scholarly journals Stable atmospheric methane in the 2000s: key-role of emissions from natural wetlands

2013 ◽  
Vol 13 (23) ◽  
pp. 11609-11623 ◽  
Author(s):  
I. Pison ◽  
B. Ringeval ◽  
P. Bousquet ◽  
C. Prigent ◽  
F. Papa
Keyword(s):  
South America ◽  
Process Model ◽  
Methane Emissions ◽  
Time Variability ◽  
Positive Trend ◽  
Tropical Wetlands ◽  
Top Down ◽  
Bottom Up ◽  
Natural Wetlands

Abstract. Two atmospheric inversions (one fine-resolved and one process-discriminating) and a process-based model for land surface exchanges are brought together to analyse the variations of methane emissions from 1990 to 2009. A focus is put on the role of natural wetlands and on the years 2000–2006, a period of stable atmospheric concentrations. From 1990 to 2000, the top-down and bottom-up visions agree on the time-phasing of global total and wetland emission anomalies. The process-discriminating inversion indicates that wetlands dominate the time-variability of methane emissions (90% of the total variability). The contribution of tropical wetlands to the anomalies is found to be large, especially during the post-Pinatubo years (global negative anomalies with minima between −41 and −19 Tg yr−1 in 1992) and during the alternate 1997–1998 El-Niño/1998–1999 La-Niña (maximal anomalies in tropical regions between +16 and +22 Tg yr−1 for the inversions and anomalies due to tropical wetlands between +12 and +17 Tg yr−1 for the process-based model). Between 2000 and 2006, during the stagnation of methane concentrations in the atmosphere, the top-down and bottom-up approaches agree on the fact that South America is the main region contributing to anomalies in natural wetland emissions, but they disagree on the sign and magnitude of the flux trend in the Amazon basin. A negative trend (−3.9 ± 1.3 Tg yr−1) is inferred by the process-discriminating inversion whereas a positive trend (+1.3 ± 0.3 Tg yr−1) is found by the process model. Although processed-based models have their own caveats and may not take into account all processes, the positive trend found by the B-U approach is considered more likely because it is a robust feature of the process-based model, consistent with analysed precipitations and the satellite-derived extent of inundated areas. On the contrary, the surface-data based inversions lack constraints for South America. This result suggests the need for a re-interpretation of the large increase found in anthropogenic methane inventories after 2000.

scholarly journals Stable atmospheric methane in the 2000s: key-role of emissions from natural wetlands

2013 ◽  
Vol 13 (4) ◽  
pp. 9017-9049 ◽  
Author(s):  
I. Pison ◽  
B. Ringeval ◽  
P. Bousquet ◽  
C. Prigent ◽  
F. Papa
Keyword(s):  
Process Model ◽  
Regional Analysis ◽  
Methane Emissions ◽  
Positive Trend ◽  
Tropical Wetlands ◽  
Tropical Regions ◽  
Global Emission ◽  
Natural Wetlands ◽  
Atmospheric Inversions

Abstract. Two atmospheric inversions (one fine-resolved and one process-discriminating) and a process-based model for land surface exchanges are brought together to analyze the variations of methane emissions from 1990 to 2009. A focus is put on the role of natural wetlands and on the years 2000–2006, a period of stable atmospheric concentrations. From 1990 to 2000, the two inversions agree on the time-phasing of global emission anomalies. The process-discriminating inversion further indicates that wetlands dominate the time-variability of methane emissions with 90% of the total variability. Top-down and bottom-up methods are qualitatively in good agreement regarding the global emission anomalies. The contribution of tropical wetlands on these anomalies is found to be large, especially during the post-Pinatubo years (global negative anomalies with minima between −41 and −19 Tg y−1 in 1992) and during the alternate 1997–1998 el-Niño/1998–1999 la-Niña (maximal anomalies in tropical regions between +16 and +22 Tg y−1 for the inversions and anomalies due to tropical wetlands between +12 and +17 Tg y−1 for the process-based model). Between 2000 and 2006, during the stagnation of methane concentrations in the atmosphere, total methane emissions found by the two inversions on the one hand and wetland emissions found by the process-discriminating-inversion and the process model on the other hand are not fully consistent. A regional analysis shows that differences in the trend of tropical South American wetland emissions in the Amazon region are mostly responsible for these discrepancies. A negative trend (−3.9 ± 1.3 Tg y−1) is inferred by the process-discriminating inversion whereas a positive trend (+1.3 ± 0.3 Tg y−1) is found by the process model. Since a positive trend is consistent with satellite-derived extent of inundated areas, this inconsistency points at the difficulty for atmospheric inversions using surface observations to properly constrain tropical regions with few available observations. A consequence is the need to revisit the large increase in anthropogenic emissions computed at the global scale by some inventories for the early 2000s, although process-based models have also their own caveats and may not take into account all processes.

