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Building on near-real-time and spatially explicit estimates of daily carbon dioxide (CO2) emissions, here we present and analyze a new city-level dataset of fossil fuel and cement emissions, Carbon Monitor Cities, which provides daily estimates of emissions from January 2019 through December 2021 for 1500 cities in 46 countries, and disaggregates five sectors: power generation, residential (buildings), industry, ground transportation, and aviation. The goal of this dataset is to improve the timeliness and temporal resolution of city-level emission inventories and includes estimates for both functional urban areas and city administrative areas that are consistent with global and regional totals. Comparisons with other datasets (i.e. CEADs, MEIC, Vulcan, and CDP-ICLEI Track) were performed, and we estimate the overall annual uncertainty range to be ±21.7%. Carbon Monitor Cities is a near-real-time, city-level emission dataset that includes cities around the world, including the first estimates for many cities in low-income countries.

Responses to COVID-19 have resulted in unintended reductions of city-scale carbon dioxide (CO2) emissions. Here, we detect and estimate decreases in CO2 emissions in Los Angeles and Washington DC/Baltimore during March and April 2020. We present three lines of evidence using methods that have increasing model dependency, including an inverse model to estimate relative emissions changes in 2020 compared to 2018 and 2019. The March decrease (25%) in Washington DC/Baltimore is largely supported by a drop in natural gas consumption associated with a warm spring whereas the decrease in April (33%) correlates with changes in gasoline fuel sales. In contrast, only a fraction of the March (17%) and April (34%) reduction in Los Angeles is explained by traffic declines. Methods and measurements used herein highlight the advantages of atmospheric CO2 observations for providing timely insights into rapidly changing emissions patterns that can empower cities to course-correct CO2 reduction activities efficiently.

Eddy-covariance (EC) flux measurements in Indianapolis were used to quantify the impact of the COVID-19 lockdown on CO and CO2 emissions from a highway and a suburban neighborhood. CO2 fluxes were measured for 6 weeks pre-lockdown (January 22, 2020–March 3, 2020) and during lockdown (March 25, 2020– May 5, 2020) using EC instrumentation at 41 m AGL. Fossil fuel CO2 emissions (CO2ff) were estimated by calculating eddy diffusivity to obtain CO flux and then scaling by the CO:CO2ff emissions ratio (RCO). Flux measurements segregated by wind direction were compared to hourly emissions from the 2020 Hestia inventory model. The lockdown CO2ff average weekday emissions from the highway estimated by EC decreased by 51.5 ± 10.9% (11.2 ± 2.2 µmol m−2 s−1) compared to pre-lockdown, similar to Hestia's estimate 56 ± 7% (12 ± 1 µmol m−2 s−1). The EC measurements detected a significant (2.2 ± 0.7 µmol m−2 s−1) but smaller magnitude decrease in CO2ff emissions from the suburban neighborhood. The daily cycles of CO2ff emissions were significantly correlated with Hestia estimates from the highway but not from the suburbs. This study demonstrates that EC flux towers and high-resolution inventory models in regions with mixed and spatially heterogeneous sources can quantify abrupt changes in sector- and source-specific CO2 fluxes. [ABSTRACT FROM AUTHOR]

Building on near-real-time and spatially explicit estimates of daily carbon dioxide (CO2) emissions, here we present and analyze a new city-level dataset of fossil fuel and cement emissions, Carbon Monitor Cities, which provides daily estimates of emissions from January 2019 through December 2021 for 1500 cities in 46 countries, and disaggregates five sectors: power generation, residential (buildings), industry, ground transportation, and aviation. The goal of this dataset is to improve the timeliness and temporal resolution of city-level emission inventories and includes estimates for both functional urban areas and city administrative areas that are consistent with global and regional totals. Comparisons with other datasets (i.e. CEADs, MEIC, Vulcan, and CDP-ICLEI Track) were performed, and we estimate the overall annual uncertainty range to be ±21.7%. Carbon Monitor Cities is a near-real-time, city-level emission dataset that includes cities around the world, including the first estimates for many cities in low-income countries. Measurement(s) carbon dioxide emissions Technology Type(s) carbon monitor Sample Characteristic - Environment city Sample Characteristic - Location worldwide [ABSTRACT FROM AUTHOR]

Estimates of greenhouse gas emissions, quantified at fine space and time scales, has become a critical component of new multi-constraint flux information systems in addition to providing relevant information to decisionmakers when considering GHG mitigation opportunities. The Vulcan Project is an effort to estimate bottom-up fossil fuel emissions and CO2 emissions from cement production (FFCO2) for the entire United States landscape at space and time scales that satisfy both scientific and policy needs. Here, we report on version 3.0 of the Vulcan emissions which quantifies FFCO2 emissions for the U.S. at a spatial resolution of 1 km × 1 km and hourly temporal resolution for the 2010–2015 time period. We provide a complete description of the updated methods, data sources, results, and comparison to a global gridded FFCO2 data product. We estimate FFCO2 emissions for the year 2011 of 1589.3 TgC with a 95 % confidence interval of 1299/1917 TgC (+18.3 %/−20.6 %), implying a one-sigma uncertainty of ~±10%. We find that per capita FFCO2 emissions are larger in states dominated by the electricity production and industrial sectors and smaller in states dominated by onroad and residential/commercial building emissions. The center of mass (CoM) of FFCO2 emissions in the US are located in the state of Missouri with mean seasonality that moves on a NE/SW near-elliptical path. Comparison to ODIAC, a global gridded FFCO2 emissions estimate shows large differences in both total emissions (100.1 TgC for year 2011) and spatial patterns. The spatial correlation (R²) between the two data products was 0.38 and the mean absolute difference at the individual gridcell scale was 80.04 %. The Vulcan v3.0 FFCO2 emissions data product offers an immediate high-resolution estimate of emissions in every city within the U.S., providing a large potential savings of time and effort for cities planning to develop self-reported city inventories. [ABSTRACT FROM AUTHOR]

The Eagle Ford Shale in southern Texas is home to a booming unconventional oil and gas industry, the climate and air quality impacts of which remain poorly quantified due to uncertain emissions estimates. We used the atmospheric enhancement of alkanes from Texas Commission on Environmental Quality volatile organic compound monitors across the shale, in combination with back trajectory and dispersion modeling, to quantify C2-C4 alkane emissions for a region in southern Texas, including the core of the Eagle Ford, for a set of 68 days from July 2013 to December 2015. Emissions were partitioned into raw natural gas and liquid storage tank sources using gas and headspace composition data, respectively, and observed enhancement ratios. We also estimate methane emissions based on typical ethane-to-methane ratios in gaseous emissions. The median emission rate from raw natural gas sources in the shale, calculated as a percentage of the total produced natural gas in the upwind region, was 0.8% with an interquartile range (IQR) of 0.5%-1.4%, close to the U.S. Environmental Protection Agency's (EPA) current estimates. However, storage tanks contributed 24% of methane emissions, 54% of ethane, 82% percent of propane, 90% of n-Butane, and 83% of isobutane emissions. The inclusion of liquid storage tank emissions results in an emission rate of 2.2% (IQR of 0.9 4.9%) relative to produced natural gas, exceeding the EPA estimate by a factor of two. We conclude that leaks from liquid storage tanks are likely a major source for the observed non-methane hydrocarbon enhancements in the northern hemisphere. [ABSTRACT FROM AUTHOR]