Impact of Climate Change on Agricultural Production in the Sahel – Part 2. Case Study for Groundnut and Cowpea in Niger

During the last 30 years, the climate of the West African Sahel has undergone various changes, especially in terms of rainfall. This has large consequences for the poor-resource farmers depending mainly on rainfed agriculture. This paper investigates the impacts of current climate variability and future climate change on groundnut and cowpea production in Niger for three major agricultural regions, including the groundnut basin.Niger was one of the largest West African groundnut producing and exporting countries. Groundnut production – as a cash crop – dropped fromabout 312,000 tons in the mid 1960s (about 68% exported) to as low as 13,000tons in 1988 and increased again to 110,000 tons in 2000. Cowpea, a food crop, showsa different tendency, going from 4,000 tons in the mid fifties to a maximum of 775,000 tons in 1997, and its cultivated area is still increasing. It is also a cash crop in local economies (especially for women).To highlight the impact of climate change on groundnut and cowpea production (significantly determined by rainfall in July, August and September), the following components of the rainfall regime were calculated for the period 1951–1998: mean annual and monthly rainfall, beginning, end and lengthof the rainy season, number of rainy days per month, amount of rainfall per rainy day and the maximum length of dry spell per month. Three sub-periods whose duration varied per region were defined: for Dosso 1951–1968,1969–1984 and 1985–1998; for Maradi 1951–1970, 1971–1987 and1988–1998; and for Zinder 1951–1966, 1967–1984 and 1985–1998. A change in rainfallregime components was observed between the three sub-periods, which were characterized in chronological order by wet, dry and intermediate conditions. To assess the impact of climate variability and change on groundnut and cowpea production, a statistical modeling approach has been followed, based on thirteen predictors as described and discussed in the preceding paper. Climate change is mimicked in terms of reduced total amount of rainfall for the three main rainfall months and an increased temperature, while maintaining other significant predictors at a constant level. In 2025,production of groundnut is estimated to be between 11 and 25% lower, while cowpeayield will fall maximally 30%. Various strategies to compensate thispotential loss are presented for the two crops.     

Changes in Soybean Yields in the Midwestern United States as a Result of Future Changes in Climate, Climate Variability, and CO2 Fertilization

This modeling study addresses the potential impacts of climate change and changing climate variability due to increased atmospheric CO₂ concentration on soybean (Glycine max (L.) Merrill) yields in theMidwestern Great Lakes Region. Nine representative farm locations and six future climate scenarios were analyzed using the crop growth model SOYGRO. Under the future climate scenarios earlierplanting dates produced soybean yield increases of up to 120% above current levels in the central and northern areas of the study region. In the southern areas, comparatively small increases (0.1 to 20%) and small decreases (–0.1 to–25%) in yield are found. The decreases in yield occurred under the Hadley Center greenhouse gas run (HadCM2-GHG), representing a greater warming, and the doubled climate variability scenario – a more extreme and variableclimate. Optimum planting dates become later in the southern regions. CO₂fertilization effects (555 ppmv) are found to be significant for soybean, increasing yields around 20% under future climate scenarios.For the study region as a whole the climate changes modeled in this research would have an overall beneficial effect, with mean soybean yield increases of 40% over current levels.     

Creating Carbon Offsets in Agriculture through No-Till Cultivation: A Meta-Analysis of Costs and Carbon Benefits

Carbon terrestrial sinks are often seen as a low-cost alternative to fuel switching and reduced fossil fuel use for lowering atmospheric CO₂. To determine whether this is true for agriculture, one meta-regression analysis (52 studies, 536 observations) examines the costs of switching from conventional tillage to no-till, while another (51 studies, 374 observations) compares carbon accumulation under the two practices. Costs per ton of carbon uptake are determined by combining the two results. The viability of agricultural carbon sinks is found to vary by region and crop, with no-till representing a low-cost option in some regions (costs of less than $10 per tC), but a high-cost option in others (costs of 100–$400 per tC). A particularly important finding is that no-till cultivation may store no carbon at all if measurements are taken at sufficient depth. In some circumstances no-till cultivation may yield a triple dividend of carbon storage, increased returns and reduced soil erosion, but in many others creating carbon offset credits in agricultural soils is not cost effective because reduced tillage practices store little or no carbon.     

