Sunday, October 24, 2010

Climate scepticism, anthropogenic global warming and drought in south east Australia

With the release of the CSIRO report on Climate variability and change in south-eastern Australia (CSIRO: South East Australia becoming drier, Global Warming implicated) CSIRO hydrologist and lead author Dr David Post has come under criticism for comments on whether anthropogenic global warming has contributed to drought conditions in south east Australia.

Dr David Post said in a CSIRO media release on October 22 that "The research indicates that these changes can be linked to global warming, making it a likely contributor to the recent drought."

In January 2010 David Post released a report on the potential climate impacts regarding Water Yield availability in Tasmania. He was interviewed in regard to this report in the Canberra Times and was attributed with saying there was "no evidence" linking drought to climate change in eastern Australia: "At this stage, we'd prefer to say we're talking about natural variability. The science is not sufficiently advanced to say it's climate change, one way or the other. The jury is still out on that," (Canberra Times, Jan 19, 2010 - Jury still out on climate change: CSIRO.

This attributed statement was reported widely by other news and climate sceptic blogs. Micheal Smith reported on 4BC (No Link - Drought and Climate Change - CSIRO - Jan 19, 2010) and climate sceptic Andrew Bolt (The climate sure is changing at the CSIRO Jan 21, 2010) discussed the quote.

However Michael Smith followed up his report with a phone interview with Dr David Post on radio 4BC on January 21, 2010 where Post clarified his statements: "I would say there were a number of inaccuracies in that article. This was not a direct quote from me." and "everything I was quoted in the story was related to Tasmania".

David Post said that the CSIRO water yield report on the impacts of climate change on Tasmania looked at a range of modelled impacts which ranged from a one per cent increase in rainfall to a 7 percent decrease with a prediction of about a 3 percent reduction in rainfall across Tasmania by 2030. (CSIRO points the finger - Jan 21, 2010, 4BC)

To a direct question from Michael Smith whether there is a link between anthropogenic climate change and drought in south east Australia David Post told Michael Smith there is "insufficient evidence to definitively link climate change to the recent droughts."

Statements by scientists quite often contain caveats and qualifications, and often speak in probabilities rather than definites. While in January Dr Post was careful in saying there was a not a definitive link, he did not talk about the likelihood or probability of anthropogenic climate change as a contributing factor to drought and the changing climate in south eastern Australia. The latest study appears to have added substantially to the knowledge of climate change in the region and thus increased Dr Post's confidence in the link between global warming and drought in SE Australia.

While the inaccurate statement from the Canberra Times has been well amplified by climate sceptics, there has been little journalistic effort to ensure Dr Post was accurately represented in later articles.

The misrepresentation is still doing the rounds with climate sceptic Warwick Hughes talking about Dr Post's "climate flip-flop", (Oct 23, 2010 - CSIRO's Dr David Post huge climate flip-flop) . Perhaps Warwick needs to do his research a little better?

I conclude with a quote from the Climate variability and change in south-eastern Australia report which states on page 29: "there is increasing evidence that the large-scale circulation affecting the climate of south-eastern Australia is changing due to global warming. In particular, the observed increase in the intensity of the sub-tropical ridge appears to be linked to changes in the Hadley Cell, which in turn are being driven by global warming. Under conditions of climate change, it follows that the early decades of the last century may not be appropriate measures of the current climate. Moreover, the climate may continue to change in future decades. Indeed projections of rainfall in south-eastern Australia from global climate models suggest that rainfall may continue to decrease. Any long-term trend associated with global warming will be modulated by decade-scale variability due to internal factors, such as ENSO, and external factors, such as volcanoes and solar radiation."