Atmospheric Methane: Estimates of Its Past, Present and Future and Its Role in Effecting Changes in Atmospheric Chemistry

1991 ◽  
pp. 99-126
Author(s):  
I. Aselmann
Keyword(s):  
Atmospheric Chemistry ◽  
Atmospheric Methane

scholarly journals Global stratospheric measurements of the isotopologues of methane from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer

2015 ◽  
Vol 8 (10) ◽  
pp. 11171-11207
Author(s):  
E. M. Buzan ◽  
C. A. Beale ◽  
C. D. Boone ◽  
P. F. Bernath
Keyword(s):  
Fourier Transform ◽  
Atmospheric Chemistry ◽  
Climate Model ◽  
Fourier Transform Spectrometer ◽  
Atmospheric Methane ◽  
Community Climate Model ◽  
Atmospheric Sinks ◽  
Chemistry Experiment ◽  
Methane Concentrations ◽  
Balloon Measurements

Abstract. This paper presents an analysis of observations of methane and its two major isotopologues, CH3D and 13CH4 from the Atmospheric Chemistry Experiment (ACE) satellite between 2004 and 2013. Additionally, atmospheric methane chemistry is modeled using the Whole Atmospheric Community Climate Model (WACCM). ACE retrievals of methane extend from 6 km for all isotopologues to 75 km for 12CH4, 35 km for CH3D, and 50 km for 13CH4. While total methane concentrations retrieved from ACE agree well with the model, values of δD–CH4 and δ13C–CH4 show a bias toward higher δ compared to the model and balloon-based measurements. Calibrating δD and δ13C from ACE using WACCM in the troposphere gives improved agreement in δD in the stratosphere with the balloon measurements, but values of δ13C still disagree. A model analysis of methane's atmospheric sinks is also performed.

scholarly journals Atmospheric chemistry: Increasing atmospheric methane

Nature ◽  
1983 ◽  
Vol 301 (5901) ◽  
pp. 568-568 ◽  
Author(s):  
W.L. Chameides
Keyword(s):  
Atmospheric Chemistry ◽  
Atmospheric Methane

scholarly journals An analysis of atmospheric CH<sub>4</sub> concentrations from 1984 to 2008 with a single box atmospheric chemistry model

2012 ◽  
Vol 12 (11) ◽  
pp. 30259-30282 ◽  
Author(s):  
Z. Tan ◽  
Q. Zhuang
Keyword(s):  
Growth Rate ◽  
Atmospheric Chemistry ◽  
Methane Flux ◽  
Methane Emissions ◽  
Atmospheric Methane ◽  
Significant Drop ◽  
Oxidizing Power ◽  
The Mean

Abstract. We present a single box atmospheric chemistry model involving atmospheric methane (CH4), carbon monoxide (CO) and radical hydroxyl (OH) to analyze atmospheric CH4 concentrations from 1984 to 2008. When OH is allowed to vary, the modeled CH4 is 20 ppb higher than observations from the NOAA/ESRL and AGAGE networks for the end of 2008. However, when the OH concentration is held constant at 106 molecule cm−3, the simulated CH4 shows a trend approximately equal to observations. Both simulations show a clear slowdown in the CH4 growth rate during recent decades, from about 13 ppb yr−1 in 1984 to less than 5 ppb yr−1 in 2003. Furthermore, if the constant OH assumption is credible, we think that this slowdown is mainly due to a pause in the growth of wetland methane emissions. In simulations run for the Northern and Southern Hemispheres separately, we find that the Northern Hemisphere is more sensitive to wetland emissions, whereas the southern tends to be more perturbed by CH4 transportation, dramatic OH change, and biomass burning. When measured CO values from NOAA/ESRL are used to drive the model, changes in the CH4 growth rate become more consistent with observations, but the long-term increase in CH4 is underestimated. This shows that CO is a good indicator of short-term variations in oxidizing power in the atmosphere. The simulation results also indicate the significant drop in OH concentrations in 1998 (about 5% lower than the previous year) was probably due to an abrupt increase in wetland methane emissions during an intense EI Niño event. Using a fixed-lag Kalman smoother, we estimate the mean wetland methane flux is about 128 Tg yr−1 through the period 1984–2008. This study demonstrates the effectiveness in examining the role of OH and CO in affecting CH4.

