Dramatically increased rate of observed hot record breaking in recent Australian temperatures

Persistent extreme temperatures were observed in Australia during 2012-2014. We examine changes in the rate of hot and cold record breaking over the observational record for Australia- and State-wide temperatures. The number of new hot (high-maximum and high-minimum temperatures) temperature records increases dramatically in recent decades, while the number of cold records decreases. In a stationary climate, cold and hot records are expected to occur in equal frequency on longer than interannual time scales; however, during 2000-2014, new hot records outnumber new cold records by 12 to one on average. Coupled Model Intercomparison Project phase 5 experiments reveal increased hot temperature record breaking occurs in simulations that impose anthropogenic forcings but not in natural forcings-only experiments. This disproportionate hot to cold record breaking rates provides a useful indicator of nonstationarity in temperatures, which is related to the underlying mean observed Australian warming trend of 0.9°C since high-quality records began in 1910.