92 research outputs found
Active Amplification of the Terrestrial Albedo to Mitigate Climate Change: An Exploratory Study
This study explores the potential to enhance the reflectance of solar
insolation by the human settlement and grassland components of the Earth's
terrestrial surface as a climate change mitigation measure. Preliminary
estimates derived using a static radiative transfer model indicate that such
efforts could amplify the planetary albedo enough to offset the current global
annual average level of radiative forcing caused by anthropogenic greenhouse
gases by as much as 30 percent or 0.76 W/m2. Terrestrial albedo amplification
may thus extend, by about 25 years, the time available to advance the
development and use of low-emission energy conversion technologies which
ultimately remain essential to mitigate long-term climate change. However,
additional study is needed to confirm the estimates reported here and to assess
the economic and environmental impacts of active land-surface albedo
amplification as a climate change mitigation measure.Comment: 21 pages, 3 figures. In press with Mitigation and Adaptation
Strategies for Global Change, Springer, N
Use of SMS texts for facilitating access to online alcohol interventions: a feasibility study
A41 Use of SMS texts for facilitating access to online alcohol interventions: a feasibility study
In: Addiction Science & Clinical Practice 2017, 12(Suppl 1): A4
Pulmonary Function and Blood DNA Methylation A Multiancestry Epigenome-Wide Association Meta-analysis
Rationale: Methylation integrates factors present at birth and modifiable across the lifespan that can influence pulmonary function. Studies are limited in scope and replication. Objectives: To conduct large-scale epigenome-wide meta-analyses of blood DNA methylation and pulmonary function. Methods: Twelve cohorts analyzed associations of methylation at cytosine-phosphate-guanine probes (CpGs), using Illumina 450K or EPIC/850K arrays, with FEV1, FVC, and FEV1/FVC. We performed multiancestry epigenome-wide meta-analyses (total of 17,503 individuals; 14,761 European, 2,549 African, and 193 Hispanic/Latino ancestries) and interpreted results using integrative epigenomics. Measurements and Main Results: We identified 1,267 CpGs (1,042 genes) differentially methylated (false discovery rate,,0.025) in relation to FEV1, FVC, or FEV1/FVC, including 1,240 novel and 73 also related to chronic obstructive pulmonary disease (1,787 cases). We found 294 CpGs unique to European or African ancestry and 395 CpGs unique to never or ever smokers. The majority of significant CpGs correlated with nearby gene expression in blood. Findings were enriched in key regulatory elements for gene function, including accessible chromatin elements, in both blood and lung. Sixty-nine implicated genes are targets of investigational or approved drugs. One example novel gene highlighted by integrative epigenomic and druggable target analysis is TNFRSF4. Mendelian randomization and colocalization analyses suggest that epigenome-wide association study signals capture causal regulatory genomic loci. Conclusions: We identified numerous novel loci differentially methylated in relation to pulmonary function; few were detected in large genome-wide association studies. Integrative analyses highlight functional relevance and potential therapeutic targets. This comprehensive discovery of potentially modifiable, novel lung function loci expands knowledge gained from genetic studies, providing insights into lung pathogenesis
Rare genetic variants explain missing heritability in smoking
Common genetic variants explain less variation in complex phenotypes than inferred from family-based studies, and there is a debate on the source of this âmissing heritabilityâ. We investigated the contribution of rare genetic variants to tobacco use with whole-genome sequences from up to 26,257 unrelated individuals of European ancestries and 11,743 individuals of African ancestries. Across four smoking traits, single-nucleotide-polymorphism-based heritability (hSNP2) was estimated from 0.13 to 0.28 (s.e., 0.10â0.13) in European ancestries, with 35â74% of it attributable to rare variants with minor allele frequencies between 0.01% and 1%. These heritability estimates are 1.5â4 times higher than past estimates based on common variants alone and accounted for 60% to 100% of our pedigree-based estimates of narrow-sense heritability (hped2, 0.18â0.34). In the African ancestry samples, hSNP2 was estimated from 0.03 to 0.33 (s.e., 0.09â0.14) across the four smoking traits. These results suggest that rare variants are important contributors to the heritability of smoking
