Climate scientists say an internal US Environmental Protection Agency memo on how officials should talk to the public about global warming doesn't reflect reality.
EPA's public affairs office put out "a set of talking points about climate change" to help the agency have a consistent message, the Huffington Post reported this week.
The Associated Press, which also obtained the memo, contacted 15 climate scientists.
They all said EPA wasn't accurately portraying the degree of knowledge that researchers know about climate change and humanity's role.
For decades, scientists have being saying that the burning of fossil fuels increases greenhouse gases, such as carbon dioxide, which trap heat and change the planet's climate in many ways.
EPA defended the memo.
"Human activity impacts our changing climate in some manner. The ability to measure with precision the degree and extent of that impact, and what to do about it, are subject to continuing debate and dialogue."
"To say that 'human activity impacts our changing climate 'in some manner', is analogous to saying the Germans were involved in WW II 'in some manner'," David Titley, a professor of meteorology at Pennsylvania State University and retired US Navy admiral, said in an email.
The EPA memo contradicts a November 2017 federal science report, signed off by 13 government agencies, including the EPA.
That report says the world has warmed 0.65°C since 1950 and that the likely human contribution to this was between 92% and 123%.
It's more than 100% on one end, because some natural forces - such as volcanoes and orbital cycle - are working to cool Earth, but are being overwhelmed by the effects of greenhouse gases, said study co-author Katharine Hayhoe of Texas Tech.
Hayhoe, one of the scientists who criticised the EPA memo, said the debate now is more about whether humanity's role is merely close to 100% of the warming or if it is it much more and offsetting natural cooling.
"While there has been extensive research and a host of published reports regarding climate change, clear gaps remain including our understanding of the role of human activity and what we can do about it."
Two scientists, Jonathan Overpeck, dean of environmental science at the University of Michigan, and Michael Oppenheimer at Princeton University each described the idea of gaps in scientific knowledge as "flat out wrong".
Scientists said there are some details that aren't completely known, but not gaps in knowledge about what is causing the problem and humanity's role.
"Suggesting that there are gaps that remain in our understanding of the role of human activity and possible solutions to the problem is false equivalence at its finest," said Kathie Dello, an Oregon State University climate scientist.
"We know it's us and we know what we have to do about it."
Asked to provide any sources for the agency's contention that the contribution of man-made carbon emissions in climate change is unsettled, EPA spokesperson Enesta Jones issued this statement:
"The talking points were developed by the Office of Public Affairs. The Agency's work on climate adaptation continues under the leadership of Dr (Joel) Scheraga."
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