scholarly journals Global geological methane emissions: An update of top-down and bottom-up estimates

Elem Sci Anth ◽  
2019 ◽  
Vol 7 ◽  
Author(s):  
Giuseppe Etiope ◽  
Stefan Schwietzke

A wide body of literature suggests that geological gas emissions from Earth’s degassing are a major methane (CH4) source to the atmosphere. These emissions are from gas-oil seeps, mud volcanoes, microseepage and submarine seepage in sedimentary (petroleum-bearing) basins, and geothermal and volcanic manifestations. Global bottom-up emission estimates, ranging from 30 to 76 Tg CH4 yr–1, evolved in the last twenty years thanks to the increasing number of flux measurements, and improved knowledge of emission factors and area distribution (activity). Based on recent global grid maps and updated evaluations of mud volcano and microseepage emissions, the global geo-CH4 source is now (bottom-up) estimated to be 45 (27–63) Tg yr–1, i.e., ~8% of total CH4 sources. Top-down verifications, based on independent approaches (including ethane and isotopic observations) from different authors, are consistent with the range of the bottom-up estimate. However, a recent top-down study, based on radiocarbon analyses in polar ice cores, suggests that geological, fossil (14C-free) CH4 emissions about 11,600 years ago were much lower (<15 Tg yr–1, 95% CI) and that this source strength could also be valid today. Here, we show that (i) this geo-CH4 downward revision implies a fossil fuel industry CH4 upward revision of at least 24–35%. (ii) The 95% CI estimates of the recent radiocarbon analysis do not overlap with those of 5 out of 6 other bottom-up and top-down studies (no overlap for the 90% CI estimates). (iii) The contrasting lines of evidence require further discussion, and research opportunities exist to help explain this gap.

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Adriano Mazzini ◽  
Alessandra Sciarra ◽  
Giuseppe Etiope ◽  
Pankaj Sadavarte ◽  
Sander Houweling ◽  
...  

AbstractQuantifying natural geological sources of methane (CH4) allows to improve the assessment of anthropogenic emissions to the atmosphere from fossil fuel industries. The global CH4 flux of geological gas is, however, an object of debate. Recent fossil (14C-free) CH4 measurements in preindustrial-era ice cores suggest very low global geological emissions (~ 1.6 Tg year−1), implying a larger fossil fuel industry source. This is however in contrast with previously published bottom-up and top-down geo-emission estimates (~ 45 Tg year−1) and even regional-scale emissions of ~ 1–2 Tg year−1. Here we report on significant geological CH4 emissions from the Lusi hydrothermal system (Indonesia), measured by ground-based and satellite (TROPOMI) techniques. Both techniques indicate a total CH4 output of ~ 0.1 Tg year−1, equivalent to the minimum value of global geo-emission derived by ice core 14CH4 estimates. Our results are consistent with the order of magnitude of the emission factors of large seeps used in global bottom-up estimates, and endorse a substantial contribution from natural Earth’s CH4 degassing. The preindustrial ice core assessments of geological CH4 release may be underestimated and require further study. Satellite measurements can help to test geological CH4 emission factors and explain the gap between the contrasting estimates.


Elem Sci Anth ◽  
2021 ◽  
Vol 9 (1) ◽  
Author(s):  
B. F. Thornton ◽  
G. Etiope ◽  
S. Schwietzke ◽  
A. V. Milkov ◽  
R. W. Klusman ◽  
...  

Global bottom-up and top-down estimates of natural, geologic methane (CH4) emissions (average approximately 45 Tg yr–1) have recently been questioned by near-zero (approximately 1.6 Tg yr–1) estimates based on measurements of 14CH4 trapped in ice cores, which imply that current fossil fuel industries’ CH4 emissions are underestimated by 25%–40%. As we show here, such a global near-zero geologic CH4 emission estimate is incompatible with multiple independent, bottom-up emission estimates from individual natural geologic seepage areas, each of which is of the order of 0.1–3 Tg yr–1. Further research is urgently needed to resolve the conundrum before rejecting either method or associated emission estimates in global CH4 accounting.


PsycCRITIQUES ◽  
2005 ◽  
Vol 50 (19) ◽  
Author(s):  
Michael Cole
Keyword(s):  
Top Down ◽  

Author(s):  
Sadari Sadari ◽  
Nurhidayat Nurhidayat ◽  
Rafiqah Rafiqah
Keyword(s):  
Top Down ◽  

Humanisme religius telah mengantarkan pada era kesadaran bahwa peradaban manusia harus memiliki dua arus yang saling menunjang. Selama ini arus balik dalam bidang ekonomi hanya menonjolkan arus balik vertikal atas kebawah (model top down) yang didominasi oleh sistem ekonomi kapitalis dan sosialis, sedangkan di sisi lain mengesampingkan arus balik vertikal dari bawah ke atas (model bottom up) yang didominasi oleh sistem ekonomi syariah, sehingga dampaknya adalah adanya kesenjangan ekonomi yang sangat tajam. Paper ini mewujudkan peran penting, yakni menghubungkan dua arus tersebut secara timbal-balik, yakni mempertemukan arus pertama dengan arus balik kedua, sehingga akan menghasilkan dampak yang positif, progresif, kreatif dan produktif, kemudian pada akhirnya akan dapat meng-optomal-kan ekonomi syariah untuk menciptakan goodgovernance, post goodgovernance secara berkelanjutan, tentunya dengan bantuan peran media kontemporer yang kian update. Ekonomi syariah juga merupakan pilar dan nilai dasar, dari sikap keyakinan dan sikap rasionalitas untuk sanggup menciptakan terwujudnya pemberdayaan dan kesejahteraan sekaligus pengentasan kemiskinan dalam masyarakat di Indonesia.


Sign in / Sign up

Export Citation Format

Share Document