Jones, Roger ORCID: 0000-0001-6970-2797 (2012) Detecting and attributing nonlinear anthropogenic regional warming in southeastern Australia. Journal of Geophysical Research, 117 (D4). ISSN 0148-0227

Abstract

[1] Nonlinear anthropogenic warming is detected and attributed as a series of step changes in observed and simulated climate for southeastern Australia (SEA). A stationary period of 1910–1967 and non-stationary period of 1968–2010 was established using statistically significant step-changes (pH0 < 0.01) in the relationship between observed minimum (Tmin) and maximum (Tmax) temperature (0.6°C in 1968) and Tmax and rainfall (P; 0.7°C in 1997). Regressions between these pairings during stationary conditions were used to determine how Tmin and Tmax would have evolved under non-stationary conditions. Assuming these relationships remain constant, the resulting residuals were attributed to anthropogenic regional warming. This warming was initiated as step changes in 1968 forTmin (0.7°C) and 1973 for Tmax (0.5°C), coinciding with step changes in zonal (24–44°S) and southern hemisphere mean air temperatures (Tav). A step change in 1997 in Tmax (0.8°C) coincided with a statistically significant step change in global mean air temperature of 0.3°C. This analysis was repeated using regionally averaged output from eleven climate model simulations. Regional warming in all models commenced with step changes in Tmin ranging from 0.4 to 0.7°C between 1964 and 2003. Tmax underwent step changes ranging from 0.7 to 1.1°C simultaneously or within several decades. Further step changes, combined with rising trends, were simulated under increasing radiative forcing to 2100. This highlights limitations in the current use of the signal-to-noise model that considers anthropogenic climate change as a monotonic curve. The identification of multiple step changes in a changing climate provides important information for planning adaptation.

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