US climate report offers dire outlook, with temperatures expected to cross key thresholds

A major federal climate report shows that the U.S. is unlikely to meet national or international climate targets and warns of dire consequences for the country.

The Fifth National Climate Assessment, released Tuesday, finds that the planet is very likely to heat up by an average of between 4.5 and 7.2 degrees Fahrenheit (2.5 and 4.0 degrees Celsius) compared to pre-industrial times — outpacing goals of both the U.S. and international community.

While it puts the likely warming window in that range, the report notes that scientists cannot rule out further warming and “potentially catastrophic outcomes.”

“Higher values are not definitively ruled out, and feedback loops such as changes to cloud cover may lead to more warming in the future,” it said. 

It noted that “tipping points” such as the loss of the Greenland and West Antarctic ice sheets, loss of the Amazon rainforest and cloud disappearance risk creating further accelerations to planetary warming. 

Yet, even at the projected rise in average global temperature, the report notes that the U.S. is likely to see significant temperature changes — and the warmer days and extreme weather that comes with them.

At 3.6 degrees Fahrenheit of global warming, the average U.S. temperature is very likely to increase by between 4.4 and 5.6 degrees. The northern and western parts of the country are likely to experience this warming at disproportionate levels, the report said.

The congressionally mandated report was put forward by the U.S. Global Change Research Program, which is made up of 14 federal agencies.

The previous version of the report was put forward in 2018, under the Trump administration. That report likewise warned that climate change would disrupt the lives of Americans. 

Its release on the day after Thanksgiving raised questions about whether the administration was trying to bury it. The New York Times later reported that officials attempted unsuccessfully to push scientists to downplay their conclusions in the Trump-era report. 

The new report said the U.S.’s recent rates of planet-warming emissions decline is not enough to stave off global warming or meet its climate goals.

Between 2005 and 2019, greenhouse gas emissions decreased by less than 1 percent per year on average. They would need to decline by more than 6 percent per year on average to achieve the country’s current target of bringing its emissions down to net-zero by the middle of the century.

It reported that emissions could further be cut by improving energy efficiency; electrifying more energy uses such as transportation and heating while also bringing down emissions from electricity use; shifting toward less meat consumption; and reducing food waste. 

The report listed consequences all around the country, noting that at this level of warming, the Southeast will see six more days over 100 degrees Fahrenheit each year and the Midwest will see 10 more days over 95 degrees. 

It said that further warming will create more risks for the nation’s water supply, food security, infrastructure, health, ecosystems and economy.

For example, climate change is expected to make food less available and more expensive as high temperatures reduce crop yields and introduce disease, while droughts and wildfires may threaten water supplies and put more heat stress on livestock. 

Air pollution could also worsen, especially since chemical reactions that produce smog speed up with higher temperatures and more sunlight. And if climate change reaches “severe” levels — with warming between 9 and 14 degrees Fahrenheit — about 25,000 more people may be killed on a yearly basis in 2100 than in 2000.

It also highlights key regional impacts of the warming planet. 

The northeastern U.S. is already seeing more rain and snow, and “extreme precipitation events” have increased by about 60 percent in the region. In the future, increases in heat waves are expected to also increase mortality rates in the Northeast’s urban areas.

Meanwhile, in the Southwest, climate change is exacerbating water supply issues. The report says that between 1913 and 2017, average water discharge from the Colorado River decreased by 9.3 percent for each 1.8 degrees Fahrenheit of warming. 

It also said that changes in the timing of streams that come from melting snow are expected to disrupt water infrastructure and hydropower to meet the region’s needs. 

Dave White, lead author of the report’s Southwest regional chapter, pointed out that declines in water availability in the area worsened by climate change, could reverberate well beyond the borders of Arizona, New Mexico, Utah, Colorado, Nevada and California.

“You just need to think about the benefits that water from this region provides,” White told The Hill. “It affects your ability to have affordable and healthy foods year-round.”

He added that Western water is also crucial for the region’s semiconductor manufacturing, saying “in many ways, it touches everyone in the country.”