Technical information supporting the 2020 climate (projected rainfall) Environmental Trend and Condition Report Card

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Technical information supporting the 2020 climate (projected rainfall) Environmental Trend and Condition Report Card

Department for Environment and Water November, 2020

DEW Technical note 2020/22

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Department for Environment and Water Government of South Australia

November 2020

81-95 Waymouth St, ADELAIDE SA 5000 Telephone +61 (8) 8463 6946

Facsimile +61 (8) 8463 6999 ABN 36702093234

www.environment.sa.gov.au

Disclaimer

The Department for Environment and Water and its employees do not warrant or make any representation

regarding the use, or results of the use, of the information contained herein as regards to its correctness, accuracy, reliability, currency or otherwise. The Department for Environment and Water and its employees expressly

disclaims all liability or responsibility to any person using the information or advice. Information contained in this document is correct at the time of writing.

With the exception of the Piping Shrike emblem, other material or devices protected by Aboriginal rights or a trademark, and subject to review by the Government of South Australia at all times, the content of this document is licensed under the Creative Commons Attribution 4.0 Licence. All other rights are reserved.

ISBN 978-1-925964-60-8

Preferred way to cite this publication

Department for Environment and Water (2020). Technical information supporting the 2020 climate (projected rainfall) Environmental Trend and Condition Report Card 2020/22, Government of South Australia, Department for Environment and Water, Adelaide.

Download this document at https://data.environment.sa.gov.au

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Acknowledgements

This document was prepared by Graham Green (DEW). Improvements were made to this report and the associated report card, based on reviews by Jason Vanlaarhoven, Fi Taylor and Michelle Bald.

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Summary

This document describes the indicators, data sources, analysis methods and results used to develop this report and the associated report card. The reliability of data sources for their use in this context are also described.

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1 Introduction

1.1 Environmental trend and condition reporting

The Minister for Environment and Water under the Landscape South Australia Act 2019 is required to 'monitor, evaluate and audit the state and condition of the State's natural resources, coasts and seas; and to report on the state and condition of the State's natural resources, coasts and seas' (9(1(a-b)). Environmental trend and condition report cards are produced as the primary means for the Minister to undertake this reporting. The Environment Protection Act 1993, also requires the development of a State of the Environment Report (SOE), and states that the SOE must:

 Include an assessment of the condition of the major environmental resources of South Australia 112(3(a))

 Include a specific assessment of the state of the River Murray, especially taking into account the Objectives for a Healthy River Murray under the River Murray Act 2003 112(3(ab))

 Identify significant trends in environmental quality based on an analysis of indicators of environmental quality 112(3(b)).

1.2 Purpose and benefits of SA’s trend and condition report cards

South Australia’s environmental trend and condition report cards focus on the State’s priority environmental assets and the pressures that impact on these assets. The report cards present information on trend, condition and information reliability in a succinct visual summary.

The full suite of report cards capture patterns in trend and condition at a state scale, and give insight to changes in a particular asset over time. They also highlight gaps in our knowledge on priority assets that prevents us from assessing trend and condition, and might impede our ability to make evidence based decisions.

Both the trend and condition are considered important, however, the report cards give particular emphasis to trend. Trend shows how the environment has responded to past drivers, decisions, and actions, and is what we seek to influence through future decisions and actions.

The recognised benefits of trend and condition report cards include to:

 Provide insight into our environment by tracking its change over time

 Interpret complex information in a simple and accessible format

 Provide a transparent and open evidence base for decision-making

 Highlight those knowledge gaps that will impede South Australia’s ability to make decisions

 Drive alignment of environmental reporting, ensuring we ‘do once, use many times’

 Identify opportunities for further investment and on-ground action.

The initial development of the South Australian environmental trend and condition report cards was guided by the NRM State and Condition Reporting Framework (Government of South Australia 2012). The format, design and accessibly of the report cards has been modified and improved with each release. Environmental Trend and Condition Report Cards are designed to align with and inform both South Australian and National State of the Environment Reporting.

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2 Methods

2.1 Indicators

The indicators considered in the projected rainfall report card are:

 for the trend assessment, the projected percentage changes in average annual rainfall and average spring rainfall to 2050

 A condition rating is not applicable for projected rainfall as this is a projection of future rainfall change, for which there is no current or historic condition.

2.2 Data sources and collection

The rainfall trend information and graphs were prepared using data from the regional projections of the SA Climate Ready / Goyder Institute downscaled climate change projections dataset (Charles and Fu, 2015) and their mean projections of rainfall change in each Landscape region in the time horizons of 2030 and 2050.

The SA Climate Ready / Goyder Institute 2015 project generated detailed, local scale data for each region using 15 Global Climate Models (GCM) and applying a technique called “downscaling” at 200 selected weather stations.

