Emissions of carbon associated with cities comprise a large component of the anthropogenic source. A number of cities have announced plans to reduce greenhouse gas emissions, but the scientific knowledge to quantitatively track emissions and assess the efficacy of mitigation is lacking. As the global population increasingly resides in urban regions, scientific knowledge about how much, where, and why a particular city emits carbon becomes increasingly important.
To address this gap, researchers have initiated studies of carbon emissions and cycling in several U.S. cities, making it timely to develop a collaborative network to exchange information on community standards and common measurements, facilitate data sharing, and create analysis frameworks and cross-city syntheses to catalyze a new generation of researchers and enable new collaborations tackling important objectives (see below) that are difficult to address in isolation. We propose here a synthesis/analysis network focusing on the urban carbon cycle to capture and disseminate recent progress and spur future developments in this important arena.
Our synthesis/analysis network entrains a cross-section of U.S. cities with varying characteristics: size, population density, vegetation, urban form, infrastructure, development rates, climate, and meteorological patterns. The project focuses initially on cities in the U.S. with low barriers of entry, but we envision that this network should lay the foundation for broad national and international collaboration (a collaborator from Germany will participate at no cost).
The proposed project emphasizes research on CO2, but the synthesis will also include other species of interest in urban settings, especially methane and tracers that enable partitioning of emissions by source type (stable isotopes, radiocarbon, CO).
 Conduct workshops for idea exchange, data harmonization & integration, inventory comparison, stakeholder outreach, network design, inverse modeling, collaboration
 Create publicly available CO2 and CH4 mixing ratio datasets that have undergone consistent QA/QC and formatting for multiple urban areas
 Develop and disseminate anthropogenic and biospheric flux inventories that would be compared against one another and validated against local bottom-up information
 Develop a powerful new cross-city atmospheric modeling system, with inputs based on , , and , and on new high resolution operational meteorological products, designed to be operable, scalable, widely applicable, and web-available.
 Estimate of carbon emissions in different U.S. cities, by applying  and .
 Engage stakeholders including city and state-level officials and NGOs, including: assessing user needs, building a learning community at public agencies, and creating conduits for data exchange between policymakers and scientists.