The former is forecast to rise steadily from 139 million tonnes in 2016 to 158 million tonnes by 2056, counter to expectations that thermal coal use will have to be cut if Paris climate goals - including net-zero emissions by developed nations by about 2050 - are to be met.

Coking coal, used to make steel, would almost double over the 40 years to 47 million tonnes by these predictions.

Even though nations burning NSW coal are accountable for the resulting emissions, the extraction and transport of the fossil fuel are sizeable contributors to the state's own pollution. The Berejiklian government has an aspirational goal of reaching net-zero emissions by 2050.

The NSW Minerals Council says the state is well-placed to grab a share of increased Asian demand for thermal coal that might top 400 million tonnes by 2030, citing researcher Commodity Insights.

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But Tim Buckley, an energy analyst with the Institute for Energy Economics and Financial Analysis, said growth forecasts for coal imply the world ignores the Paris targets.

"Under its Sustainable Development Scenario, the International Energy Agency forecasts seaborne thermal coal would decline by 65 per cent by 2040, and cease by 2050," Mr Buckley said.

"It is telling that NSW government forecasts for coal demand are entirely consistent with the 'forecasts' of the Minerals Council of Australia, a group that releases a 50-page 2018 report forecasting a rosy picture for thermal coal demand over the coming decades, but without even mentioning climate change," he said.

Mr Buckley said Japan currently takes 44 per cent of the state's thermal coal exports but major companies are already planning to reduce coal use. Itochu, a trading giant, last week announced it would stop developing new coal-fired power plants and thermal coal mines - a move marking "a major pivot" for the company, he said.

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'Critical decade'

"Anyone who understands climate change knows in this critical decade we should be phasing out coal mining, not ramping up production," said Cate Faehrmann, the Greens environment spokeswoman. She added she was "absolutely floored" to see the scale of expected coal shipments.

“Australians are battling devastating drought and horrific bushfires made worse by climate change, and yet the government is happily predicting that three times as much [thermal] coal will be dug up in NSW as is planned at the Adani mega-mine over the next decades," she said, referring to the Carmichael mine proposal in Queensland.

The NSW Minerals Council is pushing for NSW to back new coal-fired power plants, saying "multiple sets of polling conducted by the industry show greater than 60 per cent support", according to its election policy priorities.

A spokeswoman for Transport for NSW said it was "uncertain whether the existing coal power stations in Australia are being closed down without like-replacement".

"The Commonwealth government is considering the bids, which include coal-fired power stations," she said.

Transport's estimates contrast with the outspoken position of NSW senior ministers such as Don Harwin, the energy minister, who say the state must reduce reliance on coal for power generation.