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1.
Anthropogenic emissions of methane (CH4) and nitrous oxide (N2O) from livestock agriculture (enteric fermentation, animal waste management systems, and pasture manure) and plant growing of the Russia (CH4 emissions from rice fields, direct and indirect N2O emissions from agricultural lands) are considered. In 2004, the total emissions of these greenhouse gases in the agricultural sector amounted to 1.4 × 105 thousand t CO2-equivalent, which corresponds to 45% of the 1990 level (3.1 × 105 thousand t CO2-equivalent). In 2004, the contribution of N2O to the total agricultural emissions was approximately twice (67.0%) that of CH4 (33.0%). Direct N2O emissions from agricultural soils (0.5 × 105 thousand t CO2-equivalent) and CH4 emissions from the internal fermentation of domestic animals (0.4 × 105 thousand t CO2-equivalent) are the most significant sources in the agricultural sector of the Russian Federation. In 2004, all these agricultural sources emitting methane and nitrous oxide contributed about 7% CO2-equivalent to the total emission of the anthropogenic greenhouse gases in Russia.  相似文献   

2.
Presented is the assessment of the contribution that such major types of the land use in Russia as arable lands, forage lands, settlements, and peatery make to anthropogenic fluxes of carbon dioxide CO2, methane CH4, and nitrogen oxide N2O, The assessment is based on the methods of computation monitoring carried out in the period from 2000 to 2011. The results of the study demonstrated that every year arable lands cause the emission of CO2 and N2O of about 117.0 and 74.9 million t CO2 equiv, and peatery, 0.54 and 105.4 thousand t CO2 equiv, respectively. The balance of soil carbon in hayfields and pastures is close to zero. The average emissions of CH4 and N2O from the manure of pasture animals amount to 0.2 and 5.0 million t CO2 equiv/year, and those from grass fires, 276.1 and 372.5 thousand t CO2 equiv/year, respectively. The carbon balance in permanent soils of settlements is also almost close to zero, and newly built-up lands are the source of CO2 (9.5 million t/year). The natural overgrowing of fallow lands leads to the accumulation of the soil carbon (about 92.4 million t CO2/year). It was revealed that the intensity of CO2 emission is defined by the soil carbon balance and that of other gases, by the amount of nitrogen fertilizers, plant residues, and manure coming to the soil. The total emission from the land use is 106.9 million t CO2 equiv/year that makes up 4.9% of the total anthropogenic emission of greenhouse gases in the Russian Federation.  相似文献   

3.
This paper provides estimates of emissions of two important but often not well-characterized greenhouse gas (GHG) emissions related to transportation energy use: methane (CH4) and nitrous oxide (N2O). The paper focuses on emissions of CH4 and N2O from motor vehicles because unlike emissions of CO2, which are relatively easy to estimate, emissions of CH4 and N2O are a function of many complex aspects of combustion dynamics and of the type of emission control systems used. They therefore cannot be derived easily and instead must be determined through the use of published emission factors for each combination of fuel, end-use technology, combustion conditions, and emission control system. Furthermore, emissions of CH4 and N2O may be particularly important with regard to the relative CO2-equivalent GHG emissions of the use of alternative transportation fuels, in comparison with the use of conventional fuels. By analyzing a database of emission estimates, we develop emission factors for N2O and CH4 from conventional vehicles, in order to supplement recent EPA and IPCC estimates, and we estimate relative emissions of N2O and CH4 from different alternative fuel passenger cars, light-duty trucks, and heavy-duty vehicles.  相似文献   

4.
During 18–23 July 1990, 31 smoke samples were collected from an aircraft flying at low altitudes through the plumes of tropical savanna fires in the Northern Territory, Australia. The excess (above background) mixing ratios of 17 different trace gases including CO2, CO, CH4, several non-methane hydrocarbons (NMHC), CH3CHO, NO x (– NO + NO2), NH3, N2O, HCN and total unspeciated NMHC and sulphur were measured. Emissionratios relative to excess CO2 and CO, and emissionfactors relative to the fuel carbon, nitrogen or sulphur content are determined for each measured species. The emission ratios and factors determined here for carbon-based gases, NO x , and N2O are in good agreement with those reported from other biomass burning studies. The ammonia data represent the first such measurements from savanna fires, and indicate that NH3 emissions are more than half the strength of NO x emissions. The emissions of NO x , NH3, N2O and HCN together represent only 27% of the volatilised fuel N, and are primarily NO x (16%) and NH3 (9%). Similarly, only 56% of the volatilised fuel S is accounted for by our measurements of total unspeciated sulphur.  相似文献   

