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National Climate Assessment predicts growing threats to society, economy

By Chelsea Harvey | 11/14/2023 06:23 AM EST

The federal report details how climate change will alter nearly every facet of American life — and how the U.S. can help avoid “potentially catastrophic outcomes.”

Devastation from Hurricane Michael is visible in Mexico Beach, Fla., in 2018.

Devastation from Hurricane Michael is visible in Mexico Beach, Fla., in 2018. Gerald Herbert/AP

A long-awaited federal climate report, released Tuesday, delivers a blunt warning: Rapidly curb planet-warming emissions or face dire consequences to human health, infrastructure and the economy.

The of the National Climate Assessment presents the most comprehensive evaluation to date of U.S. climate science, impacts and action. Dozens of authors, including representatives from multiple federal agencies, contributed to the congressionally mandated report.

The assessment details how climate change is already battering the nation with extreme heat, hurricanes, wildfires, droughts, floods and swiftly rising sea levels. It estimates that “billion-dollar disasters” are happening every three weeks on average — up from every four months in the 1980s.

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U.S. youth are growing up amid these realities, said White House National Climate Adviser Ali Zaidi on a call with reporters last week.

“They have not just intellectually started to appreciate the concept of this crisis — it is their lived experience to see the sky turn orange, to breathe in the smoke from wildfires hundreds of miles away, to see lives and livelihoods washed away by floods and the fury of hurricanes,” he said.

But he emphasized that the report’s takeaway “should be a sense of hope and possibilities.”

“We’ve got climate solutions that can be made in America and are being made in America that we’re deploying brick by brick and block by block,” he said. “That gives us hope.”

The new assessment is the first such report released under the Biden administration, which has made climate change a centerpiece of its agenda. It comes as the world has already warmed by more than 1 degree Celsius since the preindustrial era, with greenhouse gas concentrations in the atmosphere higher than at any point in at least the last 800,000 years.

Every corner of the country is now experiencing the consequences of global warming, often in different ways. Extreme precipitation and flooding is on the rise in the Northeast, while drought and wildfires are worsening in the West. Sea levels are rising significantly faster than the global average in the Southeast, and strengthening Atlantic hurricanes are a growing threat to the East and Gulf coasts.

Rapid warming, melting sea ice and thawing permafrost are transforming the Alaskan landscape, disproportionately threatening Indigenous communities and disrupting cultural practices and traditions. Sea-level rise and saltwater intrusion are growing threats to freshwater supplies in Hawaii and U.S. Pacific territories.

And with every fraction of a degree that the climate warms, more damage and greater economic losses will follow, the report warns.

“Low-probability and potentially catastrophic outcomes are not impossible, and these risks persist even under current policies,” the report says, later adding: “How much more the world warms depends on the choices societies make today. The future is in human hands.”

While U.S. emissions are falling — dropping by 12 percent between 2009 and 2019 — far more dramatic cuts are needed, according to the assessment. The country’s emissions would need to fall by about 6 percent each year on average to meet the Biden administration’s goal of achieving net-zero emissions by 2050.

That would require widespread societal transformation, including large expansions in wind and solar energy, improvements in energy efficiency, and the electrification of transportation and heating systems. Food and agricultural systems must become more efficient and sustainable, while protecting and restoring carbon-rich natural landscapes.

Many of these options are already economically feasible, the report states.

For example, the country could ramp up the share of renewables and expand the use of electric vehicles and heat pumps, said Steven Davis, an earth system scientist at the University of California, Irvine, and lead author of the report’s chapter on climate mitigation.

“Those are the clear first steps if we want to respond and curtail emissions to meet those longer-term goals,” he said.

New chapters

The U.S. Global Change Research Program has worked on the report since 2020, spanning two administrations with dramatically different approaches to climate change and environmental regulation.

The previous assessment, which also warned of the need for swifter climate action, was published in 2018. Its findings stood in direct contrast to the views of the then-Trump administration, which attempted to bury the report by releasing it the day after Thanksgiving.

The Trump administration later hampered progress on the newest assessment by for scientists to work on it and then to direct the U.S. Global Change Research Program.

When President Joe Biden took office in 2021, his administration assembled its own team to continue the report, reinstating the research program’s former executive director, Mike Kuperberg, and as the director of the assessment.

The resulting fifth installment reflects the advancement of climate science and models over the past few years. Researchers have made large strides in their ability to investigate the links between climate change and individual extreme weather events, giving scientists a growing confidence in the influence of global warming on heat waves, hurricanes, wildfires, floods and other disasters.

The new report also includes two new chapters: one on economics and one on social systems and justice. The latter reflects a growing consensus among scientists and policymakers that climate change has a disproportionate impact on marginalized communities and that addressing climate change goes hand in hand with confronting social inequities.

