Science shows that nothing does more to cause climate change than burning coal, a former head of the U.S. Environmental Protection Agency (EPA) said on Tuesday, a position in contrast to President Donald Trump's pro-fossil fuel policies.
Trump announced last year that the United States would quit a 2015 global climate pact, citing concerns for the U.S. economy and touting fossil-fuel energy anew but alarming nearly 200 signatories to the accord including close U.S. allies.
On Monday, a U.N. report said that even limiting global warming to 1.5 degrees Celsius (2.7 degrees Fahrenheit), below the 2 degree target agreed in Paris, would entail rapid and unprecedented changes across every aspect of society or the world risks even more extreme weather and loss of species.
Without real change, the world is not even on course to reach the 2C target, according to the Intergovernmental Panel on Climate Change (IPCC) report, the main scientific guide for governments on how to implement the Paris Agreement.
"We have big challenges ahead of us and I think that is what the (report) has told us...a low-carbon future is better. From a climate perspective, nothing is worse than burning coal," former EPA administrator Gina McCarthy told a Financial Times climate finance summit in London.
"I would like to see climate change presented as what science is telling us rather than a political statement, which is what many in the U.S. are positioning it as," she added, referring to the Trump administration.
Under the Paris Agreement rules, the United States cannot actually pull out of the pact until late 2020.
"The U.S. is pretty much on target to reach its (climate) targets at least in the short-term - the market is driving this," said McCarthy, who ran the EPA under Trump's predecessor Barack Obama from 2013-2017.
"Markets drive change more quickly than regulation. Governments are not going to be the ones which make it run as fast as it needs to."
But Trump aims to roll back many environmental rules put in place by Obama, such as acting to replace a clean power plant policy with weaker environmental rules for such plants.
The U.S. government also intends to freeze mandates that ensure new cars pollute less and cut limits on the greenhouse gas methane that is released during oil production.
McCarthy said such moves, however, do not necessarily translate into action.
"The announcements and proposals made by the new administration have not been finalised, they are not based on science and the law, and that is not exactly a winning formula when you go to the courts," she said.
"There is a long process behind all of this and eventually they will end up in the courts for a long period of time. Those rules were solidly done and based on science and the law, and it will take a lot to do undo them."
The IPCC report will be a talking point at the Katowice Climate Change Conference in Poland in December.