Changing World Extreme Temperature Statistics

TL;DR

This study analyzes global temperature record trends using a nonparametric statistic, revealing significant increases in all-time high temperature records in most regions, indicating regional climate regime shifts since the mid-20th century.

Contribution

It introduces a nonparametric method to quantify the rate of temperature record occurrences across multiple regions, highlighting regional differences and recent shifts in climate regimes.

Findings

All-time high records increased significantly in most regions.

All-time low records decreased significantly outside North America.

Regional climate regime shifts occurred in the 1990s in Europe, North Africa, and North Asia.

Abstract

We use the Global Historical Climatology Network--daily database to calculate a nonparametric statistic that describes the rate at which all-time daily high and low temperature records have been set in nine geographic regions (continents or major portions of continents) during periods mostly from the mid-20th Century to the present. This statistic was defined in our earlier work on temperature records in the 48 contiguous United States. In contrast to this earlier work, we find that in every region except North America all-time high records were set at a rate significantly (at least $3\sigma$) higher than in the null hypothesis of a stationary climate. Except in Antarctica, all-time low records were set at a rate significantly lower than in the null hypothesis. In Europe, North Africa and North Asia the rate of setting new all-time highs increased suddenly in the 1990's, suggesting a change in regional climate regime; in most other regions there was a steadier increase.