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 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 Impact of atomic chlorine on the modelling of total methane and its <sup>13</sup>C : <sup>12</sup>C isotopic ratio at global scale

2019 ◽  
Author(s):  
Joël Thanwerdas ◽  
Marielle Saunois ◽  
Antoine Berchet ◽  
Isabelle Pison ◽  
Didier Hauglustaine ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Transport Model ◽  
Isotopic Ratio ◽  
Circulation Model ◽  
Global Scale ◽  
Major Influence ◽  
Atmospheric Methane ◽  
Global Circulation Model ◽  
Substantial Impact ◽  
The Impact

Abstract. Methane (CH4) is the second strongest anthropogenic greenhouse gas after carbon dioxide (CO2) and is responsible for about 20 % of the warming induced by long-lived greenhouse gases since pre-industrial times. Oxidation by the hydroxyl radical (OH) is the dominant atmospheric sink for methane, contributing to approximately 90 % of the total methane loss. Chemical losses by reaction with atomic oxygen (O1D) and chlorine radicals (Cl) in the stratosphere are other sinks, contributing about 3 % to the total methane destruction. Moreover, the reaction with Cl is very fractionating, thus it has a much larger impact on δ13C-CH4 than the reaction with OH. In this paper, we assess the impact of atomic Cl on atmospheric methane mixing ratios, methane atmospheric loss and atmospheric δ13C-CH4. The offline version of the Global Circulation Model (GCM) LMDz, coupled to a chemistry module including the major methane chemical reactions, is run to simulate CH4 concentrations and δ13C-CH4 at the global scale. Atmospheric methane sink by Cl atoms in the stratosphere is found to be 7.32 ± 0.16 Tg/yr. Methane observations from vertical profiles obtained using AirCore samplers above 11 different locations across the globe and balloon measurements of δ13C-CH4 and methane are used to assess the impact of the Cl sink in the chemistry transport model. Above 10 km, the presence of Cl in the model is found to have only a small impact on the vertical profile of total methane but a major influence on δ13C-CH4 values, significantly improving the agreement between simulations and available observations. Stratospheric Cl is also found to have a substantial impact on surface δ13C-CH4 values, leading to a difference of +0.27 ‰ (less negative values) after a 19-year run. As a result, this study suggests that the Cl sink needs to be properly taken into account (magnitude and trends) in order to better understand trends in the atmospheric δ13C-CH4 signal when using atmospheric chemistry transport models for forward or inverse calculations.

scholarly journals Biological scaling in green algae: the role of cell size and geometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Helena Bestová ◽  
Jules Segrestin ◽  
Klaus von Schwartzenberg ◽  
Pavel Škaloud ◽  
Thomas Lenormand ◽  
...  
Keyword(s):  
Growth Rate ◽  
Population Growth ◽  
Population Growth Rate ◽  
Internal Diffusion ◽  
Scaling Exponent ◽  
Power Scaling ◽  
Nutrient Distribution ◽  
Metabolic Scaling ◽  
Key Factor ◽  
Size And Morphology

AbstractThe Metabolic Scaling Theory (MST), hypothesizes limitations of resource-transport networks in organisms and predicts their optimization into fractal-like structures. As a result, the relationship between population growth rate and body size should follow a cross-species universal quarter-power scaling. However, the universality of metabolic scaling has been challenged, particularly across transitions from bacteria to protists to multicellulars. The population growth rate of unicellulars should be constrained by external diffusion, ruling nutrient uptake, and internal diffusion, operating nutrient distribution. Both constraints intensify with increasing size possibly leading to shifting in the scaling exponent. We focused on unicellular algae Micrasterias. Large size and fractal-like morphology make this species a transitional group between unicellular and multicellular organisms in the evolution of allometry. We tested MST predictions using measurements of growth rate, size, and morphology-related traits. We showed that growth scaling of Micrasterias follows MST predictions, reflecting constraints by internal diffusion transport. Cell fractality and density decrease led to a proportional increase in surface area with body mass relaxing external constraints. Complex allometric optimization enables to maintain quarter-power scaling of population growth rate even with a large unicellular plan. Overall, our findings support fractality as a key factor in the evolution of biological scaling.