Sensory regulation of quadrupedal locomotion: a top-down or bottom-up control system?

2012 ◽  
Vol 108 (3) ◽  
pp. 709-711 ◽  
Author(s):  
Yann Thibaudier ◽  
Marie-France Hurteau
Keyword(s):  
Control System ◽  
Central Pattern Generators ◽  
Top Down ◽  
Bottom Up ◽  
Sensory Inputs ◽  
Sensory Regulation ◽  
Before And After ◽  
Pattern Generators

Propriospinal pathways are thought to be critical for quadrupedal coordination by coupling cervical and lumbar central pattern generators (CPGs). However, the mechanisms involved in relaying information between girdles remain largely unexplored. Using an in vitro spinal cord preparation in neonatal rats, Juvin and colleagues ( Juvin et al. 2012 ) have recently shown sensory inputs from the hindlimbs have greater influence on forelimb CPGs than forelimb sensory inputs on hindlimb CPGs, in other words, a bottom-up control system. However, results from decerebrate cats suggest a top-down control system. It may be that both bottom-up and top-down control systems exist and that the dominance of one over the other is task or context dependent. As such, the role of sensory inputs in controlling quadrupedal coordination before and after injury requires further investigation.

Role of top-down and bottom-up forces on the invasibility of intertidal macroalgal assemblages

2013 ◽  
Vol 76 ◽  
pp. 178-186 ◽  
Author(s):  
Fátima Vaz-Pinto ◽  
Celia Olabarria ◽  
Francisco Arenas
Keyword(s):  
Top Down ◽  
Bottom Up

Computational Models of Learning Mechanisms in Psychosis

2017 ◽  
Author(s):  
Andreas Heinz
Keyword(s):  
Mental Disorders ◽  
Psychiatric Disorders ◽  
Computational Models ◽  
The Self ◽  
Psychotic Experiences ◽  
Learning Mechanisms ◽  
Top Down ◽  
Bottom Up ◽  
Surrounding World

Psychotic experiences may best be described as an alteration in the self-ascription of thoughts and actions, which is associated with a profoundly altered experience of oneself and the surrounding world. Computational models of key symptoms of psychiatric disorders are discussed with respect to the attribution of salience and self-relatedness to otherwise irrelevant stimuli and the role of top-down modelling in the generation of delusions. Top-down and bottom-up approaches in understanding mental disorders and their computational models are compared and critically reflected.

The role of the third sector working with the hard and soft structures of public–private partnerships to promote individual health and reinvigorated, healthier communities

2020 ◽  
pp. 301-318
Author(s):  
Tony Chasteauneuf ◽  
Tony Thornton ◽  
Dean Pallant
Keyword(s):  
Health Outcomes ◽  
Local Authority ◽  
Third Sector ◽  
Public Private Partnerships ◽  
Top Down ◽  
Bottom Up ◽  
The Third ◽  
Individual Health ◽  
The Third Sector

This chapter discusses the role of the third sector working with the hard and soft structures of public–private partnerships to promote healthier individuals and communities. It considers how a recommitment to the 'local authority' of citizens and beneficiaries offers the possibility of revitalised and healthier individuals and reinvigorated and healthier communities, which are unachievable through the hard and soft structures of the commissioner/provider statutory approach. The chapter then identifies the pivotal dynamic of one-to-one relationships in these processes and their association with health outcomes (emotional, physical, and spiritual) alongside the opportunities and challenges in agencies engaging/re-engaging with the agency of citizens and beneficiaries. It explores the tension between the 'agency' of citizens and beneficiaries that constitutes bottom-up power and 'agencies' with top-down power. The chapter also looks at the benefits of embracing the expertise and investment of individuals and their communities in their personal and shared lives, how this can be supported and how it can be undermined.

scholarly journals Variability and quasi-decadal changes in the methane budget over the period 2000–2012

