Greenhouse gas emissions, also referred to as Scope Three or downstream emissions, were cited as part of the reasons for refusing the proposed Rocky Hill and Bylong mine projects.

Planning Minister Rob Stokes introduced legislation on Thursday to remove part of a clause in the State Environmental Planning Policy (Mining, Petroleum and Extractive Industries) 2007 that would prevent the consideration of downstream emissions.

The government has argued the proposed revised legislation was necessary to "clarify concerns" around the export of coal.

It follows an intensive campaign by the NSW Minerals Council that urged the government to change the law.

But an open letter signed by more than 40 scientists, climate experts, economists and academics, says the emissions generated by burning coal were the main source of emissions from coal mined in NSW.

"We strongly urge the NSW government not to cave in to pressure from coal lobbyists to overrule NSW laws that require the full climate impact to be considered in the assessment of new coal mines," the letter, coordinated by The Australia Institute, said.

"...We also strongly urge the government to defend its own Independent Planning Commission against unwarranted and misleading attacks."

Signatories include climate scientists Professor Will Steffen, from the Australian National University, Professor Katrin Meissner from the UNSW's Climate Change Research Centre.

The Lock the Gate Alliance said the proposed legislation was an attempt to blindfold the Independent Planning Commission and pretend that because most of the state's coal is burned somewhere else the effect of the consequent greenhouse pollution was irrelevant.

"Given that the burning of coal in power stations is one of the primary causes of global heating world-wide and in Australia, it is extraordinary that the minister is going to erase the consideration of that impact during assessment of coal mining projects," Lock the Gate spokeswoman Georgina Woods said

"You can't erase the impacts of climate change by blinding yourself to its causes.

"The only way we are going to deal with the climate crisis is by being honest about what role we're playing in it, and the effect it is having and will have on the water, weather and liveability of our state."

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