Global atmospheric methane: budget, changes and dangers

Contraceptive diaphragms offer a discreet method of pregnancy protection that women can use when needed with no side effects. Incorporating antiretroviral HIV microbicides into such devices may also provide protection against HIV infection. The paper gives a brief outline of the work being conducted...

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Bibliographic Details
Published in:Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
Main Authors: Dlugokencky, Edward J., Nisbet, Euan, Fisher, Rebecca, Lowry, David
Format: Report
Language:English
Published: 2011
Subjects:
global methane budget
climate
greenhouse gas mitigation
isotope geochemistry
biogeochemical cycles
CARBON-DIOXIDE
GROWTH-RATE
EMISSIONS
CH4
VARIABILITY
TERMINATION
GREENLAND
PLANTS
GAS
Faculty of Science\Earth Sciences
Research Groups and Centres\Earth Sciences\Ancient and Modern Earth Systems
Research Groups and Centres\Earth Sciences\Geochemistry
Greenland
Online Access:https://repository.royalholloway.ac.uk/items/137776de-7427-79e8-1287-8c86b8106154/2/
https://doi.org/10.1098/rsta.2010.0341
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Summary:Contraceptive diaphragms offer a discreet method of pregnancy protection that women can use when needed with no side effects. Incorporating antiretroviral HIV microbicides into such devices may also provide protection against HIV infection. The paper gives a brief outline of the work being conducted by PATH, CONRAD and QUB on the development of a microbicide-releasing SILCS diaphragm. The design, engineering and manufacturing challenges that have been encountered will be discussed, as well as the potential impact such a device could have in the developing world. A factor of 2.5 increase in the global abundance of atmospheric methane (CH4) since 1750 contributes 0.5 Wm(-2) to total direct radiative forcing by long-lived greenhouse gases (2.77 Wm-2 in 2009), while its role in atmospheric chemistry adds another approximately 0.2Wm(-2) of indirect forcing. Since CH4 has a relatively short lifetime and it is very close to a steady state, reductions in its emissions would quickly benefit climate. Sensible emission mitigation strategies require quantitative understanding of CH4's budget of emissions and sinks. Atmospheric observations of CH4 abundance and its rate of increase, combined with an estimate of the CH4 lifetime, constrain total global CH4 emissions to between 500 and 600 Tg CH4 yr(-1). While total global emissions are constrained reasonably well, estimates of emissions by source sector vary by up to a factor of 2. Current observation networks are suitable to constrain emissions at large scales (e. g. global) but not at the regional to national scales necessary to verify emission reductions under emissions trading schemes. Improved constraints on the global CH4 budget and its break down of emissions by source sector and country will come from an enhanced observation network for CH4 abundance and its isotopic composition (delta C-13, delta D (D = H-2) and delta C-14). Isotopic measurements are a valuable tool in distinguishing among various sources that contribute emissions to an air parcel, once fractionation ...

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