John Murphy (Reid, Australian Labor Party) Share this | Hansard source

I again wish to speak in this place on the grievance debate about climate change. Thanks to the efforts of the deniers of climate change, public confusion still surrounds the origins of what has become a destructive national and international crisis of catastrophic floods, storms, heatwaves, fires and cyclones. Evidence is now strong that global warming is producing these record-breaking disasters and that these events are what climate scientists earlier warned will be the consequence of massive burning of fossil fuels and land clearing. However, the climate change deniers resident in the opposition, and others who are exploiting scientific ignorance for their own gain, claim that these events are just an extreme manifestation of variations in the weather of Australia.

By their dishonest and misleading campaign, the deniers have succeeded in confusing some members of the public into believing claims that the science of climate change is as yet unproven. They have even managed to fool the Leader of the Opposition into believing that climate change science is some sort of conspiracy or communist plot, as Lord Monckton, 3rd Viscount of Brenchley, has claimed. Fortunately, there is an objective answer to the question of climate change and it resides in the statistical methods that were developed in the early 19th century by mathematicians, principally Carl Friedrich Gauss. Gauss, who was regarded as a genius by his contemporaries and by subsequent generations, developed a method of statistical analysis that showed that randomly occurring events that cluster around a mean or average value fit a bell-shaped curve, more formally known as a normal distribution. His work is very useful in understanding the causes of current climatic events.

Since the occurrence of many natural phenomena, including rainfall and floods, are randomly distributed, we can for example use Gauss’s statistical methods to make predictions as to the probable volume of rainfall or height of floods expected in any one year at a location with reasonable records. As a demonstration of this method I have an analysis of rainfall figures from Pomeroy, near Goulburn, in New South Wales, since 1901. When the recorded range of annual rainfall totals are plotted against the frequency of those annual rainfall totals we find that the curve approximates a normal distribution, with a mean or average rainfall of 708 millimetres per annum. Furthermore—and this is really the importance of the method—we can objectively predict from this chart that the probability of an annual rainfall of 227 millimetres at Pomeroy is around one in 100 and that an annual fall of 1,188 millimetres is also around one in 100, even though these exact figures may never have been recorded.

This is the scientific basis of the announcements we hear, for instance, of a one in a 100 year flood in areas for which long-term records are not available. So when we discover that records for floods or temperatures or fires have been repeatedly broken, we can estimate the probability of those events based on an objective statistical analysis, rather than on guesswork or the memories of older residents. If the figures indicate that the probabilities of many of these events are remote, we have to ask: what is behind these changes?

I want to make it clear tonight that climatologists and other scientists are not saying that global warming is directly driving events, in particular Cyclone Yasi or the floods in South-East Queensland and north-west Victoria, nor the recent disastrous Victorian and Western Australian bushfires or the other climate calamities in other parts of the world. Rather climatologists and other scientists are warning that the probability of these sorts of events is increased by rising air and sea temperatures and that these increasing temperatures are being driven by the trapping of heat by rising atmospheric carbon dioxide levels.

An examination of the occurrence of tropical cyclones will illustrate this situation. Tropical cyclones—or hurricanes or typhoons, as they are called in various parts of the world—are large-scale weather systems that commonly form over tropical waters. A recent report by scientists from University College London has quantified the effect of increasing sea surface temperatures on the formation of these monstrous storms. The study was conducted by Professor Mark Saunders and Dr Adam Lea of the Benfield University College London Hazard Research Centre and the University College London tropical storm risk forecasting venture. Their report, published in Nature, found that sea surface warming was responsible for a 40 per cent increase in Atlantic hurricane activity over the period 1995 to 2005 relative to the average incidence reported between 1950 and 2000. Furthermore, these investigators found that the sensitivity of tropical Atlantic hurricane activity to sea surface warming is large, with an increase of 0.5 degrees being associated with an approximately 40 per cent increase in Atlantic hurricane activity and frequency. So there is now strong evidence that links global warming to Atlantic hurricanes. If, in light of these reports, anybody in the opposition still thinks that the major economies of the world will do nothing to reduce carbon dioxide emissions by cutting the use of fossil fuels such as coal then they must be completely out of touch.

While one could suspect the same sorts of changes as experienced in the Atlantic may be occurring in the tropical seas to Australia’s north, in fact recent research published by Dr Scott Power of the Centre for Australian Weather and Climate Research, a partnership between the CSIRO and the Bureau of Meteorology, has shown that the incidence of tropical cyclones affecting Northern Australia has actually declined since records were first made in the 1880s. Further, Dr Power and his colleagues have shown that these changes are linked to the weakening by global warming of the Walker circulation, the weather system that drives the trade winds and that varies in concert with the La Nina and El Nino oscillations. In fact, the trend in figures recently published by Dr Power shows that fortunately the number of tropical cyclones that have crossed the Australian coast has approximately halved between 1880 and 2010, which is a very significant decline. While these figures may not give much relief to people presently recovering from the effects of Cyclone Yasi, at least there is now good evidence that global warming is not driving an increase in the frequency of cyclonic activity in waters near Australia, although the size and strength of the cyclones that do occur may be greater thanks to measurably warmer sea water.

While Northern Australia may be experiencing fewer cyclones, other less desirable changes in the weather also appear to be occurring, with a high probability that they too are being driven by global warming. The Annual Australian climate statement 2010 produced by the Bureau of Meteorology reported that: spring 2010 had the warmest northern tropical sea surface temperatures on record; New South Wales, Queensland and the Northern Territory had the wettest spring on record; the Murray-Darling Basin had the wettest year on record; south-west Western Australia had the driest year on record; and, overall, the 10 years ending in 2010 were Australia’s warmest decade on record.

The wet La Nina phase of the Southern Oscillation appears to be becoming more intense and so too is the hot and dry El Nino phase, leading, as we have recently experienced, to more intense and prolonged droughts and extreme hot, dry weather conditions in Australia. Although 2010 and now 2011 were La Nina years that produced records for rainfall, 2009, an El Nino year, produced records in the opposite direction. As we recall, extreme hot weather conditions occurred throughout that year as follows. A new maximum temperature of 48.8 degrees was recorded at Hopetoun in Victoria during the heatwave in January to early February. In Tasmania at the same time a new maximum of 42.2 degrees was recorded at Scamander. These conditions contributed greatly to the disastrous Black Saturday bushfires that we have been reminded about today in this place. Further, an unprecedented wintertime heatwave occurred across large parts of inland Australia, resulting in the warmest August on record. Finally, a third heatwave occurred in November that led to a record eight consecutive days above 35 degrees in Adelaide.

Although the finer details of the mechanism of the El Nino-La Nina cycle remain to be worked out, evidence is growing that these record-breaking weather conditions are being driven by the effects of global warming that all the evidence shows is the consequence of increasing atmospheric carbon dioxide levels. So, while the deniers in the opposition continue their campaign of obstruction against the very necessary measures that the government is introducing to reduce carbon dioxide emissions, the evidence for the effects of global warming, now in the form of extreme weather events, grows even stronger. In conclusion, I ask: how much worse does the weather have to get before the informed members of the opposition stand up for the climate change action that we so desperately need?

See this speech in context