Effects of organic and mineral fertilizer nitrogen on greenhouse gas emissions and plant-captured carbon under maize cropping in Zimbabwe
Optimizing a three-way pact comprising crop yields, fertility inputs and greenhouse gases may minimize the contribution of croplands to global warming. Fluxes of N2O, CO2 and CH4 from soil were measured under maize (Zea mays L.) grown using 0, 60 and 120 kg N hm-2 as NH4NO3-N and composted manure-N in three seasons on clay (Chromic luvisol) and sandy loam (Haplic lixisol) soils in Zimbabwe. The fluxes were measured using the static chamber methodology involving gas chromatography for ample air analysis. Over an average of 122 days we estimated emissions of 0.1 to 0.5 kg N2O-N hm?2, 711 to 1574 kg CO2-C hm?2 and?2.6 to 5.8 kg CH4-C hm?2 from six treatments during season II with the highest fluxes. The posed hypothesis that composted manure-N may be better placed as a mitigation option against soil emissions of GHG than mineral fertilizer-N was largely supported by N2O fluxes during the wet period of the year, but with high level of uncertainty. Nitrogen addition might have stimulated both emissions and consumption of CH4 but the sink or source strength depended highly on soil water content. We concluded that the application of mineral-N and manure input may play an important role with reference to global warming provided the season can support substantial crop productivity that may reduce the amount of N2O loss per unit yield. Confidence in fluxes response to agricultural management is still low due to sporadic measurements and limited observations from the southern African region
The effects of catena positions on greenhouse gas emissions along a seasonal wetland (dambo) transect in tropical Zimbabwe
Wetlands are major natural sources of greenhouse gases (GHGs). In central and southern Africa, one of the most extensive wetlands are dambos (seasonal wetlands) which occupy 20â25% of land area. However, there are very little data on GHG methane (CH4), carbon dioxide (CO2) and nitrous oxide (N2O) emissions from dambos, and this study presents the first estimates from dambos in Zimbabwe. The objective was to evaluate the effects of catena positions; upland, dambo mid-slope and dambo bottom, on GHG emissions along an undisturbed dambo transect. Methane emissions were â0.3, 29.5 and â1.3 mg mâ2 hrâ1, N2O emission were 40.1, 3.9 and 5.5 ”g m2 hrâ1, while CO2 emissions were 2648.9, 896.2 and 590.1 mg mâ2 hrâ1 for upland, mid-slope and bottom catena, respectively. Our results showed that uplands were important sources of N2O and CO2, and a sink for CH4, while the dambo mid-slope position was a major source of CH4, but a weak source of CO2 and N2O. Dambo bottom catena was weak source GHGs. Overall, dambos were major sources of CH4 and weak sources of N2O and CO2.We concluded that, depending on catenal position, dambos can be major or minor sources of GHGs
Nitrous oxide and methane emissions from cultivated seasonal wetland (dambo) soils with inorganic, organic and integrated nutrient management
In many smallholder farming areas southern Africa, the cultivation of seasonal wetlands (dambos) represent an important adaptation to climate change. Frequent droughts and poor performance of rain-fed crops in upland fields have resulted in mounting pressure to cultivate dambos where both organic and inorganic amendments are used to sustain crop yields. Dambo cultivation potentially increases greenhouse gas (GHG) emissions. The objective of the study was to quantify the effects of applying different rates of inorganic nitrogen (N) fertilisers (60, 120, 240 kg N haâ1) as NH4NO3, organic manures (5,000, 10,000 and 15,000 kg haâ1) and a combination of both sources (integrated management) on GHG emissions in cultivated dambos planted to rape (Brassica napus). Nitrous oxide (N2O) emissions in plots with organic manures ranged from 218 to 894 ”g mâ2 hâ1, while for inorganic N and integrated nutrient management, emissions ranged from 555 to 5,186 ”g mâ2 hâ1 and 356â2,702 ”g mâ2 hâ1 respectively. Cropped and fertilised dambos were weak sources of methane (CH4), with emissions ranging from â0.02 to 0.9 mg mâ2 hâ1, while manures and integrated management increased carbon dioxide (CO2) emissions. However, crop yields were better under integrated nutrient management. The use of inorganic fertilisers resulted in higher N2O emission per kg yield obtained (6â14 g N2O kgâ1 yield), compared to 0.7â4.5 g N2O kgâ1 yield and 1.6â4.6 g N2O kgâ1 yield for organic manures and integrated nutrient management respectively. This suggests that the use of organic and integrated nutrient management has the potential to increase yield and reduce yield scaled N2O emissions
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