2017 ◽  
Author(s):  
Marielle Saunois ◽  
Philippe Bousquet ◽  
Benjamin Poulter ◽  
Anna Peregon ◽  
Philippe Ciais ◽  
...  
Keyword(s):  
Biomass Burning ◽  
Methane Emissions ◽  
Data Driven ◽  
Atmospheric Methane ◽  
Top Down ◽  
Bottom Up ◽  
Ch4 Emissions ◽  
Ensemble Mean ◽  
The Mean ◽  
The Tropics

Abstract. Following the recent Global Carbon project (GCP) synthesis of the decadal methane (CH4) budget over 2000–2012 (Saunois et al., 2016), we analyse here the same dataset with a focus on quasi-decadal and inter-annual variability in CH4 emissions. The GCP dataset integrates results from top-down studies (exploiting atmospheric observations within an atmospheric inverse-modelling frameworks) and bottom-up models, inventories, and data-driven approaches (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations). The annual global methane emissions from top-down studies, which by construction match the observed methane growth rate within their uncertainties, all show an increase in total methane emissions over the period 2000–2012, but this increase is not linear over the 13 years. Despite differences between individual studies, the mean emission anomaly of the top-down ensemble shows no significant trend in total methane emissions over the period 2000–2006, during the plateau of atmospheric methane mole fractions, and also over the period 2008–2012, during the renewed atmospheric methane increase. However, the top-down ensemble mean produces an emission shift between 2006 and 2008, leading to 22 [16–32] Tg CH4 yr−1 higher methane emissions over the period 2008–2012 compared to 2002–2006. This emission increase mostly originated from the tropics with a smaller contribution from mid-latitudes and no significant change from boreal regions. The regional contributions remain uncertain in top-down studies. Tropical South America and South and East Asia seems to contribute the most to the emission increase in the tropics. However, these two regions have only limited atmospheric measurements and remain therefore poorly constrained. The sectorial partitioning of this emission increase between the periods 2002–2006 and 2008–2012 differs from one atmospheric inversion study to another. However, all top-down studies suggest smaller changes in fossil fuel emissions (from oil, gas, and coal industries) compared to the mean of the bottom-up inventories included in this study. This difference is partly driven by a smaller emission change in China from the top-down studies compared to the estimate in the EDGARv4.2 inventory, which should be revised to smaller values in a near future. Though the sectorial partitioning of six individual top-down studies out of eight are not consistent with the observed change in atmospheric 13CH4, the partitioning derived from the ensemble mean is consistent with this isotopic constraint. At the global scale, the top-down ensemble mean suggests that, the dominant contribution to the resumed atmospheric CH4 growth after 2006 comes from microbial sources (more from agriculture and waste sectors than from natural wetlands), with an uncertain but smaller contribution from fossil CH4 emissions. Besides, a decrease in biomass burning emissions (in agreement with the biomass burning emission databases) makes the balance of sources consistent with atmospheric 13CH4 observations. The methane loss (in particular through OH oxidation) has not been investigated in detail in this study, although it may play a significant role in the recent atmospheric methane changes.

Imprinting Beyond the Founding Phase: How Sedimented Imprints Develop over Time

2020 ◽  
Vol 31 (6) ◽  
pp. 1579-1600
Author(s):  
Lien De Cuyper ◽  
Bart Clarysse ◽  
Nelson Phillips
Keyword(s):  
Process Model ◽  
External Environment ◽  
Top Down ◽  
Bottom Up ◽  
Social Venture ◽  
Changes Over Time ◽  
Over Time ◽  
Do So

In this study, we build on the foundational observations of Selznick and Stinchcombe that organizations bear the lasting imprint of their founding context and explore how characteristics shaped during founding are coherently carried forward through time. To do so, we draw on an ethnography of a social venture where the entrepreneurs left soon after founding. In examining how an initial organizational imprint evolves beyond a venture’s founding phase, we focus on the actions and interactions of organizational members, the founders’ imprint, the venture’s new leadership, and the external environment. The process model we develop shows how the organizational imprint evolves as a consequence of the interplay between top-down and bottom-up forces. We first find that the initial imprint is transmitted through a bottom-up mechanism of imprint reinforcement, and second, that the venture is reimprinted after the founding period through two processes which we call imprint reforming and imprint coupling. The result of this is the formation of a sedimented imprint. Our findings further illuminate that, although the initial imprint sticks, its function and manifestation changes over time.

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