5.
Strategies for mitigating the increasing concentration of carbon dioxide (CO2) in the atmosphere include sequestering carbon (C) in soils and vegetation of terrestrial ecosystems. Carbon and nitrogen (N) move through terrestrial ecosystems in coupled biogeochemical cycles, and increasing C stocks in soils and vegetation will have an impact on the N cycle. We conducted simulations with a biogeochemical model to evaluate the impact of different cropland management strategies on the coupled cycles of C and N, with special emphasis on C-sequestration and emission of the greenhouse gases methane (CH4) and nitrous oxide (N2O). Reduced tillage, enhanced crop residue incorporation, and farmyard manure application each increased soil C-sequestration, increased N2O emissions, and had little effect on CH4 uptake. Over 20 years, increases in N2O emissions, which were converted into CO2-equivalent emissions with 100-year global warming potential multipliers, offset 75–310% of the carbon sequestered, depending on the scenario. Quantification of these types of biogeochemical interactions must be incorporated into assessment frameworks and trading mechanisms to accurately evaluate the value of agricultural systems in strategies for climate protection.  相似文献   

6.
Increasing atmospheric concentrations of greenhouse gases are expected to result in global climatic changes over the next decades. Means of evaluating and reducing greenhouse gas emissions are being sought. In this study an existing simulation model of a tropical savanna woodland grazing system was adapted to account for greenhouse gas emissions. This approach may be able to be used in identifying ways to assess and limit emissions from other rangeland, agricultural and natural ecosystems.GRASSMAN, an agricultural decision-support model, was modified to include sources, sinks and storages of greenhouse gases in the tropical and sub-tropical savanna woodlands of northern Australia. The modified model was then used to predict the changes in emissions and productivity resulting from changes in stock and burning management in a hypothetical grazing system in tropical northeastern Queensland. The sensitivity of these results to different Global Warming Potentials (GWPs) and emission definitions was then tested.Management options to reduce greenhouse gas emissions from the tropical grazing system investigated were highly sensitive to the GWPs used, and to the emission definition adopted. A recommendation to reduce emissions by changing burning management would be toreduce fire frequency if both direct and indirect GWPs of CO2, CH4, N2O, CO and NO are used in evaluating emissions, but toincrease fire frequency if only direct GWPs of CO2, CH4 and N2O are used. The ability to reduce greenhouse gas emissions from these systems by reducing stocking rates was also sensitive to the GWPs used. In heavily grazed systems, the relatively small reductions in stocking rate needed to reduce emissions significantly should also reduce the degradation of soils and vegetation, thereby improving the sustainability of these enterprises.The simulation studies indicate that it is possible to alter management to maximise beef cattle production per unit greenhouse gases or per unit methane emitted, but that this is also dependent upon the emission definition used. High ratios of liveweight gain per unit net greenhouse gas emission were found in a broadly defined band covering the entire range of stocking rates likely to be used. In contrast, high values of liveweight gain per unit anthropogenic greenhouse gas emission were found only at very low stocking rates that are unlikely to be economically viable.These results suggest that policy initiatives to reduce greenhouse gas emissions from tropical grazing systems should be evaluated cautiously until the GWPs have been further developed and the implications of emission definitions more rigorously determined.  相似文献   

7.
The allocation of CO2 emissions to specific sources is a major policy issue for international aviation, especially for determining allocations for emissions trading schemes. This paper addresses the problem by recommending a possible methodology to allocate emissions to specific sources using detailed air traffic data. The basis for the calculations is an air traffic sample for one full-day of traffic from the UK. In order to analyse aircraft fuel burn use and hence CO2 emissions, the Reorganized Air Traffic Control Mathematical Simulator (RAMS Plus) and the Advanced Emission Model (AEM III) are used. The results from these detailed simulations are compared with two of the most widely-used aviation CO2 emission estimates to have been made for the UK: the SERAS study and NETCEN estimate. Their estimates for the year 2000 are 26.1 and 31.4 Mt, respectively. In addition, the most recent NETCEN estimate for the year 2003 is 34.1 Mt of CO2. Our estimate of total aviation CO2 emissions, using detailed simulations and real air traffic data, is 34.7 Mt for the year 2004. In addition, emission estimates are compared with two global aviation emission inventories: AERO2K and SAGE. Contributions of the highest-emitting flights and aircraft types are identified. International departures dominate; 6% of flights account for 50% of total emissions. The largest aircraft emit the most per flight-km, although not per passenger-km. Different methodologies and their implications are also discussed.  相似文献   

