HL extension: Sustainable development practice questions.

A cloud provider shifts flexible tasks such as video encoding and model training into the hours when the local grid is carrying the most wind and solar power, a practice it has operated across its own data centres since 2020. What does this achieve?

• The total electricity used by the data centre falls in proportion
• The data centre no longer needs a connection to the public grid
• The same work is done with a lower carbon intensity of supply
• The emissions of all electricity generated in the region are removed

Answer: The same work is done with a lower carbon intensity of supply

Shifting when the work runs changes the generation mix that serves it, not the amount of energy the work requires, so the gain appears in grams of carbon dioxide per kilowatt-hour rather than in kilowatt-hours. The constraint is that only interruptible workloads can be moved, which is why serving a live user request remains the hard case.

From October 2021 a large video platform stopped serving advertisements alongside content that contradicts the established scientific consensus on the causes of climate change, and stopped paying its creators for such content. Judged as an intervention, what is its main limitation?

• It applies only to videos uploaded before the policy was announced
• It requires each viewer to opt in before the rule takes any effect
• It deletes the videos, so the claims can no longer be examined at all
• It removes a revenue stream but leaves the content and its reach

Answer: It removes a revenue stream but leaves the content and its reach

Demonetisation changes the incentive to produce a genre; it does not change what the recommender puts in front of someone who has already watched one, so reach can survive the loss of payment. Judging an intervention means asking which link it actually cuts - production, distribution or belief - rather than whether the announcement sounded firm.

A monitoring platform run by a research institute has published near-real-time satellite alerts of forest loss since 2016, mapping cleared areas within days. A national environment agency subscribes to the alerts. Which limitation matters most when judging the alerts as a climate intervention?

• Detection is not enforcement, which needs staff able to reach the site
• Satellite images cannot distinguish cleared ground from cloud shadow
• The alerts are released only to the government of the country concerned
• Forest loss becomes visible only once the cleared area exceeds a square kilometre

Answer: Detection is not enforcement, which needs staff able to reach the site

Monitoring changes what is known, and the emission is avoided only if that knowledge reaches an actor with the mandate, the budget and the road access to act, which is where such programmes most often fail. The same logic governs methane plumes seen from orbit: a leak located is not a leak closed.

Between 2015 and 2022 the computing work done in the world's data centres grew several-fold while their electricity use grew only modestly, because servers and cooling became far more efficient. A student concludes that emissions from data centres must therefore have fallen. What is the best correction?

• Efficiency estimates are uncertain, so no conclusion can be drawn at all
• Emissions depend on total energy and on how that energy is generated
• Cooling improvements are not counted towards a data centre's own energy
• Electricity use grew at all, so the reported efficiency gains cannot be real

Answer: Emissions depend on total energy and on how that energy is generated

Efficiency per unit of work is a ratio while emissions are an absolute quantity, so a falling ratio is compatible with rising totals whenever demand grows, and totals fall only if the electricity supply also decarbonises. Separating relative from absolute decoupling is the distinction that carries the marks.

Using Source C, identify the assumption on which the company's carbon-neutrality claim depends.

• That subscribers' devices are powered by renewable electricity
• That the volume of streaming will not grow in later years
• That the 30 per cent figure was checked by an outside auditor
• That the protected forest would otherwise have been cleared

Answer: That the protected forest would otherwise have been cleared

Retiring a credit cancels an emission only if the protection it paid for is additional to what would have happened anyway, and a 2023 investigation by news organisations reported that most of the rainforest credits it examined failed that test, a finding the standard-setter disputed. The other statements would affect the reported trend or the scope of the count, not whether the neutrality claim itself holds.

A city plans the height of a new flood barrier using output from a high-resolution climate model of the kind developed by the European Commission's Destination Earth initiative since 2022. What does the nature of that output require of the planners?

• Rerunning the model until two runs return exactly the same value
• Choosing whichever projection the model reports as most likely
• Designing to a range of projections rather than to a single figure
• Replacing the model output with the highest flood level ever recorded there

Answer: Designing to a range of projections rather than to a single figure

A projection is conditional on an emissions pathway and on the model's own physics, so it arrives as a distribution, and compressing it into one number transfers that uncertainty silently into concrete. The implication is distributional: whoever fixes the design range decides which residents are protected in the tail of the distribution.