scholarly journals COVID-19 lockdown NO<sub>x</sub> emission reductions can explain most of the coincident increase in global atmospheric methane

2021 ◽  
Author(s):  
David Stevenson ◽  
Richard Derwent ◽  
Oliver Wild ◽  
William Collins
Keyword(s):  
Growth Rate ◽  
Atmospheric Chemistry ◽  
Global Scale ◽  
Chemical System ◽  
Nox Emissions ◽  
Atmospheric Methane ◽  
Emission Reductions ◽  
Great Utility ◽  
Key Factor ◽  
Global Growth

Abstract. Compared to 2019, the global growth rate of atmospheric methane rose by about 50 % in 2020, reaching 15 ppb/yr. Models of global atmospheric chemistry show that reductions in nitrogen oxide (NOx) emissions reduce levels of the hydroxyl radical, and lengthen the methane lifetime. Using estimates of NOx emission reductions associated with COVID-19 lockdowns around the world in 2020, together with model-derived regional and sectoral sensitivities of methane to NOx emissions, we find that NOx emissions reductions can fully explain the observed surge in the global methane growth rate. Whilst changes in NOx emissions are probably not the only important factor that has influenced methane since the beginning of 2020, it is clear that they are a key factor that will need to be included within any attribution study, and that they may well be the dominant driver of these recent methane changes. The major global scale changes in composition of the Earth’s atmosphere measured during lockdown provide unprecedented constraints on the sensitivity of the atmospheric chemical system to changes in emissions, and are of great utility for evaluating policy-relevant models.

scholarly journals Investigation of the global methane budget over 1980–2017 using GFDL-AM4.1

2019 ◽  
Author(s):  
Jian He ◽  
Vaishali Naik ◽  
Larry W. Horowitz ◽  
Ed Dlugokencky ◽  
Kirk Thoning
Keyword(s):  
Atmospheric Chemistry ◽  
Latitudinal Gradient ◽  
Methane Emissions ◽  
Anthropogenic Emissions ◽  
Atmospheric Methane ◽  
Recent Past ◽  
Methane Budget ◽  
Global Trend ◽  
Emission Changes ◽  
Global Emissions

Abstract. Changes in atmospheric methane abundance have implications for both chemistry and climate as methane is both a strong greenhouse gas and an important precursor for tropospheric ozone. A better understanding of the drivers of trends and variability in methane abundance over the recent past is therefore critical for building confidence in projections of future methane levels. In this work, the representation of methane in the atmospheric chemistry model AM4.1 is improved by optimizing total methane emissions (to an annual mean of 576 ± 32 Tg yr−1) to match surface observations over 1980–2017. The simulations with optimized global emissions are in general able to capture the observed global trend, variability, seasonal cycle, and latitudinal gradient of methane. Simulations with different emission adjustments suggest that increases in methane sources (mainly from energy and waste sectors) balanced by increases in methane sinks (mainly due to increases in OH levels) lead to methane stabilization (with an imbalance of 5 Tg yr−1) during 1999–2006, and that increases in methane sources combined with little change in sinks (despite small decreases in OH levels) during 2007–2012 lead to renewed methane growth (with an imbalance of 14 Tg yr−1 for 2007–2017). Compared to 1999–2006, both methane emissions and sinks are greater (by 31 Tg yr−1 and 22 Tg yr−1, respectively) during 2007–2017. Our results also indicate that the energy sector is more likely a major contributor to the methane renewed growth after 2006 than wetland, as increases in wetland emissions alone are not able to explain the renewed methane growth with constant anthropogenic emissions. In addition, a significant increase in wetland emissions would be required starting in 2006, if anthropogenic emissions declined, for wetland emissions to drive renewed growth in methane, which is a less likely scenario. Simulations with varying OH levels indicate that 1 % change in OH levels could lead to an annual mean of ~ 4 Tg yr−1 difference in the optimized emissions and 0.08 year difference in the estimated tropospheric methane lifetime. Continued increases in methane emissions along with decreases in tropospheric OH concentrations during 2008–2015 prolong methane lifetime and therefore amplify the response of methane concentrations to emission changes. Uncertainties still exist in the partitioning of emissions among individual sources and regions.

