Environmental impact comparator
Comparisons of concrete choices, each with its named study and the exact sentence that carries its figure. No total, no score: this page teaches you to read an impact figure, including the ones you will see elsewhere.
Impact on what?
A heat pump beats a gas boiler on climate in 17 European countries out of 18. On the fine particles we breathe, in 4 out of 18. Same device, same study, same method. Until you have said what the impact is on, there is no right answer, and that is why this page gives no single score: it would mean weighing the climate against the air, and that weighting is a choice, not a calculation.
The comparisons
Each card carries two labels. The first says how far the comparison can be trusted. The second says what moves its result: the country, the way it is used, the accounting horizon, the range of effects counted, or the indicator chosen. The second one is what nobody else shows.
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What is not here
A named absence is worth more than a hole. Here is what this page does not contain, and why.