COVID-19: Impacts of California's Stay-At-Home order and economic recovery on fossil fuel-derived carbon emissions in California
Abstract
Anthropogenic activities dominate the emission of fossil carbon (i.e. 14C-free CO2) that sustain the buildup of carbonaceous greenhouse gases in the atmosphere, with detrimental effects on climate and ecosystems. The economic success and decline of major economies have contributed to measurable rises and hiatuses in the growth rate of atmospheric CO2, and policies to decarbonize economies have been enacted. However, attributing changes in atmospheric CO2 to human activities is not trivial due to the small size of anthropogenic relative to biosphere CO2 fluxes and their complex emissions sources and remains a key challenge for verifying emission reduction efforts.
This study took advantage of major economic disruptions in California during the COVID-19 pandemic to assess the sensitivity of combining ground-based observations of ambient CO2 and its radiocarbon (14C) content for quantifying changes in fossil CO2 emissions. 40 million Californians (12% of U.S. population) were ordered to "Stay-At-Home" for 46 days (March 19 to May 4, 2020) and physical distancing mandates continued to impede economic activities throughout the summer. California's fossil CO2 emissions are dominated by transportation and industry (65% of emissions), and its climate and coastal proximity facilitate large seasonal changes in the magnitude of biogenic CO2 emissions and their sources. Reductions in the ambient enhancements of carbonaceous greenhouse gases (CO2 and CO) and pollutants (NH3) in 2020 were quantified using monthly mobile surveys of over 750 km of road in Southern California and compared to similar transects conducted in July 2019. Changes in fossil CO2 emissions were assessed by analyzing the 14C content of approximately 150 winter-annual grass samples collected by citizen scientists across California, which record the 14C of ambient CO2 in their tissue, and apportioning this data into contributions from fossil vs. biogenic sources with isotope mass balancing. The plant-based estimates were compared to long-term, monthly-integrated measurements of ambient 14CO2 at UC Irvine and a previous assessment of 14CO2 in winter-annual grasses in California in 2004/2005. Finally, the magnitude of changes in fossil CO2 emissions was compared to changes in indicators of economic activity (energy consumption & transport activity) during the same period. The COVID-19-related shutdown of the world's 5th largest economy (California) provides a real-life test case for quantifying the carbon-reduction potential of a massive shift to tele-commuting with related reduction in vehicle and air traffic, and our ability to quantify these changes with observations of fossil CO2 in the atmosphere.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMA081...01Y
- Keywords:
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- 0305 Aerosols and particles;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0345 Pollution: urban and regional;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3360 Remote sensing;
- ATMOSPHERIC PROCESSES