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Atmospheric measurements show that emissions of hydrofluorocarbons (HFCs) and hydrochlorofluorocarbons are now the primary drivers of the positive growth in synthetic greenhouse gas (SGHG) radiative forcing. We infer recent SGHG emissions and examine the impact of future emissions scenarios, with a particular focus on proposals to reduce HFC use under the Montreal Protocol. If these proposals are implemented, overall SGHG radiative forcing could peak at around 355 mW m À2 in 2020, before declining by approximately 26% by 2050, despite continued growth of fully fluorinated greenhouse gas emissions. Compared to "no HFC policy" projections, this amounts to a reduction in radiative forcing of between 50 and 240 mW m À2 by 2050 or a cumulative emissions saving equivalent to 0.5 to 2.8 years of CO 2 emissions at current levels. However, more complete reporting of global HFC emissions is required, as less than half of global emissions are currently accounted for.

We present an analytical method for the in situ measurement of atmospheric nitrogen trifluoride (NF(3)), an anthropogenic gas with a 100-year global warming potential of over 16,000. This potent greenhouse gas has a rising atmospheric abundance due to its emission from a growing number of manufacturing processes and an expanding end-use market. Here we present a modified version of the "Medusa" preconcentration gas chromatography/mass spectrometry (GC/MS) system of Miller, B. R.; Weiss, R. F.; Salameh, P. K.; Tanhua, T.; Greally, B. R.; Mühle, J.; Simmonds, P. G. Anal. Chem.2008, 80 (5), 1536-1545. By altering the techniques of gas separation and chromatography after initial preconcentration, we are now able to make atmospheric measurements of NF(3) with relative precision <2% (1σ) for current background clean air samples. Importantly, this method augments the currently operational Medusa system, so that the quality of data for species already being measured is not compromised and NF(3) is measured from the same preconcentrated sample. We present the first in situ measurements of NF(3) from La Jolla, California made 11 times daily, illustrating how global deployment of this technique within the AGAGE (Advanced Global Atmospheric Gases Experiment) network could facilitate estimation of global and regional NF(3) emissions over the coming years.

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