Scientists have “a comprehensive understanding now of how climate change disproportionately affects those who have done the least to cause the problem,” Katharine Hayhoe, chief scientist at The Nature Conservancy and an author of the new assessment, said on a call with reporters. “We know that these impacts exacerbate social inequities, including racial and gender-based disparities. And we’re now recognizing that climate solutions must also be solutions for justice and equity.”

Economic threats

The new assessment makes it clear that nearly every facet of human society across the U.S. is likely to be altered by the impacts of global warming.

Natural landscapes and ecosystems are shifting. Ocean warming and acidification causes coral bleaching events and threatens fisheries. Sea-level rise erases coastal forests. Droughts and wildfires convert woodlands into grasslands. Sea ice and glaciers are melting, and permafrost is thawing.

The report warns that the country’s energy infrastructure is largely unprepared for today’s climate impacts, making it vulnerable to power and fuel interruptions. Wildfires, floods and hurricanes have been known to destroy entire communities, sweeping away homes, buildings, roads and bridges.

Insurance costs could skyrocket past the limits of affordability, according to the report. Private insurers are expected to abandon high-risk areas in the future, a phenomenon already occurring in some places prone to wildfires and hurricanes.

That lack of access to affordable insurance will place a greater financial burden on residents in high-hazard areas, particularly low-income communities in which many people may not have the resources to relocate.

The report warns that worsening climate impacts are expected to threaten a variety of industries, including fisheries; agriculture; and outdoor recreation like skiing, hunting and fishing.

Overall, annual U.S. GDP growth is expected to slow by about 0.13 percentage point with every 1 degree Fahrenheit the Earth’s global temperatures rise.

Rising deaths

Meanwhile, climate impacts pose a growing risk to human health and well-being.

Scientists warn that heat is the largest weather-related killer in the U.S. But other climate-related events — like floods, droughts, wildfires, smoke and the spread of infectious diseases — are also increasing mortality risks.

Vulnerable populations suffer disproportionate health impacts related to climate change, said Mary Hayden, a researcher at the University of Colorado, Colorado Springs, and lead author of the new report’s chapter on human health. These include people of color and sexual and gender minorities, she noted.

“We talk about social inequities, establishing that climate-related impacts disproportionately harm communities and people who have been marginalized,” she said.

The assessment also includes a new emphasis on not only physical health, but mental and emotional health, she added. A growing body of research indicates that climate change can increase anxiety, depression and other adverse mental health outcomes. The report also notes that under-resourced communities often suffer greater mental and spiritual health burdens.

Youth are particularly vulnerable, Hayden added.

“Sixty percent of a thousand surveyed U.S. adolescents reported anxiety about climate change,” she said. “Nearly half believe that humanity is doomed, despite evidence to the contrary.”

Children today are more likely to witness damage to their schools, homes or communities. Research has found that children experiencing four or more such adverse events have a three- to sixfold increased risk of anxiety, substance abuse and depression, Hayden said.

Increased access to mental health care, psychological resilience training and youth climate education programs are “critical to ensuring the resilience of our nation,” she said.

The need for adaptation

World nations are striving to keep global warming well below 2 C, or 1.5 C if possible. Limiting warming to 1.5 C, a threshold that experts agree is rapidly approaching, would require global emissions to fall by nearly half by 2030 and to reach net zero by midcentury.

The Biden administration has set goals in line with those targets. But while cutting emissions is crucial, the U.S. must also adapt to the climate impacts it’s already experiencing, the report says.

Today’s energy systems and infrastructure were largely designed for a cooler climate system and must be strengthened for a more extreme future, according to the report. It urges stronger actions to safeguard human health and ensure that the country’s most vulnerable populations are protected.

States and cities have increased adaptation efforts in recent years, with projects to restore or buffer natural landscapes, manage floods, build sea walls, expand access to air conditioning, designate cooling centers and develop early warning systems for climate disasters.

“Years ago we were challenged to find any examples,” said Hayhoe, the Nature Conservancy scientist. “Today, we have cities and states taking action.”

But most of those adaptation efforts are small-scale, incremental activities, the report warns. And they’re not enough to keep pace with the progression of climate change.

The report says transformative adaptation efforts are still needed — ones that include wide input from the communities they’ll affect, particularly historically marginalized populations and underserved communities.

Arati Prabhakar, director of the White House Office of Science and Technology Policy, said the assessment presents several takeaways: Climate change is already affecting daily life, and the U.S. is making efforts to address planet-warming emissions.

The infrastructure law and Biden’s signature climate law, the Inflation Reduction Act, “give us hope, because they tell us we can do big things at the scale that’s required, at the scale that the climate actually notices,” Prabhakar said.

“And that is so important,” she added, “because the third message in the assessment is this: Much more work is needed to overcome the climate crisis.”