The White House opened its gates to a gaggle of science reporters Tuesday as administration officials and scientists released a much-anticipated assessment of global warming’s impacts on the United States. The message – global warming is upon us – was delivered clearly and forcefully, several times over.

Hardly a novel finding, but, in a sign of the times, the audience proved receptive. The report echoed over the wires (see the Washington Post, New York Times) and filled up email in-boxes as environmental groups and politicians put their seal on the document.

President Barack Obama’s chief science adviser, John Holdren, called the report “the most up-to-date, comprehensive and authoritative assessment” of global warming in the United States. The document focuses on regional impacts, he added, “talking about climate where people actually experience it: in their back yards.”

At 196 pages, the document represents the final installment in a series of 21 assessments produced under the auspices of the Global Change Research Program, itself part of the US Climate Change Science Program. An earlier version of the document attracted some criticism last year, in part because it was released for public comment before the rest of the assessments were complete, but everything worked out in due course.

The report incorporates the work of the Intergovernmental Panel on Climate Change as well as more recent studies regarding key issues like rising sea levels. Indeed, many scientists say the IPCC’s fourth assessment underestimates the danger of rising seas – simply because it’s out of date. On this particular issue, the report’s co-chair, Jerry Melillo, a biologist at the Marine Biological Laboratory in Woods Hole, Massachusetts, says the team projected a potential sea-level rise of up 3 or 4 feet by the end of the century – enough to wipe out the southern tip of Florida.

Speakers at Tuesday’s press conference were careful to stick to the science, despite repeated attempts by journalists to draw them out. Holdren, for instance, declined to weight in on whether politicians who read the report would be wise to vote in favor of climate change legislation that might come up for a vote in the House of Representatives in the coming weeks. Nonetheless, the message rang true.

“Climate change is happening now,” said Jane Lubchenco, who heads the National Oceanic and Atmospheric Administration, the lead agency on the report. Climate trends are worrisome, indeed, she said, but it’s not too late to act. “Trends are not destiny.”