The National Climate Assessment is the product of a major scientific collaboration among 13 federal agencies, and the U.S. government is legally bound to release it regardless of which political party is in power.
This year's report, released during the long Thanksgiving weekend in the U.S., is notable for being sharply at odds with the position of President Donald Trump and members of his administration, who have consistently dismissed the scientific consensus that human activity is accelerating climate change and have actively worked to roll back or altogether dismantle policies intended to reduce greenhouse gas emissions.
As recently as Wednesday, President Trump was making light of climate science after unusually cold weather settled over the northeast, tweeting, "Brutal and Extended Cold Blast could shatter ALL RECORDS - Whatever happened to Global Warming?"
He followed up on Thursday from his home in South Florida by observing, "This is the coldest weather in the history of the Thanksgiving Day Parade in NYC, and one of the coldest Thanksgivings on record!"
Despite the president's meteorological assessments, the 1,656-page federal report is blunt and unwavering, with scientists from the Energy and Defense Department, as well as NASA and other agencies concluding the world's climate is "changing faster than at any point in the history of modern civilization, primarily as a result of human activities."
The Lower 48 states have warmed 1.8 degrees (1 degree Celsius) since 1900 with 1.2 degrees in the last few decades, according to the report.
By the end of the century, the U.S. could be 3 to 12 degrees (1.6 to 6.6 degrees Celsius) hotter depending on the quantity of greenhouse gases released into the atmosphere, the report warns.
And although it was written long before the deadly fires in California this month and before Hurricanes Florence and Michael raked the East Coast and Florida, the assessments says warming-charged extremes "have already become more frequent, intense, widespread or of long duration."
The report notes the last few years have far surpassed U.S. records for damaging weather, costing nearly $400 billion since 2015.
If greenhouse gas emissions were to continue to increase through the century at their current rate, the report says, the annual cost to the U.S. economy would be roughly $500 billion or about 2.5 percent of its gross domestic product.
The largest costs of climate change over the next eight decades would come from continued record wildfires in the western U.S., massive crop failures in the Midwest, a jump in heat-related deaths throughout the nation, and widespread flooding, particularly along the coasts, the assessment said.
"Annual losses in some economic sectors are projected to reach hundreds of billions of dollars by the end of the century — more than the current gross domestic product (GDP) of many U.S. states," the report said. It'll be especially costly on the nation's coasts because of rising seas and severe storm surges, which will lower property values. And in some areas, such as parts of Alaska and Louisiana, coastal flooding will likely force people to relocate.
The report does not offer prescriptive solutions to the potential crisis it describes, but is instead intended to inform government policy going forward, the scientists who worked on it said.
However, it does note that the costs it describes could be "substantially reduced over the course of the 21st century" through a sustained global effort to rein in greenhouse gas emission.
If they're not reined in, the scientists warn, "it is very likely that some physical and ecological impacts will be irreversible for thousands of years, while others will be permanent."
The latest installment of the National Climate Assessment echoes many of the themes of the previous report. That document, released in May 2014, guided the Obama administration as it drafted its landmark Clean Power Plan with wide-ranging regulations aimed at curbing harmful emissions from coal-fired power plants. Obama’s administration also promoted the use of renewable forms of energy and signed on to the 2015 Paris Agreement.
Trump has taken a decidedly different approach, accusing his predecessor of waging a "war of coal" and almost gleefully rolling back a host of environmental regulations.
The current president also withdrew the United States from the global climate deal.
The new assessment appears unlikely to influence Trump's thinking. Despite predictions that climate change-related sea-level rise alone could cost the nation $118 billion and heat-related deaths another $141 billion, the White House on Friday sought to downplay its predictions, dismissing them as "largely based on the most extreme scenario."
Sheldon Whitehouse, a Democratic senator from Rhode Island, accused the administration of trying to "bury the effects of climate change in a Black Friday news dump."
Andrew Light, an international policy expert at the World Resources Institute, agreed, telling the Associated Press releasing the report on Black Friday, the start of the Christmas gift-buying season marked by huge sales and extended store hours, "is a transparent attempt by the Trump Administration to bury this report and continue the campaign of not only denying but suppressing the best of climate science."
The global environmental group 350.org assailed both the report and the White House, Friday, saying via Twitter that the National Climate Assessment "falls short of calling out the true culprit of the climate crisis: the fossil fuel industry. Meanwhile, the Trump Administration continues to roll back climate policy and prop up Big Oil."
For additional information:
National Climate Assessment
https://nca2018.globalchange.gov/
