Stochastic and anthropogenic influences on repeated record-breaking temperature extremes in Australian spring of 2013 and 2014

We examine the contribution of synoptic and interannual processes and anthropogenic warming to repeated record-breaking warmth in the Australian spring of 2013 and 2014. Climatic conditions similar to those in 2013 and 2014 have occurred in the past, the regional and large-scale interannual processes associated with these extreme temperatures were not unusual, and the repetition of the very warm temperatures is likely to be a function of stochastic interannual variability. However, analysis using observations and climate model simulations shows that without an anthropogenically driven warming trend, it is unlikely that the 2013 and 2014 temperature anomalies would have been consecutively record breaking. Climate models demonstrate that the likelihood of consecutive record-breaking spring temperatures similar to 2013 and 2014 changes from < 1% in simulations using natural forcing only to between 11% and 25% for the period 2006-2020 using simulations containing both natural and anthropogenic forcings.