Possible Impacts of Global Warming on the Hydrology of the Ogallala Aquifer Region

The Ogallala or High Plains aquifer provides water for about 20% of the irrigated land in the United States. About 20 km³ (16.6 million acre-feet) of water are withdrawn annually from this aquifer. In general, recharge has not compensated for withdrawals since major irrigation development began in this region in the 1940s. The mining of the Ogallala has been pictured as an analogue to climate change in that many GCMs predict a warmer and drier future for this region. In this paper we attempt to anticipate the possible impacts of climate change on the sustainability of the aquifer as a source of water for irrigation and other purposes in the region. We have applied HUMUS, the Hydrologic Unit Model of the U.S. to the Missouri and Arkansas-White-Red water resource regions that overlie the Ogallala. We have imposed three general circulation model (GISS, UKTR and BMRC) projections of future climate change on this region and simulated the changes that may be induced in water yields (runoff plus lateral flow) and ground water recharge. Each GCM was applied to HUMUS at three levels of global mean temperature (GMT) to represent increasing severity of climate change (a surrogate for time). HUMUS was also run at three levels of atmospheric CO₂ concentration (hereafter denoted by [CO₂]) in order to estimate the impacts of direct CO₂ effects on photosynthesis and evapotranspiration. Since the UKTR and GISS GCMs project increased precipitation in the Missouri basin, water yields increase there. The BMRC GCM predicts sharply decreased precipitation and, hence, reduced water yields. Precipitation reductions are even greater in the Arkansas basin under BMRC as are the consequent water yield losses. GISS and UKTR climates lead to only moderate yield losses in the Arkansas. CO₂-fertilization reverses these losses and yields increase slightly. CO₂ fertilization increases recharge in the base (no climate change) case in both basins. Recharge is reduced under all three GCMs and severities of climate change.     

Paper 2. agricultural impacts of and responses to climate change in the Missouri-Iowa-Nebraska-Kansas (MINK) region

The climate of the 1930s was used as an analog of the climate that might occur in Missouri, Iowa, Nebraska and Kansas (the MINK region) as a consequence of global warming. The analog climate was imposed on the agriculture of the region under technological and economic conditions prevailing in 1984/87 and again under a scenario of conditions that might prevail in 2030. The EPIC model of Williamset al. (1984), modified to allow consideration of the yield enhancing effects of CO₂ enrichment, was used to evaluate the impacts of the analog climate on the productivity and water use of some 50 representative farm enterprises. Before farm level adjustments and adaptations to the changed climate, and absent CO₂ enrichment (from 350 to 450 ppm), production of corn, sorghum and soybeans was depressed by the analog climate in about the same percent under both current and 2030 conditions. Production of dryland wheat was unaffected. Irrigated wheat production actually increased. Farm level adjustments using low-cost currently available technologies, combined with CO₂ enrichment, eliminated about 80% of the negative impact of the analog climate on 1984/87 baseline crop production. The same farm level adjustments, plus new technologies developed in response to the analog climate, when combined with CO₂ enrichment, converted the negative impact on 2030 crop production to a small increase. The analog climate would have little direct effect on animal production in MINK. The effect, if any, would be by way of the impact on production of feed-grains and soybeans. Since this impact would be small after on-farm adjustments and CO₂ enrichment, animal production in MINK would be little affected by the analog climate.     

How is CO2 affecting yields and technological progress? A statistical analysis

This paper analyzes the impact of climate, crop production technology, and atmospheric carbon dioxide (CO₂) on current and future crop yields. The analysis of crop yields endeavors to advance the literature by estimating the effect of atmospheric CO₂ on observed crop yields. This is done using an econometric model estimated over pooled historical data for 1950–2009 and data from the free air CO₂ enrichment experiments. The main econometric findings are: 1) Yields of C3 crops (soybeans, cotton, and wheat) directly respond to the elevated CO₂, while yields of C4 crops (corn and sorghum) do not, but they are found to indirectly benefit from elevated CO₂ in times and places of drought stress; 2) The effect of technological progress on mean yields is non-linear; 3) Ignoring atmospheric CO₂ in an econometric model of crop yield likely leads to overestimates of the pure effects of technological progress on crop yields of about 51, 15, 17, 9, and 1 % of observed yield gain for cotton, soybeans, wheat, corn and sorghum, respectively; 4) Average climate conditions and climate variability contribute in a statistically significant way to average crop yields and their variability; and 5) The effect of CO₂ fertilization generally outweighs the effect of climate change on mean crop yields in many regions resulting in an increase of 7–22, 4–47, 5–26, 65–96, and 3–35 % for yields of corn, sorghum, soybeans, cotton, and wheat, respectively.     

