Wildfires have devastated California this year, and a new report projects that climate change will increase the frequency and intensity of these blazes. Credit: Josh Edelson/AFP/Getty

Arriving on the heels of deadly wildfires in California, the US government’s latest national climate assessment makes one thing clear: communities across the country are increasingly vulnerable to such dangers as the world warms.

The analysis, produced by 13 federal agencies and required by law every 4 years, was released on 23 November. “The impacts of climate change are already being felt in communities across the country," it says, warning that neither global efforts to fight climate change nor regional efforts to adapt to it "currently approach the scales needed to avoid substantial damages to the U.S. economy, environment, and human health”.

For many scientists, the report’s mere existence comes as a relief. They had worried that President Donald Trump’﻿s administration — which has challenged climate science, aggressively promoted fossil fuels and rolled back environmental regulations — would meddle with the report’s findings or block its release outright. That did not happen, and the result is a document whose core message contradicts positions taken by Trump and other administration officials.

Trump has repeatedly blamed the fires raging in California on poor forest management — ignoring evidence that global warming is increasing the frequency and intensity of these blazes. On 17 November, for instance, he deflected questions about climate change as he toured the town of Paradise, California, after it was levelled by the deadliest wildfire in the state’s history. The Camp Fire has now burnt more than 250 square kilometres and killed at least 84 people, with more than 500 hundred still missing.

“The president just keeps saying that nothing is due to climate change, but the truth is the truth,” says Donald Wuebbles, a climate scientist at the University of Illinois at Urbana-Champaign who worked on the climate report. “I think they decided that fighting it was going to cost them a lot more than not fighting it.”

Going to extremes

The report lays out the latest in climate-change science, but it also examines how global warming is likely to affect different regions of the country and sectors of the economy.

Higher temperatures and drier conditions have led to more large fires in the western United States, the report says, and that trend will continue as the planet warms and the fire season lengthens in future decades.

Persistent droughts have helped to accelerate the depletion of groundwater for drinking and agriculture in the southwestern and midwestern United States, the analysis says. Along the east coast, the combination of rising seas and extreme precipitation has boosted flood risks.

Dams and levees are ageing across the country, and the risk of them ﻿failing﻿ will increase as storms become more powerful. The United States’ estimated economic losses from major storms, floods and droughts in 2017 topped US$290 billion — the biggest annual sum recorded over nearly four decades, according to the US National Oceanic and Atmospheric Administration.

“We have significant challenges today, and climate change will only exacerbate those challenges,” says Upmanu Lall, director of the Columbia Water Center at Columbia University in New York City. Lall is the lead author of the assessment’s chapter on water.

If current trends in global greenhouse-gas emissions continue, the report says, annual losses in some sectors of the US economy could 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”.

Political climate

The latest report is the fourth in a series stretching back to 2000, but the process of releasing the analyses — every four years, as required by law — has not always gone smoothly.

Environmentalists sued the administration of President George W. Bush in 2004 for missing the legal deadline to release the second national climate assessment. Ultimately, a federal court ordered the government to produce the analysis.

Although the Trump administration has released a complete fourth report, many scientists remain concerned that the government will bury it in the public archives instead of taking action to address its findings. Some also speculated that the decision to release the report on Black Friday, the day after the US Thanksgiving holiday, was part of an attempt to downplay the report’s findings.

“The message is crystal clear: climate change is not a political football — it’s an existential threat to our nation and our people,” said Rhea Suh, president of the Natural Resources Defense Council, an advocacy group in New York City, in a statement. “It’s time to cut the fossil fuel pollution that’s driving global climate change.”

Government scientists participating in a press conference about the report sidestepped multiple questions about whether the White House had tried to suppress the report by releasing it during a holiday weekend. They said that the government wanted to release the report before the next round of United Nations climate talks, which begin on 2 December in Katowice, Poland.

What’s next

But the federal government seems unlikely to take the lead on translating the report’s findings into action. Last year, the Trump administration disbanded a federal advisory committee that was intended to help communities, businesses and state and local governments make use of the national climate assessment.

“Identifying vulnerabilities is important, but it’s not enough,” says Richard Moss, a visiting climate scientist at Columbia University’s Earth Institute who headed the disbanded panel. “We are at the point where action has to take place.”

That committee, which was headed by Moss, has since reconstituted itself as the Independent Advisory Committee on Applied Climate Assessment, with funding from the state of New York, Columbia University and the American Meterological Society, among other sources.

The panel plans to release recommendations in early 2019 to help businesses and government at all levels to apply the climate assessment’s findings. It is also working to create a consortium to help businesses and policymakers make better use of scientific information as they seek to curb emissions and adapt to climate change.