scholarly journals Can we explain the observed methane variability after the Mount Pinatubo eruption?

2016 ◽  
Vol 16 (1) ◽  
pp. 195-214 ◽  
Author(s):  
N. Bândă ◽  
M. Krol ◽  
M. van Weele ◽  
T. van Noije ◽  
P. Le Sager ◽  
...  
Keyword(s):  
Growth Rate ◽  
Biomass Burning ◽  
Southern Oscillation ◽  
Partial Recovery ◽  
Sources And Sinks ◽  
Time Period ◽  
Pinatubo Eruption ◽  
Emission Changes

Abstract. The CH4 growth rate in the atmosphere showed large variations after the Pinatubo eruption in June 1991. A decrease of more than 10 ppb yr−1 in the growth rate over the course of 1992 was reported, and a partial recovery in the following year. Although several reasons have been proposed to explain the evolution of CH4 after the eruption, their contributions to the observed variations are not yet resolved. CH4 is removed from the atmosphere by the reaction with tropospheric OH, which in turn is produced by O3 photolysis under UV radiation. The CH4 removal after the Pinatubo eruption might have been affected by changes in tropospheric UV levels due to the presence of stratospheric SO2 and sulfate aerosols, and due to enhanced ozone depletion on Pinatubo aerosols. The perturbed climate after the eruption also altered both sources and sinks of atmospheric CH4. Furthermore, CH4 concentrations were influenced by other factors of natural variability in that period, such as El Niño–Southern Oscillation (ENSO) and biomass burning events. Emissions of CO, NOX and non-methane volatile organic compounds (NMVOCs) also affected CH4 concentrations indirectly by influencing tropospheric OH levels.Potential drivers of CH4 variability are investigated using the TM5 global chemistry model. The contribution that each driver had to the global CH4 variability during the period 1990 to 1995 is quantified. We find that a decrease of 8–10 ppb yr−1 CH4 is explained by a combination of the above processes. However, the timing of the minimum growth rate is found 6&nash;9 months later than observed. The long-term decrease in CH4 growth rate over the period 1990 to 1995 is well captured and can be attributed to an increase in OH concentrations over this time period. Potential uncertainties in our modelled CH4 growth rate include emissions of CH4 from wetlands, biomass burning emissions of CH4 and other compounds, biogenic NMVOC and the sensitivity of OH to NMVOC emission changes. Two inventories are used for CH4 emissions from wetlands, ORCHIDEE and LPJ, to investigate the role of uncertainties in these emissions. Although the higher climate sensitivity of ORCHIDEE improves the simulated CH4 growth rate change after Pinatubo, none of the two inventories properly captures the observed CH4 variability in this period.

scholarly journals Can we explain the observed methane variability after the Mount Pinatubo eruption?

2015 ◽  
Vol 15 (13) ◽  
pp. 19111-19160
Author(s):  
N. Bândă ◽  
M. Krol ◽  
M. van Weele ◽  
T. van Noije ◽  
P. Le Sager ◽  
...  
Keyword(s):  
Growth Rate ◽  
Biomass Burning ◽  
Partial Recovery ◽  
Mount Pinatubo ◽  
Sources And Sinks ◽  
Time Period ◽  
Pinatubo Eruption ◽  
Emission Changes

Abstract. The CH4 growth rate in the atmosphere showed large variations after the Pinatubo eruption in June 1991. A decrease of more than 10 ppb yr-1 in the growth rate over the course of 1992 was reported and a partial recovery in the following year. Although several reasons have been proposed to explain the evolution of CH4 after the eruption, their contributions to the observed variations are not yet resolved. CH4 is removed from the atmosphere by the reaction with tropospheric OH, which in turn is produced by O3 photolysis under UV radiation. The CH4 removal after the Pinatubo eruption might have been affected by changes in tropospheric UV levels due to the presence of stratospheric SO2 and sulfate aerosols, and due to enhanced ozone depletion on Pinatubo aerosols. The perturbed climate after the eruption also altered both sources and sinks of atmospheric CH4. Furthermore, CH4 concentrations were influenced by other factors of natural variability in that period, such as ENSO and biomass burning events. Emissions of CO, NOX and NMVOCs also affected CH4 concentrations indirectly by influencing tropospheric OH levels. Potential drivers of CH4 variability are investigated using the TM5 global chemistry model. The contribution that each driver had to the global CH4 variability during the period 1990 to 1995 is quantified. We find that a decrease of 8–10 ppb yr-1 CH4 is explained by a combination of the above processes. However, the timing of the minimum growth rate is found 6–9 months later than observed. The long-term decrease in CH4 growth rate over the period 1990 to 1995 is well captured and can be attributed to an increase in OH concentrations over this time period. Potential uncertainties in our modelled CH4 growth rate include emissions of CH4 from wetlands, biomass burning emissions of CH4 and other compounds, biogenic NMVOC and the sensitivity of OH to NMVOC emission changes. Two inventories are used for CH4 emissions from wetlands, ORCHIDEE and LPJ, to investigate the role of uncertainties in these emissions. Although the higher climate sensitivity of ORCHIDEE improves the simulated CH4 growth rate change after Pinatubo, none of the two inventories properly captures the observed CH4 variability in this period.

