Airborne Measurements Suggest That Halocarbon Emissions from the New York City Urban Region Have Comparable Climate...

Urban centers concentrate high usage of halocarbons largely for refrigeration, air conditioning (A/C), heat pumps, and fire suppression. Loss of these gases to the atmosphere has a large climate impact. Here, we quantify halocarbon emissions from the New York City region during the East Coast Outflow airborne campaigns in 2018 and 2020. We quantify urban-scale emissions using discrete airborne flask samples collected during downwind plume sampling. We find that inventories of the urban region underestimate halocarbon emissions. For A/C species, higher emissions in 2018 correspond with higher temperatures, suggesting emissions may vary with appliance usage. The climate impact (100-year time horizon) of our observed halocarbon emissions is comparable to coincident methane emissions, equal to ∼10% of urban CO₂ emissions. Without leakage mitigation and effective phase-down efforts, high halocarbon emissions could undercut the benefits of switching to heat pumps and present a positive warming feedback with increasing air conditioning demand.