Massive Government Report Says Climate Is Warming And Humans Are The Cause
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It is "extremely likely" that human activities are the "dominant cause" of global warming, according to the the most comprehensive study ever of climate science by U.S. government researchers.
The climate report, obtained by NPR, notes that the past 115 years are "the warmest in the history of modern civilization." The global average temperature has increased by about 1.8 degree Fahrenheit over that period. Greenhouse gases from industry and agriculture are by far the biggest contributor to warming.
The findings contradict statements by President Trump and many of his Cabinet members, who have openly questioned the role humans play in changing the climate.
"I believe that measuring with precision human activity on the climate is something very challenging to do," EPA Administrator Scott Pruitt said in an interview earlier this year. "There's tremendous disagreement about the degree of impact."
That is not consistent with the conclusions of the 600-plus page Climate Science Special Report, which is part of an even larger scientific review known as the fourth National Climate Assessment. The NCA4, as it's known, is the nation's most authoritative assessment of climate science. The report's authors include experts from leading scientific agencies, including the National Oceanic and Atmospheric Administration, NASA and the Department of Energy, as well as academic scientists.
The report states that the global climate will continue to warm. How much, it says, "will depend primarily on the amount of greenhouse gases (especially carbon dioxide) emitted globally." Without major reductions in emissions, it says, the increase in annual average global temperature could reach 9 degrees Fahrenheit. Efforts to reduce emissions, it says, would slow the rate of warming.
"This is good, solid climate science," says Richard Alley, a geoscientist at Penn State University who says he made minor contributions to the report's conclusions on sea level rise. "This has been reviewed so many times in so many ways, and it's taking what we know from ... a couple of centuries of climate science and applying it to the U.S."
The assessments are required by an act of Congress; the last one was published in 2014. Alley says this year's goes further in attributing changes in weather to the warming climate, especially weather extremes. "More heat waves and fewer cold snaps, this is very clear," he says. The report also notes that warmer temperatures have contributed to the rise in forest fires in the West, and that the incidence of those fires is expected to keep rising.
Some of the clearest effects involve sea level rise. "Coastal flooding, you raise the mean level of the ocean, everything else equal you get more coastal flooding," Alley says. The report notes that sea level has risen 7 to 8 inches since 1900, and 3 inches of that occurred since 1993. The report says that rate is faster than during any century over the past 2,800 years.
The report also points out that heavy rainfall is increasing in intensity and frequency across the U.S., especially in the Northeast, and that's expected to keep increasing.
Other connections are harder to nail down, Alley says, such as whether a particular hurricane can be attributed to climate change.
"The Climate Science Special Report is like going to a doctor and being given a report on your vital signs," says environmental scientist Rachel Licker of the Union of Concerned Scientists. She notes that the authors assessed more than 1,500 scientific studies and reports in making their conclusions.
Alley adds that the new report "does a better job of seeing the human fingerprint in what's happening." He says that while he hasn't read all of it yet, he sees no evidence that it has been soft-pedaled or understates the certainty of the science.
Alley notes that "there's a little rumbling" among climate scientists who are concerned that the Trump administration will ignore this effort. "I think the authors really are interested in seeing [the report] used wisely by policy makers to help the economy as well as the environment."
The report has been submitted to the Office of Science and Technology Policy at the White House. Trump has yet to choose anyone to run that office; it remains one of the last unfilled senior positions in the White House staff.
On Friday, thirteen agencies within the United States government jointly issued the Climate Science Special Report, declaring that roughly 90% of climate change is caused by human activity, most notably the production of  by the burning of .  This directly contradicts assertions made by politicians within the administration of the current president, Donald Trump.

The report notes, "It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century... For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence."

Officially, the report was submitted through the Trump Administration's Office of Science and Technology Policy, to which President Trump has not appointed a head. The official response from the rest of the White House, given to the press by White House spokesperson Raj Shah, reads as follows: "The climate has changed and is always changing. As the Climate Science Special Report states, the magnitude of future climate change depends significantly on 'remaining uncertainty in the sensitivity of Earth's climate to  emissions... In the United States, energy related carbon dioxide emissions have been declining, are expected to remain flat through 2040, and will also continue to decline as a share of world emissions."

The report clocks in at roughly 500 pages and places the human contribution to the increase in the Earth's temperature at 92–123% since 1950.  As explained by co-author Katherine Hayhoe, the space over 100% indicates counteraction of forces that have a cooling effect, like sun-blocking dust kicked into the upper atmosphere by .  Overall, the report calls the past 115 years "the warmest in the history of modern civilization."

The study cites several factors, called "tipping points," that might make global climate change more intense, such as changes in  and other major patterns in ocean currents, the loss of arctic and antarctic ice sheets, and the release of methane, a greenhouse gas, from rotting material as previously  ground begins to thaw and cites both the wildfires in California and  for effects due to global climate change.  It predicts one scenario in which ocean levels rise as much as 8  (2.4 ) by the year 2100.

Unlike with previous studies on climate change released by U.S. government agencies, said one lead author, David Fahey of the , the Trump Administration does not appear to have made an effort to block publication of the report or alter the wording describing its scientific findings, though there were some alterations to the description of U.S. policy with respect to the . Fahey remarked, "I'm quite confident to say there has been no political interference in the scientific messages from this report... Whatever fears we had weren't realized."

Head of the   and Secretary of Energy Rick Perry have both said publicly that carbon dioxide does not cause much global warming.

Phil Duffy of the  noted, "This is a federal government report whose contents completely undercut the Trump Administration's policies, completely undercut the statements made by senior members of the administration." President Trump has announced plans to withdraw the United States form the Paris Climate Accords, in which participating countries pledge to reduce carbon emissions, and to loosen federal laws regulating fossil fuels.

The Climate Science Special Report is part of the fourth National Climate Assessment, the last of which was in 2014. The National Climate Assessments are required by a law passed by the United States Congress in 1990.



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