School of Earth Sciences - Research Publications

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    Forecasting wildlife die-offs from extreme heat events
    Ratnayake, HU ; Kearney, MR ; Govekar, P ; Karoly, D ; Welbergen, JA (WILEY, 2019-08-01)
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    Geoengineering governance-by-default: an earth system governance perspective
    Talberg, A ; Christoff, P ; Thomas, S ; Karoly, D (SPRINGER, 2018-04-01)
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    How geoengineering scenarios frame assumptions and create expectations
    Talberg, A ; Thomas, S ; Christoff, P ; Karoly, D (SPRINGER JAPAN KK, 2018-07-01)
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    The Role of Health Co-Benefits in the Development of Australian Climate Change Mitigation Policies
    Workman, A ; Blashki, G ; Karoly, D ; Wiseman, J (MDPI, 2016-09-01)
    Reducing domestic carbon dioxide and other associated emissions can lead to short-term, localized health benefits. Quantifying and incorporating these health co-benefits into the development of national climate change mitigation policies may facilitate the adoption of stronger policies. There is, however, a dearth of research exploring the role of health co-benefits on the development of such policies. To address this knowledge gap, research was conducted in Australia involving the analysis of several data sources, including interviews carried out with Australian federal government employees directly involved in the development of mitigation policies. The resulting case study determined that, in Australia, health co-benefits play a minimal role in the development of climate change mitigation policies. Several factors influence the extent to which health co-benefits inform the development of mitigation policies. Understanding these factors may help to increase the political utility of future health co-benefits studies.
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    Higher frequency of Central Pacific El Nino events in recent decades relative to past centuries
    Freund, MB ; Henley, BJ ; Karoly, DJ ; McGregor, HV ; Abram, NJ ; Dommenget, D (NATURE PUBLISHING GROUP, 2019-06-01)
    El Niño events differ substantially in their spatial pattern and intensity. Canonical Eastern Pacific El Niño events have sea surface temperature anomalies that are strongest in the far eastern equatorial Pacific, whereas peak ocean warming occurs further west during Central Pacific El Niño events. The event types differ in their impacts on the location and intensity of temperature and precipitation anomalies globally. Evidence is emerging that Central Pacific El Niño events have become more common, a trend that is projected by some studies to continue with ongoing climate change. Here we identify spatial and temporal patterns in observed sea surface temperatures that distinguish the evolution of Eastern and Central Pacific El Niño events in the tropical Pacific. We show that these patterns are recorded by a network of 27 seasonally resolved coral records, which we then use to reconstruct Central and Eastern Pacific El Niño activity for the past four centuries. We find a simultaneous increase in Central Pacific events and a decrease in Eastern Pacific events since the late twentieth century that leads to a ratio of Central to Eastern Pacific events that is unusual in a multicentury context. Compared to the past four centuries, the most recent 30 year period includes fewer, but more intense, Eastern Pacific El Niño events.
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    Seasonal dependence of rainfall extremes in and around Jakarta, Indonesia
    Lestari, S ; King, A ; Vincent, C ; Karoly, D ; Protat, A (Elsevier, 2019)
    This study investigates the interannual, seasonal, and intraseasonal variation in rainfall extremes (REs) in Jakarta and surroundings. We used datasets of daily rainfall at three sites at coastal, inland and mountainous environments during 1974–2016 (42 years), Sea Surface Temperature, 850-hPa zonal and meridional winds, and Outgoing Longwave Radiation during 1979–2016 (37 years). The results show that intensity and frequency of REs, and their relative contribution to the total rainfall, have strong relationships with the Indian Ocean Dipole and El Niño Southern Oscillation in the dry season (Jun–Nov) but weak relationships in the wet season (Dec–May) at all sites. During active Madden-Julian Oscillation (MJO) period, the daily average rainfall and the number of RE days relative to all days show strong variation between MJO phases at all sites and the MJO signature differs between the three stations. At the coastal and inland sites, there is a less marked variation of the number of RE events relative to all days with MJO phases. Compared to lower altitudes, the high-altitude station has a greater number of RE events relative to all days in the wet season and a lower intensity of REs relative to total rainfall amount in the dry season. The results of the study suggest that the REs vary in each station due to highly localised differences in responses to large-scale conditions.
