North central Victorian climate: past, present and future

Abstract

North central Victoria has experienced significant natural climate change over the past 20 000 years. At the height of the last ice age, the region was colder by 5°C or more with uplands and slopes under subalpine vegetation. Modern vegetation patterns were not established until the early Holocene. The first half of the Holocene was wetter than today, while the second half was affected by a less stable climate influenced by a strengthening El Niño–Southern Oscillation. Climate immediately prior to European occupation may have been wetter than during the historical period. Thus the pre-European climate and land surface influences on regional water balance may have been different to that which is generally assumed. Climate during the historical period was statistically homogenous, but with drier and wetter periods. Modest warming began in the mid 20th century, by about 0.4°C per century from 1950 to 1996. From 1997, maximum temperature has undergone a significant upward step change (p<0.01) of 0.9°C. Rainfall has decreased by 19%, with May–October rainfall undergoing a significant (p=0.05) downward step change from 2000. Maximum temperature is now non-stationary with respect to rainfall and is experiencing an upward trend consistent with climate model projections. These changes are equal to or greater than those projected for 2030, and are significantly affecting agriculture and forestry, ecosystems, fire risk and water resources. Evidence from pre-historic, historic and model projections of future climate for this region suggest that climate change can often be abrupt, with ‘stable’ periods showing considerable decadal variability. Prudent risk management would treat the post 1996 climate as the new baseline and plan for further changes.