Search results

Filter

Filetype

Your search for "*" yielded 533810 hits

Global change pressures on soils from land use and management

Soils are subject to varying degrees of direct or indirect human disturbance, constituting a major global change driver. Factoring out natural from direct and indirect human influence is not always straightforward, but some human activities have clear impacts. These include land-use change, land management and land degradation (erosion, compaction, sealing and salinization). The intensity of land

Implications of climate mitigation for future agricultural production

Climate change is projected to negatively impact biophysical agricultural productivity in much of the world. Actions taken to reduce greenhouse gas emissions and mitigate future climate changes, are thus of central importance for agricultural production. Climate impacts are, however, not unidirectional; some crops in some regions (primarily higher latitudes) are projected to benefit, particularly

Reconciling precipitation with runoff : Observed hydrological change in the midlatitudes

Century-long observed gridded land precipitation datasets are a cornerstone of hydrometeorological research. But recent work has suggested that observed Northern Hemisphere midlatitude (NHML) land mean precipitation does not show evidence of an expected negative response to mid-twentieth-century aerosol forcing. Utilizing observed river discharges, the observed runoff is calculated and compared wi

Effect of land-use change and management on biogenic volatile organic compound emissions - selecting climate-smart cultivars

Land-use change (LUC) has fundamentally altered the form and function of the terrestrial biosphere. Increasing human population, the drive for higher living standards and the potential challenges of mitigating and adapting to global environmental change mean that further changes in LUC are unavoidable. LUC has direct consequences on climate not only via emissions of greenhouse gases and changing t

Emissions of biogenic volatile organic compounds and subsequent photochemical production of secondary organic aerosol in mesocosm studies of temperate and tropical plant species

Silver birch (Betula pendula) and three Southeast Asian tropical plant species (Ficus cyathistipula, Ficus benjamina and Caryota millis) from the pantropical fig and palm genera were grown in a purpose-built and environmentcontrolled whole-tree chamber. The volatile organic compounds emitted from these trees were characterised and fed into a linked photochemical reaction chamber where they underwe

Multisectoral climate impact hotspots in a warming world

The impacts of global climate change on different aspects of humanity's diverse life-support systems are complex and often difficult to predict. To facilitate policy decisions on mitigation and adaptation strategies, it is necessary to understand, quantify, and synthesize these climate-change impacts, taking into account their uncertainties. Crucial to these decisions is an understanding of how im

Assessing agricultural risks of climate change in the 21st century in a global gridded crop model intercomparison

Here we present the results from an intercomparison of multiple global gridded crop models (GGCMs) within the framework of the Agricultural Model Intercomparison and Improvement Project and the Inter-Sectoral Impacts Model Intercomparison Project. Results indicate strong negative effects of climate change, especially at higher levels of warming and at low latitudes; models that include explicit ni

Influence of boundary layer dynamics and isoprene chemistry on the organic aerosol budget in a tropical forest

We study the organic aerosol (OA) budget in a tropical forest by analyzing a case that is representative for the OP3 campaign at Borneo. A model is designed that combines the essential dynamical and chemical processes that drive the diurnal evolution of reactants in the atmospheric boundary layer (BL). In this way, the model simultaneously represents the effects and interactions of various dynamic

A futures-based analysis for urban air quality remediation

Strong sustainability credentials are now considered an important aspect of any new urban development. However, actions to improve sustainability (described here as solutions) must not only perform under present conditions but must also continue to deliver their benefits however the future develops. This paper examines sustainability with respect to air quality (AQ) for a 6?6 ha case study in Lanc

A Lagrangian model of air-mass photochemistry and mixing using a trajectory ensemble : The Cambridge Tropospheric Trajectory model of Chemistry And Transport (CiTTyCAT) version 4.2

A Lagrangian model of photochemistry and mixing is described (CiTTyCAT,stemming from the Cambridge Tropospheric Trajectory model of Chemistry AndTransport), which is suitable for transport and chemistry studies throughoutthe troposphere. Over the last five years, the model has been developed inparallel at several different institutions and here those developments havebeen incorporated into one "co

