Wildfire smoke trends worsening for Western U.S.

The warming climate has made wildfires and smoke increasingly common. Researchers in the Department of Atmospheric Sciences evaluated data from a number of sources to look at air quality trends in the West. A new paper by doctoral student Kai Wilmot with Gannet Hallar and John Lin (GCSC-affiliated faculty) and Derek Mallia (past GCSC fellow) is published in Environmental Research Letters.

 

The following was originally published in At the U:

From the Pacific Northwest to the Rocky Mountains, summers in the West are marked by wildfires and smoke. New research from the University of Utah ties the worsening trend of extreme poor air quality events in Western regions to wildfire activity, with growing trends of smoke impacting air quality clear into September. The work is published in Environmental Research Letters.

“In a big picture sense, we can expect it to get worse,” says Kai Wilmot, lead author of the study and doctoral student in the Department of Atmospheric Sciences. “We’re going to see more fire area burned in the Western U.S. between now and in 2050. If we extrapolate our trends forward, it seems to indicate that a lot of urban centers are going to have trouble in meeting air quality standards in as little time as 15 years.”

Drawing the connection

Many of the West’s inhabitants have seen smoky summer skies in recent years. Last year, dramatic images of an orange-tinted San Francisco Bay Area called attention to the far-reaching problem of wildfire smoke. Wilmot, a native of the Pacific Northwest, has seen the smoke as well and, with his colleagues, looked at trends of extreme air quality events in the West from 2000 to 2019 to see if they correlated with summer wildfires.

Using air measurements of PM2.5, or the amount of particulate matter in the air with diameters less than 2.5 microns, from the Environmental Protection Agency and the IMPROVE monitoring network, along with measurements of fire area burned and the PM2.5 emitted from those fires, the researchers found consistent trends in air quality that correlated with wildfire activity—but that had different spatial patterns in August than in September.

Trends in August and September

Over the years studied, the researchers noticed that the mean air quality was worsening in the Pacific Northwest in the average August when sensors indicated wildfire smoke events.

“That’s pretty dramatic,” Wilmot says, “that extreme events are strong enough to pull the mean up so that we’re seeing an overall increase in particulate matter during August across much of the Pacific Northwest and portions of California. The Pacific Northwest seems like it’s just really getting the brunt of it.”

The reason for that, he says, is that the regions around the Pacific Northwest, in British Columbia and Northern California, both experience wildfires around August. The mountainous Pacific Northwest, Wilmot says, sits in the middle.

But by September, the researchers found, wildfire activity slows in British Columbia and shifts to the Rocky Mountains. The smoke shifts too—the researchers saw emerging trends correlating wildfire smoke with declines in September air quality in Wyoming and Montana. “We see the PM2.5trends start to pick up a bit more in the Rockies and they become more statistically significant, a little bit stronger and more spatially coherent,” Wilmot says.

What about Utah? The study findings show that the magnitude and significance of air quality trends increases as you go from the southern states of Arizona and New Mexico toward the Pacific Northwest. In Utah, Wilmot says, air quality trends are near the edge of statistical significance, with evidence for impact from wildfires, but evidence that’s less robust than in the Pacific Northwest and California. “Thinking about events like the smoke transport from fires in the Bay Area this past summer,” Wilmot says, “I would not be surprised to see trends in Utah become increasingly convincing with additional data.”

Looking to the future

Other researchers in other studies have suggested that the future will bring more fire areas burned in the Western U.S., with an accompanying increase in wildfire smoke exposure throughout the West and the impacts of that smoke on human health.

Wilmot notes that the trends the researchers see in the Pacific Northwest in August are “pretty robust,” he says, while the September trends in Montana and Wyoming are still “emerging.”

“I think the concern is that, given more time, those emerging trends are going to start looking a lot more like what we’re seeing in August,” he says. “I hope that’s not the case, but it seems entirely within the realm of possibility.”

His next step is to develop simulation models to more precisely link wildfire emissions in urban centers to smoke source regions.

“The big picture,” he says, “is aiming to help forest management in terms of identifying wildfire emissions hotspots that are particularly relevant to air quality in the Western U.S., such that if we had funding to spend on some sort of intervention to limit wildfire emissions, we would know where to allocate those funds first to get the most out of it.”

Find the full study here.

Indigenous land-use reduced catastrophic wildfires on the Fish Lake Plateau

Vachel Carter (2011-12 GCSC fellow) is the lead author on a paper resulting from a study that assesses the human influence on prehistoric wildfires. GCSC affiliate faculty from multiple disciplines who were part of the study are: Simon Brewer and Andrea Brunelle, Department of Geography; Brian Codding, Department of Anthropology; and Mitchell J. Power, Natural History Museum of Utah. Such interdisciplinary research is a key aim of the GCSC.

