A federally mandated report set for release Friday will provide an in-depth examination of how climate change is already affecting Americans.

The National Climate Assessment is prepared by the nation's top scientists every four years for the president, the Congress and the public. This is the fourth such report. The last version, released in 2014, was the largest, most comprehensive U.S.-focused climate change report ever produced.

The National Oceanic and Atmospheric Administration said the report is an "authoritative assessment of the science of climate change with a focus on the U.S., and serves as the foundation for efforts to assess climate-related risks and inform decision-making about responses."

A draft of the report released in August found human activities are causing the average temperature to quickly rise in the U.S., and Americans are already feeling the impact of climate change. Scientists from 13 federal agencies also found that recent decades have been the warmest of the past 1,500 years.

It also said “many lines of evidence demonstrate that human activities, especially emissions of greenhouse (heat-trapping) gases, are primarily responsible for recent observed climate change.”

The draft report concluded that even if humans immediately stopped emitting greenhouse gases, the world would still feel at least an additional 0.50 degrees Farenheit of warming over this century compared to today. Since that is unlikely, the projected actual rise is more than 3 degrees, according to the report.

More:Draft climate change report at odds with Trump administration

On Wednesday, a group of nine Democratic senators, led by Al Franken, D-Minn., sent a second letter to Commerce Secretary Wilbur Ross, asking what the Trump administration will do with the report findings and how the president will be briefed on climate change.

"Unless serious action is taken to rapidly reduce emissions, the United States will continue to warm several degrees over this century, with damages to infrastructure, ecosystems, and human health," the letter said.

The second part of the assessment — which focuses on the impacts of climate change on human systems and ecosystems — will be released as a draft for public comment Friday, NOAA said.

The expected contents of the report contradict claims by President Trump and his team, who have continually downplayed the human contribution to climate change and questioned the ability of scientists to predict its effects.

Earlier this year, President Trump said he planned to withdraw the U.S. from the landmark Paris climate agreement, which requires countries to establish ambitious targets to reduce the greenhouse gasses that cause global warming.

Contributing: John Bacon, USA TODAY