History of chemically and radiatively important atmospheric gases from the Advanced Global Atmospheric Gases Experiment (AGAGE)

Abstract

Abstract. We present the organization, instrumentation, datasets, data interpretation, modeling, and accomplishments of the multinational global atmospheric measurement program AGAGE (Advanced Global Atmospheric Gases Experiment). AGAGE is distinguished by its capability to measure globally, at high frequency, and at multiple sites all the important species in the Montreal Protocol and all the important non-carbon-dioxide (non-CO2) gases assessed by the Intergovernmental Panel on Climate Change (CO2 is also measured at several sites). The scientific objectives of AGAGE are important in furthering our understanding of global chemical and climatic phenomena. They are the following: (1) to accurately measure the temporal and spatial distributions of anthropogenic gases that contribute the majority of reactive halogen to the stratosphere and/or are strong infrared absorbers (chlorocarbons, chlorofluorocarbons – CFCs, bromocarbons, hydrochlorofluorocarbons – HCFCs, hydrofluorocarbons – HFCs and polyfluorinated compounds (perfluorocarbons – PFCs), nitrogen trifluoride – NF3, sulfuryl fluoride – SO2F2, and sulfur hexafluoride – SF6) and use these measurements to determine the global rates of their emission and/or destruction (i.e., lifetimes); (2) to accurately measure the global distributions and temporal behaviors and determine the sources and sinks of non-CO2 biogenic–anthropogenic gases important to climate change and/or ozone depletion (methane – CH4, nitrous oxide – N2O, carbon monoxide – CO, molecular hydrogen – H2, methyl chloride – CH3Cl, and methyl bromide – CH3Br); (3) to identify new long-lived greenhouse and ozone-depleting gases (e.g., SO2F2, NF3, heavy PFCs (C4F10, C5F12, C6F14, C7F16, and C8F18) and hydrofluoroolefins (HFOs; e.g., CH2 = CFCF3) have been identified in AGAGE), initiate the real-time monitoring of these new gases, and reconstruct their past histories from AGAGE, air archive, and firn air measurements; (4) to determine the average concentrations and trends of tropospheric hydroxyl radicals (OH) from the rates of destruction of atmospheric trichloroethane (CH3CCl3), HFCs, and HCFCs and estimates of their emissions; (5) to determine from atmospheric observations and estimates of their destruction rates the magnitudes and distributions by region of surface sources and sinks of all measured gases; (6) to provide accurate data on the global accumulation of many of these trace gases that are used to test the synoptic-, regional-, and global-scale circulations predicted by three-dimensional models; and (7) to provide global and regional measurements of methane, carbon monoxide, and molecular hydrogen and estimates of hydroxyl levels to test primary atmospheric oxidation pathways at midlatitudes and the tropics. Network Information and Data Repository: http://agage.mit.edu/data or http://cdiac.ess-dive.lbl.gov/ndps/alegage.html (https://doi.org/10.3334/CDIAC/atg.db1001).

The Impact of Continuing CFC‐11 Emissions on Stratospheric Ozone

“…Although CFC‐11 emissions declined from the late 1980s to the early 2000s, they were fairly constant during 2002–2012. Montzka et al () showed that emissions then increased during 2013–2016, to an average of approximately 72.5 gigagrams per year (Gg/year) (as updated in Engel & Rigby, ; see also Prinn et al, ). Global emissions during 2014–2016 were roughly 10 Gg/year (~15%) higher than the 2002–2012 average, and significantly larger than 2006 and 2012 projections based on reported production and estimates of the bank and bank release fraction (see Engel & Rigby, ).…”

Advancing Scientific Understanding of the Global Methane Budget in Support of the Paris Agreement

“…Observations of atmospheric CH 4 mole fraction and their “isotopologues” (section ) play a fundamental role in monitoring the global carbon cycle. The current global “background” network (Figure ) of CH 4 mole fraction observations consists of multinational and national measurement programs (including, but not limited to, NOAA Global Greenhouse Gas Reference Network, Integrated Carbon Observation System, and Advanced Global Atmospheric Gases Experiment, Dlugokencky et al, ; Prinn et al, , http://www.icos-ri.eu). Background measurements indicate the CH 4 mole fraction in air that has been well mixed in the global atmosphere.…”

“…While observations of methyl chloroform (CH 3 CCl 3 , MCF) trends have been widely used for this purpose, it is known that uncertainties in its emissions can lead to uncertainties in the derived [OH], similar to, or larger than, the inferred [OH] variability (Rigby et al, ; Turner et al, ). In the coming years, estimation of [OH] using MCF will become more uncertain as its atmospheric mole fraction declines (Prinn et al, ). While some recent MCF, budget‐based studies have suggested that [OH] changes could be a major contributor to recent methane growth rate variability, albeit with very large uncertainty (Rigby et al, ; Turner et al, ), atmospheric photochemical models do not tend to find evidence for strong variability in global [OH] (e.g., Figure , Nicely et al, ).…”

Perfluorocyclobutane (PFC-318, <i>c</i>-C<sub>4</sub>F<sub>8</sub>) in the global atmosphere

“…2 Experimental methods 2.1 Instrumentation, data availability, and calibration c-C 4 F 8 and ∼ 40 other halogenated compounds were measured by AGAGE in 2 L air samples with the Medusa cryogenic pre-concentration systems with a gas chromatograph (GC, Agilent 6890) and quadrupole mass selective detector (MSD) (Miller et al, 2008;Prinn et al, 2018). Data from 12 in situ measurement sites and 14 Medusa instruments were used.…”