President Barack Obama has declared climate change to be the greatest threat to the future of the planet in a passionate White House speech on the details of his plan to cut US carbon emissions by 32 per cent by 2030 compared with 2005 levels.
"Climate change is no longer just about the future that we're predicting for our children or grandchildren, it's about the reality that we're living with every day," he said.
"We are the first generation to feel the impacts of climate change, and the last generation to be able to do something about it."
The address outlined the first plan in the US to mandate reductions in carbon emissions from coal-fired plants, by far the nation's largest single source of climate change gasses.
The move signals that Mr Obama is determined to use the full force of his authority to act on climate change in the last 18 months of his presidency. It confirms that he believes that only by taking strong domestic action will the US be in a position to lead the world in coming to an agreement to significantly reduce global carbon emissions in the upcoming Paris climate talks.
It also suggests that the President wants to see climate change become a central issue in the 2016 election.
Under what is already being referred to as the Obama Rule, the administration – via the Environmental Protection Agency –will set each state an emissions-reduction target based on their existing energy consumption. The states would then draft their own plans to meet those targets, and would receive financial incentives for meeting or beating the targets.
The President said the plan would avoid up to 3600 premature deaths and lead to 90,000 fewer asthma attacks in children, while saving consumers $US155 billion ($213 billion) in energy bills between 2020 and 2030 due to the lower cost of renewables.
The Republican response was swift and savage.
"Climate change will not be solved by grabbing power from states or slowly hollowing out our economy. The real challenge is how do we grow and prosper in order to foster more game-changing innovations and give us the resources we need to solve problems like this one," GOP candidate Jeb Bush said.
The Republican Party's Senate majority leader Mitch McConnell described the plan as "a triumph of blind ideology over sound policy and honest compassion".
Senator Ted Cruz, who is also running for the Republican nomination, called it a "lawless and radical attempt to destabilise the nation's energy".
Indeed, all of the Republican candidates for the 2016 election – aside from the nearly forgotten George Pataki – either deny that climate change exists or argue it is not worth mitigating.
It is expected that some Republican state governors will challenge the President's authority to enforce his plan in the courts.
By contrast all the Democratic candidates acknowledge climate change and back the plan, with Martin O'Malley and Hillary Clinton, vowing to adopt it and go further.
President Obama has been determined to act on climate change since he won re-election.
The President pressed Congress to pass a cap and trade system in 2009, but failed to win enough support.
Since then he has used his own authority to take action, including directing funds from stimulus measures to renewable energy projects and mandating strict new fuel economy provisions.
Last month he announced a program to help low and income families get access to rooftop solar power.
Soon after his re-election in 2012 Mr Obama discussed possible measures he could take in his second term with a climate adviser Heather Zichal. She recommended that he "throw everything he can" into the issue, she told The National Journal.
"His immediate reaction wasn't, 'Well, what do you think the politics of that are, or wouldn't it be hard to do?' There was no question," Ms Zichal recalled. "It was just, 'That's a great idea. But we have to go big, and we have to go bold.'"