scholarly journals Vertical Distribution of Arctic Methane in 2009–2018 Using Ground-Based Remote Sensing

2020 ◽  
Vol 12 (6) ◽  
pp. 917
Author(s):  
Tomi Karppinen ◽  
Otto Lamminpää ◽  
Simo Tukiainen ◽  
Rigel Kivi ◽  
Pauli Heikkinen ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Vertical Distribution ◽  
Atmospheric Chemistry ◽  
Polar Vortex ◽  
The Arctic ◽  
Fourier Transform Spectrometer ◽  
Atmospheric Methane ◽  
The Vertical Distribution ◽  
Chemistry Experiment

We analyzed the vertical distribution of atmospheric methane (CH 4 ) retrieved from measurements by ground-based Fourier Transform Spectrometer (FTS) instrument in Sodankylä, Northern Finland. The retrieved dataset covers 2009–2018. We used a dimension reduction retrieval method to extract the profile information, since each measurement contains around three pieces of information about the profile shape between 0 and 40 km. We compared the retrieved profiles against Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) satellite measurements and AirCore balloon-borne profile measurements. Additional comparison at the lowest tropospheric layer was done against in-situ measurements from a 50-m-high mast. In general, the ground-based FTS and ACE-FTS profiles agreed within 10% below 20 km and within 30% in the stratosphere between 20 and 40 km. Our method was able to accurately capture reduced methane concentrations inside the polar vortex in the Arctic stratosphere. The method produced similar trend characteristics as the reference instruments even when a static prior profile was used. Finally, we analyzed the time series of the CH 4 profile datasets and estimated the trend using the dynamic linear model (DLM).

Continuous CH4 and  d13CH4 measurements in London demonstrate under-reported natural gas leakage

2021 ◽  
Author(s):  
Eric Saboya ◽  
Giulia Zazzeri ◽  
Heather Graven ◽  
Alistair J. Manning ◽  
Sylvia Englund Michel
Keyword(s):  
Natural Gas ◽  
Atmospheric Chemistry ◽  
Dispersion Model ◽  
Measurement Data ◽  
Atmospheric Methane ◽  
Bottom Up ◽  
Keeling Plot ◽  
Regional Emissions ◽  
The Uk ◽  
Gas Leaks

&lt;p&gt;Assessment of bottom-up greenhouse gas emissions estimates through independent methods is needed to demonstrate whether reported values are accurate or if bottom-up methodologies need to be refined. Previous studies of measurements of atmospheric methane (CH&lt;sub&gt;4&lt;/sub&gt;) in London revealed that inventories substantially underestimated the amount of natural gas CH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;&amp;#160;1,2&lt;/sup&gt;. We report atmospheric CH&lt;sub&gt;4&lt;/sub&gt;&amp;#160;concentrations and &amp;#948;&lt;sup&gt;13&lt;/sup&gt;CH&lt;sub&gt;4&lt;/sub&gt;&amp;#160;measurements from Imperial College London since early 2018 using a Picarro G2201-i analyser. Measurements from Sept. 2019-Oct. 2020 were compared to the values simulated using the dispersion model NAME coupled with the UK national atmospheric emissions inventory, NAEI, and the global inventory, EDGAR, for emissions outside the UK. Simulations of CH&lt;sub&gt;4&lt;/sub&gt;&amp;#160;concentration and &amp;#948;&lt;sup&gt;13&lt;/sup&gt;CH&lt;sub&gt;4&lt;/sub&gt;&amp;#160;values were generated using nested NAME back-trajectories with horizontal spatial resolutions of 2 km, 10 km and 30 km. Observed concentrations were underestimated in the simulations by 22 % for all data, and by 16 % when using only 13:00-17:00 data. There was no correlation between the measured and simulated &amp;#948;&lt;sup&gt;13&lt;/sup&gt;CH&lt;sub&gt;4&lt;/sub&gt;&amp;#160;values. On average, simulated natural gas mole fractions accounted for 28 % of the CH&lt;sub&gt;4 &lt;/sub&gt;added by regional emissions, and simulated water sector mole fractions accounted for 32 % of the CH&lt;sub&gt;4&lt;/sub&gt;added by regional emissions. To estimate the isotopic source signatures for individual pollution events, an algorithm was created for automatically analysing measurement data by using the Keeling plot approach. Nearly 70 % of isotopic source values were higher than -50 &amp;#8240;, suggesting the primary CH&lt;sub&gt;4 &lt;/sub&gt;sources in London are natural gas leaks. The model-data comparison of &amp;#948;&lt;sup&gt;13&lt;/sup&gt;CH&lt;sub&gt;4 &lt;/sub&gt;and Keeling plot results both indicate that emissions due to natural gas leaks in London are being underestimated in the UK NAEI and EDGAR.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;&lt;sup&gt;1&amp;#160;&lt;/sup&gt;Helfter, C.&amp;#160;et al.&amp;#160;(2016),&amp;#160;Atmospheric Chemistry and Physics,&amp;#160;16(16), pp. 10543-10557&lt;/p&gt;&lt;p&gt;&lt;sup&gt;2&lt;/sup&gt;&amp;#160;Zazzeri, G. et al.&amp;#160;(2017),&amp;#160;Scientific Reports,&amp;#160;7(1), pp. 1-13&lt;/p&gt;