Future Climate Impact on the Productivity of Sugar Beet (Beta vulgaris L.) in Europe

The impact of future climate change on sugar beet yields is assessed over western Europe using future (2021–2050) climate scenario data from a General Circulation Model (GCM) and the Broom's Barn simulation model of rain-fed crop growth and yield. GCM output for the 1961–1990 period is first compared with observed climate data and shown to be reliable for regions west of 24° E. Comparisons east of this meridian were less reliable with this GCM (HadCM2) and so were omitted from simulations of crop yield. Climate change is expected to bring yield increases of around 1 t/ha of sugar in northern Europe with decreases of a similar magnitude in northern France, Belgium and west/central Poland, for the period 2021–2050. Averaged for the study area (weighted by current regional production), yields show no overall change due to changed climate. However, this figure masks significant increases in yield potential (due to accelerated growth in warmer springs) and in losses due to drought stress. Drought losses are predicted to approximately double in areas with an existing problem and to become a serious new problem in NE France and Belgium. Overall west and central Europe simulated average drought losses rise from 7% (1961–1990) to 18% (2021–2050). The annual variability of yield (as measured by the coefficient of variation) will increase by half, from 10% to 15% compared to 1961–1990, again with potentially serious consequences for the sugar industry. The importance of crop breeding for drought tolerance is further emphasised. These changes are independent of the 9% yield increase which we estimate, on the basis of work by Demmers-Derks et al. (1998), is the likely direct effect of the increase in atmospheric CO₂ concentration by 2021–2050.     

Carbon prices and greenhouse gases abatement from agriculture,forestry and land use in Nepal

The Agriculture, forestry and other land use (AFOLU) sector as a whole accounts for more than 80% of the total greenhouse gas (GHG) emission in Nepal. This study estimates the GHG emissions from the AFOLU sector in the business as usual (BAU) case during 2010–2050 and identifies the economically attractive countermeasures to abate GHG emissions from the sector at different carbon prices. It also estimates the carbon price elasticity of GHG abatement from the sector. The study finds that enteric fermentation processes in the livestock and emissions from agricultural soils are the two major contributors of GHG emission in AFOLU sector. It identifies no-regret abatement options in the AFOLU sector that could mitigate about 41.5% of the total GHG emission during 2016–2050 in the BAU scenario. There would be a net cumulative carbon sequestration of 16 million tonnes of carbon dioxide equivalent (MtCO₂e) at $10 per tonne of carbon dioxide equivalent (tCO₂e) during the period. Carbon price above $75/tCO₂e is not found to be much effective in achieving significant additional reduction in GHG emissions from the AFOLU sector.     

Solar-hydrogen electricity generation in the context of global CO2 emission reduction

The relative costs and CO₂ emission reduction benefits of advanced centralized fossil fuel electricity generation, hybrid photovoltaic-fossil fuel electricity generation, and total solar electricity generation with hydrogen storage are compared. Component costs appropriate to the year 2000–2010 time frame are assumed throughout. For low insolation conditions (160 W m^–2 mean annual solar radiation), photovoltaic electricity could cost 5–13 cents/kWh by year 2000–2010, while for high insolation conditions (260 W m^–2) the cost could be 4–9 cents/kWh. Advanced fossil fuel-based power generation should achieve efficiencies of 50% using coal and 55% using natural gas. Carbon dioxide emissions would be reduced by a factor of 2 to 3 compared to conventional coal-based electricity production in industrialized countries. In a solar-fossil fuel hybrid, some electricity would be supplied from solar energy whenever the sun is shining and remaining demand satisfied by fossil fuels. This increases total capital costs but saves on fuel costs. For low insolation conditions, the costs of electricity increases by 0–2 cents/kWh, while the cost of electricity decreases in many cases for high insolation conditions. Solar energy would provide 20% or 30% of electricity demand for the low and high insolation cases, respectively. In the solar-hydrogen energy system, some photovoltaic arrays would provide current electricity demand while others would be used to produce hydrogen electrolytically for storage and later use in fuel cells to generate electricity. Electricity costs from the solar-hydrogen system are 0.2–5.4 cents/kWh greater than from a natural gas power plant, and 1.0–4.5 cents/kWh greater than from coal plant for the cost and performance assumptions adopted here. The carbon tax required to make the solar-hydrogen system competitive with fossil fuels ranges from $70–660/tonne, depending on the cost and performance of system components and the future price of fossil fuels.Leakage of hydrogen from storage into the atmosphere, and the eventual transport of a portion of the leaked hydrogen to the stratosphere, would result in the formation of stratospheric water vapor. This could perturb stratospheric ozone amounts and contribute to global warming. Order-of-magnitude calculations indicate that, for a leakage rate of 0.5% yr^–1 of total hydrogen production -which might be characteristic of underground hydrogen storage - the global warming effect of solarhydrogen electricity generation is comparable to that of a natural gas-solar energy hybrid system after one year of emission, but is on the order of 1% the impact of the hybrid system at a 100 year time scale. Impacts on stratospheric ozone are likely to be minuscule.     

