Climate atlas maps likely path

The cool, damp conclusion to Tasmania's 2020 vintage may have diverted our attention recently, but data collected by the Australian Government's Bureau of Meteorology indicate last summer was the country's second warmest on record. The mean maximum temperature for the three-month period was 2.11ºC warmer than average.

And that summer rainfall in Tasmania? Well, it depends on where you were in the State. Most of Tasmania had less than average summer rainfall, with some sites in the south-east having only half of their long-term average.

"There's enormous variability in rainfall across the Australian continent," says Hobart climate scientist Dr Tom Remenyi.

"We are farming the most variable area of the entire planet."

Remenyi speaks with the voice of experience. He is among six Tasmanian researchers that have been working closely with the Australian wine industry to map out its path to the year 2100. The team's three-year project culminated in last month's release of Australia's Wine Future: A Climate Atlas.

"The atlas is based on the most up-to-date climate projections, at the finest resolution available, and across all regions of Australia," Remenyi explains.

Its 487 pages of research and analysis were funded by Wine Australia and undertaken with the support of the University of Tasmania.

The document took four years to produce and examines two keys aspects of climate change in Australia. The first addresses short-term climate variability. The second looks at the long-term impacts of global warming and climate change. 

Weaving all that into a single publication presented Remenyi with more immediate, professional challenges – how to make complex data and principles of climatology both meaningful and useable to stakeholders in the country's 71 wine regions.

That's largely been managed via references to commonly used climate measures, including growing season temperature, growing season rainfall, frost risk days, and aridity. Figures for each of those, along with a handful of other climate indices, were obtained for the 20 years spanning 1997 to 2017. Baseline data for the same variables, observed between 1961 and 1990, are then compared to provide evidence for short-term climate change.

Data for the same set of variables obtained from six global climate models are used to determine Australia's projected climate to June 2100. 

As lead author and science translator for A Climate Atlas, Remenyi believes warm summers like the one we've just had are going to become what he calls "a new normal… not just something extreme that we're never going to have to deal with again.

"The Australian wine industry is the first wine industry in the world to have this kind of information made available to them, at the resolution that is relevant to growers on the ground. That gives them an enormous chance to choose their future – by adapting their management practices in the vineyard, for example, or by selecting the kinds of grape varieties that are going to be most appropriate for the climate of the future."

The word 'adaptation' features prominently throughout the atlas and its supporting documentation. Like it or not, Remenyi says we are all going to have to learn to live with the impacts of climate change as they become more evident in coming decades.

Australia's wine industry will have changed significantly by the time 2100 arrives.

Average temperatures across all regions are expected to increase by around 3.0ºC following a high emissions scenario. Those in Tasmania will be slightly less than average, but still well in excess of 2.0ºC. We have the moderating influences of the nearby Tasman Sea and Indian Ocean to thank for that.

Even so, by 2041, Tasmania's smallest winegrowing district – the North West Coast – is predicted to be almost a full degree warmer during the growing season than is now being experienced by the East Coast. Rainfall then will have declined from its current average of 500mm to 442mm, barely 44mm more than the present figure for the East Coast.

Meanwhile, the average growing season temperature on the East Coast will rise to 16.9ºC by 2100. That will bring it roughly into line with conditions currently being experienced by Robe (17.0ºC) on South Australia's Limestone Coast.

Little wonder trophy-winning producers on the East Coast – like Freycinet, Gala Estate, Milton and Spring Vale – are looking to Shiraz for future successes. Each has made significant investments already.

And it's not just growing season temperatures that will see marked increases over the coming decades. Aridity – a measure of soil dryness that takes into account rainfall and evaporation – is also projected to increase in most Australian wine regions.

"Declining rainfall – especially winter rainfall – is really going to cause water storages to be put under stress in many regions of the country," Remenyi warns.

"Finding new water is really going to play an important part in this climate scenario moving forwards."

Free copies of A Climate Atlas can be downloaded from the Climate Futures website. Further information on the project itself can be obtained from Wine Australia.

First published 25 July 2020: www.tasmaniantimes.com