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Embattled climate scientists working in 13 various US government agencies threw down the gauntlet before the Trump administration by releasing an over 600-page report on climate change in the US, the work of several years intended to comply with a Congressional requirement for such a report every four years.

The scientists involved in releasing the leaked document — the fifth draft of the 2018 report — told the Times they were releasing the document early in draft form for fear that the Trump Administration and Trump’s Environmental Protection Agency Administrator, climate change denier Scott Pruitt, would attempt to deep-six, or at least drastically revise their work and conclusions.

Their fears are understandable. Trump has called climate change a hoax and a Chinese conspiracy designed to harm the US, and Pruitt, while recently at least acknowledging that the global climate is getting hotter, claims that it is both impossible to know to what extent human activity is to blame, and that the trend going forward is impossible to predict.

The latest report, however, debunks all of those ignorant assertions by the country’s current leadership, warning that the warming trend both globally and in the US is undeniable, and dire.

According to the document, which is dated June 28 and titled “US Global Change Research Program: Climate Science Special Report” (CSSR):

“Since the last National Climate Assessment was published (in 2014), 2014 became the warmest year on record globally, 2015 surpassed 2014 by a wide margin; and 2016 surpassed 2015. Sixteen of the last 17 years are the warmest years on record for the globe.”

The report goes on to state that “many lines” of scientific evidence “demonstrate that it is extremely likely” (meaning 95-100% certain) “that human influence has been the dominant cause of the observed warming since the mid-20th century.” They explain that “There are no convincing alternative explanations supported by the extent of the observational evidence. Solar output changes and internal natural variability can only contribute marginally to the observed changes in climate over the last century, and we find no convincing evidence for natural cycles in the observational record that could explain the observed changes in climate.”

The grim picture looking out to 2100, which it must be noted is easily within the lifetime of children living today:

“With significant reductions in emissions of greenhouse gases, the global annually averaged temperature rise could be limited to 3.6 degrees Fahrenheit or less. Without major reductions in these emissions, the increase in annual average global temperatures relative to pre-industrial times could reach 9 degrees Fahrenheit or more by the end of this century.”

Think about that last number. Imagine average temperatures where you live in summer rising by 9 degrees. This year, the temperature in Phoenix has been hitting 120. Adding nine degrees to that would make it a fatal risk to go outside for most people, even briefly. Even in the Northeast, it would mean many 100+ degree days in summer, which would preclude outdoor work like construction, roadwork, yard work or farming.

The study, in terms of its global conclusions, was based upon the last report of the United Nations Intergovernmental Panel on Climate Change, released in 2014. That data, though, has already been overtaken by events, from the unanticipated thawing of the ice sheet in Antarctica, to the ongoing pace of melting of both the ice sheet on Greenland and the ice sheet that covers the Arctic Ocean, now close to disappearing during the summer months, and even this past winter suffering some melting episodes. Also not anticipated in the last IPCC report was the dramatic melting of permafrost, both in the Siberian and North American tundra regions, and also under the shallow parts of the Arctic Ocean north of Siberia, Alaska and Canada. That melting is starting to release vast quantities of long-trapped CO2 and worse yet, methane gas — a global warming chemical that is anywhere from 20-80 times as powerful as carbon dioxide and which could set off a runaway warming that could make the planet more like Venus than Earth.

The government scientists don’t talk about that possibility, but they do say that a 9-degree increase in global and US temperatures by then end of this century is a possibility if nothing is done soon to slow or reverse the continued pumping of more carbon into the atmosphere. And that is now increasingly likely given the Trump administration’s troglodyte and anti-science insistence on rolling back all Obama and Bush-era efforts to reduce carbon-based fuel use in cars, trucks and power plants.

But the report doesn’t limit itself to talking about temperatures rising.

It talks too about sea-level rise, increasing ocean acidification, and weather changes such as more powerful storms, worsening droughts and flooding, and of course threats to food supplies as droughts and intense weather events expand and increase in severity and frequency.

In the case of sea-level rise, the report says seas worldwide have risen an average of 7 inches since 1900. That might not seem like a lot to an landlubber, but for someone with a home near the shore it can mean the difference to having your house survive a major storm or wash away. Furthermore, they note that sea levels are rising at the fastest rate they have risen in 2000 years, and that the pace is accelerating. Using 2014 IPCC data, the projections are for sea level to rise by another 1-4 feet by 2100, but that doesn’t include new evidence of melting in Antarctica, which if it continues could mean a sea-level rise of 8 feet globally by the end of this century! Moreover that would not be the end of it. The rise would continue as increased global warming in turn leads to an increased rate of ice melting at both poles (which between them have enough water to raise the world’s oceans by over 200 feet.

