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Abstract:

We present the instrumentation, data and accomplishments of the multinational global atmospheric high frequency measurement program, AGAGE (Advanced Global Atmospheric Gases Experiment). AGAGE and its predecessors have been operating since 1978. The history of the trace gas composition of the global atmosphere over the past 4 decades as measured by AGAGE is reviewed. AGAGE now measures, at 13 globally-distributed sites, over 50 trace gases including all the important species in the Montreal Protocol to protect the ozone layer and all the important non-carbon-dioxide (non-CO₂) gases assessed by the Intergovernmental Panel on Climate Change.  Using these observations, the magnitudes and distributions by region of emissions and sinks of the measured gases are estimated. The anthropogenic gases include chlorocarbons, chlorofluorocarbons – CFCs, bromocarbons, hydrochlorofluorocarbons – HCFCs, hydrofluorocarbons– HFCs and polyfluorinated compounds (perfluorocarbons – PFCs), nitrogen trifluoride – NF₃, sulfuryl fluoride – SO₂F₂, and sulfur hexafluoride – SF₆. The biogenic-anthropogenic gases include methane – CH₄, nitrous oxide – N₂O, carbon monoxide – CO, molecular hydrogen – H₂, methyl chloride – CH₃Cl, and methyl bromide – CH₃Br. AGAGE has detected new atmospheric gases such as SO₂F₂, NF₃, heavy PFCs (C₄F₁₀,C₅F₁₂, C₆F₁₄, C₇F₁₆, and C₈F₁₈) and hydrofluoroolefins (HFOs). In general the chemicals regulated by the Montreal Protocol all show rising concentrations and inferred emissions before regulation, and decreasing inferred emissions, and ultimately concentrations, after regulation. Also the concentrations and emissions of the chemicals replacing the regulated ones all show rapid increases. AGAGE also determines the average concentrations and trends of the tropospheric “cleanser” hydroxyl radical (OH), from the measured rates of destruction of atmospheric trichloroethane (CH₃CCl₃) and estimates of its emissions, showing year-to-year changes but no multi-decadal trend in OH. Overall, the accomplishments of AGAGE are furthering our understanding of critical global chemical and climatic phenomena.

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Prinn_et_al_AGAGE_History_essd-10-985-2018.pdf	4.5 MB