Description and first results of an explicit electrical scheme in a 3D cloud resolving model

The three-dimensional non-hydrostatic mesoscale model MésoNH of the French community offers the numerical environment to develop a cloud electrification scheme in a consistent way with the original mixed phase microphysical scheme. The charge separation mechanisms are entirely due to non-inductive processes and result from elastic ice–snow, ice–graupel and snow–graupel collisions. The electric charges carried by each of the five hydrometeor categories are transported along the airflow and are exchanged according to the various microphysical mass transfer rates but assuming a power law distribution of the individual charges as a function of the particle size. The electric field is diagnosed at each time step after integrating the electric potential induced by a net charge density in the Poisson equation. Finally, a lightning ash is triggered when the electric field locally steps over a given threshold. It propagates in two opposite directions until the magnitude of the electric field falls below a prescribed value. A fractal branching algorithm is then activated to extend lightning streamers away from the main channel and toward cloudy regions where substantial charge densities are present. Charges are neutralized along the tortuous lightning path with a simple procedure that preserves total charge conservation.The complete electrification scheme tested for an ideal case of vigorous supercellular storm shows an intense electrical activity all along its lifecycle. We show that the model is able to produce a direct tripolar structure of the charges as the result of a temperature charge reversal of − 10 °C and of the different sedimentation rates of the hydrometeors.     

Potential Soil C Sequestration on U.S. Agricultural Soils

Soil carbon sequestration has been suggested as a means to help mitigate atmospheric CO₂ increases, however there is limited knowledge aboutthe magnitude of the mitigation potential. Field studies across the U.S. provide information on soil C stock changes that result from changes in agricultural management. However, data from such studies are not readily extrapolated to changes at a national scale because soils, climate, and management regimes vary locally and regionally. We used a modified version of the Intergovernmental Panel on Climate Change (IPCC) soil organic C inventory method, together with the National Resources Inventory (NRI) and other data, to estimate agricultural soil C sequestration potential in the conterminous U.S. The IPCC method estimates soil C stock changes associated with changes in land use and/or land management practices. In the U.S., the NRI provides a detailed record of land use and management activities on agricultural land that can be used to implement the IPCC method. We analyzed potential soil C storage from increased adoption of no-till, decreased fallow operations, conversion of highly erodible land to grassland, and increased use of cover crops in annual cropping systems. The results represent potentials that do not explicitly consider the economic feasibility of proposed agricultural production changes, but provide an indication of the biophysical potential of soil C sequestration as a guide to policy makers. Our analysis suggests that U.S. cropland soils have the potential to increase sequestered soil C by an additional 60–70 Tg (10¹²g) C yr^{– 1}, over present rates of 17 Tg C yr^–1(estimated using the IPCC method), with widespread adoption of soil C sequestering management practices. Adoption of no-till on all currently annually cropped area (129Mha) would increase soil C sequestration by 47 Tg C yr^–1. Alternatively, use of no-till on 50% of annual cropland, with reduced tillage practices on the other 50%, would sequester less – about37 Tg C yr^–1. Elimination of summer fallow practices and conversionof highly erodible cropland to perennial grass cover could sequester around 20 and 28Tg C yr^–1, respectively. The soil C sequestration potentialfrom including a winter cover crop on annual cropping systems was estimated at 40Tg C yr^–1. All rates were estimated for a fifteen-yearprojection period, and annual rates of soil C accumulations would be expected to decrease substantially over longer time periods. The total sequestration potential we have estimated for the projection period (83 Tg C yr^–1) represents about 5% of 1999total U.S. CO₂ emissions or nearly double estimated CO₂ emissionsfrom agricultural production (43 Tg C yr^–1). For purposes ofstabilizing or reducing CO₂ emissions, e.g., by 7% of 1990 levels asoriginally called for in the Kyoto Protocol, total potential soil C sequestration would represent 15% of that reduction level from projected 2008 emissions(2008 total greenhouse gas emissions less 93% of 1990 greenhouse gasemissions). Thus, our analysis suggests that agricultural soil C sequestration could play a meaningful, but not predominant, role in helping mitigate greenhouse gas increases.     

