Tropical cyclone perceptions, impacts and adaptation in the Southwest Pacific: an urban perspective from Fiji, Vanuatu and Tonga

The destruction caused by tropical cyclone (TC) Pam in March 2015 is considered one of the worst natural disasters in the history of Vanuatu. It has highlighted the need for a better understanding of TC impacts and adaptation in the Southwest Pacific (SWP) region. Therefore, the key aims of this study are to (i) understand local perceptions of TC activity, (ii) investigate impacts of TC activity and (iii) uncover adaptation strategies used to offset the impacts of TCs. To address these aims, a survey (with 130 participants from urban areas) was conducted across three SWP small island states (SISs): Fiji, Vanuatu and Tonga (FVT). It was found that respondents generally had a high level of risk perception and awareness of TCs and the associated physical impacts, but lacked an understanding of the underlying weather conditions. Responses highlighted that current methods of adaptation generally occur at the local level, immediately prior to a TC event (preparation of property, gathering of food, finding a safe place to shelter). However higher level adaptation measures (such as the modification to building structures) may reduce vulnerability further. Finally, we discuss the potential of utilising weather-related traditional knowledge and non-traditional knowledge of empirical and climate-model-based weather forecasts to improve TC outlooks, which would ultimately reduce vulnerability and increase adaptive capacity. Importantly, lessons learned from this study may result in the modification and/or development of existing adaptation strategies

Characterizing Australia's east coast cyclones (1950–2019)

East coast cyclones (ECCs) provide an essential reprieve from dry periods across eastern Australia. They also deliver flood‐producing rains with significant economic, social and environmental impacts. Assessing and comparing the influence of different types of cyclones is hindered by an incomplete understanding of ECC typology, given their widely variable spatial and temporal characteristics. This study employs a track‐clustering method (probabilistic curve‐aligned regression model) to identify key cyclonic pathways for ECCs from 1950 to 2019. Six spatially independent clusters were successfully distinguished and further sub‐classified (coastal, continental and tropical) based on their genesis location. The seasonality and long‐term variability, intensity (maximum Laplacian value ± two days) and event‐based rainfall were then evaluated for each cluster to quantify the impact of these storms on Australia. The highest quantity of land‐based rainfall per event is associated with the tropical cluster (Cluster 6), whereas widespread rainfall was also found to occur in the two continental lows (Cluster 4 and 5). Cyclone tracks orientated close to the coast (clusters 1, 2 and 3) were determined to be the least impactful in terms of rainfall and intensity, despite being the most common cyclone type. In terms of interannual variability, sea surface temperature anomalies suggest an increased cyclone frequency for clusters 1 (austral winter) and 4 (austral spring) during a central Pacific El Niño. Further, cyclone incidence during IOD‐negative conditions was more pronounced in winter for clusters 1, 2, 3 – and clusters 4 and 5 in spring. All cyclones also predominantly occurred in SAM‐positive conditions. However, winter ECCs for clusters 1 and 3 had a higher frequency in SAM‐negative. This new typology of ECCs via spatial clustering provides crucial insights into the systems that produce extreme rainfall across eastern Australia and should be used to inform future hazard management of cyclone events. This article is protected by copyright. All rights reserved

Steps toward "useful" hydroclimatic scenarios for water resource management in the Murray-Darling Basin

There is currently a distinct gap between what climate science can provide and information that is practically useful for (and needed by) natural resource managers. Improved understanding, and model representations, of interactions between the various climate drivers (both regional and global scale), combined with increased knowledge about the interactions between climate processes and hydrological processes at the regional scale, is necessary for improved attribution of climate change impacts, forecasting at a range of temporal scales and extreme event risk profiling (e.g., flood, drought, and bushfire). It is clear that the science has a long way to go in closing these research gaps; however, in the meantime water resource managers in the Murray‐Darling Basin, and elsewhere, require hydroclimatic projections (i.e., seasonal to multidecadal future scenarios) that are regionally specific and, importantly, take into account the impacts, and associated uncertainties, of both natural climate variability and anthropogenic change. The strengths and weaknesses of various approaches for supplying this information are discussed in this paper

Water resource management in a changing climate: can we afford to wait for the climate models to give us the answer?