ON THE CONSUMPTION/DISTRIBUTION THEOREM UNDER THE LONG-RUN GROWTH CRITERION SUBJECT TO A DRAWDOWN CONSTRAINT

2010 ◽  
Vol 13 (06) ◽  
pp. 931-957 ◽  
Author(s):  
MICHAEL J. KLASS ◽  
KRZYSZTOF NOWICKI
Keyword(s):  
Growth Rate ◽  
Short Term ◽  
Long Run ◽  
Time Period ◽  
Total Capital ◽  
Growth Criterion ◽  
Drawdown Constraint ◽  
Riskless Asset ◽  
Distribution Theorem

Consider any discrete time sequence of investment fortunes Fn which has a finite long-run growth rate [Formula: see text] when subject to the present value capital drawdown constraint Fne-rn ≥ λ* max 0≤k≤nFke-rk, where 0 ≤ λ* < 1, in the presence of a riskless asset affording a return of er dollars per time period per dollar invested. We show that money can be withdrawn for consumption from the invested capital without either reducing the long-run growth rate of such capital or violating the drawdown constraint for our capital sequence, while simultaneously increasing the amount of capital withdrawn for consumption at the identical long-term rate of V(r, λ*). We extend this result to an exponentially increasing number of consumption categories and discuss how additional yearly contributions can temporarily augment the total capital under management. In addition, we assess the short-term practicality of creating such an endowment/consumption/distribution program.

scholarly journals Limited impact of El Niño–Southern Oscillation on variability and growth rate of atmospheric methane

2018 ◽  
Vol 15 (21) ◽  
pp. 6371-6386 ◽  
Author(s):  
Hinrich Schaefer ◽  
Dan Smale ◽  
Sylvia E. Nichol ◽  
Tony M. Bromley ◽  
Gordon W. Brailsford ◽  
...  
Keyword(s):  
Climate Change ◽  
Growth Rate ◽  
Biomass Burning ◽  
El Niño ◽  
El Nino ◽  
Southern Oscillation ◽  
El Nino Southern Oscillation ◽  
Atmospheric Methane ◽  
Ch4 Production ◽  
A Minor

Abstract. The El Niño–Southern Oscillation (ENSO) has been suggested as a strong forcing in the methane cycle and as a driver of recent trends in global atmospheric methane mole fractions [CH4]. Such a sensitivity of the global CH4 budget to climate events would have important repercussions for climate change mitigation strategies and the accuracy of projections for future greenhouse forcing. Here, we test the impact of ENSO on atmospheric CH4 in a correlation analysis. We use local and global records of [CH4], as well as stable carbon isotopic records of atmospheric CH4 (δ13CH4), which are particularly sensitive to the combined ENSO effects on CH4 production from wetlands and biomass burning. We use a variety of nominal, smoothed, and detrended time series including growth rate records. We find that at most 36 % of the variability in [CH4] and δ13CH4 is attributable to ENSO, but only for detrended records in the southern tropics. Trend-bearing records from the southern tropics, as well as all studied hemispheric and global records, show a minor impact of ENSO, i.e. < 24 % of variability explained. Additional analyses using hydrogen cyanide (HCN) records show a detectable ENSO influence on biomass burning (up to 51 %–55 %), suggesting that it is wetland CH4 production that responds less to ENSO than previously suggested. Dynamics of the removal by hydroxyl likely counteract the variation in emissions, but the expected isotope signal is not evident. It is possible that other processes obscure the ENSO signal, which itself indicates a minor influence of the latter on global CH4 emissions. Trends like the recent rise in atmospheric [CH4] can therefore not be attributed to ENSO. This leaves anthropogenic methane sources as the likely driver, which must be mitigated to reduce anthropogenic climate change.

scholarly journals Impact of El Niño Southern Oscillation on the interannual variability of methane and tropospheric ozone

