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Talk Abstracts

Prof. Tony McMichael: Climate Change: A Hazard to Human Health? (15 September 2003)

Recent increases in (and patterns of) global temperature suggest that human-induced global climate change is now occurring. Many non-human physical and biological systems have recently been affected by warming. So: when might human health impacts appear? The expected health impacts of climate change are diverse. Most entail changes in the frequency or severity of familiar health risks - such as those due to floods, storms and fires; deaths from heat-waves; the range and seasonality of infectious diseases; agricultural productivity and nutrition; freshwater supplies; and the repercussions of economic dislocation and population displacement. Most health impacts will be adverse.

In this unusual environmental situation we cannot await conventionally-defined "conclusive" evidence before taking action to lessen the apparent or anticipated impacts. Climate change is weakening various of Earth's life-support systems, and some such changes may be critical or irreversible. This warrants both international preventive and local adaptive actions now.

Dr John Finnigan: Earth System Science in the Early Anthropocene (29 October 2003)

The human race has entered the Anthropocene, the geological epoch where human influence on the planet's systems is as profound as that of natural forces. Earth Sciences must now include human agents, their societies and social constructions like economies, if they are to be used to understand and predict the functioning of the earth's life support systems. The challenge is to find ways to analyse human-biophysical systems rigorously so as to answer questions about the sustainability and resilience of societies and their interaction with the biosphere. The obstacles to doing this are many. The first is that the ability of human agents to learn and adapt, both individually and in social groups leads to strong non-linear feedbacks with all the barriers that this places to the application of conventional mathematical analysis. The second is that the rules governing social interactions are poorly known and very resistant to quantification. Recent advances in Complex systems Science, however, are offering glimpses of a way forward in the quest for rigorous analysis of human ecosystems. Multi-agent computer simulations of societies interacting with their environments have been successful in capturing the essentials of social and economic behaviour. These simulations can be analysed as 'dynamics on networks' where the patterns of connections between the active players in the ecosystem (human and non-human) place strong constraints on what system dynamics can emerge. Much of the behaviour of the system is reflected in the evolving topology of the underlying networks and these in turn can be analysed using mathematical techniques borrowed from fields like statistical physics and quantum mechanics. Remarkably, the emergence of attractors and phenomena analogous to Bose-Einstein condensation can be seen in the network dynamics and interpreted as changes in social and biophysical states of the underlying human ecosystem.

Prof. Sue Grimmond: Urban Climates (17 February 2004)

Approximately half of the world's population, over three billion people, live in urban areas. By 2025, the United Nations predicts that this number will double, and that the proportion of the global population who are urban residents will rise to two-thirds. Land surface and atmospheric alteration by urbanization leads to the development of distinct urban climates. Ultimately these urban climate effects are due to differences in the exchanges of heat, mass, and momentum between the city and its pre-existing landscape. The understanding, prediction, and mitigation of urban climate effects thus are intricately tied to knowledge of surface - atmosphere exchanges in urban environments. In this talk, results from measurement and modeling studies conducted in a range of urban areas in North America, Europe and Africa will be used to consider the variability of surface-atmospheric exchanges both within and between cities, and their fundamental controls.

Len Ferrari and Ted Pender: National Science Symposium: A Report on Serious Environmental Pollution in our Homes from Unflued Gas Heaters (20 August 2004)

This very comprehensive study, commissioned by the Department of Environment and Heritage measured the concentrations of nitrogen dioxide, carbon monoxide, carbon dioxide and formaldehyde in 116 homes in the three cities during the winter and spring of 2003. It is estimated there are 1 million unflued gas heaters in Australia potentially exposing up to 4 million people to toxic exhaust gases.

Ten different brands of heaters (8 MJ/h to over 30 MJ/h) were encountered in homes ranging from 1 to over 100 years old and the indoor air quality was generally much more polluted than outside. In fact the average level of nitrogen dioxide indoors was found to be 10 times higher than the average level outdoors. The nitrogen dioxide concentration in two thirds of homes was found to exceed the WHO recommended level up to an extreme case which was over 8 times the WHO level.

The presentation will examine the results found in these homes and their implications.

