58 research outputs found
Variability and quasi-decadal changes in the methane budget overthe period 2000â2012
Following the recent Global Carbon Project (GCP)
synthesis of the decadal methane (CH4/ budget over 2000â
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 topdown
studies (exploiting atmospheric observations within an
atmospheric inverse-modelling framework) and bottom-up
models (including process-based models for estimating land
surface emissions and atmospheric chemistry), inventories of
anthropogenic emissions, and data-driven approaches.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 2000â2012, 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 2000â2006, during
the plateau of atmospheric methane mole fractions, and also
over the period 2008â2012, during the renewed atmospheric
methane increase. However, the top-down ensemble mean
produces an emission shift between 2006 and 2008, leading
to 22 [16â32] Tg CH4 yr1 higher methane emissions
over the period 2008â2012 compared to 2002â2006. 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
seem 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 2002â2006 and 2008â2012 differs from
one atmospheric inversion study to another. However, all topdown
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 Emission Database for Global Atmospheric Research
(EDGARv4.2) inventory, which should be revised to smaller
values in a near future. We apply isotopic signatures to the
emission changes estimated for individual studies based on
five emission sectors and find that for six individual top-down
studies (out of eight) the average isotopic signature of the
emission changes is not consistent with the observed change
in atmospheric 13CH4. However, the partitioning in emission
change 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. In addition, a decrease in
biomass burning emissions (in agreement with the biomass
burning emission databases) makes the balance of sources
consistent with atmospheric 13CH4 observations.
In most of the top-down studies included here, OH concentrations
are considered constant over the years (seasonal variations
but without any inter-annual variability). As a result,
the methane loss (in particular through OH oxidation) varies
mainly through the change in methane concentrations and not
its oxidants. For these reasons, changes in the methane loss
could not be properly investigated in this study, although it
may play a significant role in the recent atmospheric methane
changes as briefly discussed at the end of the paper.Published11135â111616A. Geochimica per l'ambienteJCR Journa
The global methane budget 2000â2017
Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. Atmospheric emissions and concentrations of CH4 continue to increase, making CH4 the second most important human-influenced greenhouse gas in terms of climate forcing, after carbon dioxide (CO2). The relative importance of CH4 compared to CO2 depends on its shorter atmospheric lifetime, stronger warming potential, and variations in atmospheric growth rate over the past decade, the causes of which are still debated. Two major challenges in reducing uncertainties in the atmospheric growth rate arise from the variety of geographically overlapping CH4 sources and from the destruction of CH4 by short-lived hydroxyl radicals (OH). To address these challenges, we have established a consortium of multidisciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate new research aimed at improving and regularly updating the global methane budget. Following Saunois et al. (2016), we present here the second version of the living review paper dedicated to the decadal methane budget, integrating results of top-down studies (atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up estimates (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations).
For the 2008â2017 decade, global methane emissions are estimated by atmospheric inversions (a top-down approach) to be 576âTgâCH4âyrâ1 (range 550â594, corresponding to the minimum and maximum estimates of the model ensemble). Of this total, 359âTgâCH4âyrâ1 or âŒâ60â% is attributed to anthropogenic sources, that is emissions caused by direct human activity (i.e. anthropogenic emissions; range 336â376âTgâCH4âyrâ1 or 50â%â65â%). The mean annual total emission for the new decade (2008â2017) is 29âTgâCH4âyrâ1 larger than our estimate for the previous decade (2000â2009), and 24âTgâCH4âyrâ1 larger than the one reported in the previous budget for 2003â2012 (Saunois et al., 2016). Since 2012, global CH4 emissions have been tracking the warmest scenarios assessed by the Intergovernmental Panel on Climate Change. Bottom-up methods suggest almost 30â% larger global emissions (737âTgâCH4âyrâ1, range 594â881) than top-down inversion methods. Indeed, bottom-up estimates for natural sources such as natural wetlands, other inland water systems, and geological sources are higher than top-down estimates. The atmospheric constraints on the top-down budget suggest that at least some of these bottom-up emissions are overestimated. The latitudinal distribution of atmospheric observation-based emissions indicates a predominance of tropical emissions (âŒâ65â% of the global budget, <â30ââN) compared to mid-latitudes (âŒâ30â%, 30â60ââN) and high northern latitudes (âŒâ4â%, 60â90ââN). The most important source of uncertainty in the methane budget is attributable to natural emissions, especially those from wetlands and other inland waters.
