Question 1
Distinguish between weather and climate.
[2]
Question 2
Atmospheric concentration increased from approximately 280 ppm before widespread industrialization to 420 ppm in the 2020s.
Calculate the percentage increase in atmospheric concentration. Show your working.
[2]
Outline why atmospheric concentration can continue to rise even if annual anthropogenic emissions remain constant.
[2]
Question 3
Explain how an ice core can provide evidence of past atmospheric concentrations and temperatures.
[3]
Question 4
Figure 1 shows global fossil-fuel and cement emissions and atmospheric concentration from 1750 to 2025. The monthly atmospheric concentration series for 2021 to 2025 is also shown.
Identify the period during which both variables began their most rapid sustained increase.
[1]
Calculate the percentage increase in atmospheric concentration between 1750 and 2025.
[2]
Explain why atmospheric concentration continued to increase as shown, even though some emitted was absorbed by natural sinks.
[2]
Suggest one biological process responsible for the seasonal oscillation in the monthly atmospheric series.
[1]
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Question 5
The figure compares Earth's energy flows under the natural and enhanced greenhouse effects.
Explain how anthropogenic greenhouse-gas emissions produce the enhanced greenhouse effect and global warming.
[4]
Question 6
Two forests experience the same severe drought and wildfire. Forest X contains many tree species and high genetic diversity. Forest Y is dominated by one tree species with low genetic diversity.
Explain why Forest X is likely to be more resilient than Forest Y.
[4]
Question 7
A coastal city experiences more frequent storm-surge flooding. A low-income district is built on low-lying land and has limited healthcare, drainage and insurance coverage.
Outline two impacts that the flooding may have on the district.
[2]
Explain one reason why the district has low societal resilience to this flooding.
[2]
Question 8
A planetary-boundary assessment proposes an atmospheric boundary of 350 ppm. The concentration recorded for a recent year was 424 ppm.
Calculate the percentage by which the recent concentration exceeds the proposed boundary. Show your working.
[2]
Outline one conclusion and one limitation associated with using this boundary.
[2]
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Question 9
Distinguish between a direct climate measurement and a proxy measurement.
[2]
Outline one advantage and one limitation of using pollen from peat cores to reconstruct past climate.
[2]
Question 10
Figure 1(a) shows changes in global mean atmospheric carbon dioxide concentration from 1750 to 2024. Figure 1(b) shows global anthropogenic carbon dioxide emissions by source for 1960 and 2022.
Global anthropogenic carbon dioxide emissions by source; land-use change is excluded.
| Source | 1960 / | 2022 / |
|---|---|---|
| Coal | 3.9 | 15.1 |
| Oil | 3.6 | 11.9 |
| Natural gas | 0.9 | 7.8 |
| Cement production | 0.7 | 1.7 |
| Flaring | 0.3 | 0.7 |
| Total | 9.4 | 37.2 |
Calculate the percentage increase in atmospheric carbon dioxide concentration between 1750 and 2024.
[2]
Describe two features of the atmospheric carbon dioxide trend shown in Figure 1(a).
[2]
Distinguish between annual anthropogenic carbon dioxide emissions and atmospheric carbon dioxide concentration.
[2]
Explain why the seasonal oscillation in Figure 1(a) does not contradict the long-term increase in atmospheric carbon dioxide concentration.
[2]
Evaluate the extent to which Figures 1(a) and 1(b) support an anthropogenic explanation for the increase in atmospheric carbon dioxide concentration.
[5]
Question 11
Marine heat stress and live coral cover were monitored at the fictional Pelican Bank reef between 2016 and 2024. Heat stress is measured in degree heating weeks (DHW); values above 8 DHW are associated with severe bleaching.
Annual maximum marine heat stress and mean live coral cover at Pelican Bank reef.
| Year | Maximum heat stress / DHW | Mean live coral cover / % | Recorded event |
|---|---|---|---|
| 2016 | 2 | 42 | — |
| 2017 | 3 | 41 | — |
| 2018 | 4 | 40 | — |
| 2019 | 5 | 39 | — |
| 2020 | 4 | 37 | Major cyclone |
| 2021 | 7 | 34 | — |
| 2022 | 6 | 32 | — |
| 2023 | 18 | 17 | — |
| 2024 | 6 | 15 | — |
| Severe bleaching threshold | — | — |
Calculate the percentage decrease in live coral cover between 2016 and 2024.
