The causes of climate change

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

Explain in your own words what the greenhouse effect is and why it is called that.

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.

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

Order these ways of getting to school from lowest to highest emissions: one person travelling by car, walking, travelling by bus. Explain the criterion you have followed.

State whether these statements are true or false and correct the false ones: the greenhouse effect is a phenomenon created by humans; burning petrol emits $\text{CO}_2$; solar energy emits more greenhouse gases than coal.

Explain the relationship between burning fossil fuels (coal, oil, gas) and the increase of $\text{CO}_2$ in the atmosphere.

Name two energy sources that do not emit $\text{CO}_2$ when producing electricity and two that do.

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.

Cattle emit methane during digestion. Explain how livestock farming contributes to climate change and cite one measure that would reduce this impact.

A car emits about 120 g of $\text{CO}_2$ per kilometre. Calculate the emissions of a daily 30 km journey and those of a whole year (250 days), and propose two alternatives to reduce them.

Coal-fired power stations emit much more $\text{CO}_2$ per kilowatt-hour than renewable ones. Explain why the transition to renewable energies is considered key in the fight against climate change.

Flying fruit in from another continent emits much more $\text{CO}_2$ than buying it in season at the local market. Explain the relationship between these emissions and climate change and reason why local, seasonal consumption is recommended.

Country A emits 15 t of $\text{CO}_2$ per year per capita and has 10 million inhabitants. Country D emits 1.5 t per year per capita and has 200 million inhabitants. An international treaty requires both to reduce their total emissions by 20 % in five years. Calculate the total emissions of each country, compare the real impact that this cut would demand on the lifestyle of an average citizen of A versus one of D, and justify why negotiating reductions based solely on the national total is unfair.

Following the eruption of Mount Pinatubo in 1991, the global average temperature dropped by about 0.5 °C for almost two years, even though the volcano ejected millions of tonnes of $\text{CO}_2$. Investigate the role of sulfur dioxide ($\text{SO}_2$) aerosols and emitted ash to explain the physical mechanism that caused this temporary cooling, and use this fact to refute those who mistakenly claim that volcanic eruptions are the cause of sustained global warming in recent decades.

The town council of a municipality with an industrial estate, large numbers of tourists, and a regional landfill wants to cut its carbon footprint, but its budget only allows funding two of these three options: 1) electrifying urban buses and municipal machinery; 2) capturing biogas from the landfill and using it to generate energy, to avoid $\text{CH}_4$ emissions; 3) installing solar panels on the roofs of industrial warehouses to reduce electricity use from the fossil-fuel grid. Analyse the differential impact of each option (gas avoided, immediacy, and magnitude) and justify which two you would prioritise.

At a climate summit, Country X (a wealthy nation, highly industrialised since the 19th century, currently with low annual emissions) demands that Country Y (a developing country, currently the world's largest emitter in absolute terms, but with low per capita emissions) reduce its emissions at the same rate. Acting as a UN mediator, formulate an agreement proposal based on the principle of "common but differentiated responsibilities", taking into account historical cumulative emissions versus current emissions, and justify why your proposal is equitable for both parties.

Permafrost, the permanently frozen soil of the Arctic, stores enormous amounts of carbon. Explain what can happen if it thaws and why scientists consider it a process that feeds back into warming.

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.

A climate model warns that a 1 °C increase in Arctic water temperature can trigger a positive feedback loop. Design a cause-and-effect flow chart that links in an orderly manner: increase in atmospheric temperature, melting of sea ice, variation in surface albedo, and absorption of solar radiation by the ocean. Based on your diagram, predict what would happen to the planet's thermal self-regulation capacity if the Arctic Ocean became completely ice-free during the summer.

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.