Guest essay by Eric Worrall

Aussie Climate Scientist Steve Sherwood, Director of the Climate Change Research Centre at the University of New South Wales, thinks in the future Australia will experience more rain, less rain or something in between.

More rain on the horizon as climate change affects Australia, study finds Australians will need to batten down the hatches with more intense rain storms predicted as a result of higher humidity driven by a rise in global temperatures. New findings from the ARC Centre of Excellence for Climate System Science, published in Nature Climate Change on Tuesday, reveal that a two-degree rise in average global temperatures would lead to a 10-30 per cent increase in extreme downpours. The study’s authors predict that while some parts of the continent will become wetter, others will experience increasing drought. Steve Sherwood, a professor at the Climate Change Research Centre at the University of NSW who contributed to the research, said global warming would have a clear impact on rainfall. “There is no chance that rainfall in Australia will remain the same as the climate warms,” he said. “With two degrees of global warming, Australia is stuck with either more aridity, much heavier extreme rains, or some combination of the two.” …

Read more: http://www.smh.com.au/environment/more-rain-on-the-horizon-as-climate-change-affects-australia-study-finds-20170115-gts0l1.html

The study referenced by the press article;

Future increases in extreme precipitation exceed observed scaling rates Models and physical reasoning predict that extreme precipitation will increase in a warmer climate due to increased atmospheric humidity. Observational tests using regression analysis have reported a puzzling variety of apparent scaling rates including strong rates in midlatitude locations but weak or negative rates in the tropics. Here we analyse daily extreme precipitation events in several Australian cities to show that temporary local cooling associated with extreme events and associated synoptic conditions reduces these apparent scaling rates, especially in warmer climatic conditions. A regional climate projection ensemble6 for Australia, which implicitly includes these effects, accurately and robustly reproduces the observed apparent scaling throughout the continent for daily precipitation extremes. Projections from the same model show future daily extremes increasing at rates faster than those inferred from observed scaling. The strongest extremes (99.9th percentile events) scale significantly faster than near-surface water vapour, between 5.7–15% °C−1 depending on model details. This scaling rate is highly correlated with the change in water vapour, implying a trade-off between a more arid future climate or one with strong increases in extreme precipitation. These conclusions are likely to generalize to other regions.

Read more: http://www.nature.com/nclimate/journal/vaop/ncurrent/full/nclimate3201.html

Sherwood’s University of New South Wales is also home to Climate researcher Chris Turney, leader of the infamous 2013 Ship of Fools expedition to the Antarctic.

Sadly the full study is paywalled. But from the abstract and Sherwood’s comments to the press, in my opinion Sherwood’s prediction seems unfalsifiable. Almost any imaginable future rainfall observation would fit a prediction of more aridity, more rainfall, or something in between.

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