In the first study of its kind in Australasia, scientists have used 27 natural climate records to create the first large-scale temperature reconstruction for the region over the last 1000 years.
The study was led by researchers at the University of Melbourne and used a range of natural indicators including tree rings, corals and ice cores to study Australasian temperatures over the past millennium and compared them to climate model simulations.
Lead researcher, Dr Joelle Gergis from the University of Melbourne said the results show that there are no other warm periods in the last 1000 years that match the warming experienced in Australasia since 1950.
"Our study revealed that recent warming in a 1000 year context is highly unusual and cannot be explained by natural factors alone, suggesting a strong influence of human-caused climate change in the Australasian region," she said.
The study published recently in the Journal of Climate will form the Australasian region's contribution to the 5th IPCC climate change assessment report chapter on past climate.
She said using what is known as 'palaeoclimate' or natural records, such as tree rings, corals and ice cores, are fundamental in evaluating regional and global climate variability over centuries before direct temperature records started in 1910.
Dr Gergis collated these natural records provided by decades of work by more than 30 researchers from Australia, New Zealand and around the world.
The reconstruction was developed using 27 natural climate records calculated in 3000 different ways to ensure that the results were robust.
She said reconstructions of regional temperature not only provide a climate picture of the past but also a significant platform to reduce uncertainties associated with future climate variability.
The study is part of a global collaboration, PAGES, Past Global Changes Regional 2K initiative, which is working to reconstruct the last 2000 years of climate across every region in the world in order to reduce uncertainties associated with future climate change projections.
Collaborators include the Climate Change Research Centre and the ARC Centre of Excellence for Climate System Science, University of New South Wales where the climate modeling was conducted.
The study was funded by the Australian Research Council, Federal Department of Climate Change and Energy Efficiency and Past Global Changes (PAGES).
- Joλlle Gergis, Raphael Neukom, Steven J. Phipps, Ailie J. E. Gallant, David J. Karoly. Evidence of unusual late 20th century warming from an Australasian temperature reconstruction spanning the last millennium. Journal of Climate, 2012; 120516111330001 DOI: 10.1175/JCLI-D-11-00649.1
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