Sprigg Geobiology Seminar: Five reasons why we might underestimate past climate change

As part of the Sprigg Geobiology Seminar Series, Associate Professor Greg Jordan, from the School of Biological Sciences, University of Tasmania will join us to deliver a seminar entitled “Five reasons why we might underestimate past climate change“.

I am mainly interested in the evolution of vegetation and plant species, and work at both global and local levels. I combine different kinds of evidence – fossils, evolutionary trees based on DNA and the distribution and physiology of living species. Some important are: the remarkable things that comparing the structure of fossil and living leaves can tell us about how our vegetation and flora evolved; the importance of extinction in understanding evolution; and what the modern distribution of species tells us about their history. My work focusses mainly on the fabulous southern hemisphere family Proteaceae (banksias, proteas, grevilleas and many others) and on conifers. I also work on forest ecology, looking at the impact of disturbance on biodiversity.

I’ll talk about some mechanisms that cause us to underestimate rates of climate change and maximum differences in climate through time. I’ll ask the question of whether they are significant and then run through some ideas about what we might do about it. Researchers using proxy evidence to look at past climates may well be familiar with some or all of these concepts, but may not have assembled all of these ideas into single framework. This talk is primarily about biological evidence for past climates, but notes that most evidence for terrestrial palaeoclimates has a biological underpinning.

The first reason is well known, and I will not dwell on it – time averaging of samples almost always represent periods, not single point in time. The other reasons result from our use of proxy evidence – you measure one thing and hope that it tells you about something else. Many proxies have known mechanistic bases, others are purely correlational, but almost all are vulnerable because they depend on calibration using correlations observed in the modern world (or occasionally over short recent time series). These other reasons are changes in existing realised niches, evolutionary changes in the biological relationships underpinning the proxy, the impacts of lag times, especially for multiproxy estimates, and finally the role of extinction of species and ecotypes.

When: Friday 27th May, 12:10pm
Where: Mawson Lecture Theatre, North Terrace Campus
Hosted by: Cesca McInerney (


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