[2]
Describe the relationship between heat stress and live coral cover shown in the figure.
[2]
Explain how the heat stress recorded in 2023 could have caused the observed change in coral cover.
[2]
Suggest one reason why the figure does not establish heat stress as the only cause of coral-cover loss.
[1]
Question 12
Two neighbouring coastal communities experienced the same maximum flood depth after a tropical storm. Figure 3 summarizes their characteristics and recovery. In the graph, the percentages labelled “Returned home” are the percentages of households displaced by the storm that had returned home.
Compare the recovery of essential infrastructure in Aruna and Belesa.
[2]
Calculate the difference between the percentages of essential infrastructure restored in the two communities after six months.
[1]
Explain two factors shown in the fact file that may have increased Aruna's societal resilience.
[2]
Suggest why a greater percentage of displaced households had returned to Belesa after one month despite its lower income.
[2]
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Question 13
Figure 4 presents selected indicators used to assess the planetary boundary for climate change. The boundary indicates an increasing risk of large-scale change rather than a point at which catastrophe is certain.
Calculate the percentage by which the 2024 atmospheric concentration exceeded the proposed boundary.
[2]
Using the figure, outline two observations that support the assertion that the climate boundary has been transgressed.
[2]
Discuss why exceeding the proposed boundary does not prove that every climate tipping point has already been crossed.
[2]
Question 14
Explain how hindcasting is used to test a global climate model, including one limitation of the process.
[4]
Question 15
The figure shows projected global mean sea-level change under three emissions scenarios.
Projected global mean sea-level change relative to 2025, with central projections and uncertainty ranges.
| Year | Low central / m | Low range / m | Intermediate central / m | Intermediate range / m | High central / m | High range / m |
|---|---|---|---|---|---|---|
| 2025 | ||||||
| 2050 | ||||||
| 2100 |
Calculate the difference between the central projections for the high- and low-emission scenarios in 2100.
[1]
Explain why the projections diverge and their uncertainty ranges widen towards 2100.
[3]
Question 16
Scientists reconstructed atmospheric carbon dioxide concentration and global temperature over the past 800 000 years using Antarctic ice cores. Figure 2(a) presents a simplified reconstruction. Figure 2(b) summarizes three climate proxies.
Figure 2(a): simplified Antarctic ice-core reconstruction; final row is a modern atmospheric measurement.
| Time / years before present | Atmospheric / ppm | Temperature anomaly / |
|---|---|---|
| 800 000 | 180 | |
| 760 000 | 280 | |
| 700 000 | 185 | |
| 650 000 | 275 | |
| 600 000 | 180 | |
| 540 000 | 290 | |
| 480 000 | 185 | |
| 420 000 | 285 | |
| 340 000 | 190 | |
| 300 000 | 300 | |
| 270 000 | 185 | |
| 240 000 | 290 | |
| 180 000 | 185 | |
| 125 000 | 280 | |
| 70 000 | 190 | |
| 20 000 | 185 | |
| 0 (pre-industrial) | 280 | 0 |
| Modern | 423 | — |
Comparison of climate proxies used to reconstruct past environments.
| Ice cores | Tree rings | Lake sediments |
|---|---|---|
| Evidence: trapped gases and oxygen-isotope ratios | Evidence: annual ring width or density | Evidence: pollen, shells and grain size |
| Coverage: up to about years | Coverage: centuries to several millennia | Coverage: thousands to hundreds of thousands of years |
| Limitation: dating uncertainty; gas-age/ice-age difference | Limitation: affected by age, disease, moisture and competition | Limitation: mixing and uncertain deposition rates |
State the type of correlation between reconstructed atmospheric carbon dioxide concentration and temperature anomaly in Figure 2(a).
[1]
Describe two pieces of evidence from Figure 2(a) for this correlation.
[2]
Compare the modern atmospheric carbon dioxide concentration with the range reconstructed for the previous 800 000 years.
[2]
Explain how ice cores can provide evidence of both past atmospheric carbon dioxide concentration and temperature.
[3]
Evaluate the reliability of the evidence in Figures 2(a) and 2(b) for concluding that carbon dioxide causes climate change.
[5]
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Question 17
A monitoring programme studied a fictional subtropical reef, Pelican Bank, between 2018 and 2024. The reef experienced an exceptional marine heatwave in 2023. Local pressures included tourism, wastewater discharge and two tropical storms.