Estimating the consequences of CO2-induced climatic change on north american grain agriculture using general circulation model information

A procedure to estimate the potential climatic effects of a doubling of atmospheric carbon dioxide concentration on agricultural production is illustrated. The method combines use of atmospheric general circulation models (GCMs) and process-oriented crop models. Wheat and corn (maize) yields in three important North American grain cropping regions are treated. Combined use of these two types of models can provide insights into the impacts of climate changes at the level of plant physiology, and potential means by which agricultural production practices may adapt to these changes.Specific agronomic predictions are found to depend critically on the details of the projected climate change. Uncertainties in the specification of the doubled-CO₂ climate by the GCM, particularly with respect to precipitation, dictate that agricultural predictions derived from them at this time must be regarded only as illustrative of the impact assessment method.     

The impact of climate change on continuous corn production in the Southern U.S.A.

The Goddard Institute for Space Studies (GISS) General Circulation Model (GCM) has been used in conjunction with a field level plant process model (CERES-Maize) and a field level pesticide transport model (PRZM) to study the impacts of doubled levels of atmospheric CO₂ on various aspects of corn production in the Southern U.S.A. Grid-box scale GCM output has been applied to a 38-year time series of historical weather data at 28 different locations for several typical soil profiles throughout the South. Limitations on the use of the climate scenario in conjunction with the process models are discussed. Major shortcomings include: 1) no direct impacts of atmospheric CO₂ on plant growth and development in the plant process model; 2) neither macro-pore solute transport nor chemical decay rate response to temperature are included in the pesticide transport model; and 3) the climate change scenario output does not provide information concerning changes in temperature extremes and variability or precipitation frequency, intensity or duration. The latter are particularly critical parameters for the detailed simulation of hydrological processes. In spite of these omissions, the combination of the three models facilitates the study of the impacts of GCM modeled climate change on several inter-related agro-climatic issues of interest to agricultural policy makers. These issues include: changes in dryland and irrigated corn yields; changes in sowing and harvest dates; modification of crop water demand; and estimates of effects on pesticide losses from the soil surface and through leaching from the bottom of the active corn root zone. Model generated results which address these issues are presented but must be used with caution in light of the GCM and process model limitations. The results of this study suggest that substantial changes in agricultural production and management practices may be needed to respond to the climate changes expected to take place throughout the Southern U.S.A.     

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.     

Climate Change Impacts for the Conterminous USA: An Integrated Assessment

Human activities have altered the distribution and quality of terrestrial ecosystems. Future demands for goods and services from terrestrial ecosystems will occur in a world experiencing human-induced climate change. In this study, we characterize the range in response of unmanaged ecosystems in the conterminous U.S. to 12 climate change scenarios. We obtained this response by simulating the climatically induced shifts in net primary productivity and geographical distribution of major biomes in the conterminous U.S. with the BIOME 3 model. BIOME 3 captured well the potential distribution of major biomes across the U.S. under baseline (current) climate. BIOME 3 also reproduced the general trends of observed net primary production (NPP) acceptably. The NPP projections were reasonable for forests, but not for grasslands where the simulated values were always greater than those observed. Changes in NPP would be most severe under the BMRC climate change scenario in which severe changes in regional temperatures are projected. Under the UIUC and UIUC + Sulfate scenarios, NPP generally increases, especially in the West where increases in precipitation are projected to be greatest. A CO₂-fertilization effect either amplified increases or alleviated losses in modeled NPP. Changes in NPP were also associated with changes in the geographic distribution of major biomes. Temperate/boreal mixed forests would cover less land in the U.S. under most of the climate change scenarios examined. Conversely, the temperate conifer and temperate deciduous forests would increase in areal extent under the UIUC and UIUC + Sulfate scenarios. The Arid Shrubland/Steppe would spread significantly across the southwest U.S. under the BMRC scenario. A map overlay of the simulated regions that would lose or gain capacity to produce corn and wheat on top of the projected distribution of natural ecosystems under the BMRC and UIUC scenarios (Global mean temperature increase of +2.5 °C, no CO₂ effect) helped identify areas where natural and managed ecosystems could contract or expand. The methods and models employed here are useful in identifying; (a) the range in response of unmanaged ecosystem in the U.S. to climate change and (b) the areas of the country where, for a particular scenario of climate change, land cover changes would be most likely.     