8.
In the first Kyoto commitment period Russia could be the major supplier for the greenhouse gases (GHG) emissions market. Potential Russian supply depends on the ability of Russia to keep GHG emissions lower than the Kyoto target. In the literature there is no common understanding of the total trading potential of Russia at the international carbon market. In this paper we focus on CO2 emission, which constituted nearly 80%of Russian GHG emission. We compare different projections of Russian CO2emission and analyze the most important factors, which predetermine the CO2emission growth. In a transition economy these factors are: Gross Domestic Product(GDP) dynamic, changes of GDP structure, innovation activity, transformation of export-import flows and response to the market signals. The input-output macroeconomic model with the two different input-output tables representing old and new production technologies has been applied for the analysis to simulate technological innovations and structural changes in the Russian economy during transition period. The Russian supply at the international GHG market without forest sector may be up to 3 billion metric ton of CO2 equivalent. Earlier actions to reduce CO2 emission are critical to insure theRussiansupply at the international carbon market. With regard to the current status of the Russian capital market, the forward trading with OECD countries is only the possibility to raise initial investments to roll no-regret and low-cost GHG reduction. This paper discusses uncertainties of RussianCO2emission dynamics and analyzes the different incentives to lower the emission pathway.  相似文献   

9.
The MAGICC (Model for the Assessment of Greenhouse gas Induced Climate Change) model simulation has been carried out for the 2000–2100 period to investigate the impacts of future Indian greenhouse gas emission scenarios on the atmospheric concentrations of carbon dioxide, methane and nitrous oxide besides other parameters like radiative forcing and temperature. For this purpose, the default global GHG (Greenhouse Gases) inventory was modified by incorporation of Indian GHG emission inventories which have been developed using three different approaches namely (a) Business-As-Usual (BAU) approach, (b) Best Case Scenario (BCS) approach and (c) Economy approach (involving the country’s GDP). The model outputs obtained using these modified GHG inventories are compared with various default model scenarios such as A1B, A2, B1, B2 scenarios of AIM (Asia-Pacific Integrated Model) and P50 scenario (median of 35 scenarios given in MAGICC). The differences in the range of output values for the default case scenarios (i.e., using the GHG inventories built into the model) vis-à-vis modified approach which incorporated India-specific emission inventories for AIM and P50 are quite appreciable for most of the modeled parameters. A reduction of 7% and 9% in global carbon dioxide (CO2) emissions has been observed respectively for the years 2050 and 2100. Global methane (CH4) and global nitrous oxide (N2O) emissions indicate a reduction of 13% and 15% respectively for 2100. Correspondingly, global concentrations of CO2, CH4 and N2O are estimated to reduce by about 4%, 4% and 1% respectively. Radiative forcing of CO2, CH4 and N2O indicate reductions of 6%, 14% and 4% respectively for the year 2100. Global annual mean temperature change (incorporating aerosol effects) gets reduced by 4% in 2100. Global annual mean temperature change reduces by 5% in 2100 when aerosol effects have been excluded. In addition to the above, the Indian contributions in global CO2, CH4 and N2O emissions have also been assessed by India Excluded (IE) scenario. Indian contribution in global CO2 emissions was observed in the range of 10%–26%, 6%–36% and 10%–38% respectively for BCS, Economy and BAU approaches, for the years 2020, 2050 and 2100 for P50, A1B-AIM, A2-AIM, B1-AIM & B2-AIM scenarios. CH4 and N2O emissions indicate about 4%–10% and 2%–3% contributions respectively in the global CH4 and N2O emissions for the years 2020, 2050 and 2100. These Indian GHG emissions have significant influence on global GHG concentrations and consequently on climate parameters like RF and ∆T. The study reflects not only the importance of Indian emissions in the global context but also underlines the need of incorporation of country specific GHG emissions in modeling to reduce uncertainties in simulation of climate change parameters.  相似文献   

