The natural conservatism of science has often led climatologists to be cautious in their pronouncements about global warming.

More than once they have drawn criticism for burying their fundamental message – that society is running some huge risks — in caveats and cavils.

To judge from the draft of a new report issued by a federal advisory committee, that hesitation may soon fall by the wayside. The draft, just introduced for public comment before it becomes final, is the latest iteration of a major series of reports requested by Congress on the effects of climate change in the United States.

I caution that it is a draft, so we don’t know what final language will make it into the report. I am always hesitant to give too much credence to drafts that could change substantially, but in its current form, the document minces no words.

“Climate change is already affecting the American people,” declares the opening paragraph of the report, issued under the auspices of the Global Change Research Program, which coordinates federally sponsored climate research. “Certain types of weather events have become more frequent and/or intense, including heat waves, heavy downpours, and, in some regions, floods and droughts.

“Sea level is rising, oceans are becoming more acidic, and glaciers and Arctic sea ice are melting. These changes are part of the pattern of global climate change, which is primarily driven by human activity.”

When it is final, this report will be an official document of the United States government. Let it be noted that this aggressive language about climate change comes two months after the end of a presidential campaign in which the subject was barely mentioned, to the frustration of a great many voters.

That climate silence occurred partly because the television reporters moderating the presidential debates did not pose a single question on the topic.

For some reason, the government put out this draft without the usual advance notice to journalists that accompanies major federal reports, so I confess I have not yet had time to read all 1,193 pages. But I did spend Monday trolling through big sections of the report.

If it survives in substantially its current form, the document will be a stark warning to the American people about what has already happened and what is coming.

“Climate change, once considered an issue for a distant future, has moved firmly into the present,” the draft document says. “Americans are noticing changes all around them.

“Summers are longer and hotter, and periods of extreme heat last longer than any living American has ever experienced. Winters are generally shorter and warmer. Rain comes in heavier downpours, though in many regions there are longer dry spells in between.”

The report cites stronger scientific evidence—developed since the last report of this type was published in 2009—that human activities, especially the burning of fossil fuels, are the primary cause of these changes.

It warns that if humanity fails to get a handle on emissions, the changes are likely to accelerate. And it cites numerous ways, from health problems to wildfires to extreme weather events, that climate change threatens human welfare – not in some distant land in some far-off time, but here in the United States, and soon.

As I mentioned, the authors of the report, led by Jerry Melillo of the Marine Biological Laboratory in Woods Hole, Mass., are asking for public comments, due by April 12.

This page is an overall interface that allows people to download the draft by chapter or in its entirety, while you need to go to this page and create a login to make comments on the draft.

By Justin Gillis – green.blogs.nytimes.com