David J. Karoly

David J. Karoly
University of Melbourne | MSD · School of Earth Sciences

About

253
Publications
64,488
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21,859
Citations
Introduction
David Karoly is an honorary Professor in the School of Geography, Earth and Atmospheric Sciences and an honorary Senior Research Fellow in Melbourne Climate Futures at the University of Melbourne. He was Leader of the Earth Systems and Climate Change Hub, in the Australian Government's National Environmental Science Program, based in CSIRO, until June 2021. David does research on climate variability and climate change. He was elected as a Fellow of the Australian Academy of Science in 2019.
Additional affiliations
February 2022 - present
University of Melbourne
Position
  • honorary Professor
Description
  • I am an honorary Professor in the School of Geography, Earth and Atmospheric Sciences and an honorary Senior Research Fellow in Melbourne Climate Futures.
July 2021 - January 2022
CSIRO Oceans & Atmosphere
Position
  • Researcher
February 2018 - June 2021
CSIRO Oceans and Atmosphere, Aspendale, Australia
Position
  • Leader

Publications

Publications (253)
Article
Research on the interaction between the Madden–Julian oscillation (MJO) and rainfall around Jakarta is limited, although the influence of the MJO on increased rainfall is acknowledged as one of the primary causes of flooding in the region. This paper investigates the local rainfall response around Jakarta to the MJO. We used C-band Doppler radar in...
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To mitigate the risk posed by extreme rainfall events, we require statistical models that reliably capture extremes in continuous space with dependence. However, assuming a stationary dependence structure in such models is often erroneous, particularly over large geographical domains. Furthermore, there are limitations on the ability to fit existin...
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Urgent and ambitious climate action is required to avoid catastrophic climate change and consequent health impacts. Political will is a critical component of the ambitious climate action equation. The current level of political will observed for many national governments is considered inadequate, with numerous political leaders yet to commit to cli...
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Given the consequences and global significance of El Niño-Southern Oscillation (ENSO) events it is essential to understand the representation of El Niño diversity in climate models for the present day and the future. In recent decades, El Niño events have occurred more frequently in the central Pacific (CP). Eastern Pacific (EP) El Niño events have...
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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, Aust...
Data
El Niño events of the past 400 years. Instrumental and reconstructed El Niño events. Years in italic are identified in the instrumental record (HadISST 1950-2015) and bold highlight events picked up by both reconstruction and the instrumental data. Details in Freund et al 2019 and supplement: Higher frequency of Central Pacific El Niño events in re...
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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 loc...
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Climate extremes, such as droughts or heat waves, can lead to harvest failures and threaten the livelihoods of agricultural producers and the food security of communities worldwide. Improving our understanding of their impacts on crop yields is crucial to enhance the resilience of the global food system. This study analyses, to our knowledge for th...
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The cities of Melbourne, Sydney and Adelaide are home to almost half of the Australian population, and are often exposed to extreme rainfall events and high year-to-year rainfall variability. However the majority of studies into rainfall in these cities, and southeastern Australia in general, are limited to the 20th century due to data availability...
Article
Extreme heat events pose increasing challenges to biodiversity conservation worldwide, yet our ability to predict the time, place and magnitude of their impacts on wildlife is limited. Extreme heat events in Australia are known to kill thousands of flying‐foxes (Pteropus spp.), and such die‐offs are expected to become more frequent and widespread i...
Article
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 Radia...
Article
Tasmania saw a warm and very dry spring and summer in 2015–16, including a record dry October, which had significant, wide-ranging impacts. A previous study using two probabilistic event-attribution techniques found a small but statistically significant increase in the likelihood of the record dry October due to anthropogenic influence. Given the h...
Article
The 2015 Paris Agreement requires increasingly ambitious emissions reduction efforts from its member countries. Accounting for ancillary positive health outcomes (health co-benefits) that result from implementing climate change mitigation policies can provide Parties to the Paris Agreement with a sound rationale for introducing stronger mitigation...
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The Southern Annular Mode (SAM) is the leading mode of atmospheric interannual variability in the Southern Hemisphere (SH) extra-tropics. Here, we assess the stationarity of SAM spatial correlations with instrumental and paleoclimate proxy data for the past millennium. The instrumental period shows that temporal non-stationarities in SAM teleconnec...
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Geoengineering could remake environments and societies, and early governance can help to steer the development of technologies towards sustainable outcomes. In the absence of observational data, geoengineering research and discussions are increasingly informed by scenarios, which provide heuristic tools for ‘envisioning’ potential futures. Although...
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The Paris Agreement¹ aims to ‘pursue efforts to limit the temperature increase to 1.5 °C above pre-industrial levels.’ However, it has been suggested that temperature targets alone are insufficient to limit the risks associated with anthropogenic emissions2,3. Here, using an ensemble of model simulations, we show that atmospheric CO2 increase—an ev...
