Policymakers call for renewed efforts to cut emissions amid the report’s grim predictions of more multi-billion-dollar disasters, fiercer heatwaves and dwindling water supplies that endanger people’s health, wealth and safety.
“The takeaway from this assessment, the takeaway from all of our collective work on climate, should not be doom and despair,” said National Climate Adviser Ali Zaidi. “The takeaway … should be a sense of hope and possibilities.”
Administration officials and scientists who worked on the report said halting every fraction of a degree of warming could quell climate disruptions.
“Every degree or a tenth of a degree of additional warming brings more severe climate impacts to the U.S.,” said an administration official, who was not authorized to speak on the record. “But the flip side of that coin is true as well. It means that every degree or every tenth of a degree of warming that we avoid matters.”
Achieving President Joe Biden’s goal of net-zero emissions by 2050 remains a challenge. The U.S. would have to reduce emissions 6 percent annually, which means deploying wind and solar power at record levels while also implementing other solutions, such as carbon capture technology. Biden plans to speak about the assessment findings on Tuesday.
Hitting net-zero by 2050 “will require a transformation of the global economy, as the report noted, on a size and scale that’s never occurred in human history,” White House senior advisor John Podesta said. “That sounds like a daunting task – and it is. But the National Climate Assessment tells us that the United States is already making that transformation happen.”
Carbon dioxide, methane and nitrous oxide levels in the atmosphere have risen 47, 23 and 156 percent, respectively, since 1850. The report said human activities have unequivocally caused a bulk of that warming, boosting global temperatures 1.1 degrees Celsius over that period. Nations want to keep increases below 1.5 degrees C.
Advances in scientific understanding since the last report in 2018 have left little doubt climate change is contributing to more intense and frequent extreme weather. Heatwaves in the West have grown more common since the 1980s. Drought threats have spiked in the Southwest over the last 100 years. Extreme rainfall has increased significantly east of the Rocky Mountains. Hurricanes have grown stronger, intensified more quickly and dropped more rainfall since the 1980s. Wildfires are becoming larger and more destructive.
In the 1980s, disasters causing $1 billion or more in damage occurred once every four months. They now happen once every three weeks.
Improvements in attribution science that parses how much more severe or how human-caused climate change likely factors into specific events has helped clarify the destructive impacts of global warming, administration officials said in a call with reporters. And scientists now have a better grasp of how every additional amount of heat-trapping gases put into the atmosphere impacts the planet.
“Today we can document the risks that we face per degree of warming. We can put a number on the extent to which climate change is fueling our record-breaking weather extremes,” said Katharine Hayhoe, chief scientist at The Nature Conservancy, who worked on the report. She said federal scientists now more clearly understand how climate change has cascading effects throughout the country, shedding light on “the vulnerability of our systems from socioeconomics to national security.”
New chapters on the economic and social impacts from climate change laid out in stark terms how climate change already is upending everyday life.
Many health, economic and climate change effects fall harder on already marginalized groups, such as communities of color, undocumented immigrants, the elderly, low-income individuals and unhoused people. Those burdens are “acute” during disasters like hurricanes, which climate change is making more intense, the assessment said.
Economic, health and equity concerns often overlap, with Covid-19 offering clear examples of these issues. Air pollution from high-polluting facilities and wildfire smoke made communities of color that experience higher rates of lung and heart ailments more susceptible to Covid-19 than white Americans.
In the Southwest, hotter days have reduced worker productivity and earnings, said Dave White, director of the Global Institute of Sustainability and Innovation at Arizona State University, who led the Southwest regional chapter of the assessment. He added higher heat extremes and drought reduced agricultural yields while also straining surface and groundwater supplies — the lack of rain prompted farmers to pull even more water from dwindling aquifers.
These inequities are often the byproduct of systemic wrongs, according to the assessment. Black homeowners will face far more climate-fueled flooding in part due discriminatory practices like redlining that pushed them into less desirable areas. Outdoor workers, predominantly Latino and undocumented immigrants, face greater health and safety risks from heatwaves and wildfire smoke.
The report serves as a scientific baseline for understanding how climate change impacts the planet and people, White said. It comes at a time when the effects of a warming world have become more inescapable and offers clarity about what is at stake if climate change is not tamed, he noted.
“In an era of misinformation and disinformation and conflicting and challenging information, I think it’s really important to understand we have this really credible, authoritative report that has full transparency and can be used as a common set of facts to inform discussion,” he said.
Leaving climate change unaddressed will pose significant cross-cutting challenges, the assessment said. It is disrupting supply chains and creating conditions for the spread of infectious diseases and future pandemics akin to Covid-19, it said.
Many costs are more direct. Overall, weather-related damage tallies $150 billion in direct costs each year, though adaptation can blunt storm-related costs by up to one-third, the report said.
Climate change has also created new living conditions that come with major costs.
Temperatures are rising for Americans faster than the global average: Since 1970, temperatures jumped 2.5 degrees Fahrenheit across the continental U.S. and 4.2 degrees F in Alaska versus a 1.7 degrees F global average. Global sea levels have risen between 7 and 9.5 inches since the Industrial Revolution began, with half of that increase coming since the 1980s — the U.S. coast has experienced even greater sea-level rise than that, totaling 11 inches over the past century.
That all has hit Americans’ finances and health. Temperature increases accounted for 19 percent of federal crop insurance payouts between 1991 and 2017. A foot of sea-level rise has decreased property values 14.7 percent. Days over 90 degrees Fahrenheit boosted deaths by 0.9 per 100,000 people.
Those costs would grow if climate change is left unchecked, the report noted. Each 1 degree F of warming reduces GDP growth 0.13 percentage points. Temperature increases will raise public service spending on healthcare, infrastructure and other services 1.45 percent by 2050. Temperature, drought and agricultural production changes would boost migration from Mexico ranging from 1.4 to 6.7 million people.
Adapting to climate change without reducing emissions can only do so much, according to the report. Adaptation investment is “minimal,” and strategies are often incomplete, contradictory or incoherent. That means current efforts are lacking and unlikely to deflect the future effects of climate change.
“Our society was built for a climate that no longer exists and we need to reckon with that,” a second administration official told reporters, who was not authorized to speak on the record.