2019 ◽  
Author(s):  
Matthew J. Rowlinson ◽  
Alexandru Rap ◽  
Stephen R. Arnold ◽  
Richard J. Pope ◽  
Martyn P. Chipperfield ◽  
...  
Keyword(s):  
Growth Rate ◽  
Interannual Variability ◽  
Biomass Burning ◽  
El Niño ◽  
Atmospheric Transport ◽  
El Nino ◽  
Southern Oscillation ◽  
Fire Emissions ◽  
Tropospheric O3 ◽  
Global Mean

Abstract. The growth rate of global methane (CH4) concentrations has a strong interannual variability which is believed to be driven largely by fluctuations in CH4 emissions from wetlands and wildfires, as well as changes to the atmospheric sink. The El Niño Southern Oscillation (ENSO) is known to influence fire occurrence, wetland emission and atmospheric transport, but there are still important uncertainties associated with the exact mechanism and magnitude of this influence. Here we use a modelling approach to investigate how fires and meteorology control the interannual variability of global carbon monoxide (CO), CH4 and ozone (O3) concentrations, particularly during large El Niño events. Using a three-dimensional chemical transport model (TOMCAT) coupled to a sophisticated aerosol microphysics scheme (GLOMAP) we simulate changes to CO, hydroxyl radical (OH) and O3 for the period 1997–2014. We then use an offline radiative transfer model to quantify the impact of changes to atmospheric composition as a result of specific drivers. During the El Niño event of 1997–1998, there were increased emissions from biomass burning globally. As a result, global CO concentrations increased by more than 40 %. This resulted in decreased global mass-weighted tropospheric OH concentrations of up to 9 % and a resulting 4 % increase in the CH4 atmospheric lifetime. The change in CH4 lifetime led to a 7.5 ppb yr−1 increase in global mean CH4 growth rate in 1998. Therefore biomass burning emission of CO could account for 72 % of the total effect of fire emissions on CH4 growth rate in 1998. Our simulations indicate variations in fire emissions and meteorology associated with El Niño have opposing impacts on tropospheric O3 burden. El Niño-related atmospheric transport changes decrease global tropospheric O3 concentrations leading to a −0.03 Wm−2 change in O3 radiative effect (RE). However, enhanced fire emission of precursors such as nitrous oxides (NOx) and CO increase O3 RE by 0.03 Wm−2. While globally the two mechanisms nearly cancel out, causing only a small change in global mean O3 RE, the regional changes are large   up to −0.33 Wm−2 with potentially important consequences for atmospheric heating and dynamics.

scholarly journals Measuring the Effect of the Internet on Economic Growth: The Case of Saudi Arabia

2020 ◽  
Vol 12 (12) ◽  
pp. 61
Author(s):  
Hisham J. Bardesi
Keyword(s):  
Economic Growth ◽  
Growth Rate ◽  
Saudi Arabia ◽  
Internet Access ◽  
Ordinary Least Squares ◽  
The Internet ◽  
Macroeconomic Performance ◽  
The Impact

The purpose of this study is to examine and assess the impact of the Internet on economic growth in Saudi Arabia. Various studies show that there is a relationship between the growth rate of GDP and the Internet, as estimated by Internet user numbers. In this paper, the ordinary least squares (OLS) model is utilized to study the economic impact of Internet Access from 1994 to 2018, which has had a profound effect on the market structure of many sectors and Saudi&rsquo;s global macroeconomic performance. The study constructs a model to investigate any significant impact of the Internet on the Saudi economy. Finally, this paper suggests that an understanding of the role of the Internet is essential for policymakers who plan to promote new forms of economic growth in the future. To take a long-term view implies working on technologies that could improve the economy and people&rsquo;s lives by creating a technological ecosystem in and around Saudi Arabia, along with other major economies.

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 The role of stj fimbrial operon in the intestinal persistence of Salmonella Typhimurium in mice

Biologia ◽  
2009 ◽  
Vol 64 (5) ◽  
Author(s):  
Nefise Akkoç ◽  
Banu Özden ◽  
Begüm Tan ◽  
Mustafa Akçelik
Keyword(s):  
Salmonella Typhimurium ◽  
Model System ◽  
Mesenteric Lymph Nodes ◽  
Resistant Mouse ◽  
Knock Out ◽  
Mesenteric Lymph ◽  
Time Period ◽  
Intestinal Persistence