Annual monitoring data for Pelican Bank, 2018–2024.
| Year | Maximum summer SST anomaly / | Live hard-coral cover / | Tropical storm |
|---|---|---|---|
| 2018 | 0.4 | 50 | No |
| 2019 | 0.7 | 51 | No |
| 2020 | 0.5 | 49 | Yes |
| 2021 | 0.9 | 47 | No |
| 2022 | 1.1 | 44 | Yes |
| 2023 | 2.6 | 22 | No |
| 2024 | 1.4 | 20 | No |
Calculate the percentage decrease in live hard-coral cover between 2018 and 2023.
[2]
Describe the relationship between maximum summer sea-surface temperature anomaly and coral cover shown in Figure 3(a).
[2]
Explain how the 2023 marine heatwave could have caused the observed change in coral cover.
[3]
Explain why a reduction in biodiversity could reduce the resilience of Pelican Bank.
[2]
Evaluate the conclusion that climate change was the only cause of the decline in coral cover at Pelican Bank.
[5]
Question 18
Figure 5 shows reconstructions of Northern Hemisphere summer temperature from three sources. Values are anomalies relative to the 1901–2000 mean. Instrumental measurements begin in 1880.
Identify the record that provides data for the longest period.
[1]
Compare the tree-ring and instrumental records during their period of overlap.
[2]
Calculate the difference between the tree-ring and instrumental temperature anomalies in 2000.
[1]
Evaluate the use of these records together when reconstructing past climate and developing climate models.
[3]
Question 19
A global climate model was run under low-, intermediate- and high-emission scenarios. The table shows the modelled uncertainty ranges and central estimates for global mean sea-level rise, together with projected temperature and precipitation changes at location K.
Calculate the difference in projected global mean sea-level rise in 2100 between the high- and low-emission central estimates.
[1]
Compare the projected temperature changes at location K under the three scenarios.
[2]
Interpret the uncertainty ranges for global mean sea-level rise in 2100.
[2]
Explain why the scenario projections separate more strongly towards 2100 and why sea level continues to rise in the low-emission scenario.
[3]
Question 20
A climate model was hindcast from 1900 to 2020 using two sets of inputs. Run A included natural forcings only. Run B included natural and anthropogenic forcings. The second graph compares regional precipitation hindcasts with observations for 1981–2010.
Identify which model run most closely reproduces the observed global temperature trend after 1980.
[1]
Calculate the difference between the observed temperature anomaly and Run A in 2020.
[1]
Explain how the hindcast results provide evidence for an anthropogenic contribution to recent warming.
[2]
Evaluate the model's validity using both figures.
[3]
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Question 21
The systems diagram represents a possible transition from humid rainforest to drier open vegetation.
Explain how the positive feedback shown could cause the system to cross a critical threshold and form a new equilibrium.
[4]
Question 22
The figure shows possible interactions among four climate tipping elements.
Outline why the interactions shown constitute a possible tipping cascade rather than several independent tipping points.
[2]
Distinguish between one biotic and one abiotic tipping element shown in the figure.
[2]
Question 23
The fictional coastal city of San Isidro was flooded by a cyclone-driven storm surge in 2026. Two districts experienced similar maximum water depths but had different social and environmental conditions. The city council is considering three adaptation options.
District profiles following the 2026 cyclone-driven flood in San Isidro.
| Indicator | Harbour East | Mangrove Bay |
|---|---|---|
| Maximum flood depth / m | 1.8 | 1.8 |
| Population | 24 000 | 18 000 |
| Households receiving warning / % | 92 | 48 |
| Median household income / international dollars per year | 38 000 | 9 500 |
| Residents displaced | 2 400 | 8 100 |
| Deaths | 3 | 27 |
| Median electricity restoration time / days | 2 | 11 |
| Insured households / % | 81 | 14 |
| Intact mangrove belt width / m | 40 | 620 |
Appraisal of proposed flood-adaptation strategies for San Isidro.
| Adaptation strategy | Capital cost / million international dollars | Scale or coverage | Time frame | Benefits and limitations |
|---|---|---|---|---|
| Sea wall | 180 | 9 km of dense urban coast; district allocation unspecified | 50-year expected lifetime | Rapid, durable protection; benefits depend on location and it may transfer erosion or block some coastal access. |
| Mangrove restoration | 24 | 14 km of coast | 8–15 years to establish | Reduces wave energy and provides habitat; requires space for inland migration. |
| Warning-and-cooling network | 6 | Both districts | Within 2 years | Multilingual alerts, evacuation transport, clinics and cooling centres; does not prevent physical flooding. |
Identify the district that showed greater societal resilience to the 2026 flood.
