions caused by cutting down or burning forests.

The concentration of atmospheric $\text{CO}_2$ was 317 ppm in 1960, 354 ppm in 1990, and 414 ppm in 2020. Calculate the increase between 1960 and 2020, express it as a percentage, and relate the trend to human activities.

Analyse the following global temperature anomaly data: −0.2 °C in 1880, +0.2 °C in 1980, and +1.2 °C in 2023. Calculate the average warming rate per decade in the period 1880-1980 compared to the period 1980-2023. Based on the result, justify whether global warming follows a constant or an accelerated progression, and predict what temperature anomaly we would reach in 2050 if the rate of the last period were maintained compared to if the rate of the first had been maintained.

An advisory team proposes two strategies to curb global warming before 2040: Plan A aims to eliminate natural gas leaks and reduce intensive livestock herds (focusing on methane, $\text{CH}_4$); Plan B focuses on decommissioning coal-fired power plants (focusing on $\text{CO}_2$). Knowing that $\text{CH}_4$ warms about 80 times more than $\text{CO}_2$ over a 20-year timescale but disappears from the atmosphere in about 12 years, while $\text{CO}_2$ remains for centuries, evaluate which of the two plans would slow down warming faster in the short term and which one is essential to prevent irreversible change in the long term. Justify your verdict.

In a school debate, someone argues: «In the Cretaceous there was no ice at the poles and the Earth was much warmer than today without human intervention; therefore, the current warming is natural and we should not worry». Refute this statement by comparing the timescale (rate) at which those geological changes occurred versus that of the current change, and explain what direct consequence this difference in speed has on the adaptive capacity of ecosystems and species survival.