Global and regional emissions estimates for N&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt;O

Eri Saikawa ,Marcel Van Der Schoot ,Ray F Weiss ,Shuji Aoki ,Toshinobu Machida ,Matthew Rigby ,Paul J Fraser ,G S Dutton ,E J Dlugokencky ,Yasunori Tohjima ,L P Steele ,Ray L Langenfelds ,Christina M Harth ,Manfredi Manizza ,P B Krummel ,T Nakazawa ,Prabir K Patra ,B D Hall ,Simon O’doherty ,Ronald G Prinn ,Kentaro Ishijima ,James W Elkins

doi:10.5194/acp-14-4617-2014

Abstract

Abstract. We present a comprehensive estimate of nitrous oxide (N2O) emissions using observations and models from 1995 to 2008. High-frequency records of tropospheric N2O are available from measurements at Cape Grim, Tasmania; Cape Matatula, American Samoa; Ragged Point, Barbados; Mace Head, Ireland; and at Trinidad Head, California using the Advanced Global Atmospheric Gases Experiment (AGAGE) instrumentation and calibrations. The Global Monitoring Division of the National Oceanic and Atmospheric Administration/Earth System Research Laboratory (NOAA/ESRL) has also collected discrete air samples in flasks and in situ measurements from remote sites across the globe and analyzed them for a suite of species including N2O. In addition to these major networks, we include in situ and aircraft measurements from the National Institute of Environmental Studies (NIES) and flask measurements from the Tohoku University and Commonwealth Scientific and Industrial Research Organization (CSIRO) networks. All measurements show increasing atmospheric mole fractions of N2O, with a varying growth rate of 0.1–0.7% per year, resulting in a 7.4% increase in the background atmospheric mole fraction between 1979 and 2011. Using existing emission inventories as well as bottom-up process modeling results, we first create globally gridded a priori N2O emissions over the 37 years since 1975. We then use the three-dimensional chemical transport model, Model for Ozone and Related Chemical Tracers version 4 (MOZART v4), and a Bayesian inverse method to estimate global as well as regional annual emissions for five source sectors from 13 regions in the world. This is the first time that all of these measurements from multiple networks have been combined to determine emissions. Our inversion indicates that global and regional N2O emissions have an increasing trend between 1995 and 2008. Despite large uncertainties, a significant increase is seen from the Asian agricultural sector in recent years, most likely due to an increase in the use of nitrogenous fertilizers, as has been suggested by previous studies.

Highlights

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) with a global warming potential (GWP) approximately 300 times greater than CO2 over a 100-year time horizon (Forster et al, 2007)
1995 and 2008 to the sampling frequency error, the mismatch error varies by month at each site, taking into account the monthly we present results from our inversion to dechanges in transport in the model
Σmodel is the error associated with the global chemrive regional N2O emissions by source sector for the 13 regions using all available data from Advanced Global Atmospheric Gases Experiment (AGAGE), NOAA Cycle Greenhouse Gases (CCGG), ical transport model, which we choose to interpret as an ad- NOAA OTTO, RITS, and CATS, Commonwealth Scientific and Industrial Research Organization (CSIRO), National Institute of Environmental Studies (NIES), and Toditional measurement error

Summary

Introduction

Nitrous oxide (N2O) is a potent greenhouse gas (GHG) with a global warming potential (GWP) approximately 300 times greater than CO2 over a 100-year time horizon (Forster et al, 2007). N2O emissions are controlled under the Kyoto Protocol, but N2O production is not included in the Montreal Protocol on substances that deplete the ozone layer. Since N2O is inert within the troposphere, it has a long atmospheric lifetime of 131 ± 10 years (Prather et al, 2012). There are several known sources of N2O emissions and in this paper we categorize them as the following: agricultural soil, industrial (including all combustion sources), natural soil, ocean, and biomass burning. There are large uncertainties associated with estimated emissions from each of these sectors, but approximately 2/3 of the emissions have been attributed to the natural soil and ocean, with the remaining attributed to anthropogenic sources (Khalil et al, 2002; Denman et al, 2007; Nevison et al, 2007). The increase in atmospheric N2O mixing ratios, since at least the 1940s, has been largely attributed to increased N2O emissions from agricultural soils (Park et al, 2012)

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