  The Fisher Ideal index, developed to measure price inflation, is applied to
define a population-weighted temperature trend. This method has the advantages
that the trend is representative for the population distribution throughout the
sample but without conflating the trend in the population distribution and the
trend in the temperature. I show that the trend in the global area-weighted
average surface air temperature is different in key details from the
population-weighted trend. I extend the index to include urbanization and the
urban heat island effect. This substantially changes the trend again. I further
extend the index to include international migration, but this has a minor
impact on the trend.
