Elevated Wildfire Outlook for Interior Northwest and Alaska Reflects Natural Climate Variability and Long-term Climate Change

The National Interagency Fire Center (NIFC) on Monday (3 May 2010) issued the Wildland Fire Outlook for May through August. Among the trouble spots are areas of the West -- such as Western Montana -- where long-term declines in snowpacks, rising temperatures and insect-damaged vegetation are helping to drive a fourfold increase in large wildfires in the region over the last several decades. 

Above: Aerial view of wildfire on Mirror Plateau, Yellowstone National Park, 1988.  Source:  Jim Peaco.

Pacific Northwest and Northern Rockies

In Wildland Fire Outlook – May through August 2010,  NIFC forecasts an above normal wildfire season for the area extending from the North Cascades of Washington into northern Idaho, Western Montana and northwestern Wyoming.  Reflecting the influence of a now-fading El Nino and long term climate change, temperatures in the region so far this year have been above normal and precipitation has been below normal. Drought conditions have settled in over the area.

With much the same conditions forecast in the months ahead, a below normal snowpack will rapidly melt away and fuels will quickly dry. This will allow an early start to the fire season.  Compounding the danger in some areas -- such as northwestern Wyoming -- are large swaths of trees killed by insect infestations resulting in part from warmer winters. 

How the season unfolds will depend on ignition, especially from thunderstorms that pack a lot of fire-starting lightning, but little rain.   Should such storms rumble across the region from mid-July to September, firefighters will be working a lot of overtime -- and a lot of carbon will return to the atmosphere.

The implications of climate change for wildfires in the region were highlighted by researchers in 2006 in the journal Science (Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity, 18 Aug 2006).  The authors reported that in the Western U.S. "large wildfire activity increased suddenly and markedly in the mid-1980s, with higher large-wildfire frequency, longer wildfire durations, and longer wildfire seasons. The greatest increases occurred in mid-elevation, Northern Rockies forests...and are strongly associated with increased spring and summer temperatures and an earlier spring snowmelt."

More recently, the region was the focus of "Montana, Wyoming and Idaho Case Study --`Impacts of Climate Change on Forests of the Northern Rocky Mountains," by Steven W. Running of University of Montana, Missoula (pages 26-28 in Climate Change and the Economy: Expected Impacts and Their Implications[PDF], a report from the National Commission on Energy Policy). 

The study's key findings are (emphasis added):

1. "As temperatures rise, projected changes in Northern Rocky Mountain forests include fewer days with snow on the ground, earlier peak snowmelt, a longer growing season, and about two months of additional summer drought stress each year by late this century.
2. Increasing drought stress will increase forest disturbances including insect epidemics and wildfires. These disturbances have large impacts on society and the natural world.
3. If climate becomes drier, carbon uptake would be reduced to the extent that most forests in the region would switch from absorbing carbon to releasing it by late this century.
4. The economic impact of highest concern is the potential for a truly catastrophic wildfire in the region. There are now 360,000 people living in homes valued at $21 billion in the forest-urban interface in this region that are directly vulnerable to wildfire."

See also our earlier posts,The Cost of Protecting Montana Homes from Wildfires will more than Double by 2025 (9/8/2009) and Montana’s Spring Seasons Are Already Warming (9/8/2009).

Above: WWF's short video highlighting the connection between climate change and wildfire, and encouraging Montanans to urge their Senators to pass legislation that will slow climate change and help Montana and other states prepare for the impacts that already are starting to develop.

Alaska

Above: Shanta Creek Fire, Kenai National Wildlife Refuge, Alaska, July 2009.  Source: InciWeb. 

As early as May, well before the fire season takes off in the Northern Rockies and the Pacific Northwest, NIFC expects above average wildfire potential in Alaska. "Below normal winter snowpack over much of Alaska and anticipated developing drought over the central and southern interior will contribute to lower than normal fuel moistures," NIFC says. "Forecasts for May through August call for above normal temperatures, especially early in the season, and near normal precipitation. This will likely increase fire activity early in the fire season and perhaps bring an early start to fire season." NIFC expects the fire activity to be "closer to near average" as the season progresses.