John W. Dold: Flames and some Perspectives on Bushfires (29 June 2005)

Combustion in the context of energy production has been a well funded area of scientific study for many decades. As a result, quite a lot is known both theoretically and experimentally about the physics and chemistry of all kinds of gaseous flames in engineering applications, whether terrestrial or in zero gravity; the presentation will outline some of this body of knowledge. Scientifically, bushfires are perhaps much more intricate. They are not purely gaseous phenomena although the more significant combustion in most circumstances takes place as turbulent diffusion flames in a gaseous phase. The fluid mechanics, interphase heat transfer, solid and gaseous pyrolysis reactions (with alternative possible pathways), and the chemistry and thermodynamics of solid and gaseous oxidation make for a rich interplay of many processes. Field observations and experimental burns (under necessarily safe conditions) have led to a sound body of knowledge that has not yet been paralleled through theoretical considerations. A worthy objective is to establish that parallel, building on the understanding of gaseous combustion. If that can be achieved then theoretical considerations might even be able to go further, to offer predictions where experiment and observation are either unavailable or simply too dangerous. The talk will attempt to examine some theoretical avenues that might be explored and to speculate on the lessons that gaseous combustion studies might be able to offer.

Student Talks 2006 (28 March 2006)

Melanie O'Byrne (Research School of Earth Sciences, ANU) Interaction of incident coherent eddies with a headland wake

In this talk, I present results from laboratory studies of the effect of upstream disturbances on the wake of an idealised headland. The model headland is a half-cylinder extending through the full depth of water; the incident disturbances are generated from a small cylindrical vertical rod, or array of rods, placed upstream of the headland. For the simple case of a single upstream rod, the incident disturbance is a train of vortices. Under a range of Reynolds numbers, incident coherent eddies interact strongly with the headland wake in a frequency 'lock-on' manner. The interaction produces large disturbances in the wake vorticity field that were not otherwise present in the wake, resulting in a series of vortex dipoles downstream of the headland. I will discuss the conditions under which we have observed lock-on phenomena, and compare these with examples from the literature.

Melissa Coman (Research School of Earth Sciences, ANU) Horizontal convection and Sandström’s postulate revisited

Almost a century ago Sandström performed some simple laboratory experiments with a source of heating and of cooling in a tank of water. He concluded that a convectively-driven circulation could only exist if the geopotential level of the heat source is below the level of the cooling source. This conclusion has since been commonly interpreted to mean that the meridional gradient of heating of the ocean surface cannot on its own generate a global-scale vertical overturning of the oceans. However, Sandström’s reported observations are at odds with the vigorous circulation observed in more recent laboratory experiments and numerical simulations of ‘horizontal convection’, where the circulation in a box is driven by a gradient of temperature or heat flux along one horizontal boundary. Here we revisit Sandström’s experiments in an attempt to resolve this discrepancy. Contrary to his observations, we clearly see a convective circulation occupying the full depth of the box when the sources of heating and cooling are at the same level. We present velocity and density profiles, discuss the governing physics and offer an interpretation of Sandström’s conclusions that is consistent with the observed vigorous circulation in horizontal convection.

Samantha Burgess (Research School of Earth Sciences, ANU) Geochemical ecology of South Australian corals: establishing high resolution records to evaluate potential as a paleoclimate archive

Corals are sensitive to changes in climate, especially seasonal fluctuations in sea surface temperature. Recently, high-latitude coral communities have received increased attention due to their ability to act as refuge during global climate change and for examining environmental tolerances of different coral species. In this study, I report on high-resolution elemental ratio and stable isotope time series generated from Plesiastrea versipora to assess the fidelity of using geochemical variations to reconstruct sea surface environmental conditions in South Australian Gulfs.

The annual nature of density bands of P. versipora were verified using U/Th ages derived from multi-collector ICP-MS analyses and the resulting extension rates varied from an average of 1.2 mm/yr to 9 mm/yr for different colonies located within the same reef. High resolution (~fortnightly) laser-ablation ICP-MS analyses of established paleo-temperature proxies including B/Ca, Mg/Ca, Sr/Ca and U/Ca and milled d18O and d13C analyses were obtained from several cores of P. versipora from Gulf St Vincent (34.5°S) and Spencer Gulf (35°S), South Australia. Elemental compositions were compared to in situ sea surface temperature (SST) and satellite (IGOSS) records. There was a significant correlation between d18O and Ba/Ca (r2= 0.82) and a significant inverse correlation was observed between d18O and d13C. Barium may not have been recognised as a temperature covarying proxy in previous studies due to the smaller temperature range for lower latitude environments (~5°C versus ~12°C for this study) and other factors masking the Ba signal such as terrestrially-derived or upwelled sources.
Other trace elements analysed gave an indication of both the nutrient availability (P and Mn) and terrestrially derived pollutants (V, Y, Mo, Sn and Pb) correlating strongly with luminescent bands. Several of the stronger luminescent bands coincide temporally with known oil spills at a nearby port refinery and research is ongoing to determine if this is the point source of pollution. These data taken together suggest that P. versipora can provide valuable paleoclimate information in high-latitude environments, recording large seasonal variation in both temperature and productivity regimes with high fidelity and may also be employed to reconstruct anthropogenic activity.