Australia’s wine future: Adapting to short-term climate variability and long-term climate change

Abstract

Australia’s wine future developed tools for Australia’s grape growers to manage emerging weather and climate risks for short-term climate cycles and long-term climate change. The project assessed the impacts of short-term climate variability and trends in climate across all Australian wine regions and provided the most up-to-date climate information at the finest resolution available in Australia. Regional climate indices were tailored for particular grape varieties and regions, with the focus on heat accumulation, heatwave and frost. Adaptation options to manage emerging risks in the near future and out to longer-term planning horizons were identified.

Summary

The project brought together an extensive, multi-disciplinary research team to consider the impact of climate variability and longer-term trends in climate on the wine industry. We generated the finest available climate projections for South-eastern Australia and provided detailed information about how the climate may change in the near, mid and long-term time horizons. In addition to providing climate information, the project focused on how climate information can be used to inform adaptation decisions and identify lessons that might be transferable across regions already managing a range of climate challenges.

1. Adaptation and options for managing climate variability

Identification of current weather and climate risks for key regions
Wine growers in six case study regions (Grampians, Hunter Valley, Riverlands, Tasmania, Margaret River and Barossa) were consulted to identify weather and climate risks and the range in market requirements and management options that are currently experienced across Australia. Crop calendars, adjusted for each region, were used to consider weather risks in relation to the timing of grape growth and highlight management responses which could inform adaptation to future challenges. The calendars link the main stages of budburst, flowering, veraison and harvest to the weather and climate risks that occur at specific stages.

The interviews highlighted the very high level of flexibility and responsiveness of vineyard management to climate variability across the Australian wine regions, which offers great opportunities for transferring knowledge necessary for climate adaptation. Many wine regions are likely to be susceptible to climate change, but also have a degree of resilience because inter-annual variability in climate, especially in rainfall, is naturally high in these areas and wine growers have developed a range of short-term management options to minimise the impacts of climate variability on grape and wine quantity and quality.

Adaptation options for key regions
A Decision Analysis approach was used to identify climate sensitive decisions and understand the opportunities and barriers to the use of climate information in informing tactical and strategic decisions in vineyards. Six tactical decisions and seven strategic decisions were highlighted that would benefit from climate information at the seasonal and long-term time horizons.

Identification of analogue regions
Two methods were developed to describe current and future climate analogue regions.

The first is a visualisation approach that shows how a region compares to other regions under current and future climate conditions. This climate analogue approach is an intuitive way to understand the local impacts of climate change over time and contextualise decision making. Comparisons between regions provide insights into real impacts of change and allows lessons to be learnt from regions that currently experience the climate conditions projected for the future. This approach also provides a timeframe for potential adaptation options and could identify the limits to adaptation if there is a time in the future when no analogues remain.

The second approach is a Climate Analogue Tool that can identify similar regions globally on the basis of evaporation, humidity and radiation in addition to temperature and precipitation. It compares the climate on both daily and monthly timescales, to capture differences in extremes and seasonality as well as mean climate conditions. With further refinement and the development of a user-friendly interface, this tool could be widely used to identify future grape varieties and novel adaptation options and provide information about changing global markets.

2. Seasonal climate variability

Impact of historical climate drivers on the wine regions
The assessment of the historical impact of El Niño and Indian Ocean Dipole on viticultural climate indices across Australia found several general relationships, although there were strong seasonal and regional differences. The highest correlations with ENSO occurred in Queensland, NSW, ACT, Victoria and parts of the inland rivers irrigation areas, with drier conditions occurring during October to December in El Niño and positive IOD years. These results are consistent with published climate science, which has also shown that the impact of the main climate drivers on rainfall differs across Australia and seasonally (e.g. Risbey et al. 2009).

Changes in the modes of climate drivers may occur with ongoing climate change, but climate scientists are still debating the causes of the changes and the level of confidence in the projections (Cai et al. 2015a).

Development of Seasonal to interannual climate forecasts
The Decadal Climate Forecast Project (DCFP) at CSIRO provided a preliminary assessment of the skill of seasonal to interannual climate forecasts for the wine regions. The first part of this was an assessment of key extreme events such as heatwaves and wet extremes. For a model to have forecast skill it should simulate the distribution of extremes in a similar way to observations, and those extremes should be associated with the same synoptic and large-scale atmospheric circulations in the model and observations.

The DCFP model is broadly successful in simulating the correct distributions and synoptic and large-scale patterns for heatwaves and extreme wet periods. The second part of this work included an assessment of forecast skill for growing degree days (GDD) and cumulative rainfall at selected wine regions. These results showed improved skill relative to climatology (the best that one could do in the absence of a climate forecast) for GDD in the Margaret River and Riverland regions. The improvement in skill covers lead times from about 4 months to 2 years. Examples are presented showing how forecasts of GDD could be applied and visualised at a given point during the season to shape expectations of GDD over the remainder of the year. However, further work is needed to connect forecasts of GDD to viticultural outputs in the wine regions, and to identify windows of time when predictability is potentially higher.