The Potential Response of Terrestrial Carbon Storage to Changes in Climate and Atmospheric CO2

We use a georeferenced model of ecosystem carbon dynamics to explore the sensitivity of global terrestrial carbon storage to changes in atmospheric CO₂ and climate. We model changes in ecosystem carbon density, but we do not model shifts in vegetation type. A model of annual NPP is coupled with a model of carbon allocation in vegetation and a model of decomposition and soil carbon dynamics. NPP is a function of climate and atmospheric CO₂ concentration. The CO₂ response is derived from a biochemical model of photosynthesis. With no change in climate, a doubling of atmospheric CO₂ from 280 ppm to 560 ppm enhances equilibrium global NPP by 16.9%; equilibrium global terrestrial ecosystem carbon (TEC) increases by 14.9%. Simulations with no change in atmospheric CO₂ concentration but changes in climate from five atmospheric general circulation models yield increases in global NPP of 10.0–14.8%. The changes in NPP are very nearly balanced by changes in decomposition, and the resulting changes in TEC range from an increase of 1.1% to a decrease of 1.1%. These results are similar to those from analyses using bioclimatic biome models that simulate shifts in ecosystem distribution but do not model changes in carbon density within vegetation types. With changes in both climate and a doubling of atmospheric CO₂, our model generates increases in NPP of 30.2–36.5%. The increases in NPP and litter inputs to the soil more than compensate for any climate stimulation of decomposition and lead to increases in global TEC of 15.4–18.2%.     

Climate Change Impacts for the Conterminous USA: An Integrated Assessment

Here we simulate dryland agriculture in the United States in order to assess potential future agricultural production under a set of general circulation model (GCM)-based climate change scenarios. The total national production of three major grain crops—corn, soybeans, and winter wheat—and two forage crops—alfalfa and clover hay—is calculated for the actual present day core production area (CPA) of each of these crops. In general, higher global mean temperature (GMT) reduces production and higher atmospheric carbon dioxide concentration ([CO₂]) increases production. Depending on the climatic change scenarios employed overall national production of the crops studied changes by up to plus or minus 25% from present-day levels. Impacts are more significant regionally, with crop production varying by greater than ±50% from baseline levels. Analysis of currently possible production areas (CPPAs) for each crop indicates that the regions most likely to be affected by climate change are those on the margins of the areas in which they are currently grown. Crop yield variability was found to be primarily influenced by local weather and geographic features rather than by large-scale changes in climate patterns and atmospheric composition. Future US agronomic potential will be significantly affected by the changes in climate projected here. The nature of the crop response will depend primarily on to what extent precipitation patterns change and also on the degree of warming experienced.     

Elevation Dependence of Winter Wheat Production in Eastern Washington State with Climate Change: A Methodological Study

Crop growth models, used in climate change impact assessments to project production on a local scale, can obtain the daily weather information to drive them from models of the Earth's climate. General Circulation Models (GCMs), often used for this purpose, provide weather information for the entire globe but often cannot depict details of regional climates especially where complex topography plays an important role in weather patterns. The U.S. Pacific Northwest is an important wheat growing region where climate patterns are difficult to resolve with a coarse scale GCM. Here, we use the PNNL Regional Climate Model (RCM) which uses a sub-grid parameterization to resolve the complex topography and simulate meteorology to drive the Erosion Productivity Impact Calculator (EPIC) crop model. The climate scenarios were extracted from the PNNL-RCM baseline and 2 × CO₂ simulationsfor each of sixteen 90 km² grid cells of the RCM, with differentiation byelevation and without correction for climate biases. The dominant agricultural soil type and farm management practices were established for each grid cell. Using these climate and management data in EPIC, we simulated winter wheat production in eastern Washington for current climate conditions (baseline) and a 2 × CO₂ `greenhouse' scenario of climate change.Dryland wheat yields for the baseline climate averaged 4.52 Mg ha^–1 across the study region. Yields were zero at high elevations where temperatures were too low to allow the crops to mature. The highest yields (7.32 Mgha^–1) occurred at intermediate elevations with sufficientprecipitation and mild temperatures. Mean yield of dryland winter wheat increased to 5.45 Mg ha^–1 for the 2 × CO₂ climate, which wasmarkedly warmer and wetter. Simulated yields of irrigated wheat were generally higher than dryland yields and followed the same pattern but were, of course, less sensitive to increases in precipitation. Increases in dryland and irrigated wheat yields were due, principally, to decreases in the frequency of temperature and water stress. This study shows that the elevation of a farm is a more important determinant of yield than farm location in eastern Washington and that climate changes would affect wheat yields at all farms in the study.     

