The federal government on Friday released a massive report warning climate change is real and already having a devastating impact on the US — just days after President Trump mocked the idea of global warming.

The National Climate Assessment, a congressionally-mandated report by more than a dozen federal agencies, says climate change will bring more extreme weather disasters like wildfires, hurricanes and heat waves — and cost the economy hundreds of billions by the end of the century.

By that time, the country will be 3 to 12 degrees hotter, depending on how much action is taken to curb greenhouse gas emissions, the report warns.

“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 study says.

“The impacts of global climate change are already being felt in the United States and are projected to intensify in the future — but the severity of future impacts will depend largely on actions taken to reduce greenhouse gas emissions and to adapt to the changes that will occur.”

The report, which runs more than 1,600 pages, was issued two days after Trump riled scientists by tweeting: “Brutal and Extended Cold Blast could shatter ALL RECORDS – Whatever happened to Global Warming?”

The report left no doubt that the planet is heating up.

“Glaciers and snow cover are shrinking, and sea ice is retreating. Seas are warming, rising, and becoming more acidic, and marine species are moving to new locations toward cooler waters. Flooding is becoming more frequent along the US coastline,” the report reads.

In the last three years alone, the US “has experienced 44 billion-dollar weather and climate disasters” like hurricanes and fires — racking up a bill of around $400 billion, the study says.

“We are seeing the things we said would be happening, happen now in real life,” said co-author Katharine Hayhoe, a climate scientist at Texas Tech University.

The report estimates that deaths due to extreme heat will take a fiscal toll of between $60 billion and $140 billion by 2090, while $238 billion to $507 billion worth of real estate will be below sea level by 2100.

It also details how climate change could affect specific US regions.

In Northeastern states, rising sea levels are leading to an increase in coastal flooding that is set to get worse — and much of the region’s infrastructure isn’t up to the challenge, the report warns.

Property losses from hurricanes and other storms in the region could increase by $6 billion to $9 billion per year by the end of the century.

The report was supposed to come out in December, but the publication date was moved up to Friday — in a move some criticized as an attempt to bury the news on the busy shopping day after Thanksgiving.

With Post Wires