The 600,000-acre Rodeo-Chediski Fire frightened forest managers back in 2002.
Now, it’s scaring some climate change experts, due to a new appreciation of the striking way the massive fire interjected smoke and soot into the stratosphere.
New studies on the ability of such massive fires to create a superheated vortex that punches a hole in the atmosphere have raised questions about how such super fires will affect the climate of the whole planet in decades to come.
For instance, the Rodeo-Chediski Fire, which in 2002 forced the evacuation of Show Low and has since dramatically changed the approach of the Forest Service to thinning Rim Country forests, is one of a growing number of fires that created its own weather system and created a thick column of smoke more than 38,000 feet high, according to a study by Navel Research Laboratory meteorologist Mike Fromm.
The Rodeo-Chediski Fire created a “blowup” known to meteorologists as a pyrocumulonimbus firestorm (pyroCbs). Such a firestorm can cause such a violent updraft of smoke and heat that it will suck air in from great distances and create a ring of thunderstorms that feed energy into the vortex.
The researchers studied a number of such fires in the drought-plagued year of 2002, when the Rodeo-Chediski, the Hayman and Biscuit fires were among 17 such events.
Previously, climate experts thought smoke from such wildfires could only rarely penetrate a layer of relatively dense, stable air between the dense air of the troposphere and the cold, less-dense air of the stratosphere — which is generally 6 to 30 miles above the earth’s surface. The jet stream, which controls much of the storm and climate patterns, generally flows through this stable boundary layer, or tropopause.
However, the Naval Research Laboratory study found that big, superheated fires that can create such a blowup can readily penetrate this normally stable inversion layer. This finding can probably account for the until-now mysterious clouds detected in the lower stratosphere climate scientists have long blamed on volcanoes, even when they couldn’t connect a particular cloud to an eruption.
The finding that wildfires can inject soot and gases into the stratosphere much more often than scientists had assumed has ominous implications, in light of other studies on changes in wildfire patterns.
For instance, the inexorable projected rise in global temperatures will probably increase the area burned by wildfires in the United States by about 50 percent between now and 2050, according to a recent study by a team of Harvard scientists published in the Journal of Geophysical Research.
The researchers developed computer models by feeding in a 25-year record linking temperature and wildfires in North America. They then assumed a 3-degree temperature increase in the next 40 years, which is at the low end of the current consensus projections.
The current worst-case scenario envisions a 4- to 8-degree temperature change by 2050, according to papers presented this week at the Climate Change Conference in Cancun, Mexico.
Even at the more modest 3-degree level, the Naval Research Laboratory computer models projected a 75 percent to 175 percent increase in the average area burned. That would increase the amount of smoke injected into the atmosphere by at least 40 percent.
Such a dramatic increase in smoke in the atmosphere — especially in the upper atmosphere — could have dramatic effects, although many questions remain largely unknown.
For instance, the recent dramatic increase in smoke clouds produced by wildfires in North America has partially shaded the vulnerable ice and snow fields of the Arctic, according to a study by researchers from the University of Colorado and the National Oceanic and Atmospheric Administration published in the Journal of Geophysical Research.
The researchers looked at the impact of fires in Alaska and Canada in 2004 that burned a total of 22,000 square miles of forest.
The drifting pall of smoke increased the murkiness of the atmosphere over the Arctic 100-fold. The shadow cast by the smoke had a pronounced cooling effect on the open ocean and a less obvious effect on areas covered with bright snow, which tends to reflect back much of the sun’s energy.
But the shadow represents only one impact of that drifting cloud of smoke.
The dark, heavy particles of soot eventually settle to earth. If they’ve gotten a ride on the jet stream or reached the upper atmosphere, they can come down thousands of miles from the site of the fire.
When this layer of dark soot settles on snow fields, glaciers or ice packs, the soot can dramatically increase the amount of heat the snow absorbs, according to a study by scientists from the University of California at Irvine published in the Journal of Geophysical Research.
The dark soot from fires, coal-burning power plants, auto exhaust and other sources settles on the bright snow and then absorbs sunlight that would otherwise be reflected back into the atmosphere.
“Dark soot can heat up quickly. It’s like placing tiny toaster ovens into the snow pack,” said UCI associate professor Charlie Zender.
The Arctic has heated up by about 3 degrees in the past 200 years — about twice the global average. The researchers concluded that the increased dirtiness of the snow could account for the bulk of that warming. They noted that temperatures in the Arctic increase significantly during years with a lot of forest fires.