scholarly journals Climate versus emission drivers of methane lifetime from 1860–2100

2012 ◽  
Vol 12 (7) ◽  
pp. 18067-18105 ◽  
Author(s):  
J. G. John ◽  
A. M. Fiore ◽  
V. Naik ◽  
L. W. Horowitz ◽  
J. P. Dunne
Keyword(s):  
Climate Warming ◽  
Climate Model ◽  
Climate Forcing ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Atmospheric Methane ◽  
Future Evolution ◽  
The Individual ◽  
Future Work ◽  
Fully Coupled

Abstract. With a more-than-doubling in the atmospheric abundance of the potent greenhouse gas methane (CH4) since preindustrial times, and indications of renewed growth following a leveling off in recent years, questions arise as to future trends and resulting climate and public health impacts from continued growth without mitigation. Changes in atmospheric methane lifetime are determined by factors which regulate the abundance of OH, the primary methane removal mechanism, including changes in CH4 itself. We investigate the role of emissions of short-lived species and climate in determining the evolution of tropospheric methane lifetime in a suite of historical (1860–2005) and Representative Concentration Pathway (RCP) simulations (2006–2100), conducted with the Geophysical Fluid Dynamics Laboratory (GFDL) fully coupled chemistry-climate model (CM3). From preindustrial to present, CM3 simulates an overall 5% increase in CH4 lifetime due to a doubling of the methane burden which offsets coincident increases in nitrogen oxide (NOx) emissions. Over the last two decades, however, the methane lifetime declines steadily, coinciding with the most rapid climate warming and observed slow-down in CH4 growth rates, reflecting a possible negative feedback through the CH4 sink. The aerosol indirect effect plays a significant role in the CM3 climate and thus in the future evolution of the methane lifetime, due to the rapid projected decline of aerosols under all four RCPs. In all scenarios, the methane lifetime decreases (by 5–13%) except for the most extreme warming case (RCP8.5), where it increases by 4% due to the near-doubling of the CH4 abundance, reflecting a positive feedback on the climate system. In the RCP4.5 scenario changes in short-lived climate forcing agents reinforce climate warming and enhance OH, leading to a more-than-doubling of the decrease in methane lifetime from 2006 to 2100 relative to a simulation in which only well-mixed greenhouse gases are allowed to change along the RCP4.5 scenario (13% vs. 5%) Future work should include process-based studies to better understand and elucidate the individual mechanisms controlling methane lifetime.

scholarly journals Climate versus emission drivers of methane lifetime against loss by tropospheric OH from 1860–2100

2012 ◽  
Vol 12 (24) ◽  
pp. 12021-12036 ◽  
Author(s):  
J. G. John ◽  
A. M. Fiore ◽  
V. Naik ◽  
L. W. Horowitz ◽  
J. P. Dunne
Keyword(s):  
Greenhouse Gas ◽  
Climate Warming ◽  
Radiative Forcing ◽  
Climate Model ◽  
Climate Forcing ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Atmospheric Methane ◽  
Future Evolution ◽  
Aerosol Cloud Interactions ◽  
Projected Changes

