es403447v_si_001.pdf (437.88 kB)
High-Global Warming Potential F‑gas Emissions in California: Comparison of Ambient-Based versus Inventory-Based Emission Estimates, and Implications of Refined Estimates
journal contribution
posted on 2014-01-21, 00:00 authored by Glenn Gallagher, Tao Zhan, Ying-Kuang Hsu, Pamela Gupta, James Pederson, Bart Croes, Donald
R. Blake, Barbara Barletta, Simone Meinardi, Paul Ashford, Arnie Vetter, Sabine Saba, Rayan Slim, Lionel Palandre, Denis Clodic, Pamela Mathis, Mark Wagner, Julia Forgie, Harry Dwyer, Katy WolfTo provide information for greenhouse
gas reduction policies, the
California Air Resources Board (CARB) inventories annual emissions
of high-global-warming potential (GWP) fluorinated gases, the fastest
growing sector of greenhouse gas (GHG) emissions globally. Baseline
2008 F-gas emissions estimates for selected chlorofluorocarbons (CFC-12),
hydrochlorofluorocarbons (HCFC-22), and hydrofluorocarbons (HFC-134a)
made with an inventory-based methodology were compared to emissions
estimates made by ambient-based measurements. Significant discrepancies
were found, with the inventory-based emissions methodology resulting
in a systematic 42% under-estimation of CFC-12 emissions from older
refrigeration equipment and older vehicles, and a systematic 114%
overestimation of emissions for HFC-134a, a refrigerant substitute
for phased-out CFCs. Initial, inventory-based estimates for all F-gas
emissions had assumed that equipment is no longer in service once
it reaches its average lifetime of use. Revised emission estimates
using improved models for equipment age at end-of-life, inventories,
and leak rates specific to California resulted in F-gas emissions
estimates in closer agreement to ambient-based measurements. The discrepancies
between inventory-based estimates and ambient-based measurements were
reduced from −42% to −6% for CFC-12, and from +114%
to +9% for HFC-134a.