The country’s shale gas boom has exacerbated the coal industry’s own commodity price concerns, and the Sierra Club’s own research indicates a rosy future outlook spearheaded by natural gas.

“We project that as a result of recent coal retirements, as well as advocacy for related policy measures like efficiency and demand response and market forces including historically low natural gas prices, electric sector coal use in 2015 will be approximately 9% lower than in 2014, from 772 million tonnes to 704MMt,” the Sierra Club’s report said.

That would pull coal’s share of electric power generation down from 40% to an historic low of 36% this year.

Total installed capacity of US coal-fired electric generating units will drop below 300,000MW for the first time in more than two decades, the report said.

The report, Accelerating the US coal phase out, the group says an “unprecedented” wave of coal plant retirement had yielded deeper economy-wide carbon reductions for this year than those laid out in the comprehensive climate legislation contained in the Waxman-Markey bill which the US Senate failed to pass in 2010.

The coal plant retirements will see US carbon emission cuts meet or even exceed the Clean Power Plan’s 2030 target by up to five years ahead of schedule, the group said.

The Intergovernmental Panel on Climate Change, International Energy Agency and the Energy Information Administration have all said that hydraulic fracturing and the resultant increased use of natural gas have sent US CO2 emissions to a 27-year low.

North America’s upstream industry saw some irony in the Sierra Club’s apparent begrudging admission, given it was responsible for the “Beyond Natural Gas” campaign which sought to end the use of natural gas.

“In a hypothetical scenario set forth in the report in which all US coal-burning power plants set to retire in the next 10 years were replaced exclusively with natural gas rather than with renewables, the Sierra Club projects CO2 emissions would continue to plummet,” the Independent Petroleum Association of America noted in a blog this week.

The Sierra Club’s analysis said that while a 100% renewable scenario would, of course drive emissions even lower, the IPAA said such a scenario was not realistic.

The EIA estimates that by 2040 80% of the US’s energy will still be fossil fuel-based, and renewables will need gas to grow into a more substantial part of the country’s energy mix.

“So let’s get this straight: the Sierra Club opposes a technology that its own research shows will help address its No 1 environmental concern – global warming – by reducing carbon emissions,” the IPAA said.

“Maybe that’s why – in an attempt to save face – the organisation has been forced to take the delusional stance that its ‘Beyond Coal’ campaign is solely responsible for coal plant retirements heading into December’s climate change conference in Paris.”

The Sierra Club’s report stated that, “… as a result of our work, buoyed by plummeting clean energy prices, we have secured record coal retirements over the past five years, catapulting the US into a leadership role in transitioning our economy to lower-carbon sources of energy”

Not happy to stop there, the group’s goal is to “lock in” for retirement and replace with clean energy at least half the US coal fleet – about 166,000MW – by no later than 2025.

“Once we count those coal megawatts already retired, announced or proposed to retire, only 70,711MW remain to hit the Beyond Coal campaign’s 166,000MW target,” the group said.