Population and trends in the global mean temperature

TL;DR

This paper introduces a novel application of the Fisher Ideal index to measure global mean temperature trends, accounting for population, urbanization, and migration effects, providing a more representative understanding of temperature changes.

Contribution

It develops a population-weighted temperature trend index and extends it to include urbanization and migration, offering a more comprehensive measure of global temperature change.

Findings

Population-weighted trend differs from area-weighted trend.

Urbanization and heat island effects significantly alter the trend.

Migration has a minor impact on the temperature trend.

Abstract

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.