Abstract. With a more-than-doubling in the atmospheric abundance of the potent greenhouse gas methane (CH4) since preindustrial times, and indications of renewed growth following a leveling off in recent years, questions arise as to future trends and resulting climate and public health impacts from continued growth without mitigation. Changes in atmospheric methane lifetime are determined by factors which regulate the abundance of OH, the primary methane removal mechanism, including changes in CH4 itself. We investigate the role of emissions of short-lived species and climate in determining the evolution of methane lifetime against loss by tropospheric OH, (τCH4_OH), in a suite of historical (1860–2005) and future Representative Concentration Pathway (RCP) simulations (2006–2100), conducted with the Geophysical Fluid Dynamics Laboratory (GFDL) fully coupled chemistry-climate model (CM3). From preindustrial to present, CM3 simulates an overall 5% increase in τCH4_OH due to a doubling of the methane burden which offsets coincident increases in nitrogen oxide (NOx emissions. Over the last two decades, however, the τCH4_OH declines steadily, coinciding with the most rapid climate warming and observed slow-down in CH4 growth rates, reflecting a possible negative feedback through the CH4 sink. Sensitivity simulations with CM3 suggest that the aerosol indirect effect (aerosol-cloud interactions) plays a significant role in cooling the CM3 climate. The projected decline in aerosols under all RCPs contributes to climate warming over the 21st century, which influences the future evolution of OH concentration and τCH4_OH. Projected changes in τCH4_OH from 2006 to 2100 range from −13% to +4%. The only projected increase occurs in the most extreme warming case (RCP8.5) due to the near-doubling of the CH4 abundance, reflecting a positive feedback on the climate system. The largest decrease occurs in the RCP4.5 scenario due to changes in short-lived climate forcing agents which reinforce climate warming and enhance OH. This decrease is more-than-halved in a sensitivity simulation in which only well-mixed greenhouse gas radiative forcing changes along the RCP4.5 scenario (5% vs. 13%).

scholarly journals Evaluating the Uncertainty Induced by the Virtual Salt Flux Assumption in Climate Simulations and Future Projections

2010 ◽  
Vol 23 (1) ◽  
pp. 80-96 ◽  
Author(s):  
Jianjun Yin ◽  
Ronald J. Stouffer ◽  
Michael J. Spelman ◽  
Stephen M. Griffies
Keyword(s):  
Climate Models ◽  
Climate Model ◽  
Ocean Model ◽  
Salt Flux ◽  
Freshwater Flux ◽  
Unexpected Result ◽  
Geophysical Fluid Dynamics Laboratory ◽  
External Forcing ◽  
Future Evolution ◽  
Near Term

Abstract The unphysical virtual salt flux (VSF) formulation widely used in the ocean component of climate models has the potential to cause systematic and significant biases in modeling the climate system and projecting its future evolution. Here a freshwater flux (FWF) and a virtual salt flux version of the Geophysical Fluid Dynamics Laboratory Climate Model version 2.1 (GFDL CM2.1) are used to evaluate and quantify the uncertainties induced by the VSF formulation. Both unforced and forced runs with the two model versions are performed and compared in detail. It is found that the differences between the two versions are generally small or statistically insignificant in the unforced control runs and in the runs with a small external forcing. In response to a large external forcing, however, some biases in the VSF version become significant, especially the responses of regional salinity and global sea level. However, many fundamental aspects of the responses differ only quantitatively between the two versions. An unexpected result is the distinctly different ENSO responses. Under a strong external freshwater forcing, the great enhancement of the ENSO variability simulated by the FWF version does not occur in the VSF version and is caused by the overexpansion of the top model layer. In summary, the principle assumption behind using virtual salt flux is not seriously violated and the VSF model has the ability to simulate the current climate and project near-term climate evolution. For some special studies such as a large hosing experiment, however, both the VSF formulation and the use of the FWF in the geopotential coordinate ocean model could have some deficiencies and one should be cautious to avoid them.

scholarly journals Supplementary material to "Effects of Strongly Enhanced Atmospheric Methane Concentrations in a Fully Coupled Chemistry-Climate Model"

2020 ◽  
Author(s):  
Laura Stecher ◽  
Franziska Winterstein ◽  
Martin Dameris ◽  
Patrick Jöckel ◽  
Michael Ponater ◽  
...  
Keyword(s):  
Climate Model ◽  
Atmospheric Methane ◽  
Supplementary Material ◽  
Fully Coupled ◽  
Methane Concentrations

scholarly journals On the role of trend and variability in the hydroxyl radical (OH) in the global methane budget

2020 ◽  
Vol 20 (21) ◽  
pp. 13011-13022
Author(s):  
Yuanhong Zhao ◽  
Marielle Saunois ◽  
Philippe Bousquet ◽  
Xin Lin ◽  
Antoine Berchet ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Interannual Variations ◽  
Atmospheric Methane ◽  
Tropical Regions ◽  
Ch4 Emissions ◽  
Methane Budget