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    Amplification of risks to water supply at 1.5°C and 2°C in drying climates: a case study for Melbourne, Australia
    Henley, BJ ; Peel, MC ; Nathan, R ; King, AD ; Ukkola, AM ; Karoly, DJ ; Tan, KS (IOP Publishing, 2019-08-02)
    Human-induced climate change poses a major threat to the reliable water supply in many highly populated regions. Here we combine hydrological and climate model simulations to evaluate risks to the water supply under projected shifts in the climate at the Paris Agreement warming levels. Modelling the primary surface water sources for Melbourne, Australia, we project that the risk of severe water supply shortage to the climate-dependent portion of the system increases substantially as global warming increases from 1.5 °Cto 2.0 °C. Risks are further exacerbated by increases in water demand but substantially ameliorated by supply augmentation from desalination.Wedemonstrate that reductions in precipitation, rising temperature and growth in water demand combine to substantially amplify the risk of severe water supply shortage under near-term global warming in the absence of a climate-independent supply. This risk amplification is not as apparent in assessments based on meteorological drought alone. With the diminishing opportunity of meeting the 1.5 °CParis target, our study highlights the need to accelerate greenhouse gas mitigation efforts to reduce risks to climate dependent water supply systems.
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    Reduced heat exposure by limiting global warming to 1.5 degrees C
    King, AD ; Donat, MG ; Lewis, SC ; Henley, BJ ; Mitchell, DM ; Stott, PA ; Fischer, EM ; Karoly, DJ (Springer Nature, 2018-07-01)
    The benefits of limiting global warming to the lower Paris Agreement target of 1.5 °C are substantial with respect to population exposure to heat, and should impel countries to strive towards greater emissions reductions.
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    Understanding the role of sea surface temperature-forcing for variability in global temperature and precipitation extremes
    Dittus, AJ ; Karoly, DJ ; Donat, MG ; Lewis, SC ; Alexander, LV (Elsevier, 2018-09)
    The oceans are a well-known source of natural variability in the climate system, although their ability to account for inter-annual variations of temperature and precipitation extremes over land remains unclear. In this study, the role of sea-surface temperature (SST)-forcing is investigated for variability and trends in a range of commonly used temperature and precipitation extreme indices over the period 1959 to 2013. Using atmospheric simulations forced by observed SST and sea-ice concentrations (SIC) from three models participating in the Climate of the Twentieth Century Plus (C20C+) Project, results show that oceanic boundary conditions drive a substantial fraction of inter-annual variability in global average temperature extreme indices, as well as, to a lower extent, for precipitation extremes. The observed trends in temperature extremes are generally well captured by the SST-forced simulations although some regional features such as the lack of warming in daytime warm temperature extremes over South America are not reproduced in the model simulations. Furthermore, the models simulate too strong increases in warm day frequency compared to observations over North America. For extreme precipitation trends, the accuracy of the simulated trend pattern is regionally variable, and a thorough assessment is difficult due to the lack of locally significant trends in the observations. This study shows that prescribing SST and SIC holds potential predictability for extremes in some (mainly tropical) regions at the inter-annual time-scale.
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    Long-term stationarity of El Nino-Southern Oscillation teleconnections in southeastern Australia
    Ashcroft, L ; Gergis, J ; Karoly, DJ (Springer (part of Springer Nature), 2016-05-01)
    The El Niño–Southern Oscillation (ENSO) phenomenon plays a large role in the modulation of Aaustralian rainfall, particularly in the highly populated southeast. However, this influence is not stationary over time: weak ENSO teleconnections in Australia have been identified during 1920–1950, and palaeoclimate reconstructions indicate that a breakdown in global ENSO teleconnections may have also occurred in the early to mid-1800s. A lack of long-term instrumental data has prevented detailed examination of this intriguing earlier period. This study uses newly recovered instrumental rainfall observations to determine whether the weakening of ENSO teleconnections in the nineteenth century is apparent in eastern and southern southeastern Australia (SEA). Quantitative rainfall and rainday data from 1788 to 2012 are compared with three ENSO indices derived from palaeoclimate data. Statistical analysis suggests a weakening of the relationship between ENSO and SEA rainfall in the early nineteenth century data (~1835–1850), supporting results reported in previous global and regional studies based on palaeoclimate and documentary rainfall reconstructions. Possible causes of this weakening in teleconnection strength are then explored by examining a range of Southern Hemisphere circulation indices. The 1835–1850 period of low ENSO–SEA rainfall correlations appears to be characterised by a combination of reduced La Niña events and ENSO variance associated with a positive phase of the Interdecadal Pacific Oscillation, with the possible influence of a predominately negative phase of the Southern Annular Mode. However, current temporal and geographical data limitations prevent definitive conclusions from being drawn. Despite these caveats, this study illustrates the considerable value of historical instrumental climate data in assessing long-term variations in climate mode teleconnections, particularly in the data-poor Southern Hemisphere.