3. Projections of future climate change

The best-available dynamically-downscaled regional climate models were used in each region of Australia. A regional climate model was run to provide daily climate data at 5km resolution for 2010-2070 for south-eastern Australia (see Section 9). Over Tasmania, Queensland and Northern NSW the output was at ~10km. Over Western Australia, a secondary statistical downscaling method was applied, to increase the resolution from ~50km to 5km.

The wine sector is likely to face challenges as climate change continues. Temperature increases of 3 to 4℃, relative to 1961-1990, are projected to occur by the end of the century under the high emissions scenario (RCP 8.5), the scenario that we are currently tracking. When superimposed on natural variability, this represents a highly significant change to the climate system, resulting in more frequent and intense extreme events such as heatwaves.

Several trends in future climate are consistently found for wine regions across Australia. Annual temperature and Growing Season Temperature (GST) are projected to increase into the future for every region across Australia. This strong warming trend accelerates towards 2100, with climate change becoming progressively more influential than natural variability after 2020. Aridity is expected to increase in all wine regions across Australia. Fewer Growing Season Frost Risk Days are likely as temperatures continue to rise. More intense heatwaves are expected in many regions, with substantial increases in the Excess Heat Factor (EHF) in some regions. This index describes the severity of acute heat impacts on humans during heat waves, and the results suggest that outdoor work may be restricted in the future in some of Australia’s regions. Extremely hot years are likely to occur as much as 30 years earlier than projected by the mean trend. All of these changes will have widespread implications for the wine industry.

We have high confidence in how temperature will change into the future under particular emissions scenarios. The physical drivers of how temperature changes within the climate system are well understood, are valid across large spatial scales and are therefore straightforward to represent within climate models. This allows the models to achieve high levels of skill in the projections they produce. There is strong agreement across the ensemble of climate models we used regarding the rate and magnitude of warming projected into the future. In contrast, rainfall projections are more variable. However, very few simulations indicate increases in rainfall of sufficient magnitude to offset the projected decreases in moisture availability due to evaporation. As a result, all regions are expected to experience increased aridity in the future.

4. The Climate Atlas

The main legacy of the project is an online atlas of climate information for all Australian Geographic Indications (GI), providing information to grape growers and wine makers about climate trends for the near, mid and long-term horizons. Australia’s wine Future: A Climate Atlas will help to answer the question – What will my region’s climate look like in the future? This is essential knowledge for making good management decisions and supporting strategic decisions over the longer term such as changing varieties or vineyard sites both within and between regions. The atlas is an important resource that will help the wine industry understand how climate change could affect grape yield, profitability and wine styles across Australia into the future.

Tailored climate indices, identified as being relevant to the wine industry through consultation, were calculated for every GI. Indices representing temperature, rainfall and evaporative demand, and heat and cold extremes are presented, including:

  1. Temperature - Growing Season Temperature (GST), Growing Degree Days (GDD);
  2. Rainfall and evaporative demand - Annual, Monthly and Seasonal rainfall; Growing Season Rainfall; Number of rainy days during harvest; Annual, Monthly and Seasonal aridity; Number of dry spells before harvest;
  3. Heat extremes - extreme heat factor (EHF) during a heatwave; Heatwave duration and intensity; Number of days per year exceeding temperature thresholds (30°C, 35°C, 40°C, 45°C); Frequency of days with high human heat stress;
  4. Cold extremes - Number of days at risk of frost during the growing season; Daily minimum temperature; Annual chilling degree days; Number of days per year temperature falls below temperature thresholds (<2°C, <0°C, <-2°C).

In the Climate atlas, future trends in mean climate conditions, variability and extremes are visualised with reference to the current and historical climate. High resolution maps and time series for each region are presented to show the projected change in climate indices over time, highlighting the variability within and across the wine regions of Australia.

The use of fine-scaled climate information enabled the variability within and across Australian wine regions to be visualized. In Australia’s wine Future: A Climate Atlas, national maps are presented to show the variability across Australia in temperature, rainfall and aridity in observed climate conditions during the period 1997-2017, and the changes in climate that have already occurred since the historical period (1961-1990).

Although the wine sector is likely to face challenges as the climate continues to warm, grape growers are experienced in responding to short-term climate surprises. In the short- to medium-term, adaptation approaches may be learnt from the regions that are currently experiencing the climate conditions that Australia is predicted to see in the future. Fine-scaled climate information tailored for particular sector applications is vital for identifying such adaptation needs, while accounting for climate variability and seasonality within different regional contexts.

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