EFFECTS OF CLIMATE CHANGE ON FOREST FIRES OVER NORTH AMERICA AND IMPACT ON U.S. OZONE AIR QUALITY Rynda Hudman 1,2, Dominick Spracklen 1,3, Jennifer Logan3 Loretta J. Mickley3, Maria Val Martin3, Shiliang Wu3,4, Rose Yevich3, Alan Cantin5, Mike Flannigan5, Tony Westerling6 Affiliations: 1 School of Engineering, Harvard 2 Now at UC Berkeley 3 Now at University of Leeds 4 Now at Michigan Tech 5 Canadian Forest Service 6 UC Merced

OBSERVED INCREASE IN WILDFIRE ACTIVITY OVER NORTH AMERICA Area burned in Canada has increased since the 1960s, correlated with temp. increase. 5 year means [Gillett et al., 2004] Increased fire frequency over western U.S. in recent decades – related to warmer temp., earlier snow melt. [Westerling et al., 2007]

PREDICTING FUTURE FIRE IMPACTS ON U.S. OZONE OBSERVED AREA BURNED WEATHER & FUEL MOISTURE/ FIRE SEVERITY AREA BURNED PREDICTION Yearly Area Burned = C1X1 + C2X2 + … + C0 GISS GCM Output (2050, A1B) FUTURE AREA BURNED GEOS-CHEM CTM Emissions Future Fire Impacts on U.S. ozone air quality

PREDICTED BIOMASS CONSUMPTION BY FIRES IN THE WESTERN U.S., 1996-2055 Results shown as the number of standard deviations away from the mean for 1996-2005 50% increase in biomass consumption by 2050  40% increase in mean summertime aerosol concentration [Further details see Spracklen et al., JGR, in review]

PROJECTED WESTERN U.S. WILDFIRE NOx EMISSIONS Ozone production generally limited by supply of NOx 2046 – 2055 PROJECTED WILDFIRE NOx EMISSIONS ARE 50% LARGER THAN 1996-2005 * We assume forest emission factor of 1.6 g NO/kg DM

PREDICTED AFTERNOON (1-5pm) JULY MEAN OZONE ENHANCEMENT 1-3 PPBV 4 Years Future (2050) vs. 4 Years Present (2000) Ozone change due to future wildfire* * Note: climate effects have been subtracted out Consistent with these results, recent observational estimates of regional enhancements of 2 ppbv for each 1 million acres burned [Jaffe et al., 2008]

REGRESSIONS CAPTURE VARIABILITY IN REGIONS WITH LARGEST AREA BURNED Historical Area Burned Regressions ‘capture’ 15 – 62% of variability over Canada and Alaska. R2 of Area Burned regressions [Nancy French, MTU] [Stocks et al., 1999]

REGRESSION AGAINST AREA BURNED: Taiga Plains ALASKA/CANADA SUMMARY Most Common Predictors: Monthly/Seas. 500 mb GPH Anomaly Max/Mon./Seasonal Severity Rating Large-scale Ocean/Atmosphere circulation related to fire activity [ e.g., Skinner et al., 1999, 2002; Duffy et al., 2005] ; Severity Rating &Temp common predictor in previous regression [Balschi et al., 2008]

DOES RAIN OFFSET TEMPERATURE INCREASE? Simulated May – August 2046-2055 vs. 1996-2005 June 500mb anomaly over Fairbanks, Alaska (1940 – 2006) GISS Mean 1999-2008 : -1.4 dm 2045-2054 : 0.5 dm GISS Mean 1999-2008 : -1.4 dm 2045-2054 : 0.5 [Fairbanks GPH Courtesy of Sharon Alder, BLM]

AREA BURNED PROJECTIONS 34% increase over Alaska, 8% change over Canada w/ large regional variability Difference from other studies likely due to future scenario or GCM  need envelope study with multiple GCMs & scenarios.

PRESENT DAY FIRE IMPACTS ON OZONE Ozone enhancement from NA biomass burning 0-2 km Simulated July 2004 mean Max enhancement during July 15-24 2004

CONCLUSIONS Regressions capture much of the variability in annual area burned over the western U.S. (24-57%), Alaska (53-57%), and Canada (15-62%). Key predictors : 500 mb GPH anomaly & severity rating. 2050 climate change (A1B) increases annual mean area burned: Alaska (+34%) and the western U.S. (+54%) relative to the present-day, but unlike previous studies little change over Canada as a whole (8%), due to increases in GCM precipitation (scenario/GCM dependent). Future fires increase NOx emissions over the western United States by 50%, resulting in a large scale 1-3 ppbv enhancement in summertime afternoon ozone, though inter annual effects larger. Long-range transport impacts largest over central U.S. with large scale episodic ozone enhancements > 5 ppbv over large areas of the Northern U.S., comparable to W. U.S. ozone enhancements.

EXTRAS

CANADIAN FUTURE AREA BURNED PROJECTIONS Increased precipitation counterbalanced by increased 500mb GPH anom. Taiga Plains Increases of ~15% in summertime precipitation  -40% AB Boreal Shield West Increased GPH anomaly counterbalances increases in precipitation  + 21% AB

Soja et. al.

We capture between 50-60% for the two Alaska ecoregions Regression (in red) chosen from 22 surface met & FWI variables (1959 – 2006) and 500 mb data from Fairbanks, Alaska Note: DSR = Daily Severity Rating = f(T, RH, Rain) Ecozones

Both DSR and 500 mb anom govern variability in this region Ecozones

Area Burned and GISS Regression Met Corrected with: 1996-2006 1980-1989 60805.7 (500 mb anom) + 21113.9 (MaxDSR) - 61730.3 49665.6 (500 mb anom) + 63399.6(MeanTemp) – 838600

Station location Fire distribution Ecoregions 61 11 14 12 4 62 9 51 53 52 Ecoregions 4- Taiga Plains (120m) 12- Boreal Cordillera (415m) 62- Boreal Shield East (170m) 9- Boreal Plains (388m) 14- Montane Cordillera (747m) 51- Taiga Shield West (192m) 11- Taiga Cordillera(415m) 61- Boreal Shield West (348m) 52 – Taiga Shield East (27m) 53 – Hudson Plains(152m)

….AND FUEL CONSUMPTION Fuel bed map (1x1 km resolution) from Nadeau et al, [2005] [Maria Val Martin]

NEW EMISSIONS WILL ACCOUNT FOR SEASONAL CHANGE IN FUEL MOSITURE… Fuel Consumption Changes in Black Spruce-Lichen Woodland Forest Drier Conditions Late Season Wetter Conditions Early Season [Maria Val Martin]