While using 15 GCMs provides a broader range of possible future climate changes, the Projected Rainfall report card uses data from a subset of six of the fifteen climate models. These six models were recommended by the Goyder Institute research team as better predictors of rainfall for south eastern Australia because they were identified to perform better at representing climate drivers that are particularly influential on rainfall in South Australia, such as the El Nino Southern Oscillation (ENSO) and Indian Ocean Dipole. Further information on methods, data and outputs is available in the full regional report available at www.goyderinstitute.org . The climate projection information provided by SA Climate Ready is based on selected future climate change scenarios, projected to occur under two emissions scenarios defined by the Intergovernmental Panel on Climate Change (IPCC). The IPCC describe these as “representative concentration pathways” (RCPs). The high emissions scenario referred to in this document is RCP8.5 and the intermediate emission scenario is RCP4.5. The IPCC’s emissions scenarios are the product of a collaboration between integrated assessment modellers, climate modellers, ecosystem modellers as well as social scientists working on emissions, economics, policy, vulnerability and impacts.

The graphs of the mean projected changes in annual and spring rainfall include projections that are conditional on two scenarios of global atmospheric greenhouse gas concentrations, representing intermediate and high

greenhouse gas emission scenarios. Projections of temperature and rainfall are included which accord to the climate model projections under two representative concentration pathways: RCP 4.5 and RCP 8.5, which respectively represent intermediate and high emissions scenarios through the 21^st century. These are two of a range of four Representative Concentration Pathways (RCPs), the greenhouse gas concentration trajectories adopted by the IPCC for its fifth (and latest) Assessment Report (AR5).

For further information see: IPCC AR5 WG1 (2013), Stocker, T.F.; et al., eds., Climate Change 2013: The Physical Science Basis. Working Group 1 (WG1) Contribution to the Intergovernmental Panel on Climate Change (IPCC) 5th Assessment Report (AR5), Cambridge University Press, Archived from the original on 12 August 2014.

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3 Results

3.1 Trends in annual and spring rainfall

The text of the projected rainfall report card discusses the main features of the graphs presented in the two figures. These are graphs of projected percentage changes in the average annual rainfall (Figure 3.1) and spring rainfall (Figure 3.2) amounts in seven regions of SA at future time horizons of 2030 and 2050. The projected rainfall changes are relative to the mean rainfall projected by the same models for a historic baseline period of 1986 – 2005. Projections for the percentage changes at the 2030 and 2050 time horizon are commented on in the text of the report card.

The graphs show only the mean projections of the six “best” climate models for each region and for intermediate (RCP4.5) and high (RCP8.5) greenhouse gas emissions scenarios. There is considerable variability among the six models in their projections of rainfall change for each region. The ranges of rainfall change described in the text of the report card are simply the range between the highest and lowest mean projected rainfall change among the seven NRM regions included in the annual rainfall graph (Figure 3.1) and the spring rainfall graph (Figure 3.2)) at the time horizons of 2030 and 2050.

It should be noted that these time horizon years are not intended to represent the exact years by which rainfall is projected to change by these percentages. Rather, they are marker years, each for a thirty year period spanning the marker year. For example, the rainfall change projection for the 2050 time horizon represents the difference in the mean temperature in the period 2036 – 2065, compared with the historic baseline period of 1986 – 2005.

Figure 3.1 Projected changes in average annual rainfall in seven SA NRM regions 2030 – 2050, compared with mean annual rainfall in 1986 – 2005.

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Figure 3.2 Projected changes in average spring rainfall in seven SA NRM regions 2030 – 2050, compared with mean annual rainfall in 1986 – 2005.

3.2 Analysis of Trend, Condition and Information Reliability

3.2.1 Trend

The trend rating for projected rainfall was determined to be ‘Getting Worse’, as the projected changes for all the seven NRM regions are for a decline in rainfall in the future. A decline in rainfall is assessed to be a trend that is

‘getting worse’ due to the increased risk of water security and potential impacts to agriculture and ecosystems that may result from a drying climate in regions that already have a dry climate.

Table 3.1. Trend definitions

Trend Trend Definition Getting

better

Over a scale relevant to tracking change in the indicator it is improving in status with good confidence

Stable Over a scale relevant to tracking change in the indicator it is neither improving nor declining in status

Getting worse

Over a scale relevant to tracking change in the indicator it is declining in status with good confidence

Unknown Data are not available, or are not available at relevant temporal scales, to determine any trend in the status of this resource

Not applicable

This indicator of the natural resource does not lend itself to being classified into one of the above trend classes

3.2.2 Condition

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3.2.3 Reliability

The reliability of the information used in the report card is rated based on the average of subjective scores (1 [worst] to 5 [best]) given for information currency, applicability, level of spatial representation and accuracy.

Definitions guiding the application of these scores are provided in Table 3.2 for currency, Table 3.3 for

applicability, Table 3.4 for spatial representation and Table 3.5 for accuracy. The overall reliability rating for this report card is ‘Fair’. This is the rating ascribed to an overall score of 2 (out of a maximum of 5), based on the average of the ratings ascribed to applicability, currency and spatial representation of the information (Error!

Reference source not found.