Article
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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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 te...
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A complex, whole-of-economy issue such as climate change demands an interdisciplinary, multi-sectoral response. However, evidence suggests that human health has remained elusive in its influence on the development of ambitious climate change mitigation policies for many national governments, despite a recognition that the combustion of fossil fuels...
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Geoengineering—the deliberate interference in the climate system to affect global warming—could have significant global environmental and social implications. How to shape formal geoengineering governance mechanisms is an issue of debate. This paper describes and analyses the geoengineering governance landscape that has developed in the absence of...
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Australian seasonal rainfall is strongly affected by large-scale ocean–atmosphere climate influences. In this study, we exploit the links between these precipitation influences, regional rainfall variations, and palaeoclimate proxies in the region to reconstruct Australian regional rainfall between four and eight centuries into the past. We use an...
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There is an international effort to attempt to limit global warming to 1.5 °C above pre-industrial levels, however, there is a lack of quantitative analysis on the benefits of holding global warming to such a level. In this study, coupled climate model simulations are used to form large ensembles of simulated years at 1.5 °C and 2 °C of global warm...
Article
Extreme rainfall does not occur in spatial isolation. Rainfall occurs in a region, and within that region nearby locations are likely to experience similar impacts due to spatial dependence. While univariate extreme value models provide the easiest statistical modelling approach to rainfall extremes, practitioners and researchers adopting statistic...
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The science of event attribution meets a mounting demand for reliable and timely information about the links between climate change and individual extreme events. Studies have estimated the contribution of human-induced climate change to the magnitude of an event as well as its likelihood, and many types of event have been investigated including he...
Chapter
In many areas of the world, the observed trends of warming of temperature extremes and intensification of precipitation extremes have been attributed to human-induced climate change. The topic of calculating the “time of emergence” has expanded in recent years with a growing body of literature in this field. So when did (or when will) an anthropoge...
Chapter
In 2010–2012, Australia had its record highest 2 year rainfall, as well as repeated shorter-term extreme rainfall events and damaging floods. Later in 2013, Australia experienced its record hottest year, together with repeated shorter-term temperature records and heat waves in different regions. In this chapter, we discuss the mechanisms explaining...
Article
To avoid more severe impacts from climate change, there is international agreement to strive to limit warming to below 1.5 °C. However, there is a lack of literature assessing climate change at 1.5 °C and the potential benefits in terms of reduced frequency of extreme events. Here, we demonstrate that existing model simulations provide a basis for...
Article
Slow-moving planetary waves of high amplitudes are often associated with persistent surface weather conditions. This persistence can lead to extreme weather events with potentially serious implications for society and nature. Quasi-resonant amplification of planetary waves (QRA) has been proposed as a mechanism to generate high-amplitude hemisphere...
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Key Points • Systematic evaluation of temporal and spatial features of the IPO in CMIP5 using TPI • Decadal variance of the IPO is commonly underestimated in models relative to observations • Models that simulate the IPO spatial pattern well also tend to simulate low frequency temporal characteristics Accelerated warming and hiatus periods in...
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Full-text available
Australian seasonal rainfall is strongly influenced by large-scale ocean-atmosphere climate influences. In this study, we exploit the links between these large-scale precipitation influences, regional rainfall variations, and palaeoclimate proxies in the region to reconstruct Australian regional rainfall between four and eight centuries into the pa...
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Full-text available
The skill of 8 climate models participating in the Coupled Model Intercomparison Project Phase 5 in simulating the variability and trends in the observed areal extent of daily temperature and precipitation extremes across five large-scale regions is evaluated, using the Climate Extremes Index (CEI) framework. Focusing on Europe, North America, Asia...
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El Niño and human-induced climate change have substantially increased the likelihood of rainfall deficits and high temperatures, respectively, in Indonesia such as those experienced in the drought conditions of July–October 2015.
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Anthropogenic climate change was found to have a substantial influence on southern Australia's extreme heat in October 2015. The relative influence of El Niño conditions was less clear.
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Anthropogenic climate change and El Niño made small but significant contributions to increasing the likelihood of record low rainfall in October 2015 in Tasmania. Atmospheric variability was the main contributor.