Long-term warming is occurring in Alaska and when warmer temperatures have combined with below normal precipitation over the last decade, fire seasons have covered record expanses of the state.

Longterm warming is occurring in Alaska and when warmer temperatures have combined with below normal precipitation over the last decade, fire seasons have covered record expanses of the state.  During the 2004 season, fires scorched a record 6.6 million acres of the state.  Whereas 9.8 million acres burned in the 1990s, 18.97 million acres burned during the following decade of the 2000s.

As in other parts of the West, milder winters in Alaska are helping to spread insect infestations that are damaging and killing trees and adding to the fire danger.  For example, in its Alaska Seasonal Fire Weather/Fire Danger Outlook 2010, the Alaska Interagency Coordination Center notes:

 "Spruce bark beetle on the Kenai Peninsula and along Cook Inlet has caused nearly 2 million acres of beetle-killed timber...This hazardous fuel type can quickly dry under seemingly mild weather conditions creating a dangerous and complex environment for fire-fighters and land managers. These areas will persist, and under the right weather and ignition conditions will cause large fire problems as we have seen in the past few years. "

Among the Alaska wildfires are some in areas that have rarely seen large fires in the past -- such as the 2007 Anaktuvuk River fire on the  North Slope.  As Steven Running said in Congressional testimony on 1 November 2007:

"Fires on Alaska’s North Slope have been considered rare events. Only 134 fires north of 68º are recorded in fire history kept by the Alaska Fire Service since 1956. The 2007 Anaktuvuk River fire was an unprecedented event in that it burned in September, was so large (256,000 acres), and that it burned all the way from the coastal plain to the foothills of the Brooks Range."

Anaktuvuk River fire, Alaska, 2007.  Credit: Bureau of Land Management, Alaska Fire Service

Large amounts of carbon lie beneath the tundra and the fires such as the Anaktuvuk River fire may accelerate the release of that carbon to the atmosphere.  “Fire may be the trigger that shifts the North Slope landscape into a new state,” says Gaius (Gus) Shaver, an ecologist from the Ecosystems Center of the Marine Biological Laboratory at Woods Hole, Massachusetts (see An Arctic with Fire, by Diana Kenney, Woods Hole Marine Biological Laboratory, 2010; and Arctic Tundra is Being Lost As Far North Quickly Warms,  by Bill Sherwonit  in Environment 360, 11 January 2010).

Other Potential Hotspots

Another early trouble spot is in the northern Great Lakes region, where precipitation has been below normal and temperatures have been above normal.   For the East North Central Region (Minnesota, Wisconsin, Michigan and Iowa), January through April 2010 was the 11th warmest in the 116 year record.  For that 4-month period, there has been a pronounced warming since the early 1980s, a trend reinforced this year through the influence of an El Nino in the Pacific Ocean.

This year, the warm temperatures have been coupled to the region's 12th driest January-April on record, setting the stage for wildfires. NIFC reports that "fire danger indices across the northern Great Lakes were at or above record levels towards the end of April."  Given below normal precipitation forecast into early summer, NIFC expects above normal fire potential into June.

Another large area of concern is southern Arizona and southwestern New Mexico.  Reflecting the influence of El Nino, the area received above normal precipitation last winter (Dec 2009 - Feb 2010), stimulating the growth of grasses and other light fuels.  According to NIFC, "[r]eports from Tonto National Forest in central Arizona indicate new fine fuel growth up to one foot high."

With the hot and dry conditions of late spring and early summer, those fuels will quickly dry and can rapidly spread wildfires.  NIFC therefore expects above average potential for wildfires in the area, especially from June to mid-July -- when it expects seasonal monsoon rains to bring the fire season to a close.

Summer temperatures in the southwest have risen over the last century, one of the factors responsible for a drying of the region that is projected to continue during the course of this century.  Especially during fire seasons following relatively wet winters at lower elevations (i.e. below the snowline), the hotter conditions elevate the risk of wildfires.