scholarly journals The Abundance of Microcystin-Producing Genotypes Correlates Positively with Colony Size in Microcystis sp. and Determines Its Microcystin Net Production in Lake Wannsee

2003 ◽  
Vol 69 (2) ◽  
pp. 787-795 ◽  
Author(s):  
Rainer Kurmayer ◽  
Guntram Christiansen ◽  
Ingrid Chorus
Keyword(s):  
Growth Rate ◽  
Colony Size ◽  
Population Growth Rate ◽  
Size Class ◽  
Net Production ◽  
Cell Numbers ◽  
Size Classes ◽  
Key Factor ◽  
Genotype Composition ◽  
Working Hypotheses

ABSTRACT The working hypotheses tested on a natural population of Microcystis sp. in Lake Wannsee (Berlin, Germany) were that (i) the varying abundance of microcystin-producing genotypes versus non-microcystin-producing genotypes is a key factor for microcystin net production and (ii) the occurrence of a gene for microcystin net production is related to colony morphology, particularly colony size. To test these hypotheses, samples were fractionated by colony size with a sieving procedure during the summer of 2000. Each colony size class was analyzed for cell numbers, the proportion of microcystin-producing genotypes, and microcystin concentrations. The smallest size class of Microcystis colonies (<50 μm) showed the lowest proportion of microcystin-producing genotypes, the highest proportion of non-microcystin-producing cells, and the lowest microcystin cell quotas (sum of microcystins RR, YR, LR, and WR). In contrast, the larger size classes of Microcystis colonies (>100 μm) showed the highest proportion of microcystin-producing genotypes, the lowest proportion of non-microcystin-producing cells, and the highest microcystin cell quotas. The microcystin net production rate was nearly one to one positively related to the population growth rate for the larger colony size classes (>100 μm); however, no relationship could be found for the smaller size classes. It was concluded that the variations found in microcystin net production between colony size classes are chiefly due to differences in genotype composition and that the microcystin net production in the lake is mainly influenced by the abundance of the larger (>100-μm) microcystin-producing colonies.

scholarly journals Nitrogen addition decreases methane uptake caused by methanotroph and methanogen imbalances in a Moso bamboo forest

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Quan Li ◽  
Changhui Peng ◽  
Junbo Zhang ◽  
Yongfu Li ◽  
Xinzhang Song
Keyword(s):  
Community Structure ◽  
Forest Soils ◽  
Nitrogen Addition ◽  
N Deposition ◽  
Moso Bamboo ◽  
Bamboo Forest ◽  
N Addition ◽  
Atmospheric Methane ◽  
Key Factor ◽  
Moso Bamboo Forest

AbstractForest soils play an important role in controlling global warming by reducing atmospheric methane (CH4) concentrations. However, little attention has been paid to how nitrogen (N) deposition may alter microorganism communities that are related to the CH4 cycle or CH4 oxidation in subtropical forest soils. We investigated the effects of N addition (0, 30, 60, or 90 kg N ha−1 yr−1) on soil CH4 flux and methanotroph and methanogen abundance, diversity, and community structure in a Moso bamboo (Phyllostachys edulis) forest in subtropical China. N addition significantly increased methanogen abundance but reduced both methanotroph and methanogen diversity. Methanotroph and methanogen community structures under the N deposition treatments were significantly different from those of the control. In N deposition treatments, the relative abundance of Methanoculleus was significantly lower than that in the control. Soil pH was the key factor regulating the changes in methanotroph and methanogen diversity and community structure. The CH4 emission rate increased with N addition and was negatively correlated with both methanotroph and methanogen diversity but positively correlated with methanogen abundance. Overall, our results suggested that N deposition can suppress CH4 uptake by altering methanotroph and methanogen abundance, diversity, and community structure in subtropical Moso bamboo forest soils.

scholarly journals Atmospheric Mercury Concentrations observed at ground-based monitoring sites globally distributed in the framework of the GMOS network

2016 ◽  
Author(s):  
Francesca Sprovieri ◽  
Nicola Pirrone ◽  
Mariantonia Bencardino ◽  
Francesco D’Amore ◽  
Francesco Carbone ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Ad Hoc ◽  
Temporal Trends ◽  
Global Scale ◽  
Atmospheric Mercury ◽  
Global Network ◽  
Observation System ◽  
Large Network ◽  
Deposition Processes ◽  
The Impact