AbstractSalmonella Typhimurium contains 13 operons coding for fimbriae with unique binding specificities to host epithelial surfaces. stj operon is only detected in S. Typhimurium genome suggesting that Stj fimbria may effect serovarspecific virulence characteristics. In this study, the role of stj fimbrial operon in the long-term persistence of S. Typhimurium was identified by competitive infection experiment in genetically resistant mouse (CBA) model system. Knock-out mutation of stjA (major subunit of the Stj fimbria) gene reduced recovery of S. Typhimurium from fecal samples and its colonization to spleen, cecum and mesenteric lymph nodes over a 34-day time period (p < 0.05). This data indicate that stj fimbrial operon has a role in long-term intestinal persistence of S. Typhimurium in CBA mice.

scholarly journals ANMCO POSITION PAPER: The role of cardiology in the management of the health needs in the post-Covid-19 era

2020 ◽  
Vol 22 (Supplement_G) ◽  
pp. G217-G222
Author(s):  
Adriano Murrone ◽  
Furio Colivicchi ◽  
Loris Roncon ◽  
Pasquale Caldarola ◽  
Vincenzo Amodeo ◽  
...  
Keyword(s):  
Structural Adjustment ◽  
Hospital Admissions ◽  
Partial Recovery ◽  
Phase 2 ◽  
Hospital Units ◽  
The World ◽  
Intensity Of Care ◽  
Almost All

Abstract At the end of 2019 a new Coronavirus appeared in China and, from there, it spread to the rest of the world. On 24th May, 2020, the confirmed cases in the world were more than 5 million and the deaths almost 350.000. At the end of May, Italy reported more than 27.000 cases among healthcare professionals and 163 deaths among physicians. The National Health Systems from almost all over the world, including Italy’s, were unprepared for this pandemic, and this generated important consequences of organizational nature. All elective and urgent specialized activities were completely reorganized, and many hospital units were partially or completely converted to the care of the COVID-19 patients. A significant reduction in hospital admissions for acute heart disease were recorded during the SARS-CoV-2 pandemic and, in order to gradually resume hospital activities, the Italian National Phase 2 Plan for the partial recovery of activities, must necessarily be associated with a Phase 2 Health Plan. In regards to the cardiac outpatient activities we need to identify short term goals, i.e. reschedule the suspended outpatient activities, revise the waiting lists, review the ‘timings’ of the bookings. This will reduce the number of available examinations compared to the pre-Covid-19 era. The GP’s collaboration could represent an important resource, a structured telephone follow-up plan is advisable with the nursing staff’s involvement. It is equally important to set medium-long term goals, the pandemic could be an appropriate moment for making a virtue of necessity. It is time to reason on prescriptive appropriateness, telemedicine implementation intended as integration to the traditional management. It is time to restructure the cardiological units related to the issue of structural adjustment to the needs for functional isolation. Moreover, the creation of ‘grey zones’ with multidisciplinary management according to the intensity of care levels seems to be necessary as well as the identification of Covid dedicated cardiologies. Finally, the pandemic could represent the opportunity for a permanent renovation of the cardiological and territorial medicine activities.

scholarly journals Trend of atmospheric mercury concentrations at Cape Point for 1995–2004 and since 2007

2017 ◽  
Vol 17 (3) ◽  
pp. 2393-2399 ◽  
Author(s):  
Lynwill G. Martin ◽  
Casper Labuschagne ◽  
Ernst-Günther Brunke ◽  
Andreas Weigelt ◽  
Ralf Ebinghaus ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Wet Deposition ◽  
Southern Oscillation ◽  
Elemental Mercury ◽  
Atmospheric Mercury ◽  
Austral Spring ◽  
Mercury Emissions ◽  
Gaseous Elemental Mercury ◽  
Regional Processes

Abstract. Long-term measurements of gaseous elemental mercury (GEM) concentrations at Cape Point, South Africa, reveal a downward trend between September 1995 and December 2005 and an upward one from March 2007 until June 2015, implying a change in trend sign between 2004 and 2007. The trend change is qualitatively consistent with the trend changes in GEM concentrations observed at Mace Head, Ireland, and in mercury wet deposition over North America, suggesting a change in worldwide mercury emissions. Seasonally resolved trends suggest a modulation of the overall trend by regional processes. The trends in absolute terms (downward in 1995–2004 and upward in 2007–2015) are highest in austral spring (SON), coinciding with the peak in emissions from biomass burning in South America and southern Africa. The influence of trends in biomass burning is further supported by a biennial variation in GEM concentration found here and an El Niño–Southern Oscillation (ENSO) signature in GEM concentrations reported recently.

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