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A new climate modelling project has been developed for regional climate simulation and the attribution of weather and climate extremes over Australia and New Zealand. The project, known as weather@home Australia–New Zealand, uses public volunteers' home computers to run a moderate-resolution global atmospheric model with a nested regional model ove...
Article
Understanding how the overall risks of extreme events are changing in a warming world requires both a thermodynamic perspective and an understanding of changes in the atmospheric circulation.
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A new climate modelling project has been developed for regional climate simulation and the attribution of weather and climate extremes over Australia and New Zealand. The project, known as weather@home Australia-New Zealand, uses public volunteers' home computers to run a moderate-resolution global atmospheric model with a nested regional model ove...
Article
We present multi-proxy warm season (September–February) temperature reconstructions for the combined land–ocean region of Australasia (0°S–50°S, 110°E–180°E) covering A.D. 1000-2001. Using between two (R2) and 28 (R28) proxy records we compare four 1000-member ensemble reconstructions of regional temperature using four statistical methods: Principa...
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Chemistry–climate models are important tools for addressing interactions of composition and climate in the Earth system. In particular, they are used to assess the combined roles of greenhouse gases and ozone in Southern Hemisphere climate and weather. Here we present an evaluation of the Australian Community Climate and Earth System Simulator – ch...
Article
This study examines trends in the area affected by temperature and precipitation extremes across five large-scale regions using the climate extremes index (CEI) framework. Analyzing changes in temperature and precipitation extremes in terms of areal fraction provides information from a different perspective and can be useful for climate monitoring....
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Anthropogenic climate change very likely increased the likelihood of prolonged heat waves like that experienced in Adelaide in January 2014 by at least 16%. The influence for Melbourne is less clear.
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It is likely that human influences on climate increased the odds of the extreme high pressure anomalies south of Australia in August 2014 that were associated with frosts, lowland snowfalls and reduced rainfall.
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Climate model simulations for 2014 indicate anthropogenic climate change very likely increased the likelihood of hot and very hot November days in Brisbane by at least 25% and 44% respectively.
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Determining the time of emergence of climates altered from their natural state by anthropogenic influences can help inform the development of adaptation and mitigation strategies to climate change. Previous studies have examined the time of emergence of climate averages. However, at the global scale, the emergence of changes in extreme events, whic...
Article
The El Niño–Southern Oscillation (ENSO) phenomenon plays a large role in the modulation of Australian 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...
Article
Chemistry climate models are important tools for addressing interactions of composition and climate in the Earth System. In particular, they are used for assessing the combined roles of greenhouse gases and ozone in Southern Hemisphere climate and weather. Here we present an evaluation of the Australian Community Climate and Earth System Simulator-...
Article
Future projections of water supply under climate change scenarios are fundamental for efficient water resource planning. However, runoff projections are affected by uncertainties in the modelling process that limit their utility to decision makers. The main source of uncertainty in runoff projections are the Global Climate Models (GCMs) used to pro...
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In 2014, Central England experienced its warmest year in a record extending back to 1659. Using both state-of-the-art climate models and empirical techniques, our analysis shows a substantial and significant increase in the likelihood of record-breaking warm years, such as 2014, due to human influences on climate. With 90% confidence we find that a...
Article
Unusually hot summer conditions occurred during the 1930s over the central United States and undoubtedly contributed to the severity of the Dust Bowl drought. We investigate local and large-scale conditions in association with the extraordinary heat and drought events, making use of novel datasets of observed climate extremes and climate reanalysis...
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Two key sources of uncertainty in projections of future runoff for climate change impact assessments are uncertainty between global climate models (GCMs) and within a GCM. Within-GCM uncertainty is the variability in GCM output that occurs when running a scenario multiple times but each run has slightly different, but equally plausible, initial con...
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A new index is developed for the Interdecadal Pacific Oscillation, termed the IPO Tripole Index (TPI). The IPO is associated with a distinct ‘tripole’ pattern of sea surface temperature anomalies (SSTA), with three large centres of action and variations on decadal timescales, evident in the second principal component (PC) of low-pass filtered globa...
Book
With 93% of the food we eat grown here in Australia, the future of Australian farming matters to all of us. Australia is lucky to have a strong agricultural sector that plays a pivotal role in contributing to the Australian economy and defining Australian culture. In 2012-13 the gross value of total Australian agricultural production was $48 billio...
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The objective of this paper is to identify better performing Coupled Model Intercomparison Project phase 3 (CMIP3) global climate models (GCMs) that reproduce grid-scale climatological statistics of observed precipitation and temperature for input to hydrologic simulation over global land regions. Current assessments are aimed mainly at examining t...