Abstract. Long-term monitoring data of ambient mercury (Hg) on a global scale to assess its emission, transport, atmospheric chemistry, and deposition processes is vital to understanding the impact of Hg pollution on the environment. The Global Mercury Observation System (GMOS) project was funded by the European Commission (www.gmos.eu), and started in November 2010 with the overall goal to develop a coordinated global observing system to monitor Hg on a global scale, including a large network of ground-based monitoring stations, ad-hoc periodic oceanographic cruises and measurement flights in the lower and upper troposphere, as well as in the lower stratosphere. To date more than 40 ground-based monitoring sites constitute the global network covering many regions where little to no observational data were available before GMOS. This work presents atmospheric Hg concentrations recorded worldwide in the framework of the GMOS project (2010–2015), analyzing Hg measurement results in terms of temporal trends, seasonality and comparability within the network. Major findings highlighted in this paper include a clear gradient of Hg concentrations between the Northern and Southern Hemisphere, confirming that the gradient observed is mostly driven by local and regional sources, which can be anthropogenic, natural or a combination of both.

scholarly journals Modelling bi-directional fluxes of methanol and acetaldehyde with the FORCAsT canopy exchange model

2016 ◽  
Author(s):  
Kirsti Ashworth ◽  
Serena H. Chung ◽  
Karena A. McKinney ◽  
Ying Liu ◽  
Bill J. Munger ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Atmospheric Chemistry ◽  
Forest Canopy ◽  
Global Scale ◽  
Exchange Model ◽  
Forest Site ◽  
Canopy Exchange ◽  
Harvard Forest ◽  
Leaf Level ◽  
Underlying Mechanisms

Abstract. The FORCAsT canopy exchange model was used to investigate the underlying mechanisms governing foliage emissions of methanol and acetaldehyde, two short chain oxygenated volatile organic compounds ubiquitous in the troposphere and known to have strong biogenic sources, at a northern mid-latitude forest site. The explicit representation of the vegetation canopy within the model allowed us to test the hypothesis that stomatal conductance regulates emissions of these compounds to an extent that its influence is observable at the ecosystem-scale, a process not currently considered in regional or global scale atmospheric chemistry models. We found that FORCAsT could only reproduce the magnitude and diurnal profiles of methanol and acetaldehyde fluxes measured at the top of the forest canopy at Harvard Forest if light-dependent emissions were introduced to the model. With the inclusion of such emissions FORCAsT was able to successfully simulate the observed bi-directional exchange of methanol and acetaldehyde. Although we found evidence that stomatal conductance influences methanol fluxes and concentrations at scales beyond the leaf-level, particularly at dawn and dusk, we were able to adequately capture ecosystem exchange without the addition of stomatal control to the standard parameterisations of foliage emissions, suggesting that ecosystem fluxes can be well enough represented by the emissions models currently used.

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 Prospects for Vietnam’s Economy in 2013

2013 ◽  
Vol 215 ◽  
pp. 02-11
Author(s):  
NGÂN TRẦN HOÀNG
Keyword(s):  
Economic Growth ◽  
Growth Rate ◽  
World Economy ◽  
Inflation Rate ◽  
Economic Restructuring ◽  
Short Term ◽  
Economic Growth Model ◽  
The World ◽  
Global Growth

In 2012, Vietnam?s economy faced great challenges. The world economy experienced more difficulties and complicated upheavals. International trade fell drastically while global growth rate was lower than predicted target, which affected badly the Vietnamese economy because of its full integration into the world economy and large openness. In this context, principal targets set for 2013 are macroeconomic stability, lower inflation rate, higher growth rate, three strategic breakthroughs associated with restructuring of the economy, and a new economic growth model. This paper analyzes obstacles to Vietnam?s economic growth, and offers short-term solutions to bottlenecks and long-term ones to the economic restructuring.

The growth rate and distribution of atmospheric methane

1994 ◽  
Vol 99 (D8) ◽  
pp. 17021 ◽  
Author(s):  
E. J. Dlugokencky ◽  
L. P. Steele ◽  
P. M. Lang ◽  
K. A. Masarie
Keyword(s):  
Growth Rate ◽  
Atmospheric Methane
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