Expert opinion is an interesting thing. Consider the article ''2011 the warmest La Nina year on record'' (published in The Canberra Times on January 21, p7) in which global temperature statistics compiled by the US National Oceanic and Atmospheric Administration were reported.
I found that article unremarkable until the last two paragraphs, which mentioned other figures released by the NOAA on the ''bumping up'' of ''billion dollar weather disasters in the US'' from 12 to 14 for the year 2011.
The article ended with a quote from the director of climate analysis of the US National Centre for Atmospheric Research. ''Where these events occur is largely driven by natural variability, but the fact that [these events] are breaking records and causing tremendous damage ... is undoubtedly because of the human stimulus.''
The director of climate analysis for the centre is clearly an expert and his opinion therefore carries considerable weight. On the other hand, the Intergovernmental Panel on Climate Change is a panel of experts, and has gathered and analysed the research of hundreds of individual experts to formulate the most up-to-date thinking on the influence of climate change - including anthropogenic factors - on extreme weather events.
At the risk of perpetuating a ''he said/she said'' debate, I would like to draw attention to the latest in an interesting series of reports by the IPCC: the Summary for Policymakers of the Special Report on Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation released in November 2011.
On page 7 of that report it is stated that: ''Increasing exposure of people and economic assets has been the major cause of the long-term increases in economic losses from weather- and climate-related disasters (high confidence). Long-term trends in economic disaster losses adjusted for wealth and population increases have not been attributed to climate change, but a role for climate change has not been excluded (medium evidence, high agreement).'' And further, that ''Trends in exposure and vulnerability are major drivers of changes in disaster risk (high confidence).''
The latest IPPC thinking therefore - based as it is on careful analysis of research of hundreds of individual experts - is that the increasing number of ''billion dollar weather disasters in the US'' and elsewhere is due to human encroachment in high risk areas, and to a build up of economic assets in those areas. The IPCC does not point to an increase in the number and/or severity of events caused by ''the human stimulus'' for those weather disasters. Importantly, these conclusions are made with ''high confidence'' and ''high agreement'' amongst and between IPCC experts.
Of course, human encroachment in high risk areas is not a very headline-grabbing reason for an increase in the economic cost of climate disasters. And if human encroachment is the reason for the increase, then there are actually some ''doable'' initiatives to retard that cost escalation. In fact, the IPCC makes several sensible recommendations on that point. Regrettably it has been my observation that sensible comments by the IPCC are not often quoted in the media. But an individual expert who blames ''the human stimulus'' for climate disasters - well, that is a far more newsworthy claim.
As I said, expert opinion is an interesting thing.
Karen Macpherson is an Adjunct Professional Associate at the University of Canberra. Her PhD and post-doctoral work has been in the field of critical thinking.
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