[1]
Calculate how many times greater the displacement rate was in Mangrove Bay than in Harbour East.
[3]
Explain two factors that may account for the difference in societal resilience between the districts.
[4]
Suggest two reasons why residents of the two districts might have different perspectives on the proposed sea wall.
[2]
Evaluate which adaptation strategy, or combination of strategies, the city council should prioritize.
[5]
Question 24
The Arken climate research service combines direct measurements and proxy evidence in a global climate model. Scientists tested the model by hindcasting global mean temperature change from 1900 to 2020.
Comparison of direct and proxy climate records used in climate reconstruction.
| Climate record | Evidence type | Time resolution | Record length | Key limitation |
|---|---|---|---|---|
| Weather-station temperature | Direct instrument measurement | Daily | 142 years | Local urbanization effects |
| Satellite surface temperature | Direct remote sensing | Near-daily | 46 years | Sensor calibration |
| Tree-ring width | Proxy indicator | Annual | 900 years | Moisture, age and competition |
| Ice-core oxygen-isotope ratios | Proxy indicator | Multidecadal in older ice | 120 000 years | Dating and calibration uncertainty |
Distinguish between a direct climate measurement and a climate proxy, using one example from the figures for each.
[2]
Compare the usefulness of the weather-station and ice-core records shown in Figure 5(b).
[3]
Calculate the difference between the observed 2020 temperature anomaly and the anomaly produced by the natural-forcings-only model.
[1]
Explain how the results in Figure 5(c) strengthen the attribution of recent warming to human activity.
[3]
Evaluate the validity of using this hindcast to predict future climate change.
[6]
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Question 25
Climate models were used to project changes for the fictional Lydian Delta under low-, intermediate- and high-emission scenarios. All changes are relative to the 1995–2014 mean.
Projected changes relative to the 1995–2014 mean under three emission scenarios.
| Scenario | Year | Temperature change / | Precipitation change / | Sea-level rise / m |
|---|---|---|---|---|
| All scenarios | 2020 | 0.3 | 0 | 0.05 |
| Low emissions | 2100 | |||
| Intermediate emissions | 2100 | |||
| High emissions | 2100 |
Calculate the difference between projected high- and low-emission temperature change in 2100.
[1]
Compare the 2100 precipitation projections under the three scenarios.
[3]
Explain why sea level may continue to rise even if emissions follow the low-emission scenario.
[3]
Suggest two impacts of the high-emission scenario on ecosystems or societies in the Lydian Delta.
[2]
Evaluate how useful these scenario projections are for planning adaptation in the Lydian Delta.
[5]
Question 26
A model study investigated four interacting climate tipping elements under two warming scenarios. The arrows in Figure 8(a) show proposed causal links; arrow width represents the assessed strength of each link. Figure 8(b) shows the percentage of model runs in which each element crossed its critical threshold by 2200.
Identify the tipping element classified as involving both biotic and abiotic factors.
[1]
Using Figure 8(a), outline a pathway by which Greenland ice-sheet loss could eventually reinforce further ice-sheet loss.
[2]
Calculate how many times greater the percentage of model runs crossing the Atlantic-overturning threshold was under warming than under warming.
[1]
Analyse how the two figures demonstrate both the risk and uncertainty associated with tipping cascades.
[3]
Question 27
Distinguish between the natural greenhouse effect and the enhanced greenhouse effect.
[4]
Explain how human activities and climate feedback processes can alter Earth's global energy balance.
[7]
Using real-world evidence, to what extent is recent climate change attributable to human activities rather than natural processes?
[9]
Question 28
Outline how biodiversity and habitat connectivity can influence the resilience of an ecosystem exposed to climate change.
[4]
Explain how climate change can affect ecosystems at local, regional and global scales.
[7]
Using named examples, evaluate the effectiveness of ecosystem-management strategies in maintaining resilience under climate change.
