Open letter to the Victorian Governor re comments on floods and climate change

The Governor of Victoria Professor David De Kretser recently commented on the floods and climate change on Radio 3AW, making the following comment: ”I’m sorry, I’m one of these believers in climate change, I’m afraid, and … I don’t think it’s going to go away.

”There’s too many of these events, not only in Australia but throughout the whole world that are happening now … Everyone says this week [is a] one in 100, one in 200 years [event] but they are happening pretty much more frequently now.”

These comments were reported in The Age and the Herald Sun and more widely (98 news articles on Google on Jan 23). The Premier Ted Baillieu said it was too early to make a comment on climate change, then went to say that he had been told on Jan 18 by Melbourne Water that Victorians should expect 30 per cent more rainfall in the next 10 years – I’m trying to track down the source of this statement because it’s difficult to countenance. The Governor’s statement was flatly rejected by climate expert Andrew Bolt (I refuse to link) and today by commentator  Eddie McGuire, who somehow thinks climate change is a distraction.  Not if you don’t adapt to a changing climate because you’re busy recreating past, Eddie.

Following is an open letter I wrote to the Governor today and forwarded to The Age.

Dear Professor De Kretser,

I am writing to offer my support for comments you made on Radio 3AW regarding the links between climate change and flooding in Victoria. It is the role of scientists to use their knowledge to inform the public understanding of risks to the society and environment, especially when those risks are changing or likely to change. As a scientist and Governor of Victoria, you have a dual role given to the care of Victorians now in the future.

The difference between science and risk is that the bar is set higher for scientific proof. This is because humans have a bias towards confirmatory evidence. That is, they select evidence that confirms their prior beliefs and overlook evidence to the contrary. Science offers formal methods to counter this tendency, which include a sceptical approach to evidence, contestability and peer review.

For risk, the rules are subtly different. Risks such as flooding are usually subject to multiple causes that are both short and long-term. To properly investigate risks, all scientifically plausible causes need to be addressed. This may involve competing explanations or multiple causes where the contributing effects cannot be easily untangled. Addressing an immediate risk may require an immediate assessment of the underlying science without being able to engage in the protracted process of research, review and publication. Human-induced climate change and natural climate variability is a case in point.

The background to the current floods is as follows. The second half of 2010 is the second strongest La Niña on record and combined with a negative Indian Ocean Dipole between August and October. Such combinations are rare and result in enhanced rainfall totals – the last such event was in 1975 and only four were recorded from 1958 to 1975. Eastern Australian rainfall from September–December is the highest ever recorded at 425 mm. It is closely correlated with the El Niño–Southern Oscillation Index but the high total has a likelihood of occurring once in 328 years, even with this strong La Niña. The long-term trend in rainfall from 1900 with respect to the ENSO index is 12% – regional climate is getting wetter for a given ENSO event. Sea surface temperatures off the east coast of Australia are at near-record levels. The floods in Victoria by volume are the largest ever recorded and occur one month later than the previous major flood event in December 1933. The most likely explanation is that these floods reflect the interaction between an unusual climate event of natural origin and climate change.

With respect to the dry conditions experienced since 1996, the major rainfall reductions occurred over the period March to July and have been linked to a more intense sub-tropical pressure ridge blocking rain-bearing systems. That in turn is closely linked to the global warming curve, the strength of the Hadley Cell bringing dry warm air from the tropics and reductions in the number of storms generated. This year has re-set the water resource clock in south-eastern Australia but these dry conditions are likely to continue.

Long-term changes to risks should not be ignored in the recovery and rebuilding process. In this regard, the Bushfire Royal Commission got it wrong by almost totally overlooking climate change. As recently reported in the Sunday Age (Dec 19), days above high fire danger were 45% higher from 1996–2009 than they were prior to 1996. Yet in its recommendations, the Royal Commission addressed the emergency situation and only some of the underlying conditions.  The result will be better managed emergencies, better fuel management and reduced ignition sources. However, the exposure of an increasing number of people to more frequent and intense fires and the planning problems that creates has been overlooked.

It is important that this mistake is not repeated in the assessment and recovery from the recent floods. This is especially important in Queensland where the floods have been devastating. The past is an inadequate guide as to how to manage future climate-related risks and you are right to point that out.