The Hunter will experience nearly four times as many days over 35 degrees by 2090 and the region's average temperature will increase by 3.6 degrees unless current emissions levels decline, new climate modelling shows.
At the same time, the sea level at Newcastle could rise by up to 31cm resulting in inundation across low-lying parts of the city as the region struggles to adapt to a warming planet.
Updated data highlights risks
Updated NSW and Australian Regional Climate Modelling (NARCliM) projections show, relative to the 1990-2009 climate baseline, all parts of the Hunter will be subject to more extreme weather in coming decades.
The modelling, which uses low and high emissions scenarios, is considered to be the most detailed and accurate insight to date into how the region's environment will change in coming decades.
The projections will have major implications for human health, agriculture, water security, infrastructure planning and the insurance industry.
"Councils are likely to be required to develop disaster adaption plans and the NARCliM data will give a strong evidence base to develop those plans," Sarah Penny Joyce, executive officer Sydney Coastal Councils Group," said.
The Hunter is getting warmer
The warmest year on record for average and maximum temperatures in the Hunter was 2019 when the average temperature was 1.4 degrees above the 1990-2009 average.
It was a year when large parts of the region were crippled by drought and town of Murrurundi literally ran out of water.
But, according to the new modelling, that could be a taste of things to come - temperature increases are expected in all parts of the region and across all seasons.
Under a low-emissions scenario, the average temperature increase would be 1.2 degrees in 2090, but a high-emissions scenario would result in an increase of 3.6 degrees for the same period.
Upper Hunter, including towns such as Muswellbrook and Singleton, would see the greatest relative increases in temperature.
"By 2090, Merriwa is likely to experience an increase in temperature of 1.5 degrees under a low-emissions scenario and 4.1 degrees under a high-emissions scenario," a regional snapshot says.
"Comparatively, Newcastle is likely to experience an increase in temperature of 1.2 degrees under a low-emissions scenario and 3.3 degrees under a high-emissions scenario."
Rainfall expected to decline
The Hunter's rainfall presently ranges from more than 1300 mm per year on the coast and on the Barrington Tops, down to less than 600mm per year around Merriwa.
By 2090, on average, annual rainfall is projected to decrease by 8 per cent under a low emissions scenario and by 9 per cent under a high emissions scenario.
This will have major implications for the region's water security, in particular shallow dams such as Chichester and Grahamstown, which empty relatively quickly in dry conditions.
Average winter rainfall is also projected to decrease by 12 per cent under a low-emissions scenario and by 26 per cent under a high-emissions scenario.
"The Barrington Tops and southern hinterland areas of the region including Wollemi National Park are projected to experience the greatest changes," the modelling says.
"By 2090, on average, winter rainfall is projected to decrease for Wollemi National Park by 20 per cent under a low-emissions scenario and by 35 per cent under a high-emissions scenario."
Average, summer, autumn and spring rainfall is projected to change by less than 12 per cent across the region by 2090 under both a low-emissions scenario and a high-emissions scenario.
Severe fire risk increases
The number of severe fire weather days are expected to increase across most of the Hunter Region by 2050 for both a low-emissions and a high-emissions scenario, with an even greater increase projected by 2090 under a high-emissions scenario.
The greatest increases are projected to occur in the Upper Hunter including towns such as Merriwa. Only small increases are projected in some coastal areas such as Forster.
"By 2090, Merriwa is projected to experience 1.9 additional severe fire weather days per year under a low emissions scenario and 5.8 additional severe fire weather days per year under a high-emissions scenario," the modelling analysis shows.
A high-emissions scenario is projected to nearly double Merriwa's baseline period average of 5.9 severe fire weather days per year.
Comparatively, in the north-east of the region, Foster's baseline period average is one severe fire weather day per year.
By 2090, Foster is projected to experience 0.1 additional severe fire weather days per year under a low-emissions scenario and 0.4 additional severe fire weather days per year under a high-emissions scenario.
Sea level rise will accelerate
Sea level for the Hunter is projected to continue rising under all emissions scenarios.
At Newcastle, sea level is projected to rise by 14-27cm under a low-emissions scenario and by 18-31cm under a high-emissions scenario by 2050 relative to a baseline period of 1995-2014.
This will have major implications for beaches which have already experienced the impact of accelerating erosion over the past decade as well as low-lying properties.
"The inundation of low-lying streets around Lake Macquarie has increased in recent decades due to sea level rise and is Australia's most exposed estuary," the climate forecast says.
"Infrastructure and assets are expected to be increasingly vulnerable to the impacts of sea-level rise in the future."
Later in the century, sea-level rise is projected to accelerate under both emissions scenarios, with significantly faster acceleration under a high-emissions scenario.
Sea-level rise by 2100 is projected to be 30-62cm under a low-emissions scenario and 55-96cm under a high-emissions scenario. Even greater sea-level rise will occur by 2150, with a projected rise of 43-102cm under a low-emissions scenario and 90-174cm under a high-emissions scenario.
Start planning now
Climate Change and the Environment minister Penny Sharpe said the scenarios illustrated the need for strong action to reduce emissions and make households, communities, businesses and the environment more resilient to the impacts of climate change.
"The data shows two clear options - we can do nothing which will lock in more extreme weather events in the future, or we can reduce emissions now to play our part in limiting the damage," she said.
Ms Sharpe said the government had made action on climate change a whole of government priority, enshrining emissions reduction targets in law, and legislating an adaptation objective for NSW to be more resilient to a changing climate
"We can't plan for the future without the best data. That's what NARCliM provides," she said.
"This data will help protect critical infrastructure including hospitals, transport networks, dams and energy systems from climate change impacts such as extreme heat, fires and floods."
Director of climate and atmospheric science at the Department of Climate Change, Environment, Energy and Water Matthew Riley said the new climate research was being made available to everyone to create a greater understanding of how the environment was expected to change in coming decades.
"It is the finest resolution climate modelling ever made available for state's and territories in Australia," he said.