Abstract. Decadal trends and interannual variations in the hydroxyl radical (OH), while poorly constrained at present, are critical for understanding the observed evolution of atmospheric methane (CH4). Through analyzing the OH fields simulated by the model ensemble of the Chemistry–Climate Model Initiative (CCMI), we find (1) the negative OH anomalies during the El Niño years mainly corresponding to the enhanced carbon monoxide (CO) emissions from biomass burning and (2) a positive OH trend during 1980–2010 dominated by the elevated primary production and the reduced loss of OH due to decreasing CO after 2000. Both two-box model inversions and variational 4D inversions suggest that ignoring the negative anomaly of OH during the El Niño years leads to a large overestimation of the increase in global CH4 emissions by up to 10 ± 3 Tg yr−1 to match the observed CH4 increase over these years. Not accounting for the increasing OH trends given by the CCMI models leads to an underestimation of the CH4 emission increase by 23 ± 9 Tg yr−1 from 1986 to 2010. The variational-inversion-estimated CH4 emissions show that the tropical regions contribute most to the uncertainties related to OH. This study highlights the significant impact of climate and chemical feedbacks related to OH on the top-down estimates of the global CH4 budget.

Communication, Consumers, and Citizens

2012 ◽  
Vol 644 (1) ◽  
pp. 6-19 ◽  
Author(s):  
Dhavan V. Shah ◽  
Lewis A. Friedland ◽  
Chris Wells ◽  
Young Mie Kim ◽  
Hernando Rojas
Keyword(s):  
Group Level ◽  
Political Consumerism ◽  
Individual Group ◽  
Fourth Section ◽  
Occupy Movement ◽  
The Third ◽  
The Individual ◽  
Future Work ◽  
Socially Situated

The year 2011 was defined by the intersection of politics and economics: the Wisconsin protests, the Occupy Movement, anti-austerity demonstrations, the Buffett Rule, and so on. These events drew attention to the role of politics in the erosion of labor power, the rise of inequality, and the excesses of overconsumption. Moving beyond periodic and dutiful action directed at an increasingly unresponsive government, citizens tested the boundaries of what we consider civic engagement by embracing personalized forms of “lifestyle politics” enacted in everyday life and often directed at the market. These issues are the focus of this volume, which we divide into four sections. The first section attempts both to situate consumption in politics as a contemporary phenomenon and to view it through a wider historical lens. The second section advances the notion of sustainable citizenship at the individual/group level and the societal/institutional level, and understands consumption as socially situated and structured. Extending this thinking, the third section explores various forms of conscious consumption and relates them to emerging modes of activism and engagement. The fourth section questions assumptions about the effectiveness of the citizen-consumer and the underlying value of political consumerism and conscious consumption. We conclude by distilling six core themes from this collection for future work.

scholarly journals Chemical contribution to future tropical ozone change in the lower stratosphere

2013 ◽  
Vol 13 (10) ◽  
pp. 27855-27889
Author(s):  
S. Meul ◽  
U. Langematz ◽  
S. Oberländer ◽  
H. Garny ◽  
P. Jöckel
Keyword(s):  
Lower Stratosphere ◽  
Climate Model ◽  
Dominant Role ◽  
Chemical Production ◽  
Net Production ◽  
Future Evolution ◽  
Ozone Destruction ◽  
Ozone Trend ◽  
The Impact

Abstract. The future evolution of tropical ozone in a changing climate is investigated by analysing timeslice simulations with the state-of-the-art Chemistry-Climate Model EMAC. Between the present and the end of the 21st century a significant increase in ozone is found globally for the upper stratosphere and the extratropical lower stratosphere, while in the tropical lower stratosphere ozone decreases significantly. Different studies showed before that this decrease is connected to changes in tropical upwelling. By splitting the relative ozone change into the contributions from transport, chemical production, and chemical loss, the impact of chemical processes in addition to transport in this region is analysed. The dominant role of transport for future ozone changes is confirmed, but it is found that changes in ozone destruction and especially changes in the production of ozone do contribute to the relative ozone changes in the tropical lower stratosphere. The causes for the changing loss and production rates are studied by separating the contributions from the different catalytic loss cycles and the different production processes. It is shown that changes in the production are mainly due to changes in the overlying ozone column which are determined by both chemistry and transport. Changes in the ozone destruction can be attributed to a modified efficiency of the ClOx and NOx loss cycles in the lower and middle stratosphere and of the HOx loss cycle in the lowermost tropical stratosphere. The role of ozone transport in determining the ozone trend in this region is found to depend on the changes in net production, with a smaller contribution from transport to the ozone changes if the net production decreases.

