Global climate change : greenhouse effect

One of the main problems caused by climate change is the greenhouse effect. Human activities emit so-called greenhouse gases into the atmosphere, such as carbon dioxide which is produced through fossil fuel burning. These gases absorb the earth‘s radiation, forcing the earth‘s temperature, like that of in greenhouse, to rise. Global warming would lead to a rise in the global mean sea-level due to thermal expansion of the waters, and glaciers will melt at a fast rate, as will the Greenland ice cap. It is evident that climate changes would have a negative impact on agricultural production. The problem of climate change was considered in 1988 by the Toronto Conference on the Changing Atmosphere, which was attended by 300 scientist and policymakers from some 46 states. This article also tackles the implications of climate change in the Maltese Islands.peer-reviewe

Clouds in the atmospheres of extrasolar planets. IV. On the scattering greenhouse effect of CO2 ice particles: Numerical radiative transfer studies

Owing to their wavelengths dependent absorption and scattering properties, clouds have a strong impact on the climate of planetary atmospheres. Especially, the potential greenhouse effect of CO2 ice clouds in the atmospheres of terrestrial extrasolar planets is of particular interest because it might influence the position and thus the extension of the outer boundary of the classic habitable zone around main sequence stars. We study the radiative effects of CO2 ice particles obtained by different numerical treatments to solve the radiative transfer equation. The comparison between the results of a high-order discrete ordinate method and simpler two-stream approaches reveals large deviations in terms of a potential scattering efficiency of the greenhouse effect. The two-stream methods overestimate the transmitted and reflected radiation, thereby yielding a higher scattering greenhouse effect. For the particular case of a cool M-type dwarf the CO2 ice particles show no strong effective scattering greenhouse effect by using the high-order discrete ordinate method, whereas a positive net greenhouse effect was found in case of the two-stream radiative transfer schemes. As a result, previous studies on the effects of CO2 ice clouds using two-stream approximations overrated the atmospheric warming caused by the scattering greenhouse effect. Consequently, the scattering greenhouse effect of CO2 ice particles seems to be less effective than previously estimated. In general, higher order radiative transfer methods are necessary to describe the effects of CO2 ice clouds accurately as indicated by our numerical radiative transfer studies.Comment: accepted for publication in A&

Greenhouse effect in the atmosphere of Venus

Greenhouse effect in lower layers of Venus atmospher

CF3SF5 : a ‘super’ greenhouse gas

One molecule of the anthropogenic pollutant trifluoromethyl sulphur pentafluoride (CF$_3$SF$_5$), an adduct of the CF$_3$ and SF$_5$ free radicals, causes more global warming than one molecule of any other greenhouse gas yet detected in the Earth’s atmosphere. That is, it has the highest per molecule radiative forcing of any greenhouse pollutant, and the value of its global warming potential is only exceeded by that of SF$_6$. First, the greenhouse effect is described, the properties of a molecule that cause it to be a significant greenhouse gas, and therefore the contributions that physical chemistry can make to an improved understanding of the effect. Second, the chemistry of (CF$_3$SF$_5$), first discovered in the atmosphere in 2000, is taken as a case study. Experiments using tunable vacuum-UV radiation, electrons and small cations have determined some of the relevant physical properties of this molecule, including the strength of the (CF$_3$-SF$_5$) covalent bond. The main sink route to remove (CF$_3$SF$_5$) from the earth’s atmosphere is low-energy electron attachment in the mesosphere. Third, it is shown how such data are important inputs to determine the lifetime of this pollutant, ca. 1000 years, in the atmosphere. Finally, the generic lessons that can be learnt from the study of such long-lived greenhouse gases are described

Impacts of Regulating Greenhouse Gas Emissions on Livestock Trade Flows

The policies that regulate greenhouse gas emissions would provide a significant burden to emission industries as well as final consumers, which can lead to a strong influence on international trade flows of commodities. This study examines the impact of regulating greenhouse gas emissions on livestock trade flows using a commodity specific gravity model approach. This study finds that regulating greenhouse gas emissions has a negative effect on livestock trade flows from countries restricting greenhouse gas emissions to unrestricting countries, from restricting to restricting countries, and from unrestricting to restricting countries.gravity model, livestock, regulating greenhouse gas emission, trade, Environmental Economics and Policy, Livestock Production/Industries,

Comparison of climate and production in closed, semi-closed and open greenhouses

A (semi-)closed greenhouse is a novel greenhouse with an active cooling system and temporary heat storage in an aquifer. Air is cooled, heated and dehumidified by air treatment units. Climate in (semi-)closed greenhouses differs from that of conventional open greenhouses. The aims of our research were first, to analyze the effect of active cooling on greenhouse climate, in terms of stability, gradient and average levels; second, to determine crop growth and production in closed and semi-closed greenhouses. An experiment with tomato crop was conducted from December 2007 until November 2008 in a closed greenhouse with 700 W m-2 cooling capacity, two semi-closed greenhouses with 350 and 150 W m-2 cooling capacity, respectively, and an open greenhouse. The higher the cooling capacity, the more independent the greenhouse climate was of the outside climate. As the cooling ducts were placed underneath the plants, cooling led to a remarkable vertical temperature gradient. Under sunny conditions temperature could be 5°C higher at the top than at the bottom of the canopy in the closed greenhouse. Cumulative production in the semi-closed greenhouses with 350 and 150 W m-2 cooling capacity were 10% (61 kg m-2) and 6% (59 kg m-2) higher than that in the open greenhouse (55 kg m-2), respectively. Cumulative production in the closed greenhouse was 14% higher than in the open greenhouse in week 29 after planting but at the end of the experiment the cumulative increase was only 4% due to botrytis. Model calculations showed that the production increase in the closed and semi-closed greenhouses was explained by higher CO2 concentratio