Some of our global source estimates are smaller than those in previously published budgets (Saunois et al., 2016; Kirschke et al., 2013). In particular wetland emissions are about 35âTgâCH4âyrâ1 lower due to improved partition wetlands and other inland waters. Emissions from geological sources and wild animals are also found to be smaller by 7âTgâCH4âyrâ1 by 8âTgâCH4âyrâ1, respectively. However, the overall discrepancy between bottom-up and top-down estimates has been reduced by only 5â% compared to Saunois et al. (2016), due to a higher estimate of emissions from inland waters, highlighting the need for more detailed research on emissions factors. Priorities for improving the methane budget include (i) a global, high-resolution map of water-saturated soils and inundated areas emitting methane based on a robust classification of different types of emitting habitats; (ii) further development of process-based models for inland-water emissions; (iii) intensification of methane observations at local scales (e.g., FLUXNET-CH4 measurements) and urban-scale monitoring to constrain bottom-up land surface models, and at regional scales (surface networks and satellites) to constrain atmospheric inversions; (iv) improvements of transport models and the representation of photochemical sinks in top-down inversions; and (v) development of a 3D variational inversion system using isotopic and/or co-emitted species such as ethane to improve source partitioning
Photography-based taxonomy is inadequate, unnecessary, and potentially harmful for biological sciences
The question whether taxonomic descriptions naming new animal species without type specimen(s) deposited in collections should be accepted for publication by scientific journals and allowed by the Code has already been discussed in Zootaxa (Dubois & NemĂ©sio 2007; Donegan 2008, 2009; NemĂ©sio 2009aâb; Dubois 2009; Gentile & Snell 2009; Minelli 2009; Cianferoni & Bartolozzi 2016; Amorim et al. 2016). This question was again raised in a letter supported
by 35 signatories published in the journal Nature (Pape et al. 2016) on 15 September 2016. On 25 September 2016, the following rebuttal (strictly limited to 300 words as per the editorial rules of Nature) was submitted to Nature, which on
18 October 2016 refused to publish it. As we think this problem is a very important one for zoological taxonomy, this text is published here exactly as submitted to Nature, followed by the list of the 493 taxonomists and collection-based
researchers who signed it in the short time span from 20 September to 6 October 2016
Leadership, Loyalty, and Sovereignty in the Revolutionary American Southwest: The State of Franklin as Case Study
Before the Volunteer State: New thoughts on early Tennessee history, 1540-1800
Most general studies of Tennessee history begin with the arrival of Anglo-American settlers in the 1760s, with only a brief overview of the stateâs âprehistory.â This welcome volume rethinks this narrative by placing Tennesseeâs origins firmly in the seventeenth century. In ten thoughtful essays, scholars of trans-Appalachian and early American history address a number of issues that have been touched on only fleetingly within Tennessee historiography, including the dynamic balance of Native American concerns and European imperial interests, the complexity of Revolutionary-era struggles, and the associated challenges of jurisdiction, dominion, and identity formation. Collectively, the volume situates Tennessee more firmly within the context of regional, North American, and Atlantic World developments. The essays are divided into two partsâthe first focusing on the establishment and geopolitical complexities of seventeenth- and early-eighteenth-century life in and around the Tennessee River, and the second exploring the effects of the American Revolution in this geopolitical space. Topics in Part One include Indian life in the late Mississippian era, how contact with Europeans forced a process of migration and change, European understanding of Cherokee strength, and the importance of the Creeks, Cherokees, and Shawnees to early Tennessee history. Part Two offers articles about the confusing milieu into which the region was thrown during the Revolution, the central role of kinship networks for both Indians and whites, and the difficulties of identity formation as Euro-Americans expanded their presence on the Tennessee frontier. The work concludes by addressing the issue of myth and memory and how early Tennessee history was overtaken by nineteenth-century historical narratives that continue to serve as the foundation for understanding the state.Taken together, these essays provide a gateway through which to reimagine early Tennessee historyâa reimagining that demonstrates the significance of the Volunteer State within broader trends in early modern, southern, trans-Appalachian, and Atlantic World history
The Republicans are the Nation? Thomas Jefferson, William Duane, and the Evolution of the Republican Coalition, 1809 -1815,
This essay explores Thomas Jefferson's early retirement political activity and binary vision of Federalism/Republicanism within the context of the broader political economic forces of the early nineteenth century. It shows that his notions of unity and legitimacy, so rooted in the life and death struggles of 1790s state building, increasingly no longer were relevant. His participation in a minor affair illuminates this point quite well. In the spring of 1811, Jefferson played a central role in a battle over loyalty, editorial prerogative, and the maintenance of party unity. It began when William Duane, book publisher, editor of the Philadelphia Aurora and long-time power broker within the coalition, sought Jefferson's help in securing funding from Virginia Republicans. Duane was facing a financial meltdown, and he hoped that the âsage of Monticelloâ might provide him a way out. Jefferson ultimately rejected the request in the name of party harmony, the irony of which is that Duane's âschismâ reflected more of the future of the Republican movement than the harmonious nation Jefferson was hoping to preserve
Biographical Directory of the Tennessee General Assembly, Volume VII: 1992-2016
Volume VII of the Biographical Directory of the Tennessee General Assembly begins with the ending year of Volume VI, which covered 1971-1991. The Biographical Directory series is based on the two-year legislative session; this volume covers the 97th General Assembly through the 109th General Assembly, covering 1991-2016
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