Projected global climate change impact on water temperatures in five north central U.S. streams

The effect of projected global climate change due to a doubling of atmospheric CO₂ on water temperatures in five streams in Minnesota was estimated using a deterministic heat transport model. The model calculates heat exchange between the atmosphere and the water and is driven by climate parameters and stream hydrologic parameters. The model is most sensitive to air temperature and solar radiation. The model was calibrated against detailed measurements to account for seasonally variable shading and wind sheltering. Using climate projections from the GISS, GFDL and OSU GCMs as input; stream temperature simulations predict a warming of freely flowing river reaches by 2.4 °C to 4.7 °C when atmospheric CO₂ doubles. In small shaded streams water temperatures are predicted to rise by an additional 6 °C in summer if trees along stream banks should be lost due to climate change or other human activities (e.g. logging). These projected water temperature changes have significant consequences for survival and growth of fishes. Simulation with the complete heat budget equations were also used to examine simplified water temperature/air temperature correlations.     

气候变化对江苏省小麦生产的可能影响

根据国内外研究结果综合分析,得到ＣＯ２倍增时江苏省温度、降水的变化值,初步确定了ＣＯ２倍增时江苏省小麦生长季内的可能气候情景。分析未来ＣＯ２倍增时对小麦作物的直接影响、间接影响及紫外辐射影响。具体估算了温度升高、降水增加、ＣＯ２浓度上升、紫外辐射增强后江苏省小麦生育期不变和生育期缩短两种情景下的气候生产潜力,并由此分析了气候变暖对江苏省不同地区的利弊影响。结果表明：江北大部分地区小麦产量有所增加,     

Simulating Crop Net Primary Production in China from 2000 to 2050 by Linking the Crop-C model with a FGOALS＇s Model Climate Change Scenario

Net primary production （NPP） of crop represents the capacity of sequestrating atmospheric CO2 in agro-ecosystem, and it plays an important role in terrestrial carbon cycling. By linking the Crop-C model with climate change scenario projected by a coupled GCM FGOALS via geographical information system （GIS） techniques, crop NPP in China was simulated from 2000 to 2050. The national averaged surface air temperature from FGOALS is projected to increase by 1.0℃ over this period and the corresponding atmospheric CO2 concentration is 535 ppm by 2050 under the IPCC A1B scenario. With a spatial resolution of 10 ×10 km^2, model simulation indicated that an annual average increase of 0.6 Tg C yr^-1 （Tg=10^12 g） would be possible under the A1B scenario. The NPP in the late 2040s would increase by 5% （30 Tg C） within the 98×10^6 hm^2 cropland area in contrast with that in the early 2000s. A further investigation suggested that changes in the NPP would not be evenly distributed in China. A higher increase would occur in a majority of regions located in eastern and northwestern China, while a slight reduction would appear in Hebei and Tianjin in northern China. The spatial characteristics of the crop NPP change are attributed primarily to the uneven distribution of temperature change.     

RESPONSES OF A GLOBAL CGCM TO CO_2 INCREASE

The responses of the climate system to increase of atmospheric carbon dioxide(CO_2)arestudied by using a new version of the Bureau of Meteorological Research Centre(BMRC)globalcoupled general circulation model(CGCM).Two simulations are run:one with atmospheric CO_2concentration held constant at 330 ppm,the other with a tripling of atmospheric CO_2(990 ppm).Results from the 41-year control coupled integration are applied to analyze the mean state,seasonal cycle and interannual variability in the model.Comparisons between the greenhouseexperiment and the control experiment then provide estimations of the influence of increased CO_2on climate changes and climate variability.Especially discussed is the question on whether theclimate changes concerned with CO_2 inerease will impact interannual variability in tropical Pacific,such as ENSO.     

