US President Donald Trump is poised to back out of the landmark global deal to tackle climate change agreed in Paris last year in what could prove to be a major blow in curbing dangerous carbon emissions.
The Paris Agreement commits almost 200 countries to ensure that the average global temperature doesn't rise by more than 2C above pre-industrial levels, by cutting down on high-carbon energy and fuels, the Daily Telegraph reports.
The UN deal was hailed by former US President Barack Obama as a "turning point" in the fight against climate change which would "open the floodgates for low-carbon innovation at a scale we haven't seen before".
But Trump's latest attack on his predecessor's political legacy could have far-reaching implications.
Why would Trump back away from the table?
Trump has no truck with environmental concerns. He has frequently referred to climate change as "a hoax" and would sooner prioritise safeguarding US industry than sticking to green goals.
He campaigned heavily on his promise to protect the interests of US businesses, the largest of which include oil supermajor ExxonMobil as well as motor vehicle manufacturers Chevron and General Motors. Interestingly, however, the leaders of the world's biggest oil companies - BP, Shell Exxon, Total, Eni - have urged the US to respect the agreement.
Trump is also on a mission to resurrect the floundering US coal industry and support the nation's booming shale frackers.
US shale is less carbon-intensive than coal and oil but not low enough to pay a long-term role in tackling climate change in compliance with the Paris pact.
What does this mean for Barack Obama's legacy?
Obama was one of the most enthusiastic cheerleaders for the Paris deal.
Indeed, he was instrumental in metaphorically banging heads together at a Copenhagen climate summit, which set the stage for the Paris agreement.
On signing the deal, in September 2016, he said: "One of the reasons I ran for this office was to make sure that America does its part to protect this planet for future generations."
And he frequently stated that leading the fight against climate change was one of his proudest accomplishments.
"Over the past seven and a half years, we've transformed the United States into a global leader in the fight against climate change," he said.
"We have a saying in America - that you need to put your money where your mouth is. And when it comes to combatting climate change, that's what we're doing, both the United States and China. We're leading by example."
But Trump was elected in many ways as "the anti-Obama". American voters deliberately chose someone who promised to unpick Obama's work.
What does this mean for the Paris Agreement?
Climate policy leaders are concerned that a US exit from the Paris Agreement could throw the entire deal into disarray.
The US is the world's richest polluting country and its exit from the deal could prompt others to back out too if they believe the US has gained an unfair advantage in the global economy - although China and India, the other large polluters, are not thought likely to rescind the deal.
Smaller countries may view the agreement as a futile endeavour in the face of billowing emissions from the US, which is the second most polluting country on the planet, behind China.
To date, no other countries have signalled a desire to follow suit. China and India have both reaffirmed their commitment to the deal alongside continued commitment from the European Union.
But Russia, one of the world's largest fossil fuel producers, has yet to ratify the deal. Many are concerned that the lack of US involvement could still severely weaken the global commitment to the deal in the years ahead.
What does the rest of the world think?
UN secretary general António Guterres fired a warning shot this week saying that nations that choose not to rapidly shift away from fossil fuels will be "left behind" to face a "grey future".
"Some may seek to portray the response to climate change as a fundamental threat to the economy. Yet what we are witnessing in these early years of a systemic response is the opposite," he said.
Behind closed doors the EU is reportedly in talks with China to reveal a new green alliance this week. The Financial Times has reported that the two have agreed to measures to accelerate the "irreversible" shift away from fossil fuels and the "historic achievement" of the Paris agreement.
An optimistic minority have suggested that the departure of the US from the pact could make it easier for the remaining signatories to push through more ambitious targets at the group's next meeting in four years time.
What could this mean for climate change?
In short: climate change efforts are likely to fall short of the ambition to limit global warming, and cost far more to achieve even that.
Obama was clear when he signed up to the pact that global co-operation is paramount. "No nation, not even one as powerful as ours, can solve this on its own - we have to do this together," he said.
One of the major benefits of a global pact is that the scale at which low-carbon technologies would be enormous, and help to drive down costs quickly. Without the US the cost curve could remain higher for those who pursue this route.
In addition, US funding to tackle climate change may also be cut. The US has made US$3 billion available through a climate fund to help developing countries, of which US$1bn has been deployed. There's no guarantee that there will be any more where that came from.
Do we need to worry?
The catastrophic effects of climate change are well-understood and are already beginning to emerge. Rising sea levels, severe weather events, and food shortages due to crop damage could all increase in the years to come.