10.
The purpose of this paper is to describe global urban greenhouse gas emissions by region and sector, examine the distribution of emissions through the urban-to-rural gradient, and identify covariates of emission levels for our baseline year, 2000. We use multiple existing spatial databases to identify urban extent, greenhouse gas emissions (CO2, N2O, CH4 and SF6) and covariates of emissions in a “top-down” analysis. The results indicate that urban activities are significant sources of total greenhouse gas emissions (36.8 and 48.6 % of total). The urban energy sector accounts for between 41.5 and 66.3 % of total energy emissions. Significant differences exist in the urban share of greenhouse gas emissions between developed and developing countries as well as among source sectors for geographic regions. The 50 largest urban emitting areas account for 38.8 % of all urban greenhouse gas emissions. We find that greenhouse gas emissions are significantly associated with population size, density, growth rates, and per capita income. Finally, comparison of our results to “bottom-up” estimates suggest that this research’s data and techniques are best used at the regional and global scales.  相似文献   

11.
CH4和N2O作为主要温室气体,自工业革命以来排放量急剧增加,已经被列入《京都议定书》要求控制它们的排放。本文利用高光谱分辨率的辐射传输模式,计算了CH4、N2O在晴空大气和有云大气条件下的瞬时辐射效率和平流层调整的辐射效率,以及它们的全球增温潜能(GWP)和全球温变潜能(GTP),并根据模式结果拟合了CH4和N2O的辐射强迫的简单计算公式。本文的研究表明:CH4和N2O在有云大气下的平流层调整的辐射效率分别为4.142×10-4 W m-2 ppb-1和3.125×10-3 W m-2 ppb-1 (1ppb=10-9),经大气寿命调整后的辐射效率分别为3.732×10-4 W m-2 ppb-1和2.987×10-3 W m-2 ppb-1,与IPCC(2007)的相应结果高度一致。CH4和N2O 100年的全球增温潜能GWP分别为16和266;100年的脉冲排放的全球温变潜能GTPP分别为0.24和233;持续排放的全球温变潜能GTPS分别为18和268。它们在未来全球变暖和气候变化中,影响仅次于CO2,仍然起着非常关键的作用。  相似文献   

12.
This paper describes a simulation policy model of the combined greenhouse effects of trace gases. With this model, the Integrated Model for the Assessment of the Greenhouse Effect (IMAGE) scenarios for the future impact of the greenhouse effect can be made, based on different assumptions for technological and socio-economic developments. The contribution of each trace gas can be estimated separately.Basically the model, consisting of a number of coupled modules, gives policy makers a concise overview of the problem and enables them to evaluate the impact of different strategies. Because the model covers the complete cause-effect relationship it can be utilized to derive allowable emission rates for the different trace gases from set effect related targets. Regular demonstration sessions with the simulation model have proven the importance of such science based integrated models for policy development.Four different scenarios are worked out for the most important trace gases (CO2, CH4, N2O, CFC-11 and CFC-12). One of these scenarios can be regarded as a growth scenario unrestricted by environmental concerns. The others are based on different strategic policies. After the simulation of future trace gas concentrations global equilibrium temperature increases are computed. Finally the sea level rise, the most threatening effect of the greenhouse problem for the Netherlands, is estimated.Simulation results so far emphasize the importance of trace gases other than CO2. The Montreal Protocol on reduction of CFC is found to stabilize the relative contribution of these substances to the greenhouse effect.  相似文献   

13.
We have compiled historical greenhouse gas emissions and their uncertainties on country and sector level and assessed their contribution to cumulative emissions and to global average temperature increase in the past and for a the future emission scenario. We find that uncertainty in historical contribution estimates differs between countries due to different shares of greenhouse gases and time development of emissions. Although historical emissions in the distant past are very uncertain, their influence on countries?? or sectors?? contributions to temperature increase is relatively small in most cases, because these results are dominated by recent (high) emissions. For relative contributions to cumulative emissions and temperature rise, the uncertainty introduced by unknown historical emissions is larger than the uncertainty introduced by the use of different climate models. The choice of different parameters in the calculation of relative contributions is most relevant for countries that are different from the world average in greenhouse gas mix and timing of emissions. The choice of the indicator (cumulative GWP weighted emissions or temperature increase) is very important for a few countries (altering contributions up to a factor of 2) and could be considered small for most countries (in the order of 10%). The choice of the year, from which to start accounting for emissions (e.g. 1750 or 1990), is important for many countries, up to a factor of 2.2 and on average of around 1.3. Including or excluding land-use change and forestry or non-CO2 gases changes relative contributions dramatically for a third of the countries (by a factor of 5 to a factor of 90). Industrialised countries started to increase CO2 emissions from energy use much earlier. Developing countries?? emissions from land-use change and forestry as well as of CH4 and N2O were substantial before their emissions from energy use.  相似文献   