[9]
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Question 29
Outline four factors that influence the resilience of a society to climate-related hazards.
[4]
Explain how climate change can produce interconnected impacts on health, water supply, agriculture and infrastructure.
[7]
Using named examples, discuss the assertion that socio-economic inequality is more important than the magnitude of a climate hazard in determining its impact on society.
[9]
Question 30
Researchers examined the possible transition of a fictional tropical forest region, the Verde Basin, towards a drier open-woodland state. Model experiments altered the proportion of original forest remaining while holding global temperature constant at above the pre-industrial mean.
Figure 7(a). Modelled equilibrium responses in the Verde Basin at fixed warming of above the pre-industrial mean.
| Original forest remaining / % | Dry-season rainfall / mm | Equilibrium tree cover / % | Modelled region |
|---|---|---|---|
| 100 | 620 | 88 | Outside critical region |
| 80 | 590 | 84 | Outside critical region |
| 60 | 530 | 76 | Outside critical region |
| 50 | 470 | 68 | Critical region ( to ) |
| 45 | 350 | 42 | Critical region ( to ) |
| 40 | 270 | 27 | Outside critical region |
| 30 | 230 | 20 | Outside critical region |
| 20 | 210 | 16 | Outside critical region |
Describe the change in equilibrium tree cover as the proportion of original forest remaining decreases.
[2]
Distinguish between a critical threshold and a new equilibrium in the context of the Verde Basin.
[2]
Explain how one positive feedback loop in Figure 7(b) could drive the system across the critical threshold.
[3]
Predict two consequences of a transition to the open-woodland equilibrium for the global climate system or regional ecosystems.
[2]
Evaluate the strength of the evidence that the Verde Basin is approaching a tipping point.
[6]
Question 31
A research consortium assessed four interacting climate tipping elements. Arrow thickness in Figure 8(a) represents the consortium's confidence in each proposed interaction, not the magnitude of its eventual impact.
Figure 8(b): risk assessment of four climate tipping elements.
| Tipping element | Estimated warming range where risk rises rapidly / (estimate, not precise trigger) | Approximate response timescale | Reversibility on human timescales | Main global consequence |
|---|---|---|---|---|
| Greenland ice-sheet loss | Centuries to millennia | Largely irreversible | Sea-level rise and freshwater input | |
| Atlantic meridional overturning circulation weakening | Decades to centuries | Uncertain | Regional temperature and rainfall redistribution | |
| Equatorial rainforest dieback | , plus land-use pressure | Decades to centuries | Difficult to reverse | Carbon release and biodiversity loss |
| Antarctic marine ice-sheet retreat | Centuries to millennia | Largely irreversible | Long-term sea-level rise |
Identify one predominantly biotic tipping element and one predominantly abiotic tipping element shown in Figure 8(a).
[2]
Explain one possible tipping cascade linking boreal ice-sheet loss to further global warming.
[4]
Explain why interactions among these tipping elements increase uncertainty in predictions of the scale and pace of climate change.
[3]
Suggest one reason why the warming ranges in Figure 8(b) should not be interpreted as precise trigger temperatures.
[1]
Evaluate whether uncertainty about tipping cascades justifies delaying action to reduce greenhouse-gas emissions.
[5]
Question 32
Compare direct measurements and proxy measurements used to study climate change.
[4]
Explain how climate data, model structure and hindcasting are used to develop and test a global climate model.
[7]
Evaluate the reliability of global climate models for predicting future regional impacts of climate change.
[9]
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Question 33
Distinguish among a climate scenario, a critical threshold and a new equilibrium.
[4]
Explain how positive feedback may cause part of the Amazon rainforest to cross a critical threshold and shift towards a drier vegetation equilibrium.
[7]
Using named examples, evaluate the usefulness of climate-model scenarios for preventing or preparing for climate-system and ecosystem tipping points.
[9]
Question 34
Climate tipping elements can interact to form cascades, in which crossing one threshold increases the likelihood of crossing others. Answer all parts using relevant knowledge of climate systems and feedbacks.
Distinguish among biotic, abiotic and mixed tipping elements, and define a tipping cascade.
[4]
Explain one possible tipping cascade involving ice-sheet loss, Atlantic Ocean circulation and forest carbon storage.
[7]
To what extent does uncertainty about climate tipping cascades strengthen the case for precautionary climate action?
[9]
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