scholarly journals The Key Role of Coupled Chemistry–Climate Interactions in Tropical Stratospheric Temperature Variability

2020 ◽  
Vol 33 (17) ◽  
pp. 7619-7629
Author(s):  
Simchan Yook ◽  
David W. J. Thompson ◽  
Susan Solomon ◽  
Seo-Yeon Kim
Keyword(s):  
Climate Model ◽  
Internal Variability ◽  
Temperature Variability ◽  
Stratospheric Temperature ◽  
Climate Interactions ◽  
Free Running ◽  
Polar Stratosphere ◽  
Fully Coupled ◽  
Do So

AbstractThe purpose of this study is to quantify the effects of coupled chemistry–climate interactions on the amplitude and structure of stratospheric temperature variability. To do so, the authors examine two simulations run on version 4 of the Whole Atmosphere Coupled Climate Model (WACCM): a “free-running” simulation that includes fully coupled chemistry–climate interactions and a “specified chemistry” version of the model forced with prescribed climatological-mean chemical composition. The results indicate that the inclusion of coupled chemistry–climate interactions increases the internal variability of temperature by a factor of ~2 in the lower tropical stratosphere and—to a lesser extent—in the Southern Hemisphere polar stratosphere. The increased temperature variability in the lower tropical stratosphere is associated with dynamically driven ozone–temperature feedbacks that are only included in the coupled chemistry simulation. The results highlight the fundamental role of two-way feedbacks between the atmospheric circulation and chemistry in driving climate variability in the lower stratosphere.

scholarly journals Chemical contribution to future tropical ozone change in the lower stratosphere

2014 ◽  
Vol 14 (6) ◽  
pp. 2959-2971 ◽  
Author(s):  
S. Meul ◽  
U. Langematz ◽  
S. Oberländer ◽  
H. Garny ◽  
P. Jöckel
Keyword(s):  
Lower Stratosphere ◽  
Climate Model ◽  
Dominant Role ◽  
Ozone Production ◽  
Net Production ◽  
Future Evolution ◽  
Ozone Loss ◽  
The Future ◽  
Ozone Column

Abstract. The future evolution of tropical ozone in a changing climate is investigated by analysing time slice simulations made with the chemistry–climate model EMAC. Between the present and the end of the 21st century a significant increase in ozone is found globally for the upper stratosphere and the extratropical lower stratosphere, while in the tropical lower stratosphere ozone decreases significantly by up to 30%. Previous studies have shown that this decrease is connected to changes in tropical upwelling. Here the dominant role of transport for the future ozone decrease is confirmed, but it is found that in addition changes in chemical ozone production and destruction do contribute to the ozone changes in the tropical lower stratosphere. Between 50 and 30 hPa the dynamically induced ozone decrease of up to 22% is amplified by 11–19% due to a reduced ozone production. This is counteracted by a decrease in the ozone loss causing an ozone increase by 15–28%. At 70 hPa the large ozone decrease due to transport (−52%) is reduced by an enhanced photochemical ozone production (+28%) but slightly increased (−5%) due to an enhanced ozone loss. It is found that the increase in the ozone production in the lowermost stratosphere is mainly due to a transport induced decrease in the overlying ozone column while at higher altitudes the ozone production decreases as a consequence of a chemically induced increase in the overlying ozone column. The ozone increase that is attributed to changes in ozone loss between 50 and 30 hPa is mainly caused by a slowing of the ClOx and NOx loss cycles. The enhanced ozone destruction below 70 hPa can be attributed to an increased efficiency of the HOx loss cycle. The role of ozone transport in determining the ozone trend in this region is found to depend on the changes in the net production as a reduced net production also reduces the amount of ozone that can be transported within an air parcel.

