Wildfire smoke’s bad.

Like, very bad.

And it’s getting worse.

But maybe all that smoke’s still not as bad as we thought.

That’s the mixed message emerging from recent studies on the impact of wildfire smoke, including one intriguing study on the atmospheric chemistry of last year’s Woodbury Fire, a 123,000-acre brush fire in the Superstitions that at one point forced the closure of Tonto National Monument in the Tonto Basin.

Researchers from Los Alamos National Laboratory discovered that as air and sunlight interacts with the massive smoke plume, it neutralizes sunlight-trapping “brown carbon” at the edge of the plume.

The human-caused Woodbury Fire raced through 123,000 acres of brush, pinyon juniper and grassland last summer thanks to a weak, delayed monsoon, just like the 198,000-acre Bush Fire did this year. Other studies have suggested climate warming may account for an increasing number of weak, delayed monsoons that have in recent years extended Arizona’s already dangerous fire season by a month or more.

The discovery that the giant smoke plumes don’t produce quite as much heat-trapping brown carbon as feared offers a rare bit of good news. Studies have shown that the rapid increase in megafires are wafting smoke into the upper atmosphere.

The Los Alamos study measured the chemistry of four large plumes produced by the Woodbury Fire that ravaged the Superstitions, closed the Apache Trail and now threatens road and reservoir damaging erosion off denuded slopes. The scientists measured the plumes both close to the source and as the smoke drifted over New Mexico. They found the center of the plume remained loaded with brown carbon, but oxidation and other chemical changes reduced the brown carbon over time at the edge of the plume.

“Mixing and oxidation lightened the brown carbon, reducing its ability to absorb light and cause warming. This implies that the warming effects of wildfire brown carbon is likely smaller than published model assessments,” the researchers concluded.

The study’s the latest to demonstrate the huge potential benefit of burning biomass in power plants outfitted with pollution controls. Biomass power plants like NovoPower in Snowflake capture more than 90% of the pollutants in the wood slash fuels they burn. So biomass burning plants to support forest thinning projects would reduce the threat of wildfires — both by saving towns like Payson and Show Low but by saving lives miles from the fire and limiting global warming.

For instance, studies predict a doubling in the U.S. death rate from the health complications caused by wildfire smoke in coming decades — costing about 25,000 additional lives annually.

Premature deaths associated with breathing wildfire smoke will likely increase from 15,000 current to 40,000 by the turn of the century, according to a study by researchers from the University of Colorado and elsewhere published GeoHealth, a journal of the American Geophysical Union.

Particles from smoke are associated with premature death in people with heart or lung disease, heart attacks, irregular heartbeats, aggravated asthma, decreased lung function and increased respiratory symptoms. Older adults, children and people with heart or lung diseases are most at risk, according to the federal Centers of Disease Control.

The acreage burned by big fires has increased dramatically in recent decades. One NASA study found that in the past 60 years the number of fires in the West has increased from about 250 annually to more like 1,300 annually. Moreover, the West had no documented megafires before 1970, but now has an average of about six per year. Projections suggest the number of fires in forested Arizona will increase another two- or threefold by mid century.

In areas like the West, wildfire smoke has overwhelmed the reduction in health-harming emissions from things like coal-fired power plants and high-polluting cars.

An earlier NASA study found that the smoke plumes from such big fires are far more likely to lift particles into the upper atmosphere, with confusing effects on global warming trends. So-called “brown carbon” traps heat while “black carbon” can block heat, resulting in cooling of the atmosphere. Brown carbon comes from incomplete burning of fuels and has a more complex chemistry and impact. So that balance between black and brown carbon in a smoke plume can determine the effects of the smoke on global temperatures.

Studies suggest for the past 20 years wildfires have injected about 8 billion tons of carbon dioxide into the atmosphere annually, accounting for about 10% of global emissions. In one week in 2017, California wildfires emitted more carbon dioxide than all the cars and trucks in the state over the course of the full year.

Contact the writer at paleshire@payson.com

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