Conclusion

As so often has been the case over the last several decades, long term climate change trends combined with shorter term climate variability have created conditions in parts of the U.S. that are conducive to large wildfires over the coming months.  Much now depends on the weather, particularly whether dry lightning storms materialize and ignite many fires over short periods and wide areas. 

Whatever ultimately happens during this season, the trend is clear and the projections are troubling. Climate change now has joined with other factors to alter wildfire regimes in ways that are transforming vast expanses of the U.S., especially in the West.  The frequency of large wildfires in the West from 1986 through 2003 was four times the average from 1970 to 1986 -- and they burned an area more than six and a half times larger.

In 2007, CBS's 60 Minutes aired an episode called "The Age of Megafires" in which  Scott Pelley of CBS commented to Tom Boatner, a seasoned firefighter with the Bureau of Land Management, that "there are a lot of people who don't believe in climate change."

"You won't find them on the fire line in the American West anymore," Boatner replied. "'Cause we've had climate change beat into us over the last ten or fifteen years. We know what we’re seeing, and we're dealing with a period of climate, in terms of temperature and humidity and drought that's different than anything people have seen in our lifetimes."

Online resources

National Interagency Fire Center

• Wildland Fire Outlook – May through August 2010
• 2010 Fire Season Outlook calls for increase in wildfire activity in parts of Western U.S.[PDF]  Press release (4 May 2010) from the National Interagency Fire Center.
• Total Wildland Fires and Acres (1960-2009).   from the National Interagency Fire Center.

Warming and Earlier Spring Increase Western U.S. Forest Wildfire Activity.  By A. L. Westerling, H. G. Hidalgo, D. R. Cayan, T. W. Swetnam, in Science,  Vol. 313. no. 5789, pp. 940 - 943 (18 Aug 2006).  See also: Is Global Warming Causing More, Larger Wildfires?  By Stephen W. Running in Science, 18 August 2006. 

Wildfires and Climate Change.  Hearing (1 November 2007) before the U.S. Congress, House of Representatives, Select Committee on Energy Independence and Global Warming.  Includes testimony of [PDF]:

• Abigail Kimbell, Chief, U.S. Forest Service

• Dr. Steven Running, Professor of Ecology, University of Montana

• Michael Francis, Director of Forest Program and Deputy Vice President,  Wilderness Society

• Dr. Michael Medler, Member of Firefighters United for Safety Ethics and Ecology, Assistant Professor at Huxley College

State of the Climate > U.S. Wildfire > 2010.  From the National Oceanic and Atmospheric Administration.  Also includes links to summaries from earlier years.

U.S. Forest Service Fire Maps

Wildland Fire Assessment System

InciWeb

Alaska Interagency Coordination Center

• Alaska Fire Season 2009 [PDF].  1 March 2010.
• Alaska Seasonal Fire Weather/Fire Danger Outlook 2010.  26 April 2010.

Canadian Interagency Forest Fire Center

Climate-Induced Tree Mortality: Earth System Consequences [login required].  According to new research, tree mortality associated with elevated temperatures and drought has the potential to rapidly alter forest ecosystems, potentially affecting feedbacks to the Earth system.
By H. D. Adams et al.  Eos, VOLUME 91   NUMBER 17   27 April 2010. 

WWF Climate Change Blog:

• The Cost of Protecting Montana Homes from Wildfires will more than Double by 2025.  9/8/2009
• Montana’s Spring Seasons Are Already Warming.  9/8/2009

"Montana, Wyoming and Idaho Case Study --`Impacts of Climate Change on Forests of the Northern Rocky Mountains." By Steven W. Running, University of Montana, Missoula. Pages 26-28 in Climate Change and the Economy: Expected Impacts and Their Implications [PDF], a report from the National Commission on Energy Policy.  " NCEP is a bipartisan group of 20 of the nation’s leading energy experts, and is one of several projects of the Bipartisan Policy Center.

Arctic Tundra is Being Lost As Far North Quickly Warms.  By Bill Sherwonit  in Environment 360 (11 January 2010).

An Arctic with Fire. "Wildfires are transforming the Alaskan tundra—and may be an accelerant to climate change." By Diana Kenney, Woods Hole Marine Biological Laboratory, 2010.

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