President of the Australian Meteorological & Oceanographic Society on Australia's extreme rainfall

Neville Nicholls is one of Australia's leading climate scientists. He is also a long-time participant in the IPCC and current president of the Australian Meteorological & Oceanographic Society. I first met Neville in the mid 1990s (at a meeting in Vietnam I think) and I have had nothing but great respect for him ever since. In his latest "AMOS - President's Column" he asks, "What caused the eastern Australia heavy rains and floods of 2010/11?" He begins his answer by pointing to the strength of the current record La Niña event and the relationship of the SOI (Southern Oscillation Index, a measure of the strength of La Niña and El Niño events) and Australian rainfall (see his figure above). He concludes: "Given the well-known relationship between the SOI and heavy rains in eastern Australia (eg., McBride and Nicholls, 1983) we can conclude that the fundamental cause of the heavy rains this past six months was indeed this record La Niña event. Other heavy rain years (1917/18, 1950/51, 1973/74, 1975/76) were also the result of strong La Niña events. The relationship between rainfall and the SOI is very strong, with a correlation coefficient of 0.66. So, the heavy rains were not caused by global warming, but by a record la Niña event – a natural fluctuation of the climate system." But he doesn't stop there. He next asks: "But perhaps 2010/11 was a record La Niña because of global warming?" His answer: "There has not been any trend in the SOI over the past 111 years, despite the warming of global mean temperature of about 0.75°C over that period. Nor do climate models consistently predict increased strength of La Niña events from enhanced atmospheric content of greenhouse gases (eg., Vecchi and Wittenberg, 2010). So there is no reason, at this moment, for us to suspect that global warming is increasing the frequency or intensity of La Niña events. He doesn't stop there either, and next asks, "But was the impact of the 2010/11 La Niña on Australian rainfall stronger because of the record warm sea surface temperatures around northern Australia in 2010?" His answer: "These waters have increased substantially over the last century and are now about a degree warmer than early in the 20th century. If these warmer waters were enhancing the impact of La Niña on Australian rainfall we might expect to be seeing heavier rains in recent decades, relative to the rains that accompanied earlier strong La Niña events. There is some evidence of this (eg., Nicholls et al 1996), and there has been a weak tendency towards increased rainfall since 1900, independent of the influence from the El Niño – Southern Oscillation. Perhaps this trend towards increased rainfall might be related to the warmer sea surface temperatures – but much more work is needed to test this. The effect, if there is one, does not look very strong." He concludes: "The record La Niña event was the fundamental cause of the heavy rains and floods, ie it was a natural fluctuation of the climate system. There may be a global warming signal enhancing this natural variability, but if so then this effect has been quite subtle, at least thus far." By Roger Pielke Jr, professor of environmental studies at the Center for Science and Technology Policy Research at the University of Colorado at Boulder. Via Greenie Watch So yes, there has been a moderate degree of warming over the last century, but we are a long way from understanding the climate system in sufficient detail to be ascribing individual weather events to the effects of climate change, despite the efforts of political shysters like the minister for climate change, Greg Combet, and Greens senator Christine Milne to do so. Combet just yesterday: "Clearly, one of the most worrying aspects of climate change is what this could mean for the frequency and intensity of extreme weather events such as droughts, heatwaves, cyclones and floods." Milne trying to milk the cyclone Yasi tragedy for political gain: "This is a tragedy, but it is a tragedy of climate change. The scientists have been saying we are going to experience more extreme weather events, that their intensity is going to increase, (and) their frequency." Well, maybe, but then again, maybe not. The Australian has forced the CSIRO to release a number of papers by way of a freedom of information request. One of those is a paper by researcher Debbie Abbs that points to a somewhat different possible future. Her paper predicts that rising temperatures may result in a fall in the number of tropical cyclones. Despite what the newspaper's headline might suggest, the paper itself did not deal with the possible future intensity of cyclones, though Dr Abbs says that it is "expected" that the intensity of some storms will increase. The paper does highlight though something that we sceptics have been trying to get noticed for many years now, and that is the degree of uncertainty that exists in climate science. The science is by no means settled. So another researcher, meteorologist Kevin Walsh, an associate professor at the University of Melbourne, said he was "preparing to publish research with similar but less extreme findings than those of Dr Abbs." His yet to be published paper predicts that tropical cyclone activity in Australia's north will decline by 20% by 2100, and that the most intense ones will be only slightly more intense. So we can see what a scientifically illiterate 'carrion crow' Christine Milne was being when trying to take advantage of the recent destruction in Queensland, whereas Combet (rumoured to be something of a climate change sceptic himself) talks rubbish he probably at best only half believes.