The Hestia Fossil Fuel CO 2 Emissions Data Product for the Los Angeles Megacity (Hestia-LA)

High-resolution bottom-up estimation provides a detailed guide for city greenhouse gas mitigation options, offering details that can increase the economic efficiency of emissions reduction options and synergize with other urban policy priorities at the human scale. As a critical constraint to urban atmospheric CO2 inversion studies, bottom-up spatiotemporally explicit emissions data products are also necessary to construct comprehensive urban CO2 emission information systems useful for trend detection and emissions verification. The "Hestia Project" is an effort to provide bottom-up granular fossil fuel (FFCO2) emissions for the urban domain with building/street and hourly space-time resolution. Here, we report on the latest urban area for which a Hestia estimate has been completed - the Los Angeles megacity, encompassing five counties: Los Angeles County, Orange County, Riverside County, San Bernardino County and Ventura County. We provide a complete description of the methods used to build the Hestia FFCO2 emissions data product for the years 2010-2015. We find that the LA Basin emits 48.06 (+/- 5.3) MtC yr(-1), dominated by the on-road sector. Because of the uneven spatial distribution of emissions, 10% of the largest-emitting grid cells account for 93.6 %, 73.4 %, 66.2 %, and 45.3% of the industrial, commercial, on-road, and residential sector emissions, respectively. Hestia FFCO2 emissions are 10.7% larger than the inventory estimate generated by the local metropolitan planning agency, a difference that is driven by the industrial and electricity production sectors. The detail of the Hestia-LA FFCO2 emissions data product offers the potential for highly targeted, efficient urban greenhouse gas emissions mitigation policy.