14.
Summary In this paper we briefly describe the characteristics and the performance of our 1-D Muenster Climate Model. The model system consists of coupled models including gas cycle models, an energy balance model and a sea level rise model. The chemical feedback mechanisms among greenhouse gases are not included. This model, which is a scientifically-based parameterized simulation model, is used here primarily to help assess the effectiveness of various plausible policy options in mitigating the additional man-made greenhouse warming and the resulting sea level rise.For setting priorities it is important to assess the effectiveness of the various measures by which the greenhouse effect can be reduced. To this end we take a Scenario Business-as-Usual as a reference case (Leggett et al., 1992) and study the mitigating effects of the following four packages of measures: The Copenhagen Agreements on CFC, HCFC, and halon reduction (GECR, 1992), the Tropical Forest Preservation Plan of the Climate Enquete-Commission of the German Parliament on CO2 reduction (ECGP, 1990), a detailed reduction scheme for energy-related CO2 (ECGP, 1990), and a preliminary scheme for CH4, CO, and N2O reduction (Bach and Jain, 1992–1993).The required reduction depends, among others, on the desired climate and ecosystem protection. This is defined by the Enquete-Commission and others as a mean global rate of surface temperature change of ca. 0.1 °C per decade — assumed to be critical to many ecosystems — and a mean global warming ceiling of ca. 2 °C in 2100 relative to 1860.Our results show that the Copenhagen Agreements, the Tropical Forest Preservation Plan, the energy-related CO2 reduction scheme, and the CH4 and N2O reduction schemes could mitigate the anthropogenic greenhouse warming by ca. 12%, 6%, 35%, and 9% respectively. Taken together, all four packages of measures could reduce the man-made greenhouse effect by more than 60% until 2100; i.e. over the climate sensitivity range 2.5 °C (1.5 to 4.5) for 2 × CO2, the warming could be reduced from 3.5 °C (2.4 to 5.0) without specific measures to 1.3 °C (0.9 to 2.0) with the above packages of measures; and likewise, the mean global sea level rise could be reduced from 65 cm (46 to 88) without specific measures to 32 cm (22 to 47) with the above measures.Finally, the model results also emphasize the importance of trace gases other than CO2 in mitigating additional man-made greenhouse warming. According to our preliminary estimates, CH4 could in the short term make a sizable contribution to the reduction of the greenhouse effect (because of its relatively short lifetime of 10 yr), as could N2O in the medium and long term (with a relatively long lifetime of 150 yr).With 7 Figures  相似文献   

15.
Emissions of N2O, CH4, and CO2 from soils at two sites in the tropical savanna of central Venezuela were determined during the dry season in February 1987. Measured arithmetic mean fluxes of N2O, CH4, and CO2 from undisturbed soil plots to the atmosphere were 2.5×109, 4.3×1010, and 3.0×1013 molecules cm-2 s-1, respectively. These fluxes were not significantly affected by burning the grass layer. Emissions of N2O increased fourfold after simulated rainfall, suggesting that production of N2O in savanna soils during the rainy season may be an important source for atmospheric N2O. The CH4 flux measurements indicate that these savanna soils were not a sink, but a small source, for atmospheric methane. Fluxes of CO2 from savanna soils increased ninefold two hours after simulated rainfall, and remained three times higher than normal after 16 hours. More research is needed to clarify the significance of savannas in the global cycles of N2O, CH4, CO2, and other trace gases, especially during the rainy season.  相似文献   

16.
This study provides estimates of greenhouse gas emissions from the major anthropogenic sources for 142 countries. The data compilation is comprehensive in approach, including emissions from CO, CH4, and N2O, and ten halocarbons, in addition to CO2. The sources include emissions from fossil fuel production and use, cement production, halocarbons, landfills, land use changes, biomass burning, rice and livestock production and fertilizer consumption. The approach used to derive these estimates corresponds closely with the simple methodologies proposed by the Greenhouse Gas Emissions Task Force of the Intergovernmental Panel on Climate Change. The inventory includes a new estimate of greenhouse gas emissions from fossil fuel combustion based principally on data from the International Energy Agency. The research methodologies for estimating emissions from all sources is briefly described and compared with other recent studies in the literature.  相似文献   