Benchmarking sustainability in cities : The role of indicators and future scenarios

Scenarios are a useful tool to help think about and visualise the future and, as such, are utilised by many policymakers and practitioners. Future scenarios have not been used to explore the urban context in much depth, yet have the potential to provide valuable insights into the robustness of decisions being made today in the name of sustainability. As part of a major research project entitled Ur

The atmospheric chemistry of trace gases and particulate matter emitted by different land uses in Borneo

We report measurements of atmospheric composition over a tropical rainforest and over a nearby oil palm plantation in Sabah, Borneo. The primary vegetation in each of the two landscapes emits very different amounts and kinds of volatile organic compounds (VOCs), resulting in distinctive VOC fingerprints in the atmospheric boundary layer for both landscapes. VOCs over the Borneo rainforest are domi

The impact of local surface changes in Borneo on atmospheric composition at wider spatial scales : Coastal processes, land-use change and air quality

We present results fromtheOP3 campaign in Sabah during 2008 that allowus to study the impact of localemission changes over Borneo on atmospheric composition at the regional andwider scale. OP3 constituentdata provide an important constraint onmodel performance. Treatment of boundary layer processes is highlighted as an important area of model uncertainty.Model studies of land-use change confirm ea

Ground-level ozone influenced by circadian control of isoprene emissions

The volatile organic compound isoprene is produced by many plant species, and provides protection against biotic and abiotic stresses1. Globally, isoprene emissions from plants are estimated to far exceed anthropogenic emissions of volatile organic compounds2. Once in the atmosphere, isoprene reacts rapidly with hydroxyl radicals3 to form peroxy radicals, which can react with nitrogen oxides to fo

The influence of small-scale variations in isoprene concentrations on atmospheric chemistry over a tropical rainforest

Biogenic volatile organic compounds (BVOCs) such as isoprene constitute a large proportion of the global atmospheric oxidant sink. Their reactions in the atmosphere contribute to processes such as ozone production and secondary organic aerosol formation. However, over the tropical rainforest, where 50 % of the global emissions of BVOCs are believed to occur, atmospheric chemistry models have been

Modelling chemistry in the nocturnal boundary layer above tropical rainforest and a generalised effective nocturnal ozone deposition velocity for sub-ppbv NOx conditions

Measurements of atmospheric composition have been made over a remote rainforest landscape. A box model has previously been demonstrated to model the observed daytime chemistry well. However the box model is unable to explain the nocturnal measurements of relatively high [NO] and [O3], but relatively low observed [NO2]. It is shown that a one-dimensional (1-D) column model with simple O3-NOx chemis

Fluxes and concentrations of volatile organic compounds from a South-East Asian tropical rainforest

As part of the OP3 field study of rainforest atmospheric chemistry, above-canopy fluxes of isoprene, monoterpenes and oxygenated volatile organic compounds were made by virtual disjunct eddy covariance from a South-East Asian tropical rainforest in Malaysia. Approximately 500 hours of flux data were collected over 48 days in April-May and June-July 2008. Isoprene was the dominant non-methane hydro

Nitrogen management is essential to prevent tropical oil palm plantations from causing ground-level ozone pollution

More than half the world's rainforest has been lost to agriculture since the Industrial Revolution. Among the most widespread tropical crops is oil palm (Elaeis guineensis): global production now exceeds 35 million tonnes per year. In Malaysia, for example, 13% of land area is now oil palm plantation, compared with 1% in 1974. There are enormous pressures to increase palm oil production for food,

Analysis of manufacturing costs for powder metallurgy (pm) gear manufacturing processes : a case study of a helical drive gear

This paper presents a thorough manufacturing cost analysis for a powder metallurgy (PM) manufactured gear (using press and sintering technique—P/S), through a case study of a R&D 4th drive gear (a helical gearwheel) utilizing both real usage data from six companies and some estimated data from literatures. The chosen costs calculation method, performance part costing (PPC), is comprehensive an