In a 54-page Greenhouse Gas Assessment which forms part of its application to extract an additional 247 million tonnes of coal from the Muswellbrook-based mine, MACH "acknowledges" that "all sources of greenhouse gas emissions will contribute in some way towards the potential global, national, state and regional effects of climate change."

It notes that "anthropogenic climate change" is identified in various pieces of NSW legislation as a key threat, and that mean temperatures are projected to rise by up to 2.3 degrees in the 30 years after the mine's closure.

"Summer and spring will experience the greatest changes in temperatures ... increasing by 2.3 degrees by 2079," the report says. "These increases are projected to occur across the region, with a slightly greater increase in the Upper Hunter."

It cites Intergovernmental Panel on Climate Change modelling which predicts global warming will cause more extreme climatic events, such as "hot extremes, heavy rainfall events and droughts", and they will occur even more frequently if global temperatures rise by 2 degrees, rather than 1.5 degrees.

The report identifies the potential implications of climate change on local groundwater and surface water resources, and biodiversity, as well as an increase in the frequency of extreme temperature events, suggesting that "bushfire activity may become more prevalent in the region".

"It is recognised that international measures to 'decarbonise' global economies may alter the future demand for and/or supply of coal," it says, but after factoring expected global trends into coal price forecasts, including sensitivity analysis for the "social cost per tonne" of carbon emissions, the project would still generate a "substantial net benefit to NSW".

The report includes strategies to mitigate the increased risk of bushfire as well as managing as other potential climate change impacts on mining operations.

The greenhouse gas emissions associated with the burning of MACH Energy's Mt Pleasant coal would become the responsibility of those countries which import it, referred to as the "downstream consumption of coal by end users" or scope 3 emissions.

There are no climate change laws or policies prohibiting new coal mining development in NSW, and Australia had not adopted any measures under the Paris Agreement restricting coal mine expansions.

The life of the project would be completed before 2050, which is the target date for NSW achieving net zero emissions, it says.

The proposal has been panned by 140 objectors, which have included members of the Hunter Valleys equine industry, farmers, health experts, as well as initially drawing heavy criticism from the state government itself, including NSW Health.

Based on the original application, Hunter New England Health public health physician David Durrheim, has signed a letter as the Director of Health Protection for NSW Health, talking about the potential health impacts from the project's effects on air quality.

"There is no evidence of a threshold below which exposure to particulate matter is not associated with health effects," Dr Durrheim said.

The NSW Planning Department has recommended the mine's expansion be approved by the Independent Planning Commission, which is the determining body. It will hold a two-day public hearing on July 7-8, for which speakers must register by noon on Monday, June 27. Written submissions are accepted until 5pm, July 15.

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