The political ecology of Chilean salmon aquaculture, 1982–2010: A trajectory from economic development to global sustainability

Through the case of the salmon aquaculture sector in Chile, the risks involved in the development of a non-traditional export sector are reviewed, in order to point to failings (lessons not learned) and opportunities (lessons learned, new plans), and the changing scales of stakeholder interactions. In particular the paper highlights the ways in which sustainability considerations have gained ground in terms of evaluating sectoral development and what is expected from this development. These considerations have emerged as a result of the increasing globalisation of the sector, through investment, exports and international ‘attention’ from an increasingly diverse set of stakeholders. These sustainability considerations have generated a range of conflicts linked to these diverse actors. The actors are local, national and global, operating through alliances to bring pressure on others. The conflicts relate to environmental quality, foreign direct investment (FDI), local socio-economic development, regional development, national economic strategies, and new globalised issues relating to the production and consumption of foodstuffs. The contemporary panorama in the sector is significantly different from the early origins in the 1980s under the dictatorship – the period of ‘the socio-ecological silence’ – also different from the 1990s period of economic expansion – ‘the economic imperative’. Over the past twenty-five years, the Chilean aquaculture sector has evolved from experimental production to a major global industry. Regulatory frameworks and civil society awareness and mobilisation have struggled to ‘catch up’ with the dynamism of the sector, however the gap has reduced and the future of the sector within the contemporary context of ‘glocal’ sustainability is now under the microscope: the ‘sustainable globalisation perspective’. The collapse of the sector during the period 2008–2010 as a consequence of the ISA virus is a key moment with production severely diminished. The way out of the crisis, via new legislation and inspection regimes, will create a new structure of aquaculture governance. Nevertheless, the crisis marks a turning point in the industry, revealing the weaknesses built into the former productive system.     

Estimates of gross and net fluxes of carbon between the biosphere and the atmosphere from biomass burning

In order to estimate the production of charcoal and the atmospheric emissions of trace gases volatilized by burning we have estimated the global amounts of biomass which are affected by fires. We have roughly calculated annual gross burning rates ranging between about 5 Pg and 9 Pg (1 Pg = 10¹⁵ g) of dry matter (2–4 Pg C). In comparison, about 9–17 Pg of above-ground dry matter (4–8 Pg C) is exposed to fires, indicating a worldwide average burning efficiency of about 50%. The production of dead below-ground dry matter varies between 6–9 Pg per year. We have tentatively indicated the possibility of a large production of elemental carbon (0.5–1.7 Pg C/yr) due to the incomplete combustion of biomass to charcoal. This provides a sink for atmospheric CO₂, which would have been particularly important during the past centuries. From meager statistical information and often ill-documented statements in the literature, it is extremely difficult to calculate the net carbon release rates to the atmosphere from the biomass changes which take place, especially in the tropics. All together, we calculate an overall effect lof the biosphere on the atmospheric carbon dioxide budget which may range between the possibilities of a net uptake or a net release of about 2 Pg C/yr. The release of CO₂ to the atmosphere by deforestation projects may well be balanced by reforestation and by the production of charcoal. Better information is needed, however, to make these estimates more reliable.Now at the Max-Planck-Institute for Chemistry, Mainz, FRG.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Spectroscopic measurements of atmospheric carbon monoxide and methane. 1: latitudinal distribution

The results of spectroscopic total column measurements of CO and CH₄ at different points of the Northern and Southern Hemispheres in 1970–1985, are reported. Seasonal cycles of CO are evident for all the sites. The Northern Hemispheric long-term positive trend of CO seems to be 1.5–2% per year. In the Southern Hemisphere, temporal increasing was not detected and a possible upper limit for it is about 0.6% per year. Methane concentration in the Northern Hemisphere increases at a rate of 1.2% per year.     

