Identifying historical climate changes in Australia through spatial analogs

Abstract

Spatial analogs have previously been used to communicate climate projections by comparing the future climate of a location with an analogous recent climate at a different location which is typically hotter. In this study, spatial climate analogs were computed using observational data to identify and quantify past changes. A sigma dissimilarity metric was computed to compare the recent climates of nine major Australian cities and early 20th century climate across Australia. Evidence is found for climate shifts, particularly in Darwin where temperature variability is lower than in extratropical cities. Analogs designed to capture extremes, including a human health-relevant climate analog, were constructed and these also highlight significant climate shifts. The analogs may also be used to examine extreme events in the context of a reference city climate and identify unusual events. This work demonstrates the utility of climate analogs for monitoring past climate changes and extreme events as well as examining and communicating future change. Care should be taken in interpretation of the movement of analogous climates and the design of analyses, but climate analogs have many potential applications beyond previous uses. Tailored analogs could be studied to communicate climate changes relevant to specific stakeholders.