Perhaps more serious for the US over the near term, is the potential slowing down and reduction in volume of the Atlantic Meridional Overturning Circulation (AMOC), of which the Gulf Stream is a major part, the part which keeps the winters moderate along the Eastern Seaboard and in the UK and western Europe. “Under the high emissions scenario,” the scientists write dryly, “it is likely that the AMOC will weaken over the 21st century by 12% to 54%.” (A few years ago, a branch of the Gulf Stream that cuts across the mid-Atlantic to Europe simply stopped for a few weeks, to the consternation and terror of oceanographers, who couldn’t explain it, but breathed a sigh of relief when it started back up again.)

Turning to ocean acidification — which is increasing as the oceans have absorbed a quarter of the increased human-caused atmospheric carbon over the past century — the report notes that while this process has helped keep climate change in check for the past century, at the same time it has increased the acidity of the ocean at a rate not seen since the end of the dinosaur age 66 million years ago. That acidification is expected to continue to increase by 100-150% over the rest of the century, with devastating consequences for marine life and ultimately life on land too, from sea birds to humans. The base of the marine food chain is plankton most of which construct calcium-based exoskeletons which are now being eaten away by the increasing acidity of the water. If the plankton die, so do the fish that feed on them, and on up the chain to mammals and of course us humans. Dissolved oxygen in the oceans is also in decline, down by about 3.5% over the past decades, because of warming waters and decreased circulation, they note.

The government scientists, for the first time in such a document, also warn about the risks posed by the melting permafrost and the almost inevitable release of vast quantities of currently frozen and locked up carbon and methane gas. As they put it:

“Rising Alaskan permafrost temperatures (they don’t mention the must vaster permafrost regions in Canada and Siberia) are causing permafrost to thaw and become more discontinuous; this process releases additional carbon dioxide and methane resulting in additional warming. The overall magnitude of the permafrost-carbon feedback is uncertain; however it is clear that these emissions have the potential to complicate the ability to meet policy goals for the reduction of greenhouse gas concentrations.”

That’s an understated way of saying: All the plans, promises and commitments of the Paris Agreement could be pointless if the methane starts pouring out of the ground in the currently frozen but thawing north. And indeed, recent images of huge craters in Siberia, apparently caused by giant bursts of erupting methane, suggest that a catastrophe is already in the making in those regions.

Finally, in their executive summary, the scientists issue a warning, which the Trump administration, and the American people as a whole, including all those who put Trump in the White House, and climate denying Republicans in charge of Congress, deny at their own and all of our peril. They say:

“Humanity is conducting an unprecedented experiment with the Earth’s climate system through emissions from large-scale fossil-fuel combustion, widespread deforestation, and other changes to the atmosphere and landscape. While researchers and policymakers must rely on climate model projections for a representative picture of the future Earth system under these conditions, there are still elements of the Earth system that models do not capture well. For this reason, there is significant potential for humankind’s planetary experiment to result in unanticipated surprises — and the further and faster the Earth’s climate system is changed, the greater the risk of such surprises. “There are at least two types of potential surprises: compound events, where multiple extreme climate events occur simultaneously or sequentially (creating greater overall impact), and critical threshold or tipping point events, where some threshold is crossed in the climate system (that leads to large impacts). The probability of such surprises — some of which may be abrupt and/or irreversible — as well as other more predictable but difficult-to-manage impacts, increases as the influence of human activities on the climate system increases.”

It’s too much to hope that a president who thinks and functions in 140-letter Tweets, and who cannot seem to keep his mind focussed in speeches through one complete sentence, will read even the 23-page executive summary of this frightening report by “his” own scientists, much less the whole 600 pages of the full thing. His EPA stooge Pruitt probably will be too busy trying to find and punish the leakers to even look at it beyond the first pages listing the authors and contributors. But unless some people in government read it and understand its clear warning, and unless American newsrooms move beyond their breathless focus on alleged Russian meddling in the last election and on the latest Bachelorette scandal, the question will not be whether America can be “great again,” but whether there will be any America at all to speak of, come 2100.