scholarly journals Model simulations of atmospheric methane and their evaluation using AGAGE/NOAA surface- and IAGOS-CARIBIC aircraft observations, 1997–2014

2018 ◽  
Author(s):  
Peter H. Zimmermann ◽  
Carl A. M. Brenninkmeijer ◽  
Andrea Pozzer ◽  
Patrick Jöckel ◽  
Andreas Zahn ◽  
...  
Keyword(s):  
Shale Gas ◽  
Atmospheric Chemistry ◽  
General Circulation ◽  
A Priori ◽  
Circulation Model ◽  
Gas Production ◽  
Coefficient Of Determination ◽  
Atmospheric Methane ◽  
Synoptic Variability ◽  
Methane Distribution

Abstract. The global budget and trends of atmospheric methane (CH4) have been simulated with the EMAC atmospheric chemistry – general circulation model for the period 1997 through 2014. Observations from AGAGE and NOAA surface stations and intercontinental CARIBIC flights indicate a transient period of declining methane increase during 1997 through 1999, followed by seven years of stagnation and a sudden resumed increase after 2006. Starting the simulation with a global methane distribution, scaled to match the station measurements in January 1997 and using inter-annually constant CH4 sources from eleven categories together with photochemical and soil sinks, the model reproduces the observations during the transient and constant period from 1997 through 2006 in magnitude as well as seasonal and synoptic variability. The atmospheric CH4 calculations in our model setup are linearly dependent on the source strengths, allowing source segregated simulation of eleven biogenic and fossil emission categories (tagging), with the aim to analyze global observations and derive the source specific CH4 steady state lifetimes. Moreover, tagging enables a-posteriori rescaling of individual emissions with proportional effects on the corresponding inventories and offers a method to approximate the station measurements in terms of lowest RMS. Enhancing the a priori biogenic tropical wetland emissions by ~ 29 Tg/y, compensated by a reduction of anthropogenic fossil CH4 emissions, the all-station mean dry air mole fraction of 1792 nmol/mol could be simulated within a RMS of 0.37 %. The coefficient of determination R2 = 0.87 indicates good agreement with observed variability and the calculated 2000–2005 average interhemispheric methane difference between selected NH and SH stations of 119 nmol/mol matches the observations. The CH4 samples from 95 intercontinental CARIBIC flights for the period 1997–2006 are also accurately simulated by the model, with a 2000–2006 average CH4 mixing ratio of 1786 nmol/mol, and 65 % of the measured variability being captured. This includes tropospheric and stratospheric data. To explain the growth of CH4 from 2007 through 2013 in term of sources, an emission increase of 28.3 Tg/y CH4 is needed. We explore the contributions of two potential causes, one representing natural emissions from wetlands in the tropics and the other anthropogenic shale gas production emissions in North America. A 62.6 % tropical wetland contribution and of 37.4 % by shale gas emissions optimally fit the trend, and simulates CH4 from 2007–2013 with an RMS of 7.1 nmol/mol (0.39 %). The coefficient of determination of R2 = 0.91 indicates even higher significance than before 2006. The 4287 samples collected during 232 CARIBIC flights after 2007 are simulated with an RMS of 1.3 % and R2 = 0.8, indicating that the model reproduces the seasonal and synoptic variability of CH4 in the upper troposphere and lower stratosphere.