scholarly journals ENSO Transition, Duration, and Amplitude Asymmetries: Role of the Nonlinear Wind Stress Coupling in a Conceptual Model

2013 ◽  
Vol 26 (23) ◽  
pp. 9462-9476 ◽  
Author(s):  
Kit-Yan Choi ◽  
Gabriel A. Vecchi ◽  
Andrew T. Wittenberg
Keyword(s):  
Conceptual Model ◽  
Wind Stress ◽  
Climate Model ◽  
Southern Oscillation ◽  
Geophysical Fluid Dynamics Laboratory ◽  
Sustained Oscillations ◽  
Dynamical Regimes ◽  
Cold Events ◽  
The Impact

The El Niño–Southern Oscillation (ENSO) exhibits well-known asymmetries: 1) warm events are stronger than cold events, 2) strong warm events are more likely to be followed by cold events than vice versa, and 3) cold events are more persistent than warm events. Coupled GCM simulations, however, continue to underestimate many of these observed features. To shed light on these asymmetries, the authors begin with a widely used delayed-oscillator conceptual model for ENSO and modify it so that wind stress anomalies depend more strongly on SST anomalies (SSTAs) during warm conditions, as is observed. Then the impact of this nonlinearity on ENSO is explored for three dynamical regimes: self-sustained oscillations, stochastically driven oscillations, and self-sustained oscillations disrupted by stochastic forcings. In all three regimes, the nonlinear air–sea coupling preferentially strengthens the feedbacks (both positive and delayed negative) during the ENSO warm phase—producing El Niños that grow to a larger amplitude and overshoot more rapidly and consistently into the opposite phase, than do the La Niñas. Finally, the modified oscillator is applied to observational records and to control simulations from two global coupled ocean–atmosphere–land–ice models [Geophysical Fluid Dynamics Laboratory Climate Model version 2.1 (GFDL CM2.1) and version 2.5 (GFDL CM2.5)] to elucidate the causes of their differing asymmetries.

scholarly journals On the role of trend and variability of hydroxyl radical (OH) in the global methane budget

2020 ◽  
Author(s):  
Yuanhong Zhao ◽  
Marielle Saunois ◽  
Philippe Bousquet ◽  
Xin Lin ◽  
Antoine Berchet ◽  
...  
Keyword(s):  
Hydroxyl Radical ◽  
El Niño ◽  
Climate Model ◽  
El Nino ◽  
Interannual Variations ◽  
Atmospheric Methane ◽  
Tropical Regions ◽  
Ch4 Emissions ◽  
Methane Budget

Abstract. Decadal trends and interannual variations in the hydroxyl radical (OH), while poorly constrained at present, are critical for understanding the observed evolution of atmospheric methane (CH4). Through analyzing the OH fields simulated by the model ensemble of the Chemistry–Climate Model Initiative (CCMI), we find (1) the negative OH anomalies during the El Niño years mainly corresponding to the enhanced carbon monoxide (CO) emissions from biomass burning and (2) a positive OH trend during 1980–2010 dominated by the elevated primary production and the reduced loss of OH due to decreasing CO after 2000. Both two-box model inversions and variational 4D inversions suggest that ignoring the negative anomaly of OH during the El Niño years leads to a large overestimation of the increase in global CH4 emissions by up to 10 Tg yr−1 to match the observed CH4 increase over these years. Not accounting for the increasing OH trends given by the CCMI models leads to an underestimation of the CH4 emission increase by ~ 23 Tg yr−1 from 1986 to 2010. The variational inversion estimated CH4 emissions show that the tropical regions contribute most to the uncertainties related to OH. This study highlights the significant impact of climate and chemical feedbacks related to OH on the top-down estimates of the global CH4 budget.

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