Eastern Australian rainfall (and streamflow) is related to a number of large-scale climate drivers, including the El Niño/Southern Oscillation (ENSO), the Inter-decadal Pacific Oscillation (IPO), the Indian Ocean Dipole (IOD) and the Southern Annular Mode (SAM). However, identifying the process(es) causing hydroclimatic variability (on seasonal and longer time-scales) in eastern Australia, and many other parts of the world, is not a clear cut exercise. As a result the leadtime, accuracy, precision, and regional scale relevance of hydroclimatic forecasts is limited. Compounding this is the uncertainty surrounding the impacts associated with anthropogenic climate change – how will anthropogenic influences act to alter the already significant impacts associated with climate variability in eastern Australia? Accordingly, there is currently a distinct gap between what climate science can provide and information that is practically useful for (and needed by) natural resource managers. Improved understanding of interactions between the various climate drivers (both regional and global scale), combined with increased knowledge about the interactions between climate processes and hydrological processes at the regional scale, could aid in attribution of climate change impacts, forecasting at a range of temporal scales and extreme event risk profiling (e.g. flood, drought, bushfire etc.). Further discussion also focuses on the tendency of funding agencies to support climate model applications (or projects that simply produce predictions) rather than development of science or evaluation/validation of assumptions/models that are used to make the ‘predictions’. This problem needs to be addressed if we are to bridge the gap between climate science and the practically useful information that stakeholders require

A paleoclimate rainfall reconstruction in the Murray-Darling Basin (MDB), Australia: 1. Evaluation of different paleoclimate archives, rainfall networks, and reconstruction techniques

From ∼1997 to 2009 the Murray-Darling Basin (MDB), Australia's largest water catchment and reputed “food bowl,” experienced a severe drought termed the “Millennium Drought” or “Big Dry” followed by devastating floods in the austral summers of 2010/2011, 2011/2012, and 2012/2013. The magnitude and severity of these extreme events highlight the limitations associated with assessing hydroclimatic risk based on relatively short instrumental records (∼100 years). An option for extending hydroclimatic records is through the use of paleoclimate records. However, there are few in situ proxies of rainfall or streamflow suitable for assessing hydroclimatic risk in Australia and none are available in the MDB. In this paper, available paleoclimate records are reviewed and those of suitable quality for hydroclimatic risk assessments are used to develop preinstrumental information for the MDB. Three different paleoclimate reconstruction techniques are assessed using two instrumental rainfall networks: (1) corresponding to rainfall at locations where rainfall-sensitive Australian paleoclimate archives currently exist. ; (2) corresponding to rainfall at locations identified as being optimal for explaining MDB rainfall variability. It is shown that the optimized rainfall network results in a more accurate model of MDB rainfall compared to reconstructions based on rainfall at locations where paleoclimate rainfall proxies currently exist. This highlights the importance of first identifying key locations where existing and as yet unrealized paleoclimate records will be most useful in characterizing variability. These results give crucial insight as to where future investment and research into developing paleoclimate proxies for Australia could be most beneficial, with respect to better understanding instrumental, preinstrumental and potential future variability in the MDB

Reconstructing flood and drought cycles in the Murray-Darling Basin using paleoclimate archives

A dilemma facing many in the field of water resource management is the ability to adequately assess interannual to multi-decadal hydroclimatic risk - this is especially the case in Australia where instrumental records are relatively short. With rainfall records limited to approximately 100 years (and less for streamflow) there is considerable uncertainty around what to expect in terms of the magnitude and length of flood and drought cycles. This was recently demonstrated during the 'Big Dry' drought ( 1997-2010) where the severity and duration of the drought caught water managers by surprise due to record breaking low inflows into reservoirs. Similarly the flood events of 2010-2012 were also somewhat unexpected after such a prolonged dry period. One approach to improving our understanding of long-term hydroclimatic variability lies in paleoclimate archives that can serve as proxies for records of historical environmental events and processes prior to the availability of instrumental records. However, there is a lack of paleoclimate information in many areas where such insights and long term data are crucial (e.g. the Murray-Darling Basin (MDB), east Australian coast etc.). This paper assesses the suitability of available continental paleoclimate rainfall archives to capture rainfall variability in the MDB. Rainfall was modelled using multiple regression, principal component regression and climate field reconstruction. A number of metrics were used to assess the models including the coefficient of efficiency and the reduction in error. Following this work, it is possible to reconstruct rainfall using the paleoclimate proxy records and transform this into a flood and drought history for the MDB to improve assessments of long-term interannual to multidecadal variability and the associated hydroclimatic risks

Bridging the gap between end user needs and science capability: decision making under uncertainty

