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Recent Submissions
High Balance Superannuation Holders: A Statistical Overview
(2025-06-27) Ben Phillips; Richard Webster
Exploring climate change uncertainties to support adaptive management of changing flood-risk
(2013) Lawrence, Judy; Reisinger, Andy; Mullan, Brett; Jackson, Bethanna
Increasing intensity and frequency of extreme precipitation events projected as a consequence of global warming pose significant challenges for decision-making. Climate change creates a dynamic risk, but flood risk management decision-making based on single 'best estimate' scenarios is entrenched within decision-making frameworks and professional operating practices. This conceals uncertainties and focuses attention on enhancements to existing 'protection' structures, giving a false sense of security to those living within presumed 'safe' areas. A more nuanced, risk-based approach to flood frequency changes is needed to reflect climate change uncertainties, but this is constrained by the high cost and complexity of modelling. We present a quick and relatively low-cost methodology to explore the implications of alternative climate change scenarios for flood frequency, and apply it for illustrative purposes, to the Hutt River located in New Zealand's lower North Island. Annual exceedance probabilities increase under all scenarios but with considerable differences between alternative emissions scenarios and climate models. We evaluated the salience of this information for planning responses with flood management and planning practitioners. We found that 'mind-sets' changed to consider a greater range of response options according to their lock-in potential in existing and Greenfield urban settlements. Tools to rapidly explore alternative futures can therefore support evaluation of a wider range of response options at the exploratory stages of decision-making, which helps avoid planning responses that are predicated on historical experience and a single 'best estimate' scenario. This encourages responses that better reflect the changing nature of the risk.
Natural hazards in Australia
(2016-11-01) Perkins-Kirkpatrick, S. E.; White, C. J.; Alexander, L. V.; Argüeso, D.; Boschat, G.; Cowan, T.; Evans, J. P.; Ekström, M.; Oliver, E. C.J.; Phatak, A.; Purich, A.
As part of a special issue on natural hazards, this paper reviews the current state of scientific knowledge of Australian heatwaves. Over recent years, progress has been made in understanding both the causes of and changes to heatwaves. Relationships between atmospheric heatwaves and large-scale and synoptic variability have been identified, with increasing trends in heatwave intensity, frequency and duration projected to continue throughout the 21st century. However, more research is required to further our understanding of the dynamical interactions of atmospheric heatwaves, particularly with the land surface. Research into marine heatwaves is still in its infancy, with little known about driving mechanisms, and observed and future changes. In order to address these knowledge gaps, recommendations include: focusing on a comprehensive assessment of atmospheric heatwave dynamics; understanding links with droughts; working towards a unified measurement framework; and investigating observed and future trends in marine heatwaves. Such work requires comprehensive and long-term collaboration activities. However, benefits will extend to the international community, thus addressing global grand challenges surrounding these extreme events.
Regional hotspots of temperature extremes under 1.5 °C and 2 °C of global mean warming
(2019-10-11) Lewis, Sophie C.; King, Andrew D.; Perkins-Kirkpatrick, Sarah E.; Mitchell, Daniel M.
Local- and regional-scale heat extremes can increase at a significantly greater rate than global mean changes, presenting challenges for human health, infrastructure, industry and ecosystems. We examine changes in regional absolute temperature extremes for a suite of global regions under 1.5 °C and 2 °C of warming above pre-industrial levels, as described by the Paris Agreement. We focus on area-average values of observed monthly averages of daily maximum and minimum temperatures in 12 regions and calculate the most extreme monthly records observed. Next, using a large ensemble (HAPPI; Half a Degree Additional warming, Prognosis, and Projected Impacts) of decade-long simulations both of the present day and stabilised at these higher warming thresholds, we explore how changes in temperature extremes temperatures scale with global mean warming in these timeslice simulations. In the models, we focus on the 99th percentile values of monthly maximum temperatures and the 1st percentile of the monthly minimum temperatures. We define and identify hotspots of warming for various global mean warming levels, where projected changes in regional extremes are greater than global mean temperature changes. We identify overall hotspots of extremes, which are regions where the tail of the temperature distribution (above 99th percentile) warms at a faster rate than the rest of the temperature distribution in response to mean global warming increase. For monthly maximum temperatures, Central Europe, North Asia, West and East North America experience the greatest projected increases in extremes relative to means, and for monthly minimum temperatures, Central, West, East and North Asia, and East North America are identified as extremes hotspots. Although the scaling of increasing extremes with global mean temperatures is regionally variable, all regions benefit from the reduced severity of monthly maximum temperatures under lower global warming thresholds.
Determinants of rate variation in mammalian DNA sequence evolution
(1996) Bromham, Lindell; Rambaut, Andrew; Harvey, Paul H.
Attempts to analyze variation in the rates of molecular evolution among mammalian lineages have been hampered by paucity of data and by nonindependent comparisons. Using phylogenetically independent comparisons, we test three explanations for rate variation which predict correlations between rate variation and generation time, metabolic rate, and body size. Mitochondrial and nuclear genes, protein coding, rRNA, and nontranslated sequences from 61 mammal species representing 14 orders are used to compare the relative rates of sequence evolution. Correlation analyses performed on differences in genetic distance since common origin of each pair against differences in body mass, generation time, and metabolic rate reveal that substitution rate at fourfold degenerate sites in two out of three protein sequences is negatively correlated with generation time. In addition, there is a relationship between the rate of molecular evolution and body size for two nuclear-encoded sequences. No evidence is found for an effect of metabolic rate on rate of sequence evolution. Possible causes of variation in substitution rate between species are discussed.