17.
Abstract

To evaluate future climate change in the middle atmosphere and the chemistry–climate interaction of stratospheric ozone, we performed a long-term simulation from 1960 to 2050 with boundary conditions from the Intergovernmental Panel on Climate Change A1B greenhouse gas scenario and the World Meteorological Organization Ab halogen scenario using the chemistry–climate model ECHAM5/MESSy Atmospheric Chemistry (EMAC). In addition to this standard simulation we performed five sensitivity simulations from 2000 to 2050 using the rerun files of the simulation mentioned above. For these sensitivity simulations we used the same model setup as in the standard simulation but changed the boundary conditions for carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone-depleting substances (ODS). In the first sensitivity simulation we fixed the mixing ratios of CO2, CH4, and N2O in the boundary conditions to the amounts for 2000. In each of the four other sensitivity simulations we fixed the boundary conditions of only one of CO2, CH4, N2O, or ODS to the year 2000.

In our model simulations the future evolution of greenhouse gases leads to significant cooling in the stratosphere and mesosphere. Increasing CO2 mixing ratios make the largest contributions to this radiative cooling, followed by increasing stratospheric CH4, which also forms additional H2O in the upper stratosphere and mesosphere. Increasing N2O mixing ratios makes the smallest contributions to the cooling. The simulated ozone recovery leads to warming of the middle atmosphere.

In the EMAC model the future development of ozone is influenced by several factors. 1) Cooler temperatures lead to an increase in ozone in the upper stratosphere. The strongest contribution to this ozone production is cooling due to increasing CO2 mixing ratios, followed by increasing CH4. 2) Decreasing ODS mixing ratios lead to ozone recovery, but the contribution to the total ozone increase in the upper stratosphere is only slightly higher than the contribution of the cooling by greenhouse gases. In the polar lower stratosphere a decrease in ODS is mainly responsible for ozone recovery. 3) Higher NOx and HOx mixing ratios due to increased N2O and CH4 lead to intensified ozone destruction, primarily in the middle and upper stratosphere, from additional NOx; in the mesosphere the intensified ozone destruction is caused by additional HOx. In comparison to the increase in ozone due to decreasing ODS, ozone destruction caused by increased NOx is of similar importance in some regions, especially in the middle stratosphere. 4) In the stratosphere the enhancement of the Brewer-Dobson circulation leads to a change in ozone transport. In the polar stratosphere increased downwelling leads to additional ozone in the future, especially at high northern latitudes. The dynamical impact on ozone development is higher at some altitudes in the polar stratosphere than the ozone increase due to cooler temperatures. In the tropical lower stratosphere increased residual vertical upward transport leads to a decrease in ozone.  相似文献   

18.
The Denitrification-Decompostion (DNDC) model was used to estimate the impact of change in management practices on N2O emissions in seven major soil regions in Canada, for the period 1970 to 2029. Conversion of cultivated land to permanent grassland would result in the greatest reduction in N2O emissions, particularly in eastern Canada wherethe model estimated about 60% less N2O emissions for thisconversion. About 33% less N2O emissions were predicted for a changefrom conventional tillage to no-tillage in western Canada, however, a slight increase in N2O emissions was predicted for eastern Canada. GreaterN2O emissions in eastern Canada associated with the adoption of no-tillage were attributed to higher soil moisture causing denitrification, whereas the lower emissions in western Canada were attributed to less decomposition of soil organic matter in no-till versus conventional tilled soil. Elimination of summer fallow in a crop rotation resulted in a 9% decrease in N2O emissions, with substantial emissions occurringduring the wetter fallow years when N had accumulated. Increasing N-fertilizer application rates by 50% increased average emissions by 32%,while a 50% decrease of N-fertilizer application decreased emissions by16%. In general, a small increase in N2O emissions was predicted when N-fertilizer was applied in the fall rather than in the spring. Previous research on CO2 emissions with the CENTURY model (Smith et al.,2001) allowed the quantification of the combined change in N2O andCO2 emissions in CO2 equivalents for a wide range of managementpractices in the seven major soil regions in Canada. The management practices that have the greatest potential to reduce the combined N2O andCO2 emissions are conversion from conventional tillage to permanent grassland, reduced tillage, and reduction of summer fallow. The estimated net greenhouse gas (GHG) emission reduction when changing from cultivated land to permanent grassland ranged from 0.97 (Brown Chernozem) to 4.24 MgCO2 equiv. ha–1 y–1 (BlackChernozem) for the seven soil regions examined. When changing from conventional tillage to no-tillage the net GHG emission reduction ranged from 0.33 (Brown Chernozem) to 0.80 Mg CO2 equiv. ha–1 y–1 (Dark GrayLuvisol). Elimination of fallow in the crop rotation lead to an estimated net GHG emission reduction of 0.43 (Brown Chernozem) to 0.80 Mg CO2 equiv.ha–1 y–1 (Dark Brown Chernozem). The addition of 50% more or 50% less N-fertilizer both resulted in slight increases in combined CO2 and N2O emissions. There was a tradeoff in GHG flux with greaterN2O emissions and a comparable increase in carbon storage when 50% more N-fertilizer was added. The results from this work indicate that conversion of cultivated land to grassland, the conversion from conventional tillage to no-tillage, and the reduction of summerallow in crop rotations could substantially increase C sequestration and decrease net GHG emissions. Based on these results a simple scaling-up scenario to derive the possible impacts on Canada's Kyoto commitment has been calculated.  相似文献   