There is a recognised gap between what climate science can currently provide and what end users of that information require to make robust adaptation decisions about their climate-related risks. This issue has been identified as a major barrier to successful climate change adaptation outcomes and is emphasised within the water resource management and agricultural sectors because of high uncertainty surrounding precipitation projections. This paper details the outcomes of a survey and workshop aimed at better understanding this gap. To bridge the gap, it is recommended that communication and packaging of climate information be improved via a formalised 'knowledge broker'. It is also suggested that a 'terms of reference' for key climate change-related terms be developed and agreed upon by both climate science providers and end users to reduce the misuse of terminology and subsequent confusion. Further, it is recommended that additional research be conducted into natural variability and baseline risk to provide a realistic background on which climate change projections and associated uncertainties are assessed. Finally, for successful climate change adaptation, new tools and methods are needed that deal explicitly with end user needs and the practical limitations end users face (e.g. time, funding, human resources, politics) when attempting to make robust decisions under climate change-related uncertainty

Temporal and spatial variability of the cropping limit in South Australia

Since its establishment in 1865, Goyder's Line in South Australia has represented the division between land suitable for cropping and land seen as viable for grazing. Despite this, current cropping areas extend beyond Goyder's Line. In this study, the 220 mm growing season (April to October) rainfall isohyet is used as a proxy for Goyder's Line to assess its temporal and spatial variability. Using indices of the El Niño Southern Oscillation, Indian Ocean sea surface temperature variability, Southern Annular Mode and subtropical ridge, it is shown that climate state significantly influences the location of the 220 mm growing season rainfall isohyet. This implies that the boundary between viable and non-viable cropping areas (i.e. Goyder's Line or 'nature's limit') is non- stationary. These results also indicate the key influences on South Australia's climate and have important implications globally for agricultural practices operating in or bordering semi-arid environments

An investigation of coastal climate change risk assessment practice in Australia

Local government organisations in coastal Australia have historically commissioned studies aimed at understanding risks in their locality to future sea level rise as a starting point for developing adaptation strategies to climate change. Therefore, the success of the overall adaptation activities of local government are strongly influenced by the way those initial risk studies are scoped and conducted, and how the outputs of those studies underpin subsequent adaptation planning activities within the organization. Mainstreaming of adaptation planning activities within local government is critical in terms of getting stakeholder support and required resources for its implementation. This paper analyses a sample of these coastal risk assessment studies across seven states and territories in Australia, with an aim to critically investigate the current state of practice among coastal local governments. First, we develop a typology of studies that have been undertaken by or for practitioners to understand coastal climate change risks, and discuss the applicability of the studies within the policy making context of local government. Second, we identify a set of sample studies from the 'grey literature' through a systematic process and investigate to what extent they adhere to best practice risk management guidelines and principles, such as IS031000. Third, we interview stakeholders from top performing studies to identify how/if the risk studies helped their organization in progressing their adaptation planning. We find that there is a significant inconsistency among terminologies in the coastal climate change risk assessment unpublished literature as studies use "risk", vulnerability" and "hazard" concepts interchangeably despite their separate objectives and aims. Most studies perform poorly in evaluating risk against broader organizational criteria. Subsequently, it is difficult to integrate the findings of such studies into a broader organizational risk register, limiting opportunities for identified coastal climate change risks to be integrated into councils' long-term strategic decision making. Conversely, the follow up interviews of studies that performed well in scoping and consultation in our assessment demonstrate that these aspects were beneficial to stakeholders in terms of informing adaptation planning. Importantly, the findings presented in this paper confirm the need for a consistent risk assessment approach for local councils in the coastal zone to underpin successful adaptation planning. This is a critical issue, not only for Australia, but for local government organisations globally given that sea level rise is a projected threat for all populated coastal regions worldwide

Nature and causes of protracted droughts in southeast Australia: comparison between the Federation, WWII, and Big Dry droughts

Three protracted droughts have occurred during the instrumental history of Southeast Australia (SEA) – the "Federation" (~1895–1902), "World War II" (~1937–1945) and the "Big Dry" (~1997–present). This paper compares the nature and causes of these droughts in order to better inform drought management strategies in SEA. It is shown that the three droughts differ in terms of severity, spatial footprint, seasonality and seasonal rainfall make-up. This diversity arises due to the fact that the droughts are driven by different climatic teleconnections with the Pacific, Indian and Southern Oceans. Importantly, this study highlights potential flaws with drought forecasting and management in SEA and emphasises the need for further research into understanding and representing hydroclimatic drivers of drought