By Jay Landers

Although the United States has made progress in reducing greenhouse gas emissions, much remains for the nation to do in terms of responding and adapting to climate change, according to a major report recently issued by the federal government.

Released on Nov. 14, the Fifth National Climate Assessment was prepared by the U.S. Global Change Research Program. The program is congressionally mandated to produce a report at least every four years, evaluating and assessing the current state of knowledge regarding climate change, its effects on a wide range of natural and social systems, and its current and projected trends.

Declining emissions

On the one hand, the report’s findings contain a measure of optimism. “Across the country, efforts to adapt to climate change and reduce emissions have expanded since 2018, and U.S. emissions have fallen since peaking in 2007,” despite increases in population and economic activity, according to the NCA5.

Between 2005 and 2019, U.S. GHG emissions fell 12%, a trend “largely driven by” declining use of coal and greater use of natural gas and renewable energy sources for electricity generation, the report notes.

These changes decreased emissions from the electricity sector by 40%, according to the NCA5.

“Across all sectors, innovation is expanding options for reducing energy demand and increasing energy efficiency, moving to zero- and low-carbon electricity and fuels, electrifying energy use in buildings and transportation, and adopting practices that protect and improve natural carbon sinks that remove and store CO2 from the atmosphere, such as sustainable agricultural and land-management practices,” the NCA5 notes.

On the other hand, climate change and its attendant problems remain concerns. “The effects of human-caused climate change are already far-reaching and worsening across every region of the United States,” the report states. Absent “deeper cuts in global net greenhouse gas emissions and accelerated adaptation efforts, severe climate risks to the United States will continue to grow,” according to the NCA5.

Outlining challenges, opportunities

Along with a chapter on climate trends and Earth systems processes, the report includes 18 chapters on national topics, including water, energy, ecosystems, oceans, the built environment, and transportation. Also included are 10 chapters focusing on different U.S. regions, a chapter apiece on adaptation and mitigation, and separate chapters on compound events, Western wildfires, COVID-19 and climate change, risks to supply chains, and blue carbon.

For the first time, the USGCRP created an “interactive online NCA5 atlas, which allows users to explore the latest localized temperature and precipitation projections,” according to a Nov. 14 news release issued by the National Oceanic and Atmospheric Administration within the U.S. Department of Commerce. “The atlas is designed to be used by national, state, tribal and community leaders, adaptation planners, researchers, educators and the general public,” the release states.

“The Fifth National Climate Assessment can help every community, every business and every American prepare for and respond to climate change,” said Gina Raimondo, the U.S. Secretary of Commerce, in the Nov. 14 release. “While the report clearly shows the immense challenges of climate change, it also outlines the opportunity to create a more resilient nation and a stronger, more sustainable economy.”

“The report details the far-reaching effects of human-caused climate change on the U.S. and concludes that every additional increment of warming that we avoid — every action to reduce warming — matters for reducing harmful impacts,” said Rick Spinrad, Ph.D., the administrator of NOAA, in the Commerce Department’s release.

Infrastructure affected

Increasing GHG emissions from human activities have resulted in “rapid warming and other large-scale changes, including rising sea levels, melting ice, ocean warming and acidification, changing rainfall patterns, and shifts in timing of seasonal events,” the report states.

“As the world’s climate has shifted toward warmer conditions, the frequency and intensity of extreme cold events have declined over much of the U.S., while the frequency, intensity, and duration of extreme heat have increased,” according to the NCA5. “Across all regions of the U.S., people are experiencing warming temperatures and longer-lasting heatwaves. Over much of the country, nighttime temperatures and winter temperatures have warmed more rapidly than daytime and summer temperatures. Many other extremes, including heavy precipitation, drought, flooding, wildfire, and hurricanes, are becoming more frequent and/or severe, with a cascade of effects in every part of the country.”

Infrastructure — an area of key concern to civil engineers — merits special attention in the report.

“Infrastructure and services are increasingly damaged and disrupted by extreme weather and sea level rise,” according to the NCA5. “Many infrastructure systems across the country are at the end of their intended useful life and are not designed to cope with additional stress from climate change.”

Through innovation and ingenuity, civil engineers have critical roles to play in ensuring that infrastructure continues to perform as needed.

“Forward-looking designs of infrastructure and services can help build resilience to climate change, offset costs from future damage to transportation and electrical systems, and provide other benefits, including meeting evolving standards to protect public health, safety, and welfare,” the report notes. “Mitigation and adaptation activities are advancing from planning stages to deployment in many areas, including improved grid design and workforce training for electrification, building upgrades, and land-use choices.”

“The Fifth National Climate Assessment makes it clear that the risks matter, and our choices matter too,” said Katharine Hayhoe, the chief scientist for the conservation organization The Nature Conservancy and author of the report’s chapter on climate trends, in a Nov. 14 news release.

“The good news is we have solutions,” Hayhoe said. “We know what we need to do: We need to cut our carbon emissions as much as possible and as soon as possible. We need to invest in nature to take carbon out of the atmosphere as well as providing a host of other benefits for our health and biodiversity. And we need to build resilience to the impacts that are already here today.”

Transportation and emissions

Following the recent emissions reductions within the electricity generation sector, the transportation sector has been the largest U.S. emitter of GHGs since 2017, according to the report.

For this reason, the “planning, design, construction, operation, maintenance, and procurement of transportation systems” all require re-examination as part of efforts to reduce emissions and help protect the sector from risks associated with climate change, says Cris Liban, Ph.D., P.E., ENV SP, M.ASCE, the chief sustainability officer for the Los Angeles County Metropolitan Transportation Authority and lead author of the report’s chapter on transportation.

For civil engineers, key takeaways of the report’s transportation chapter include understanding the “co-benefits” of sustainable transportation systems, including environmental justice, the natural environment, and economic development, Liban says. “We offered a few options for the engineer to look at,” he says.

Engineers seeking to develop innovative infrastructure solutions while also adhering to traditional design criteria or performance standards can face challenges, Liban acknowledges. A “good framework” that can help engineers address such challenges, he says, is ASCE’s recently released Standard Practice for Sustainable Infrastructure (73-23), which Liban helped develop as chair of the Society’s Committee on Sustainability.

The NCA5 transportation chapter also focuses on the need to understand and balance potential “trade-offs” that can result from efforts to mitigate or adapt to climate change, Liban says. “We offered a framework for the engineer to think about how to consider trade-offs over the life cycle of that design or that infrastructure that they're developing,” he notes.

However, improving communication between engineers and other technical specialists and the general public remains critical, particularly in the case of “overburdened communities” that often experience the negative effects of climate change most acutely, Liban says. Often, a communication “gap” exists between what experts recommend communities do to address climate change and what members of the public can readily understand, he notes. “The gap needs to be bridged,” Liban says.

This article is published by Civil Engineering Online.

More information on ASCE’s participation in developing climate data of use to engineers is available in the Civil Engineering Source’s interview with Kris May, Ph.D., P.E., M.ASCE, CEO and principal of climate adaptation and engineering for the Pathways Climate Institute in San Francisco and author of the coasts chapter of NCA5.