Unchecked climate change will cost the US hundreds of billions of dollars and damage human health and quality of life, a US government report warns.
"Future risks from climate change depend... on decisions made today," the 4th National Climate Assessment says.
The report says climate change is "presenting growing challenges to human health and safety, quality of life, and the rate of economic growth".
The warning is at odds with the Trump administration's fossil fuels agenda.
During a blast of icy weather in Washington this week, Donald Trump tweeted, "whatever happened to global warming?"
Now, without mentioning the president, his own scientists have answered their boss's question in comprehensive detail.
Global warming is here in the United States, they say - now. It is already deadly serious and without urgent, dramatic change, it will be catastrophic.
This report is striking for two reasons. First, it is not abstract. It gives many specific examples - overwhelmed dams in South Carolina; failing crops in the parched Great Plains; a rise in insect-borne disease in Florida.
And, secondly, it majors on the economic impact, in effect challenging the White House's insistence on prioritising economic growth over environmental regulation.
With warnings about the effects on crumbling infrastructure, falling crop yields and decreasing labour productivity, the report sounds an alarm that climate change will soon cascade into every corner of American life.
The White House said the report - compiled with help from numerous US government agencies and departments - was inaccurate.
Spokeswoman Lindsay Walters said it was "largely based on the most extreme scenario, which contradicts long-established trends by assuming that... there would be limited technology and innovation, and a rapidly expanding population".
The world's leading scientists agree that climate change is human-induced and warn that natural fluctuations in temperature are being exacerbated by human activity.
Source: bbc