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Dominick Spracklen, Jennifer Logan, Loretta Mickley, Rokjin Park Shiliang Wu, Rose Yevich

Future climate change drives increases in forest fires and summertime Organic Carbon Aerosol concentrations in the Western U.S. Dominick Spracklen, Jennifer Logan, Loretta Mickley, Rokjin Park Shiliang Wu, Rose Yevich. Mike Flannigan, Tony Westerling, Dan Jaffe. Boreal wildfire and climate.

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Dominick Spracklen, Jennifer Logan, Loretta Mickley, Rokjin Park Shiliang Wu, Rose Yevich

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  1. Future climate change drives increases in forest fires and summertime Organic Carbon Aerosol concentrations in the Western U.S. Dominick Spracklen, Jennifer Logan, Loretta Mickley, Rokjin Park Shiliang Wu, Rose Yevich Mike Flannigan, Tony Westerling, Dan Jaffe

  2. Boreal wildfire and climate Climate Change Air Quality Visibility OC / BC aerosols GHGs CO Longer fire seasons, more fires…. Less fires….. Increasing Temperature Increasing Rainfall

  3. Climate change and Forest Fires Predicted ratio of area burned in 3 X CO2 compared to pre-industrial CO2 Area burned and temperature in Canada [Gillet et al., 2004] [Flannigan et al., 2005] Climate impact on fire may be complex and vary regionally due to changes in temperature and precipitation

  4. Emissions of OC Large Fire Years Wildfire OC Biogenic OC Large interannual variability in wildfire emissions. How does this impact atmospheric OC? Historical Wildfire Records in Western US Large increase in wildfires after the mid 1980s. Frequency of large fires Westerling et al. 2006 Westerling et al. 2003

  5. IMPROVE GEOS-chem 2.0 1.5 OC concentration / μg m-3 1.0 0.1 0.2 0.3 OCbiob emission / Tg 1980-1984 GEOS-chem Climatological fires Impact of variability of fires on atmospheric OC Observations (IMPROVE) GEOS-chem Global CTM OC concentration / μg m-3 Interannual variability in summertime OC concentrations driven by wildfires. Jun-Aug mean at IMPROVE sites W of 100oW

  6. Predicting climate change impacts on forest fires and Air Quality changing greenhouse gases (A1 scenario) GISS general circulation model 1950 2000 2025 2050 2075 2100 Spin-up Area Burned Regressions MM5 Mesoscale model archive met fields Predict Area Burned GEOS-CHEM Global chemistry model archive met fields archive chemistry CMAQ Regional chemistry model Calculate emissions

  7. Predicting forest fire area burned Observed daily Temperature, Wind speed, Rainfall, RH Canadian Fire Weather Index System Daily forest moisture parameters Aggregate area burned to ecosystem Linear stepwise regression Area burned database (1o x 1o) Predictors of Area Burned Stepwise linear regression between meteorological/forest moisture variables & area burned [Flannigan et al. 2005]

  8. Aggregated ecosystems (similar vegetation / climate) 12.8 151.6 4.8 51.8 6.7 105.8 1980 – 2004 Totals [Westerling et al., 2002] Area Burned / 106 acres Biomass consumed/ Tg 17.5 25.4 3.6 11.6 4.5 9.8 Pacific North West and Rocky Mountain Forests are most important for biomass consumption and regional air quality Bailey (1994) classification

  9. Observed Area Burned Predicted Area Burned Pacific Northwest/Cascade Forests. Annual Area Burned Regression against linear area burned 0.5 R2=52% 0.25 Area burned / 106 Ha 1980 1990 2000 May-Oct mean Drought Code May-Oct mean Temperature 1980 1990 2000 1980 1990 2000 Regressions ‘explains’ 50-57% of variability in annual area burned in forest ecosystems. Best predictors are often Temperature or Fuel Moisture Index.

  10. 1995 CO2 A1 Scenario CO2 Trends in GISS western US mean July Met variables Temperature / oC Rainfall / mm day-1 GISS GCM predicts ~1.8 K increase in western US July mean temperature by 2055. How does this impact wildfires?

  11. Observed Annual area burned 1980-2055 Predicted +49% 2045-2054 AB compared to 1995-2004 +87% All ecosystems show an increase in Area Burned of between 7 and 87% driven by increasing temperature.

  12. Annual total W. US Forest Fire Biomass Consumption 1996-2055 Observed Predicted Use stochastic placement of wildfires within ecosystem and ecosystem specific fuel loads. 1996-2004 mean / Tg yr-1 Observed 19.15 Predicted 20.67 +50% Predicted mean biomass consumption for 2045-2054 is 50% greater than during 1996-2004

  13. Predicted Organic Carbon concentrations in W. US for 2046-2050 2046 2047 2048 2049 2050 Implications for visibility. Mean summertime visibility degrades from ~13.2dv (1996-2004) to ~13.8dv (2046-2050). 2046-2050 A1 scenario CO2 1996-2000 OC concentration / μg m-3 +20% Summertime OC in 2046-2050 predicted to increase by 20-25%. 1996 1997 1998 1999 2000 But need longer model runs…. Jun-Aug mean at IMPROVE sites

  14. Conclusions • In western US interannual variability in summertime OC is driven by variabilty in fires. • Increased fires in western US since the mid 1980s has likely caused increase in summertime OC concentrations. • Regressions of annual area burned in western US capture 50-57% of interannual variablity. Temperature and fuel moisture are best predictors. • Using GISS GCM output, forest fire emissions of OC predicted to increase by 50% by 2045-2055 (over 1995-2004) resulting in mean summertime OC to increase by 20-25%.

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