By Matthew Carney
ABC Online, May 17, 2012
For the first time scientists have provided the most complete climate record of the last millennium and they found that the last 50 years in Australia have been the warmest.
The researchers from Melbourne University used 27 different natural indicators like tree rings and ice cores to come to their conclusion, which will be a part of the next United Nations intergovernmental panel on climate change report.
The findings show that no other period in the last 1,000 years matches the temperature rises Australia and the region has experienced in the last 50 years.
Report co-author Joelle Gergis says the findings are significant.
"It does show that the post-1950 warming is unusual in the Australasian region," she said.
"A lot of these sorts of studies have come out of the northern hemisphere and for the first time we have been able to say 'well we have collected all of our natural records from our region and this is what it shows and the warming is real and it is in the Australian region. It is not in some far away place'," she said.
Dr Gergis says the study used decades of work from 30 scientists who had been collecting natural data to reconstruct temperatures before human records started in 1910.
"So really what these are are climate proxies. They are not direct temperature records but we use them as stand-ins or surrogates for temperature records," she said.
"What we do is compare these natural records with the observed temperature records and then develop a statistical relationship and take that relationship back centuries into the past."
Co-author Professor David Karoly says the strength of the study is that it relied more on direct observations and measurements than climate modelling.
"Nothing is absolutely certain in science, but we say with very high confidence because we have repeated the analysis alone for the uncertainties that the warming in the last 50 years is very unusual and very likely cannot be explained by natural climate variability alone," he said.
Dr Gergis says the scientists have minimised the variability in their model by crunching the data 3,000 different ways.
"What we were able to see is that in 95 per cent of the reconstructions, we actually see that the post-1950 warming observed in the region is unprecedented in the context of the last millennium so it is not dependent on a loss of records back in time or the different combination of record," he said.
The government-funded study will be Australia's contribution to the fifth Intergovernmental Panel on Climate Change report due in 2014.