CITIES AND THEIR ASSOCIATED URBAN AREAS HAVE A MUCH LARGER IMPACT ON THE ENVIRONMENT AT BOTH LOCAL AND GLOBAL SCALES THAN THEIR SPATIAL FOOTPRINT ON THE EARTH S SURFACE. AT THIS TIME MORE THAN HALF OF THE WORLD S POPULATION LIVES IN URBAN AREAS (80% IN THE UNITED STATES) AND THIS PROPORTION IS PROJECTED TO CLIMB TO 70% BY 2050. THEREFORE IT IS ESSENTIAL THAT NUMERICAL MODELS USED TO STUDY THE PHYSICS CHEMISTRY AND BIOLOGY AFFECTING THE EARTH SYSTEM REPRESENT THE EFFECTS OF URBAN AREAS ON CLIMATE AND THE EFFECTS OF CHANGING CLIMATE ON URBAN AREAS. AT THE SAME TIME WE NEED TO DEVELOP STATE OF THE ART SIMPLE AND ACCURATE URBAN MODELS TO ADDRESS ISSUES RELATED TO URBAN SECURITY AGAINST THE SPECTRA OF CHEMICAL BIOLOGICAL AND RADIOLOGICAL (CBR) HAZARDS. WE ARE PROPOSING A SPECIAL INTERNATIONAL WORKSHOP AIMED AT ENHANCING THE CAPABILITIES OF GLOBAL EARTH SYSTEM MODELS (ESMS) IN REPRESENTING THE ATMOSPHERIC DYNAMICS AND CHEMISTRY UNIQUE ASPECTS OF THE BIOSPHERE AND LANDUSE AND HUMAN DIMENSIONS IN THE URBAN ENVIRONMENT. THIS 2.5-DAY MULTI-AGENCY WORKSHOP LED BY THE U.S. DEPARTMENT OF ENERGY (IN COORDINATION WITH THE NATIONAL SCIENCE FOUNDATION THE NATIONAL AERONAUTICS AND SPACE ADMINISTRATION THE NATIONAL OCEANIC AND ATMOSPHERIC ADMINISTRATION AND THE DEPARTMENT OF DEFENSE) WILL BE HELD AT ARGONNE NATIONAL LABORATORY IN THE CHICAGO AREA IN LATE SPRING 2019; THIS WORKSHOP WILL BRING TOGETHER NATIONAL AND INTERNATIONAL EXPERTS TO DEVELOP A ROADMAP FOR A BETTER REPRESENTATION OF URBAN EFFECTS IN ESMS. THIS WORKSHOP IS ESPECIALLY IMPORTANT AS THE SCIENCE COMMUNITY DEVELOPS VERY HIGH-RESOLUTION VERSIONS OF THOSE MODELS. THE WORKSHOP WILL ALSO DISCUSS EMERGING SMART CITY SENSING TECHNOLOGIES AND THEIR POSSIBLE USE IN MODEL DEVELOPMENT (E.G. NSF-FUNDED ARRAY OF THINGS NETWORK IN CHICAGO). OUTCOMES WILL INCLUDE A MEETING REPORT FOR AMERICAN GEOPHYSICAL UNION EOS AND FOR THE AMERICAN METEOROLOGICAL SOCIETY BULLETIN (BAMS) A MUCH MORE EXTENSIVE REPORT FOR DOE NASA AND THE OTHER COORDINATING AGENCIES A HIGH-PROFILE REVIEW AND/OR COMMENTARY ARTICLE ON URBAN ESM ROADMAP AND FUTURE URBAN NEEDS AND A WHITE PAPER TO WMO ON THE FINDINGS AND RECOMMENDATIONS.