Table 3.2. Guides for applying information currency

Currency score Criteria

1 Most recent information >10 years old 2 Most recent information up to 10 years old 3 Most recent information up to 7 years old 4 Most recent information up to 5 years old 5 Most recent information up to 3 years old

The rainfall projections datasets of SA Climate Ready are less than 5 years old. A currency score of 4 is determined for these data.

Table 3.3. Guides for applying information applicability

Applicability score Criteria

1 Data are based on expert opinion of the measure 2 All data based on indirect indicators of the measure 3 Most data based on indirect indicators of the measure 4 Most data based on direct indicators of the measure 5 All data based on direct indicators of the measure

The projected changes in rainfall are determined from a combination of large scale modelling of climate systems and statistical modelling of historic weather at a location. The projections of future rainfall change that result from these modelling processes are data based on indirect indicators of the measure of future rainfall. An information applicability score of 2 is determined for these data.

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Table 3.4. Guides for applying spatial representation of information (sampling design)

Spatial score Criteria

1 From an area that represents less than 5% the spatial distribution of the asset within the region/state or spatial representation unknown

2 From an area that represents less than 25% the spatial distribution of the asset within the region/state

3 From an area that represents less than half the spatial distribution of the asset within the region/state

4 From across the whole region/state (or whole distribution of asset within the region/state) using a sampling design that is not stratified

5 From across the whole region/state (or whole distribution of asset within the region/state) using a stratified sampling design

The projected changes in rainfall are determined from a combination of large scale modelling of climate systems and statistical modelling of historic weather at a variable number of locations within each region. While the large scale climate systems are representative of areas covering more than the whole of each region, the weather station locations can only be representative of the climate of a fraction (typically <25%) of each region. A spatial representation score of 2 is determined for the future rainfall projections.

Table 3.5. Guides for applying accuracy information

Reliability Criteria

1 Better than could be expected by chance 2 > 60% better than could be expected by chance 3 > 70 % better than could be expected by chance 4 > 80 % better than could be expected by chance 5 > 90 % better than could be expected by chance

As the projected changes in rainfall are only modelled projections of future changes in rainfall under scenarios of future greenhouse gas concentrations, the accuracy of the data cannot be compared against measurement.

However, the projection of regional rainfall under uncertain future climate scenarios is subject to several layers of compounding uncertainty. As a result, the accuracy of the projections has been ascribed a score of 1.

Table 3.6. Information reliability scores for projected rainfall

Indicator Applicability Currency Spatial Accuracy Reliability

Projected future mean annual and spring rainfall

4 2 2 1 2.3

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4 Discussion

The Climate: Projected rainfall report card reports on the decadal timescale outlook for rainfall change in South Australia under future climate scenarios, according to the projections of the SA Climate Ready downscaled climate change projections for South Australia (https://data.environment.sa.gov.au/Climate/SA-Climate-Ready/). These projections were developed by the CSIRO as the major component of the Goyder Institute for Water Research project “An Agreed Set of Climate Change Projections for South Australia” (Charles and Fu, 2015).

The report card provides textual comments on the trends in projected future rainfall in two graphs presented in the card. These graphs show the mean percentage change in rainfall, averaged across the projections of the six selected climate models, for each region.

4.1 Trend

The trend rating for projected rainfall was determined to be ‘Getting Worse’ as the projected changes for all the regions are for a decline in rainfall in the future.

4.2 Condition

As this assessment is of projected rainfall under future climate scenarios, a condition rating is not considered to be applicable.

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5 References

Australian Academy of Science (2015). “The science of climate change: Questions and answers”, Australian Academy of Science, Canberra, 2015 www.science.org.au/climatechange

Bureau of Meteorology (2020), About the rainfall trend maps,

http://www.bom.gov.au/climate/change/about/rain_trendmaps.shtml

CSIRO and Bureau of Meteorology 2015, Climate Change in Australia Information for Australia’s Natural Resource Management Regions: Technical Report, CSIRO and Bureau of Meteorology, Australia,

https://www.climatechangeinaustralia.gov.au/en/climate-campus/australian-climate-change/australian-trends/

DEWNR (2017). Trend and Condition Report Cards for South Australia’s Environment and Natural Resources.

Report. Department of Environment, Water and Natural Resources, Government of South Australia. Available at:

https://data.environment.sa.gov.au/NRM-Report-Cards/Documents/Trend_Condition_Report_Cards_2017.pdf Government of South Australia (2012a). Natural Resource Management State and Condition Reporting Framework SA. Report. Adelaide. Available at:

https://www.waterconnect.sa.gov.au/Content/Publications/DEWNR/91913%20NRM%20Reporting%20Framework

%202012%20Final%20Draft%20v7.pdf

Charles SP and Fu G, (2015). Statistically Downscaled Projections for South Australia – Task 3 CSIRO Final Report, Goyder Institute for Water Research Technical Report Series No. 15/1, Adelaide, South Australia.

http://www.goyderinstitute.org/_r91/media/system/attrib/file/82/CC%20Task%203%20CSIRO%20Final%20Report_

web.pdf

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Technical information supporting the 2020 climate (projected rainfall) Environmental Trend and Condition Report Card