Global temperatures could be limited to 2C above pre-industrial era if greenhouse gas emissions are slashed but "without significant reductions, annual average global temperatures could increase by 9F (5C) or more by the end of this century", a previously released chapter states.

Even 2C warming is likely to have major ramifications for societies, as the recent Intergovernmental Panel on Climate Change (IPCC) report spelled out. Heating the planet well beyond this would create a "totally different world", said Michael Oppenheimer, a climate scientist at Princeton University.

"It would be indescribable, it would turn the world upside down in terms of its climate. There would be nothing like it in the history of civilization."

Oppenheimer, with many other scientists, has said warming of around 3C is more likely given the advance of renewable energy and expected emissions reductions in the future.

"That is more of an economic, political and technology question," a report author who wished to remain unnamed told the Guardian. "It's hard to say what we are on track for right now."

The draft report warned that the current response was insufficient to stave off the worst impacts, stating that "neither global efforts to mitigate the causes of climate change nor regional efforts to adapt to the impacts currently approach the scales needed to avoid substantial damages to the US economy, environment, and human health and well-being over the coming decades".

Another report author said: "Climate change is loading the dice against us, it's going to affect our water, food and ecosystems. This report is important because it shows it's already happening where we live, not on far off islands or at the poles."

Included in the dozens of draft report chapters:

• The summary states the "earth's climate is now changing faster than at any point in the history of modern civilization, primarily as a result of human activities. The impacts of global climate change are already being felt in the United States and are projected to intensify in the future."

• Average sea levels along the US coast have increased by around 9 inches since the early 20th century as the oceans have warmed and land ice has melted. If emissions are not constrained, "many coastal communities will be transformed by the latter part of this century".

• Fisheries, tourism, human health and public safety are being "transformed, degraded or lost due in part to climate change impacts, particularly sea level rise and higher numbers of extreme weather events".

• Wildfires have burned at least 3.7 million acres in the US in all but three years from 2000 to 2016. "More frequent and larger wildfires, combined with increasing development at the wildland-urban interface portend increasing risks to property and human life," the report states.

• More than 100 million people in the US live in places with poor air quality and climate change will "worsen existing air pollution levels". Increased wildfire smoke risks heightening respiratory and cardiovascular problems, while the prevalence of asthma and hay fever is also likely to rise.

• Major groundwater supplies have declined over the last century, with this decrease accelerating since 2001. "Significant changes in water quantity and quality are evident across the country," the report finds.

• Climate change will "disrupt many areas of life" by hurting the US economy, affecting trade and exacerbating overseas conflicts. Low-income and marginalized communities will be worst hit.

The national climate assessment is mandated by Congress to compile the latest research on climate change. The last report came out in 2014. Donald Trump has since announced the US will withdraw from the Paris climate deal, with his administration working to dismantle every major policy designed at lowering emissions.

The release of the report comes as California is racked by its most deadly wildfire on record, the so-called Camp fire, which razed the town of Paradise. At least 84 people have died and tens of thousands of people have had to flee the fire, which has occurred at the same time as a smaller blaze further south, near Los Angeles.

Trump has downplayed assertions by scientists and firefighters that climate change is making California more wildfire-prone, instead pointing to "gross mismanagement" of forest areas. Ryan Zinke, the interior secretary, has said conservationist lawsuits by "radical environmental groups" were to blame.

While visiting devastated parts of California last weekend Trump was asked if what he had seen and heard had changed his mind about climate change, which he has previously called a "hoax". Trump responded to the question with a firm: "No."

"When there are daily images of California burning up it's hard for the administration to argue climate change isn't happening," said Oppenheimer. "The strategy seems to be let sleeping dogs lie and hope the public doesn't pay much attention to it."