19.
Greenhouse Gas Emissions from Hydroelectric Reservoirs in Tropical Regions   总被引：2，自引：1，他引：2  
This paper discusses emissions by power-dams in the tropics. Greenhouse gas emissions from tropical power-dams are produced underwater through biomass decomposition by bacteria. The gases produced in these dams are mainly nitrogen, carbon dioxide and methane. A methodology was established for measuring greenhouse gases emitted by various power-dams in Brazil. Experimental measurements of gas emissions by dams were made to determine accurately their emissions of methane (CH4) and carbon dioxide (CO2) gases through bubbles formed on the lake bottom by decomposing organic matter, as well as rising up the lake gradient by molecular diffusion.The main source of gas in power-dams reservoirs is the bacterial decomposition (aerobic and anaerobic) of autochthonous and allochthonous organic matter that basically produces CO2 and CH4. The types and modes of gas production and release in the tropics are reviewed.  相似文献   

20.
Today's climate policy is based on the assumption that the location of emissions reductions has no impact on the overall climate effect. However, this may not be the case since reductions of greenhouse gases generally will lead to changes in emissions of short-lived gases and aerosols. Abatement measures may be primarily targeted at reducing CO2, but may also simultaneously reduce emissions of NOx, CO, CH4 and SO2 and aerosols. Emissions of these species may cause significant additional radiative forcing. We have used a global 3-D chemical transport model and a radiative transfer model to study the impact on climate in terms of radiative forcing for a realistic change in location of the emissions from large-scale sources. Based on an assumed 10% reduction in CO2 emissions, reductions in the emissions of other species have been estimated. Climate impact for the SRES A1B scenario is compared to two reduction cases, with the main focus on a case with emission reductions between 2010 and 2030, but also a case with sustained emission reductions. The emission reductions are applied to four different regions (Europe, China, South Asia, and South America). In terms of integrated radiative forcing (over 100 yr), the total effect (including only the direct effect of aerosols) is always smaller than for CO2 alone. Large variations between the regions are found (53–86% of the CO2 effect). Inclusion of the indirect effects of sulphate aerosols reduces the net effect of measures towards zero. The global temperature responses, calculated with a simple energy balance model, show an initial additional warming of different magnitude between the regions followed by a more uniform reduction in the warming later. A major part of the regional differences can be attributed to differences related to aerosols, while ozone and changes in methane lifetime make relatively small contributions. Emission reductions in a different sector (e.g. transportation instead of large-scale sources) might change this conclusion since the NOx to SO2 ratio in the emissions is significantly higher for transportation than for large-scale sources. The total climate effect of abatement measures thus depends on (i) which gases and aerosols are affected by the measure, (ii) the lifetime of the measure implemented, (iii) time horizon over which the effects are considered, and (iv) the chemical, physical and meteorological conditions in the region. There are important policy implications of the results. Equal effects of a measure cannot be assumed if the measure is implemented in a different region and if several gases are affected. Thus, the design of emission reduction measures should be considered thoroughly before implementation.  相似文献   

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