Keith R Lassey - Academia.edu (original) (raw)
Papers by Keith R Lassey
Environmental sciences, Jun 1, 2005
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AGUFM, Dec 1, 2007
ABSTRACT An enduring consensus of the global methane budget, as expressed in recent IPCC Assessme... more ABSTRACT An enduring consensus of the global methane budget, as expressed in recent IPCC Assessment Reports, is that about 20%\ of emissions have geologic origin (ie, are free of 14CH4). Based on atmospheric 14CH4 measurements and confounded by ill-quantified 14CH4 emissions from the nuclear- power industry, this "fossil fraction" estimate is quite uncertain, typically 18± 9%. A very recent re-determination of 30± 5%\ (± 2sigma) for the fossil fraction which does not require that the nuclear-power emission be specified may still be compatible with the earlier assessment despite an upward revision by 50%. Anthropogenic emissions via identified pathways of fossil-fuel exploitation are assessed in the Fourth IPCC Assessment Report at 90± 16 Tg~yr-1. Natural emissions extrapolated conservatively from new and widespread measurements of terrestrial seeps are 50± 10 Tg~yr-1, at least three times larger than previously accepted. The aggregate fossil emission of 140± 19 Tg~yr-1 is conservative yet still accounts for 24± 5%\ of the global source of 582± 87 Tg~yr-1, a value that is compatible with both 14CH4-based estimates of the fossil fraction. Nevertheless, while the fossil contribution to the methane source inventory remains incompletely determined the currently accepted estimate of ~20%\ for the fossil fraction may need to be revised upward, with substantial consequences for pre-industrial and contemporary source inventories.
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PubMed, Aug 1, 1980
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Animal Feed Science and Technology, Mar 1, 2013
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Agricultural and Forest Meteorology, Feb 1, 2007
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Water Resources Research, Mar 1, 1988
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Australian Journal of Experimental Agriculture, 2008
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Science, Mar 10, 2016
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Ecological Modelling, 1983
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Journal of Integrative Environmental Sciences, Aug 1, 2010
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New Zealand Journal of Agricultural Research, Oct 1, 2002
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Physical review, Feb 1, 1978
We have calculated the parity violating observables in p-p and n-p scattering using a number of s... more We have calculated the parity violating observables in p-p and n-p scattering using a number of strong nucleon-nucleon potentials for a large class of weak parity violating potentials.
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Springer eBooks, 2000
The most direct way to establish the level of surface emissions of greenhouse gases is to measure... more The most direct way to establish the level of surface emissions of greenhouse gases is to measure and interpret concentration gradients in the atmosphere. We have tested the efficacy of this approach for inferring average methane fluxes from regions of pastoral agriculture a few tens of km in extent In its simplest form, vertical concentration profiles are measured upwind and downwind of the target region, based on air samples collected from light aircraft. Using simple mass balance models, the profile contrasts can be related to the mean surface flux over the intervening region. The inferred flux can then be compared with ‘bottom-up’ estimates based on livestock density and per-animal emissions. However, such simple models may poorly simulate air flows over the New Zealand terrain, and as an alternative, we deploy a state-of-the-art mesoscale meteorological model, RAMS, coupled to an atmospheric dispersion model. RAMS is used prognostically to guide the timing and siting of measurement campaigns, and diagnostically to simulate regional wind fields which are validated against local meteorological data. Source-oriented and receptor-oriented dispersion modelling techniques, in combination with aircraft-based sampling and laboratory gas analysis, provide ‘top-down’ methane flux estimates that compare favourably with ‘bottom-up’ estimates. These techniques thus enhance confidence in national emission inventories based on bottom-up estimation. However, the challenge for similar verification of nitrous oxide emission is more imposing.
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In a series of field campaigns since 1995, a team of atmospheric and ruminantnutrition scientists... more In a series of field campaigns since 1995, a team of atmospheric and ruminantnutrition scientists have measured methane emissions directly from individual ruminant livestock freely grazing representative New Zealand pastures. The technique collects integrated ‘breath’ samples during grazing, using an implanted SF6 source as a conservative calibrated tracer, an approach pioneered by Johnson et al. [1994]. Most of these measurements have been on grazing sheep (942 animal-days to Aug 1999), others on grazing dairy cows (283), with some measurements also on sheep under controlled feeding conditions (305) [eg, Lassey et al., 1997; Ulyatt et al., 1999]. The aim is to characterise the variability of emission rates, including their dependence on pasture quality and physiological condition. The research goal is two-fold: (i) to provide a better scientific basis for assessing the national emissions inventory; and (ii) to investigate options for mitigating livestock emissions. Here, we discuss the research strategy and overview the principal research findings. We note in particular, that as a source of enterically fermented methane, sheep may not be merely ‘small cattle’.
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Animal Feed Science and Technology, Jun 1, 2011
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New Zealand Journal of Agricultural Research, Dec 1, 2005
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Chemosphere - Global Change Science, Oct 1, 2001
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New Zealand Journal of Agricultural Research, Oct 1, 2002
... from dairy cows and breeding ewes, the dominant livestock types in New Zealand agriculture, f... more ... from dairy cows and breeding ewes, the dominant livestock types in New Zealand agriculture, fed on typical ryegrass/white clover dominant ... for calorimetric measurements from cows of similar intake, bodyweight or level of milk production (eg, Moe & Tyrell 1979; Wilkerson et al. ...