Effects of Climatic Change on a Water Dependent Regional Economy: A Study of the Texas Edwards Aquifer

Global climate change portends shifts in water demand and availability which may damage or cause intersectoral water reallocation in water short regions. This study investigates effects of climatic change on regional water demand and supply as well as the economy in the San Antonio Texas Edwards Aquifer region. This is done using a regional model which portrays both hydrological and economic activities. The overall results indicate that changes in climatic conditions reduce water resource availability and increase water demand. Specifically, a regional welfare loss of $2.2–$6.8million per year may occur as a result of climatic change. Additionally, if springflows are to be maintained at the currently desired level to protect endangered species, pumping must be reduced by 9–20% at an additional costof $0.5 to $2 million per year.     

Cloud condensation nuclei measurements at Mace Head, Ireland, over the period 1994–2002

Analyses of cloud condensation nuclei (CCN) number concentrations (cm^− 3) measured at the Mace Head Atmospheric Research Station, near Carna, County Galway, Ireland, using a DH Associates Model M1 static thermal diffusion cloud chamber over the period from March 1994 to September 2002 are presented in this work. Air masses are defined as being ‘marine’ if they originate from a wind direction of 180–300° and ‘continental’ air masses are defined as originating from a wind direction of 45–135°. Air masses without such filtering were classified as ‘undefined’ air masses. Air masses were found to be dominated by marine sector air, re-affirming Mace Head as a baseline atmospheric research station. CCN levels for specific air masses at Mace Head were found to be comparable with earlier studies both at Mace Head and elsewhere. Monthly averaged clean marine (wind direction of 180–300° and black carbon absorption coefficient < 1.425 Mm^− 1) CCN and marine CCN varied between 15–247 cm^− 3 and 54–670 cm^− 3, respectively. As expected, significant increases in number concentration were found in continentally sourced CCN over that of marine CCN and were found to follow a log-normal distribution significantly tighter than that of clean marine air masses. No significant trend was found for CCN over the 9-year period. While polluted continental air masses showed a slight increase in CCN concentrations over the winter months, most likely due to increased fuel usage and a lower mixed boundary layer, the dominance of marine sector air arriving at Mace Head, which generally consists of background CCN concentrations, reduced seasonal differences for polluted air. Marine air showed a distinct seasonal pattern, with elevated values occurring over the spring and summer seasons. This is thought to be due to enhanced biogenic aerosol production as a result of phytoplankton bloom activity in the North Atlantic.     

Sink Potential of Canadian Agricultural Soils

Net greenhouse gas (GHG) emissions from Canadian crop and livestock production were estimated for 1990, 1996 and 2001 and projected to 2008. Net emissions were also estimated for three scenarios (low (L), medium (M) and high (H)) of adoption of sink enhancing practices above the projected 2008 level. Carbon sequestration estimates were based on four sink-enhancing activities: conversion from conventional to zero tillage (ZT), reduced frequency of summerfallow (SF), the conversion of cropland to permanent cover crops (PC), and improved grazing land management (GM). GHG emissions were estimated with the Canadian Economic and Emissions Model for Agriculture (CEEMA). CEEMA estimates levels of production activities within the Canadian agriculture sector and calculates the emissions and removals associated with those levels of activities. The estimates indicate a decline in net emissions from 54 Tg CO₂–Eq yr^–1 in1990 to 52 Tg CO₂–Eq yr^–1 in 2008. Adoption of thesink-enhancing practices above the level projected for 2008 resulted in further declines in emissions to 48 Tg CO₂–Eq yr^–1 (L), 42 TgCO₂–Eq yr^–1 (M) or 36 Tg CO₂–Eq yr^–1 (H). Among thesink-enhancing practices, the conversion from conventional tillage to ZT provided the largest C sequestration potential and net reduction in GHG emissions among the scenarios. Although rates of C sequestration were generally higher for conversion of cropland to PC and adoption of improved GM, those scenarios involved smaller areas of land and therefore less C sequestration. Also, increased areas of PC were associated with an increase in livestock numbers and CH₄ and N₂O emissions from enteric fermentation andmanure, which partially offset the carbon sink. The CEEMA estimates indicate that soil C sinks are a viable option for achieving the UNFCCC objective of protecting and enhancing GHG sinks and reservoirs as a means of reducing GHG emissions (UNFCCC, 1992).     