Impact of future climate change on wheat production in relation to plant-available water capacity in a semiaridenvironment

Conceptions encompassing climate change are irreversible rise of atmospheric carbon dioxide (CO₂) concentration, increased temperature, and changes in rainfall both in spatial- and temporal-scales worldwide. This will have a major impact on wheat production, particularly if crops are frequently exposed to a sequence, frequency, and intensity of specific weather events like high temperature during growth period. However, the process of wheat response to climate change is complex and compounded by interactions among atmospheric CO₂ concentration_, climate variables, soil, nutrition, and agronomic management. In this study, we use the Agricultural Production Systems sIMulator (APSIM)-wheat model, driven by statistically downscaled climate projections of 18 global circulation models (GCMs) under the 2007 Intergovernmental Panel on Climate Change (IPCC) Special Report on Emission Scenarios (SRES) A2 CO₂ emission scenario to examine impact on future wheat yields across key wheat growing regions considering different soil types in New South Wales (NSW) of Australia. The response of wheat yield, yield components, and phenology vary across sites and soil types, but yield is closely related to plant available water capacity (PAWC). Results show a decreasing yield trend during the period of 2021–2040 compared to the baseline period of 1961–1990. Across different wheat-growing regions in NSW, grain yield difference in the future period (2021–2040) over the baseline (1961–1990) varies from +3.4 to ?14.7 %, and in most sites, grain number is decreased, while grain size is increased in future climate. Reduction of wheat yield is mainly due to shorter growth duration, where average flowering and maturing time are advanced by an average of 11 and 12 days, respectively. In general, larger negative impacts of climate change are exhibited in those sites with higher PAWC. Current wheat cultivars with shorter growing season properties are viable in the future climate, but breading for early sowing wheat varieties with longer growing duration will be a desirable adaptation strategy for mitigating the impact of changing climate on wheat yield.     

RESPONSES OF A GLOBAL CGCM TO CO2 INCREASE

The responses of the climate system to increase of atmospheric carbon dioxide(CO₂)arestudied by using a new version of the Bureau of Meteorological Research Centre(BMRC)globalcoupled general circulation model(CGCM).Two simulations are run:one with atmospheric CO₂concentration held constant at 330 ppm,the other with a tripling of atmospheric CO₂(990 ppm).Results from the 41-year control coupled integration are applied to analyze the mean state,seasonal cycle and interannual variability in the model.Comparisons between the greenhouseexperiment and the control experiment then provide estimations of the influence of increased CO₂on climate changes and climate variability.Especially discussed is the question on whether theclimate changes concerned with CO₂ inerease will impact interannual variability in tropical Pacific,such as ENSO.     

Multi-factor impact analysis of agricultural production in Bangladesh with climate change

Diverse vulnerabilities of Bangladesh's agricultural sector in 16 sub-regions are assessed using experiments designed to investigate climate impact factors in isolation and in combination. Climate information from a suite of global climate models (GCMs) is used to drive models assessing the agricultural impact of changes in temperature, precipitation, carbon dioxide concentrations, river floods, and sea level rise for the 2040–2069 period in comparison to a historical baseline. Using the multi-factor impacts analysis framework developed in Yu et al. (2010), this study provides new sub-regional vulnerability analyses and quantifies key uncertainties in climate and production. Rice (aman, boro, and aus seasons) and wheat production are simulated in each sub-region using the biophysical Crop Environment REsource Synthesis (CERES) models. These simulations are then combined with the MIKE BASIN hydrologic model for river floods in the Ganges-Brahmaputra-Meghna (GBM) Basins, and the MIKE21 Two-Dimensional Estuary Model to determine coastal inundation under conditions of higher mean sea level. The impacts of each factor depend on GCM configurations, emissions pathways, sub-regions, and particular seasons and crops. Temperature increases generally reduce production across all scenarios. Precipitation changes can have either a positive or a negative impact, with a high degree of uncertainty across GCMs. Carbon dioxide impacts on crop production are positive and depend on the emissions pathway. Increasing river flood areas reduce production in affected sub-regions. Precipitation uncertainties from different GCMs and emissions scenarios are reduced when integrated across the large GBM Basins’ hydrology. Agriculture in Southern Bangladesh is severely affected by sea level rise even when cyclonic surges are not fully considered, with impacts increasing under the higher emissions scenario.     

PROJECTIONS OF CLIMATE CHANGE FOR THE CZECH REPUBLIC

The paper deals with a selection of the climatological baseline, GCM validity and construction of the climate change scenarios for an impact assessment in the Czech territory. The period of 1961–1990 has been selected as the climatological baseline. The corresponding database includes more than 50 monthly mean temperature and precipitation series, and 16 time series of daily meteorological data that contain also the solar radiation data. The 1× CO₂ outputs produced by four GCMs, provided by the CSMT (GISS, GFD30, GFD01, and CCCM), were compared with observed temperature and precipitation conditions in western and central Europe with a particular attention devoted to the Czech territory. The GCM ability to simulate annual cycles of temperature, precipitation and radiation was thoroughly examined. The GISS and CCCM were selected as a basis for constructing climate change scenarios as they simulated reasonably the observed patterns. According to the GISS variant, 2× CO₂ climate assumes a higher winter and lower summer warming, and an increase in annual precipitation amounts. A dangerous combination of the summer temperature increase and declining precipitation amounts is a specific feature of the CCCM scenario. An incremental scenario for temperature and precipitation is based on the combination of prescribed changes in both annual means and annual courses.     

