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Rising temperature concerns
 UWSRA researchers have found that while human-induced climate change may be decreasing the amount of water flowing into Queensland’s dams, natural variability is the main cause of reduced rainfall in Queensland over the past ten years.
CSIRO scientist Dr Wenju Cai is leading UWSRA’s Climate and Water Project, in conjunction with colleagues from the Queensland Department of Environment and Resource Management (DERM), and Griffith University.
The project team has run simulations using a downscaling climate model to transform outputs of a range of global climate models into catchment scale information with improved accuracy and geographic detail, to better inform SEQ’s water strategy.
“We found that the rainfall reduction in SEQ seemed to be multi-decadal variability, or natural variation,” Dr Cai said.
“While the rainfall reduction may not be due to climate change, we know that rising temperatures are due to climate change.
“When you have a very hot day or heatwaves water demand increases, so does evaporation, and energy consumption increases dramatically.
“One of the ways rising temperature could affect water supply is that the efficiency of converting rainfall into dam inflows will decrease.”
Dr Cai said his team had so far conducted six, 140-year simulations for SEQ and these outputs were being used by DERM for their hydrological model to more accurately predict inflows to SEQ storages.
He said global climate models provided future climate information at a resolution of several hundred kilometres, which did not resolve SEQ catchment features.
“The downscaling model we used means that for the first time we have been able to provide DERM with climate information at a resolution of 15km across SEQ to run the hydrological model,” Dr Cai said.
To take into account uncertainty arising from differences between one model and another, one approach is to use as many models as possible that perform well over the Australian region to obtain a multi-model average.
“We’ve used five global climate models. This time next year we’ll have eight models and this will help remove variability between the models and increase the accuracy of prediction. We are also going to evaluate whether an even higher resolution of 8km makes a difference to our prediction.”
Dr Cai said one of the biggest challenges in climate modelling was accurately representing the centre of Pacific tropical convection. The location of the centre of Pacific tropical convection matters to SEQ rainfall simulation as tropical convection is a very important climate driver for the tropical east coast of Australia.
"On a global scale we know that tropical circulations are expected to weaken in a warming world and tropical convection is expected to decrease, thus affecting rainfall,” he said.
“At the moment though, climate models are not converging on where the decrease will be, because the convection centre varies from one model to another and this causes differences in the prediction of impact for SEQ.”
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