Changes in Heat Index Associated with CO2-Induced Global Warming

Changes in Heat Index (a combined measure of temperature and humidity) associated with global warming are evaluated based on the output from four extended integrations of the GFDL coupled ocean-atmosphere climate model. The four integrations are: a control with constant levels of atmospheric carbon dioxide (CO₂), a second integration in which an estimate of the combined radiative forcing of greenhouse gases and sulfate aerosols over the period 1765–2065 is used to force the model, and a third (fourth) integration in which atmospheric CO₂$ increases at the rate of 1% per year to double (quadruple) its initial value, and is held constant thereafter. While the spatial patterns of the changes in Heat Index are largely determined by the changes in surface air temperature, increases in atmospheric moisture can substantially amplify the changes in Heat Index over regions which are warm and humid in the Control integration. The regions most prone to this effect include humid regions of the Tropics and summer hemisphere extra-tropics, including the southeastern United States, India, southeast Asia and northern Australia.     

Production scenarios and the effect of soil degradation on long-term food security in China

Food security in China underlies the foundation of the livelihood and welfare for over one-fifth of the world's population. Soil degradation has an immense negative impact on the productive capacity of soils. We simulated the effect of soil degradation, which occurs in combination with increases in population size, urbanization rate, cropping intensity and decrease in cropland area, on long-term food security in China using a web-based land evaluation system. Our results predict that food crops may experience a 9% loss in productivity by 2030 if the soil continues to be degraded at the current rate (business-as-usual scenario, BAU). Productivity losses will increase to the unbearable level of 30% by 2050 should the soil be degraded at twice the present rate (double-degradation scenario, 2× SD). China's capacity for producing food from agricultural crops will be either adversely affected by the loss of cropland area (130, 113 and 107 million ha in 2005, 2030 and 2050, respectively) or favorably affected by agricultural intensification (in terms of the multi-cropping index at 120, 133 and 147% in 2005, 2030 and 2050, respectively). The loss of cropland is predicted to cause a 13–18% decrease in China's food production capacity by 2030–2050 relative to its 2005 level of 482 Mt, while agricultural intensification is predicted to cause an 11–23% increase. In total, China will be able to achieve a production level of 424 and 412 Mt by 2030 and 2050, respectively, under BAU, while this production will be only 386 and 339 Mt under 2× SD, respectively. In per capita terms, the relationship between food supply and demand will turn from an 18% surplus in 2005 to 3–5%, 14–18% and 22–32% deficits by 2030–2050 under the zero-degradation (0× SD), BAU and 2× SD scenarios, respectively. Our results show that the present-day production capacity will not sustain the long-term needs of a growing population under the current management level. Technical countermeasures and policy interventions need to be enacted today in order to avoid food insecurity tomorrow.     

Water Quality Co-Effects of Greenhouse Gas Mitigation in U.S. Agriculture

This study develops first-order estimates of water quality co-effects of terrestrial greenhouse gas (GHG) emission offset strategies in U.S. agriculture by linking a national level agricultural sector model (ASMGHG) to a national level water quality model (NWPCAM). The simulated policy scenario considers GHG mitigation incentive payments of $25 and $50 per tonne, carbon equivalent to landowners for reducing emissions or enhancing the sequestration of GHG through agricultural and land-use practices. ASMGHG projects that these GHG price incentives could induce widespread conversion of agricultural to forested lands, along with alteration of tillage practices, crop mix on land remaining in agriculture, and livestock management. This study focuses on changes in cropland use and management. The results indicate that through agricultural cropland about 60 to 70 million tonnes of carbon equivalent (MMTCE) emissions can be mitigated annually in the U.S. These responses also lead to a 2% increase in aggregate national water quality, with substantial variation across regions. Such GHG mitigation activities are found to reduce annual nitrogen loadings into the Gulf of Mexico by up to one half of the reduction goals established by the national Watershed Nutrient Task Force for addressing the hypoxia problem.