The following is excerpted from an article by Lisa Potter in At the U.

“The study is the first in the region to combine charcoal, pollen, tree ring and archeological site data together to assess the human influence on prehistoric wildfires. The multiple disciplines allowed the researchers to make connections that would otherwise have been impossible.

 

“If you were to visit the Great Basin and Colorado Plateau a thousand years ago, you’d find conditions remarkably familiar to the present. The climate was warm but drier than today. There were large populations of Indigenous people known as the Fremont, who hunted and grew crops in the area. With similar climate and moderate human activity, you might expect to see the types of wildfires that are now common to the American West: infrequent, gigantic and devastating. But you’d be wrong.

“In a new study led by the University of Utah, researchers found that the Fremont used small, frequent fires, a practice known as cultural burning, which reduced the risk for large-scale wildfire activity in mountain environments on the Fish Lake Plateau—even during periods of drought more extreme and prolonged than today.

“…In Utah, many forests could benefit from frequent, smaller fires to mitigate wildfire risk. Perhaps one of the most urgent is in the Fish Lake National Forest that guards Pando, a stand of 47,000 aspen tree clones and the most massive organism on Earth. Pando has sat at the south end of Fish Lake for thousands of years, at least—some say the organism is a million years old. In recent years, the beloved grove has been shrinking. Low severity fires may help Pando, and other Utah forests, stay healthy.

” “Fuels on the Fish Lake landscape are at the highest that they’ve been in the last 1,200 years. The climate is much warmer than it was in the past. Our droughts have not been as intense as we’ve seen in the past, but they’re on their way,” Carter said. “The Fremont likely created long-lasting legacies on the Fish Lake Plateau through their cultural burning. Moving forward, ‘good fire,’ like prescribed fire, will be needed to mitigate against wildfire risk.” “

Mounting air-quality sensors on light rail saves cities money while improving data

Researchers affiliated with the GCSC have been measuring greenhouse gases in the Salt Lake valley by mounting sensors on TRAX light rail trains. Not only does this greatly improve the data that informs city planners and policy makers, but this method can provide extraordinary cost savings. The cost of one research-grade mobile sensor is about $40,000. To collect data from the same area with stationary sensors would take 30 instruments and would cost more than $1.2 million.

U of U researchers have been monitoring carbon dioxide in the Salt Lake Valley for 20 years. According to John Lin, Professor, Atmospheric Sciences, adding the TRAX-based measurements to stationary monitoring sites makes Salt Lake City one of the best-instrumented cities in the world for observing air pollution.

Read the full story in At the U. Find the publication in Environmental Science & Technology.

How vegetation effects microclimates in urbanized Salt Lake Valley

A new study by Carolina Gómez-Navarro and GCSC affiliate faculty Diane Pataki, Eric Pardyjak, and Dave Bowling, looks at how trees and grass can help mitigate excessive heat in urban areas. Hard surfaces like roofs, buildings, and pavement absorb the sun’s heat and radiate it into the surroundings, creating a “heat island effect”. While trees cast cooling shade, the team found that a more effective cooling solution occurs with a mix of trees and turf grass. Read about the study in At The U.

Anderegg: Know the Risks of Investing in Forests

William Anderegg, Assistant Professor in the School of Biological Sciences, has a central research question: What is the future of ecosystems in a changing climate?

His lab studies how drought and climate change affect forest ecosystems, and seeks to gain a better mechanistic understanding of how climate change will affect forests around the world. In a new study, Anderegg and colleagues look at the risks of banking on forests to store atmospheric carbon when forests themselves face a number of risks.

Read about the study in AtTheU.

From the Science paper:

“Forests have considerable potential to help mitigate human-caused climate change and provide society with a broad range of cobenefits…Widespread climate-induced forest die-off has been observed in forests globally and creates a dangerous carbon cycle feedback, both by releasing large amounts of carbon stored in forest ecosystems to the atmosphere and by reducing the size of the future forest carbon sink. Climate-driven risks may fundamentally compromise forest carbon stocks and sinks in the 21st century. Understanding and quantifying climate-driven risks to forest stability are crucial components needed to forecast the integrity of forest carbon sinks and the extent to which they can contribute toward the Paris Agreement goal to limit warming well below 2°C. Thus, rigorous scientific assessment of the risks and limitations to widespread deployment of forests as natural climate solutions is urgently needed.”