What does Trump say about climate change?
The White House report, issued on Friday (Saturday AEDT), also frequently contradicted President Donald Trump.
The National Climate Assessment was written long before the California fires and the hurricanes.
Report co-author Katharine Hayhoe, of Texas Tech University, said "we are seeing the things we said would be happening, happen now in real life".
Earlier this week, the USA president appeared to deride the idea of climate change in a tweet about the weather.
"This report makes it clear that climate change is not some problem in the distant future".
Climate change is also projected to increase the frequency and severity of allergic illnesses, including asthma and hay fever. But, in a bright spot, the report also references local and worldwide action to reduce emissions, even while acknowledging those efforts won't be enough.
"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 report reads.
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While it said that numerous impacts of climate change - including more frequent and more powerful storms, droughts and flooding - were already underway, the projections of further damage could change if greenhouse gas emissions were sharply curbed.
The studies clash with policy under Mr Trump, who has been rolling back Obama-era environmental and climate protections to maximise production of domestic fossil fuels, including crude oil, already the highest in the world, above Saudi Arabia and Russian Federation. President Trump has been vocal in his skepticism about man-made climate change and the effects it is allegedly having both on temperatures and extreme weather events.
Trump tweeted this week about the cold weather hitting the East including: "Brutal and Extended Cold Blast could shatter ALL RECORDS - Whatever happened to Global Warming?"
The report is the second volume of a non-partisan work of science mandated by Congress to inform policymakers about the reality of global warming, and it represents a sweeping view of the scientific consensus.
White House spokeswoman Lindsay Walters did not immediately respond to a request for comment.
She also said the climate report "is largely based on the most extreme scenario" and called for future installments to have "more transparent and data-driven process that includes fuller information on the range of potential scenarios and outcomes" - a claim that one of report's lead authors said was "demonstrably false".
The United States already warmed on average 1.8 degrees Fahrenheit over the past century and will warm at least 3 more degrees by 2100 unless fossil fuel use is dramatically curtailed, scientists from more than a dozen federal agencies concluded in their latest in-depth assessment.
"With the lives and health of millions of Americans at risk from worsened hurricanes, droughts, wildfires and air pollution, we urge President Trump and his administration to heed the dire warnings in this report and reduce greenhouse gas emissions from power plants, vehicles and other sources to save American lives", said Harold P. Wimmer, national president of the American Lung Assn. The document was originally scheduled for a mid-December release, but officials said at the last minute they would publish it on the Friday after Thanksgiving.