Reading: The Urban Heat Memo Mismatch
Two texts are presented together. Text A is an abstract: 'We deployed 48 temperature sensors across one mid-sized city during summer 2022. Afternoon readings in blocks with at least 30% tree canopy were on average 0.8 degrees Celsius cooler than blocks with under 10% canopy. The study did not measure winter conditions or humidity.' Text B is a council memo: 'A recent study proves that increasing tree canopy will reduce local temperatures by 3 degrees Celsius. We therefore recommend a RM2 million planting programme before next summer.' The memo cites Text A as its only source. A reading question asks whether the memo's recommendation is justified by the study. The options include 'yes, because trees cool cities,' 'no, because the study found a smaller average difference,' and 'no, because the study did not test a 3 degrees Celsius intervention.'
1. Which option is correct, and why?
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The correct option is 'no, because the study did not test a 3 degrees Celsius intervention.' Text A reports an observed difference of 0.8 degrees Celsius between blocks with different canopy levels in one city in summer 2022. It does not report a planting intervention, a 3 degrees Celsius effect, or winter conditions. The memo converts a small observational difference into a large predicted outcome and attaches a budget. 'No, because the study found a smaller average difference' is closer but still incomplete: the mismatch is not just size but the leap from correlation to intervention. 'Yes, because trees cool cities' relies on general knowledge, not on the text.
2. Identify one unstated assumption in the memo.
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The memo assumes that adding canopy to currently low-canopy blocks will produce the same difference observed between existing high- and low-canopy blocks. That is an assumption about causality and scale: the 0.8 degrees Celsius association might reflect other differences between blocks, such as building density, air-conditioning use, or proximity to water. The memo also assumes the effect will appear before next summer and that RM2 million is sufficient. A reading question may ask for one assumption; the strongest is the causal one, because it is what turns an association into a predicted 3 degrees Celsius outcome.
3. What additional evidence would most strengthen the memo?
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A local planting pilot with before-and-after temperature readings would strengthen it most. The memo needs evidence that changing canopy causes cooling, not just that canopy and cooler blocks co-occur. Ideally the pilot would use the same sensors, compare treated and untreated blocks, run through at least one summer, and report humidity as well as temperature. A costed maintenance plan would also help, because canopy takes years to grow. Survey data on residents' heat exposure would support the welfare rationale but would not fix the causal gap. The best answer names the design, not just 'more research'.