FIRE IS A CRITICAL COMPONENT OF THE EARTH SYSTEM AFFECTING BIOGEOCHEMICAL AND HYDROLOGICAL CYCLES. FIRE IS ALSO AN IMPORTANT SOURCE OF POLLUTANTS GREENHOUSE GASES (GHGS) AND AEROSOLS CONTRIBUTING 40% OF GLOBAL TOTAL BLACK CARBON (BC) AND CARBON MONOXIDE (CO) EMISSIONS. ADDITIONALLY AEROSOLS FROM FIRE SOURCES ACCOUNT FOR ABOUT 30% OF CLOUD CONDENSATION NUCLEI IN THE ATMOSPHERE. IN THE LAND SYSTEM FIRE CHANGES THE PRESENCE AND CHARACTERISTICS OF VEGETATION WHICH AFFECTS THE EXCHANGES OF WATER ENERGY AND MOMENTUM WITH THE ATMOSPHERE. CHANGES TO THE LAND SURFACE AND VEGETATION ADDITIONALLY IMPACT SURFACE ALBEDO AND HENCE THE EARTH RADIATION BUDGET. FIRE-WEATHER CONDITIONS CREATED BY THE CLIMATIC STATE COUPLED WITH LAND SURFACE CHARACTERISTICS AND VEGETATION DETERMINE BOTH THE OCCURRENCE AND SPREAD OF FIRES. FIRE ACTIVITY THEREFORE BOTH AFFECTS AND IS AFFECTED BY THE LAND-ATMOSPHERE SYSTEM. THE ARCTIC BOREAL ZONE IS AN IMPORTANT ILLUSTRATIVE EXAMPLE OF THESE TYPES OF FEEDBACKS. FIRE ACTIVITY IS PREDICTED TO INCREASE IN THE FUTURE AS TEMPERATURES WARM IN RESPONSE TO CLIMATE CHANGE. INCREASES IN ARCTIC FIRE ACTIVITY ARE EXPECTED TO IMPACT VEGETATION HYDROLOGY AND RADIATIVE FORCING. THE LARGE CARBON RESERVOIR IN ARCTIC SOILS HAS LED TO CONCERNS OF ITS RAPID RELEASE WHICH WOULD GREATLY EXACERBATE GLOBAL WARMING PARTICULARLY SINCE PERMAFROST TEMPERATURES ARE RISING AND FIRES ACCELERATE PERMAFROST THAW. EARTH SYSTEM MODELS (ESMS) ARE A POWERFUL TOOL TO UNDERSTAND THE CONNECTIONS BETWEEN INDIVIDUAL EARTH SYSTEM COMPONENTS AND THEIR SENSITIVITIES TO CHANGING CONDITIONS (I.E. CLIMATE CHANGE). IN THIS PROPOSAL WE CONTRIBUTE TO THE DEVELOPMENT OF THE NASA GODDARD EARTH OBSERVING SYSTEM MODEL VERSION 5 (GEOS-5) BY ENHANCING THE ABILITY OF THIS ESM TO INTEGRATE PROCESSES AND FEEDBACKS BETWEEN THE BIOSPHERE ATMOSPHERE CRYOSPHERE LAND AND OCEAN. A PRACTICAL LIMITATION OF ESMS SUCH AS GEOS-5 IS COMPUTATIONAL EXPENSE WHICH LIMITS THE POSSIBILITY OF COMPREHENSIVELY EXPLORING COMPONENT SENSITIVITY TO A VARIETY OF CONDITIONS. FURTHERMORE PRESCRIBING EMISSIONS OF AEROSOL AND TRACE GASES AS IS TYPICALLY DONE BREAKS DOWN THE FUNDAMENTAL POINT OF RUNNING AN EARTH SYSTEM MODEL; THAT IS WHEN THESE FLUXES ARE PRESCRIBED ONE CANNOT FULLY EXPLORE THE COUPLED RESPONSE OF THE EARTH SYSTEM TO CHANGING CONDITIONS. IN THIS PROPOSAL WE ADDRESS BOTH OF THESE LIMITATIONS WITH RESPECT TO BIOMASS BURNING INCLUDING ITS IMPACT ON THE LAND SURFACE AND ATMOSPHERIC CHEMISTRY AND THE ATTENDANT FEEDBACKS ON OTHER BIOGEOCHEMICAL CYCLES IN THE EARTH SYSTEM. WE PROPOSE TO QUANTIFY 1) THE RESPONSE OF FIRE ACTIVITY TO A WARMING CLIMATE AND 2) THE SENSITIVITY OF IMPORTANT COMPONENTS OF THE EARTH SYSTEM (E.G. OXIDIZING CAPACITY OF THE TROPOSPHERE BUDGETS OF GREENHOUSE GASES (GHGS) AND AEROSOLS AND RADIATIVE FORCING) TO HISTORIC AND POTENTIAL FUTURE CHANGES IN FIRE ACTIVITY. IN ORDER TO EXPLORE THE IMPACTS OF FIRE ACTIVITY AND ITS RESULTING FEEDBACKS WE PROPOSE TO (1) INTRODUCE AND EVALUATE A COUPLED PROGNOSTIC BIOMASS BURNING EMISSIONS SCHEME IN THE NASA GEOS-5 ATMOSPHERIC GENERAL CIRCULATION MODEL (AGCM) A CAPABILITY THAT IS CURRENTLY LACKING (2) CREATE A COMPUTATIONALLY-EFFICIENT TROPOSPHERIC CHEMISTRY MODULE ("QUICK CHEMISTRY") TO EXPLORE THE FEEDBACKS BETWEEN THE MAJOR GHGS (OZONE (O3) WATER VAPOR (H2OV) HALOGENS N2O CO2 AND CH4) AEROSOLS AND THE EARTH SYSTEM (3) PERFORM HISTORICAL SENSITIVITY SIMULATIONS TO QUANTIFY THE IMPACT OF FIRE ACTIVITY ON IMPORTANT COMPONENTS OF THE EARTH SYSTEM AND (4) PERFORM SIMULATIONS OF A FUTURE WARMING CLIMATE TO QUANTIFY THE POTENTIAL IMPACT ON FIRE ACTIVITY OVER THE COMING DECADES AND THE CONCOMITANT IMPACT ON AEROSOLS AND GHGS AND ALSO EXPLORE THE SENSITIVITY OF THESE IMPORTANT COMPONENTS OF THE EARTH SYSTEM TO CHANGES IN FIRE ACTIVITY.