EPA Administrator Scott Pruitt after speaking in Hazard, Kentucky, on Monday. Credit:AP It also is a personal triumph for Pruitt, who as Oklahoma attorney-general helped lead more than two dozen states in challenging the rule in the courts. In announcing the repeal, Pruitt made many of the same arguments that he had made for years to Congress and in lawsuits: that the Obama administration exceeded its legal authority in an effort to limit greenhouse gas emissions from power plants. (Last year, the Supreme Court blocked the rule from taking effect while courts assessed those lawsuits.) A leaked draft of the repeal proposal asserts that the country would save $US33 billion ($43 billion) by not complying with the regulation and rejects the health benefits the Obama administration had calculated from the original rule. Coa- and natural-gas-fired power plants are responsible for about one-third of the United States' carbon dioxide emissions. When the Clean Power Plan was unveiled in 2015, it was expected to cut power sector emissions 32 per cent by 2030, relative to 2005. While many states are already shifting away from coal power for economic reasons, experts say scrapping the rule could slow that transition. Environmental groups and several states plan to challenge the repeal proposal in federal courts, arguing against Pruitt's move on both scientific and economic grounds.

US President Donald Trump has said climate change is a Chinese hoax. Credit:AP Industry groups cheered the announcement, but have also indicated that they would prefer that Pruitt replace the Clean Power Plan with a new, more modest regulation on power plants in order to blunt any court challenges. The EPA is still required to regulate greenhouse-gas emissions because of a 2009 legal opinion known as the endangerment finding. "We have always believed that there is a better way to approach greenhouse gas emissions reductions," Karen Harbert, president of the American Chamber of Commerce's Global Energy Institute, said in a statement. "We welcome the opportunity for business to be at the table with the EPA and other stakeholders to develop an approach that lowers emissions, preserves America's energy advantage, and respects the bounds of the Clean Air Act." How would targets be changed? In order to regulate pollution from existing power plants, the EPA has to set goals for each state based on what's technically feasible and cost-effective. Under the Clean Power Plan, the Obama administration set targets by assuming utilities could improve the efficiency of their coal plants, shift from coal to cleaner natural gas, and add more renewable energy to their grids.

But Obama's approach was controversial, because the EPA assumed utilities could reduce emissions at individual plants by taking actions outside of those plants - say, by replacing coal plants with wind farms elsewhere. Industry groups and more than two dozen states challenged this move in court, arguing that the EPA can only look at clean-up measures that can be undertaken at the plants themselves. Pruitt is proposing to repeal the Clean Power Plan on this basis. He also argued that the Obama administration overstated the benefits of its rule by factoring in the gains from curbing global warming in other countries as well as from reducing harmful air pollutants other than carbon dioxide. If Pruitt does end up pursuing a replacement rule, it would almost certainly be confined to inside-the-fenceline measures, like upgrading coal-plant boilers. Previous EPA analyses found that such upgrades would lead to a roughly 4 per cent increase in efficiency at coal plants. What is the impact on emissions? While repeal of the Clean Power Plan offers a reprieve for the United States' coal industry, it is unlikely to halt the decline of coal altogether. Even in the absence of the rule, many utilities around the country have opted to shift to natural gas, wind and solar, driven by cost concerns and state-level policies. Many states, like California and New York, are already moving ahead of the targets set by the Clean Power Plan as they develop their own climate policies.

Colorado Governor John Hickenlooper, a Democrat, noted that his state planned to exceed the goals that had been set under the Clean Power Plan because the state was closing coal plants early and developing jobs in wind and other renewables. "We have dramatically cleaner air and we are saving money. My question to the EPA would be, 'Which part of that don't you like?'" Hickenlooper said. A new analysis by the research firm Rhodium Group estimated that US electricity emissions are currently on track to fall 27 to 35 per cent below 2005 levels by 2030, roughly in the range of what the Clean Power Plan originally envisioned, even if the regulation is repealed. Jody Freeman, director of the environmental law program at Harvard Law School, said the Energy Department proposal combined with the Clean Power Plan repeal signals the Trump administration is putting its thumb on the scale in favour of fossil fuels. "You see a pretty powerful message. Disavow any effort to control greenhouse gases in the power sector, and instead, intervene in the market to promote coal. It's a wow," she said.

What happens next? Pruitt's proposal for repeal will now have to go through a formal public-comment period before being finalised, a process that could take months. Pruitt will also ask the public for comment on what a replacement rule should look like, but the EPA has not offered a timeline. Loading Environmental groups and Democratic-controlled states are expected to challenge these moves on multiple fronts. New York Times