A Practice Passage: Science

In practice

This practice passage is constructed for this course, and its findings are the fictional writer's, not facts the course asserts. A science columnist writes: "Researchers planted street trees along several blocks and measured summer temperatures for two years. The tree-lined blocks were cooler at midday than nearby blocks without trees. The lesson is unmistakable: planting trees will solve our city's heat problem." Work through it in order. First, the main claim arrives in the final sentence, that planting trees will solve the city's heat problem. Second, the evidence is a measured comparison over two years, which is a stronger kind of evidence than a single anecdote, and it supports a cautious conclusion: on these blocks, trees were associated with cooler midday temperatures. Third, the problem is the leap from that finding to the claim. The study covers several blocks, not a whole city, so applying it citywide risks a hasty generalization. The word solve also promises more than the evidence measured; cooler blocks are not the same as a solved problem. Fourth, a reader should ask about other differences between the blocks. If the tree-lined blocks also had less pavement or more shade from buildings, the trees may not be the only cause, and assuming they are would be a causal fallacy. Fifth, the phrase "the lesson is unmistakable" is confident language standing in for missing qualifiers. A more accurate conclusion would read: planting trees may help reduce heat on some streets, and further study across the city could confirm it.