scholarly journals Global atmospheric methane: budget, changes and dangers

2011 ◽  
Vol 369 (1943) ◽  
pp. 2058-2072 ◽  
Author(s):  
Edward J. Dlugokencky ◽  
Euan G. Nisbet ◽  
Rebecca Fisher ◽  
David Lowry
Keyword(s):  
Atmospheric Chemistry ◽  
Radiative Forcing ◽  
Emissions Trading ◽  
Mitigation Strategies ◽  
Anthropogenic Source ◽  
Atmospheric Methane ◽  
Emission Mitigation ◽  
Observation Network ◽  
Rate Of Increase ◽  
Isotopic Measurements

A factor of 2.5 increase in the global abundance of atmospheric methane (CH 4 ) since 1750 contributes 0.5 Wm −2 to total direct radiative forcing by long-lived greenhouse gases (2.77 Wm −2 in 2009), while its role in atmospheric chemistry adds another approximately 0.2 Wm −2 of indirect forcing. Since CH 4 has a relatively short lifetime and it is very close to a steady state, reductions in its emissions would quickly benefit climate. Sensible emission mitigation strategies require quantitative understanding of CH 4 ’s budget of emissions and sinks. Atmospheric observations of CH 4 abundance and its rate of increase, combined with an estimate of the CH 4 lifetime, constrain total global CH 4 emissions to between 500 and 600 Tg CH 4  yr −1 . While total global emissions are constrained reasonably well, estimates of emissions by source sector vary by up to a factor of 2. Current observation networks are suitable to constrain emissions at large scales (e.g. global) but not at the regional to national scales necessary to verify emission reductions under emissions trading schemes. Improved constraints on the global CH 4 budget and its break down of emissions by source sector and country will come from an enhanced observation network for CH 4 abundance and its isotopic composition ( δ 13 C, δ D (D= 2 H) and δ 14 C). Isotopic measurements are a valuable tool in distinguishing among various sources that contribute emissions to an air parcel, once fractionation by loss processes is accounted for. Isotopic measurements are especially useful at regional scales where signals are larger. Reducing emissions from many anthropogenic source sectors is cost-effective, but these gains may be cancelled, in part, by increasing emissions related to economic development in many parts of the world. An observation network that can quantitatively assess these changing emissions, both positive and negative, is required, especially in the context of emissions trading schemes.

scholarly journals The added value of satellite observations of methane forunderstanding the contemporary methane budget

2021 ◽  
Vol 379 (2210) ◽  
pp. 20210106
Author(s):  
Paul I. Palmer ◽  
Liang Feng ◽  
Mark F. Lunt ◽  
Robert J. Parker ◽  
Hartmut Bösch ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Transport Model ◽  
A Priori ◽  
Added Value ◽  
Atmospheric Methane ◽  
Sources And Sinks ◽  
Methane Budget ◽  
Spatial Coverage ◽  
New Research ◽  
The Tropics

Surface observations have recorded large and incompletely understood changes to atmospheric methane (CH 4 ) this century. However, their ability to reveal the responsible surface sources and sinks is limited by their geographical distribution, which is biased towards the northern midlatitudes. Data from Earth-orbiting satellites designed specifically to measure atmospheric CH 4 have been available since 2009 with the launch of the Japanese Greenhouse gases Observing SATellite (GOSAT). We assess the added value of GOSAT to data collected by the US National Oceanic and Atmospheric Administration (NOAA), which have been the lynchpin for knowledge about atmospheric CH 4 since the 1980s. To achieve that we use the GEOS-Chem atmospheric chemistry transport model and an inverse method to infer a posteriori flux estimates from the NOAA and GOSAT data using common a priori emission inventories. We find the main benefit of GOSAT data is from its additional coverage over the tropics where we report large increases since the 2014/2016 El Niño, driven by biomass burning, biogenic emissions and energy production. We use data from the European TROPOspheric Monitoring Instrument to show how better spatial coverage and resolution measurements allow us to quantify previously unattainable diffuse sources of CH 4 , thereby opening up a new research frontier. This article is part of a discussion meeting issue ‘Rising methane: is warming feeding warming? (part 1)’.

Sign in / Sign up

Export Citation Format

Share Document