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Environmental sciences, Jun 1, 2005
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AGUFM, Dec 1, 2007
ABSTRACT An enduring consensus of the global methane budget, as expressed in recent IPCC Assessme... more ABSTRACT An enduring consensus of the global methane budget, as expressed in recent IPCC Assessment Reports, is that about 20%\ of emissions have geologic origin (ie, are free of 14CH4). Based on atmospheric 14CH4 measurements and confounded by ill-quantified 14CH4 emissions from the nuclear- power industry, this "fossil fraction" estimate is quite uncertain, typically 18± 9%. A very recent re-determination of 30± 5%\ (± 2sigma) for the fossil fraction which does not require that the nuclear-power emission be specified may still be compatible with the earlier assessment despite an upward revision by 50%. Anthropogenic emissions via identified pathways of fossil-fuel exploitation are assessed in the Fourth IPCC Assessment Report at 90± 16 Tg~yr-1. Natural emissions extrapolated conservatively from new and widespread measurements of terrestrial seeps are 50± 10 Tg~yr-1, at least three times larger than previously accepted. The aggregate fossil emission of 140± 19 Tg~yr-1 is conservative yet still accounts for 24± 5%\ of the global source of 582± 87 Tg~yr-1, a value that is compatible with both 14CH4-based estimates of the fossil fraction. Nevertheless, while the fossil contribution to the methane source inventory remains incompletely determined the currently accepted estimate of ~20%\ for the fossil fraction may need to be revised upward, with substantial consequences for pre-industrial and contemporary source inventories.
Bookmarks Related papers MentionsView impact
PubMed, Aug 1, 1980
Bookmarks Related papers MentionsView impact
Animal Feed Science and Technology, Mar 1, 2013
Bookmarks Related papers MentionsView impact
Agricultural and Forest Meteorology, Feb 1, 2007
Bookmarks Related papers MentionsView impact
Water Resources Research, Mar 1, 1988
Bookmarks Related papers MentionsView impact
Australian Journal of Experimental Agriculture, 2008
Bookmarks Related papers MentionsView impact
Science, Mar 10, 2016
Bookmarks Related papers MentionsView impact
Ecological Modelling, 1983
Bookmarks Related papers MentionsView impact
Journal of Integrative Environmental Sciences, Aug 1, 2010
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
New Zealand Journal of Agricultural Research, Oct 1, 2002
Bookmarks Related papers MentionsView impact
Physical review, Feb 1, 1978
We have calculated the parity violating observables in p-p and n-p scattering using a number of s... more We have calculated the parity violating observables in p-p and n-p scattering using a number of strong nucleon-nucleon potentials for a large class of weak parity violating potentials.
Bookmarks Related papers MentionsView impact
Bookmarks Related papers MentionsView impact
Springer eBooks, 2000
The most direct way to establish the level of surface emissions of greenhouse gases is to measure... more The most direct way to establish the level of surface emissions of greenhouse gases is to measure and interpret concentration gradients in the atmosphere. We have tested the efficacy of this approach for inferring average methane fluxes from regions of pastoral agriculture a few tens of km in extent In its simplest form, vertical concentration profiles are measured upwind and downwind of the target region, based on air samples collected from light aircraft. Using simple mass balance models, the profile contrasts can be related to the mean surface flux over the intervening region. The inferred flux can then be compared with ‘bottom-up’ estimates based on livestock density and per-animal emissions. However, such simple models may poorly simulate air flows over the New Zealand terrain, and as an alternative, we deploy a state-of-the-art mesoscale meteorological model, RAMS, coupled to an atmospheric dispersion model. RAMS is used prognostically to guide the timing and siting of measurement campaigns, and diagnostically to simulate regional wind fields which are validated against local meteorological data. Source-oriented and receptor-oriented dispersion modelling techniques, in combination with aircraft-based sampling and laboratory gas analysis, provide ‘top-down’ methane flux estimates that compare favourably with ‘bottom-up’ estimates. These techniques thus enhance confidence in national emission inventories based on bottom-up estimation. However, the challenge for similar verification of nitrous oxide emission is more imposing.
Bookmarks Related papers MentionsView impact
In a series of field campaigns since 1995, a team of atmospheric and ruminantnutrition scientists... more In a series of field campaigns since 1995, a team of atmospheric and ruminantnutrition scientists have measured methane emissions directly from individual ruminant livestock freely grazing representative New Zealand pastures. The technique collects integrated ‘breath’ samples during grazing, using an implanted SF6 source as a conservative calibrated tracer, an approach pioneered by Johnson et al. [1994]. Most of these measurements have been on grazing sheep (942 animal-days to Aug 1999), others on grazing dairy cows (283), with some measurements also on sheep under controlled feeding conditions (305) [eg, Lassey et al., 1997; Ulyatt et al., 1999]. The aim is to characterise the variability of emission rates, including their dependence on pasture quality and physiological condition. The research goal is two-fold: (i) to provide a better scientific basis for assessing the national emissions inventory; and (ii) to investigate options for mitigating livestock emissions. Here, we discuss the research strategy and overview the principal research findings. We note in particular, that as a source of enterically fermented methane, sheep may not be merely ‘small cattle’.
Bookmarks Related papers MentionsView impact
Animal Feed Science and Technology, Jun 1, 2011
Bookmarks Related papers MentionsView impact
New Zealand Journal of Agricultural Research, Dec 1, 2005
Bookmarks Related papers MentionsView impact
Chemosphere - Global Change Science, Oct 1, 2001
Bookmarks Related papers MentionsView impact
New Zealand Journal of Agricultural Research, Oct 1, 2002
... from dairy cows and breeding ewes, the dominant livestock types in New Zealand agriculture, f... more ... from dairy cows and breeding ewes, the dominant livestock types in New Zealand agriculture, fed on typical ryegrass/white clover dominant ... for calorimetric measurements from cows of similar intake, bodyweight or level of milk production (eg, Moe & Tyrell 1979; Wilkerson et al. ...
Bookmarks Related papers MentionsView impact