Climate change impacts on dryland cropping systems in the Central Great Plains,USA

Agricultural systems models are essential tools to assess potential climate change (CC) impacts on crop production and help guide policy decisions. In this study, impacts of projected CC on dryland crop rotations of wheat-fallow (WF), wheat-corn-fallow (WCF), and wheat-corn-millet (WCM) in the U.S. Central Great Plains (Akron, Colorado) were simulated using the CERES V4.0 crop modules in RZWQM2. The CC scenarios for CO₂, temperature and precipitation were based on a synthesis of Intergovernmental Panel on Climate Change (IPCC 2007) projections for Colorado. The CC for years 2025, 2050, 2075, and 2100 (CC projection years) were super-imposed on measured baseline climate data for 15–17 years collected during the long-term WF and WCF (1992–2008), and WCM (1994–2008) experiments at the location to provide inter-annual variability. For all the CC projection years, a decline in simulated wheat yield and an increase in actual transpiration were observed, but compared to the baseline these changes were not significant (p > 0.05) in all cases but one. However, corn and proso millet yields in all rotations and projection years declined significantly (p < 0.05), which resulted in decreased transpiration. Overall, the projected negative effects of rising temperatures on crop production dominated over any positive impacts of atmospheric CO₂ increases in these dryland cropping systems. Simulated adaptation via changes in planting dates did not mitigate the yield losses of the crops significantly. However, the no-tillage maintained higher wheat yields than the conventional tillage in the WF rotation to year 2075. Possible effects of historical CO₂ increases during the past century (from 300 to 380 ppm) on crop yields were also simulated using 96 years of measured climate data (1912–2008) at the location. On average the CO₂ increase enhanced wheat yields by about 30%, and millet yields by about 17%, with no significant changes in corn yields.     

A Climate Change Scenario for the Tropics

This paper describes the construction of a climate change scenario for a region representing the extended Tropics – 30° N to 30° S – using a methodology that combines results from a simple climate model and a Global Climate Model (GCM) transient climate change experiment. The estimated date by which this climate change scenario might be realized ranges from as early as the end of the 2030s to as late as well into the 22nd century. The central estimate is for this scenario to describe the climate of the 2060s, which would represent a global warming rate of about 0.2 °C per decade, with associated atmospheric CO₂ concentrations estimated to be about 560 ppmv, 55% higher than 1990 levels. The role of anthropogenic aerosols in offsetting part of this future global warming and altering the regional character of the changes has not been considered. The paper presents changes in mean temperature; mean rainfall; rainfall seasonality, variability, frequency, and intensity and soil moisture. These patterns of change derive from only one GCM climate change experiment; different experiments would yield different patterns for the same global warming. There is also some discussion about possible changes in tropical cyclone (TC) activity, although since TCs remain poorly modelled in GCMs, the full range of possibilities (from reduced activity, through no change, to increased activity) should be considered in any impact assessment.     

Comparison of Agricultural Impacts of Climate Change Calculated from High and Low Resolution Climate Change Scenarios: Part I. The Uncertainty Due to Spatial Scale

We investigated the effect of two different spatial scales of climate change scenarios on crop yields simulated by the EPIC crop model for corn, soybean, and wheat, in the central Great Plains of the United States. The effect of climate change alone was investigated in Part I. In Part II (Easterling et al., 2001) we considered the effects ofCO₂ fertilization effects and adaptation in addition to climate change. The scenarios were formed from five years of control and 2 ×CO₂ runs of a high resolution regional climate model (RegCM) and the same from an Australian coarse resolution general circulation model (GCM), which provided the initial and lateral boundary conditions for the regional model runs. We also investigated the effect of two different spatial resolutions of soil input parameters to the crop models. We found that for corn and soybean in the eastern part of the study area, significantly different mean yield changes were calculated depending on the scenario used. Changes in simulated dryland wheat yields in the western areas were very similar, regardless of the scale of the scenario. The spatial scale of soils had a strong effect on the spatial variance and pattern of yields across the study area, but less effect on the mean aggregated yields. We investigated what aspects of the differences in the scenarios were most important for explaining the different simulated yield responses. For instance, precipitation changes in June were most important for corn and soybean in the eastern CSIRO grid boxes. We establish the spatial scale of climate changescenarios as an important uncertainty for climate change impacts analysis.     

Impacts of climate change on crop evapotranspiration with ensemble GCM projections in the North China Plain

As one of the key grain-producing regions in China, the agricultural system in the North China Plain (NCP) is vulnerable to climate change due to its limited water resources and strong dependence on irrigation for crop production. Exploring the impacts of climate change on crop evapotranspiration (ET) is of importance for water management and agricultural sustainability. The VIP (Vegetation Interface Processes) process-based ecosystem model and WRF (Weather Research and Forecasting) modeling system are applied to quantify ET responses of a wheat-maize cropping system to climate change. The ensemble projections of six General Circulation Models (GCMs) under the B2 and A2 scenarios in the 2050s over the NCP are used to account for the uncertainty of the projections. The thermal time requirements (TTR) of crops are assumed to remain constant under air warming conditions. It is found that in this case the length of the crop growth period will be shortened, which will result in the reduction of crop water consumption and possible crop productivity loss. Spatially, the changes of ET during the growth periods (ET_g) for wheat range from ?7 to 0 % with the average being ?1.5?±?1.2 % under the B2 scenario, and from ?8 to 2 % with the average being ?2.7?±?1.3 % under the A2 scenario/consistently, changes of ET_g for maize are from ?10 to 8 %, with the average being ?0.4?±?4.9 %, under the B2 scenario and from ?8 to 8 %, with the average being ?1.2?±?4.1 %, under the A2 scenario. Numerical analysis is also done on the condition that the length of the crop growth periods remains stable under the warming condition via breeding new crop varieties. In this case, TTR will be higher and the crop water requirements will increase, with the enhancement of the productivity. It is suggested that the options for adaptation to climate change include no action and accepting crop loss associated with the reduction in ET_g, or breeding new cultivars that would maintain or increase crop productivity and result in an increase in ET_g. In the latter case, attention should be paid to developing improved water conservation techniques to help compensate for the increased ET_g.     

Effects of Climate Change on Rice Production in the Tropical Humid Climate of Kerala, India

The CERES-Rice v3. crop simulation model, calibrated and validated for its suitability to simulate rice production in the tropical humid climate Kerala State of India, is used for analysing the effect of climate change on rice productivity in the state. The plausible climate change scenario for the Indian subcontinent as expected by the middle of the next century, taking into account the projected emissions of greenhouse gases and sulphate aerosols, in a coupled atmosphere-ocean model experiment performed at Deutsches Klimarechenzentrum, Germany, is adopted for the study. The adopted scenario represented an increase in monsoon seasonal mean surface temperature of the order of about 1.5°C, and an increase in rainfall of the order of 2 mm per day, over the state of Kerala in the decade 2040–2049 with respect to the 1980s. The IPCC Business-as-usual scenario projection of plant usable concentration of CO₂ about 460 PPM by the middle of the next century are also used in the crop model simulation. On an average over the state with the climate change scenario studied, the rice maturity period is projected to shorten by 8% and yield increase by 12%. When temperature elevations only are taken into consideration, the crop simulations show a decrease of 8% in crop maturity period and 6% in yield. This shows that the increase in yield due to fertilisation effect of elevated CO₂ and increased rainfall over the state as projected in the climate change scenario nearly makes up for the negative impact on rice yield due to temperature rise. The sensitivity experiments of the rice model to CO₂ concentration changes indicated that over the state, an increase in CO₂ concentration leads to yield increase due to its fertilisation effect and also enhance the water use efficiency of the paddy. The temperature sensitivity experiments have shown that for a positive change in temperature up to 5°C, there is a continuous decline in the yield. For every one degree increment the decline in yield is about 6%. Also, in another experiment it is observed that the physiological effect of ambient CO₂ at 425 ppm concentration compensated for the yield losses due to increase in temperature up to 2°C. Rainfall sensitivity experiments have shown that increase in rice yield due to increase in rainfall above the observed values is near exponential. But decrease in rainfall results in yield loss at a constant rate of about 8% per 2 mm/day, up to about 16 mm/day.