Modelling the response of wheat grain yield to climate change: a sensitivity analysis

The Agricultural Production System Simulator-Wheat model was used to test the sensitivity of wheat cropping system in NSW to a range of changes in temperature, rainfall and atmospheric carbon dioxide concentration based on wheat cultivars Sunvale and Janz under two extreme soil types (kandosol and sand) at six locations. Seven change levels (from 0 to 6°C at an interval of 1°C) in temperature, five change levels (from ?20 to 20 % at an interval of 10 %) in rainfall and three change levels (0, 171 and 316 ppm) in atmospheric pCO₂ were taken into account. It was found that there was a negative relationship between median grain yield and temperature while there were positive correlations of median grain yield with atmospheric pCO₂ and rainfall across all locations and soils considered. It was also found that the rate of decrease in median grain yield was more for higher temperatures in contrast to lower temperatures, and the rate of increase in median grain yield was less for higher rainfall and pCO₂ compared with the lower levels of these two variables. This study showed that environmental factors have significant effects on wheat grain yield, with soil as the most important factor, followed by site (reflecting both soil and climate), changes in atmospheric CO₂, rainfall and temperature. This study also showed that rainfall was more important under sandy soil conditions than under kandosol soil conditions. These findings provided a sound basis for preliminary scoping and prioritising adaptation options.     

Modelling the sensitivity of Mediterranean Outflow to anthropogenically forced climate change

 The possible future impact of anthropogenic forcing upon the circulation of the Mediterranean, and the exchange through the Strait of Gibraltar is investigated using a Cox-type model of the Mediterranean at 0.25° × 0.25° resolution, forced by “control” and “greenhouse” scenarios provided by the HadCM2 coupled climate model. The current structure of the Mediterranean forced by the “control” climate is compared with observations: certain aspects of the present circulation are reproduced, but others are absent or incorrectly represented. Deficiencies are most probably due to weaknesses in the forcing climatology generated by the climate model, so some caution must be exercised in interpreting the enhanced greenhouse simulation. Comparison of the control and greenhouse scenarios suggests that deep-water production in the Mediterranean may be reduced or cease in the relatively near future. The results also suggest that the Mediterranean outflow, may become warmer and more saline, but less dense, and hence shallower. The volume of the exchange at the Strait of Gibraltar seems to be relatively insensitive to future climate change, however. Our results indicate that a parameterisation of Gibraltar exchange and Mediterranean Outflow Water (MOW) production may be able to provide adequate representation of the changes we observe for the purposes of the current generation of climate models. Received: 10 August 1998 / Accepted: 11 October 1999     

Impacts of recent climate change on wheat production systems in Western Australia

The wheatbelt of Western Australia shows a distinct Mediterranean climate with most of the rainfall occurring in the winter months. The main factor limiting plant production in this region is rainfall. Due to clearing of native vegetation, dryland salinity is a major problem in south-west Australia. Since the mid 1970s the region has experienced a significant decrease in winter rainfall. Across nine sites, growing season rainfall (May to October) decreased by an average of 11% and the sum of rainfall in June and July (June + July) decreased by 20%. We used the ASPIM-Nwheat model in combination with historic climate data to study the impact of recent climate change on the hydrology and production of wheat based farming systems by comparing results for before and after 1975. Despite the large decline in rainfall, simulated yields based on the actual weather data did not fall. At the same time, simulated drainage decreased by up to 95% which will significantly reduce the spread of dryland salinity. These results were due to the rainfall changes mainly occurring in June and July, a period when rainfall often exceeds crop demand and large amounts of water are usually lost by deep drainage. The findings will have significant implications for estimates of future climate change impacts in this region with changes in rainfall causing non-proportional impacts on production and hydrological aspects, such as deep drainage and waterlogging, where proportionality is often presumed.     

Modelling climate change impacts on maize growth and development in the Czech Republic

Summary The crop growth model CERES-Maize is used to estimate the direct (through enhanced fertilisation effect of ambient CO₂) and indirect (through changed climate conditions) effects of increased concentration of atmospheric CO₂ on maize yields. The analysis is based on multi-year crop model simulations run with daily weather series obtained alternatively by a direct modification of observed weather series and by a stochastic weather generator. The crop model is run in two settings: stressed yields are simulated in water and nutrient limited conditions, potential yields in water and nutrient unlimited conditions. The climate change scenario was constructed using the output from the ECHAM3/T42 model (temperature), regression relationships between temperature and solar radiation, and an expert judgement (precipitation). Results: (i) After omitting the two most extreme misfits, the standard error between the observed and modelled yields is 11%. (ii) The direct effect of doubled CO₂: The stressed yields would increase by 36–41% in the present climate and by 61–66% in the 2 × CO₂ climate. The potential yields would increase only by 9–10% as the improved water use efficiency does not apply. (iii) The indirect effect of doubled CO₂: The stressed yields would decrease by 27–29% (14–16%) at present (doubled) ambient CO₂ concentration. The increased temperature shortens the phenological phases and does not allow for the optimal development of the crop. The simultaneous decrease of precipitation and increase of temperature and solar radiation deepen the water stress, thereby reducing the yields. The reduction of the potential yields is significantly smaller as the effect of the increased water stress does not apply. (iv) If both direct and indirect effects of doubled CO₂ are considered, the stressed yields should increase by 17–18%, and the potential yields by 5–14%. (v) The decrease of the stressed yields due to the indirect effect may be reduced by applying earlier planting dates. Received March 9, 2001 Revised September 25, 2001     

径流对气候变化的敏感性分析

全球变暖愈来愈引起社会各界的关注 ,本文利用月水文模型 ,采取假定气候方案 ,以黄河流域为例 ,分析了径流对气候变化的敏感性。结果表明 ,径流对降水变化的响应较气温变化显著 ;一般情况下 ,半干旱地区径流较半湿润地区对气候变化敏感 ,人类活动的影响可在一定程度上削弱径流对气候变化的敏感性     

Quantifying sources of uncertainty in projected wheat yield changes under climate change in eastern Australia

Future climate projections and impact analyses are pivotal to evaluate the potential change in crop yield under climate change. Impact assessment of climate change is also essential to prepare and implement adaptation measures for farmers and policymakers. However, there are uncertainties associated with climate change impact assessment when combining crop models and climate models under different emission scenarios. This study quantifies the various sources of uncertainty associated with future climate change effects on wheat productivity at six representative sites covering dry and wet environments in Australia based on 12 soil types and 12 nitrogen application rates using one crop model driven by 28 global climate models (GCMs) under two representative concentration pathways (RCPs) at near future period 2021–2060 and far future period 2061–2100. We used the analysis of variance (ANOVA) to quantify the sources of uncertainty in wheat yield change. Our results indicated that GCM uncertainty largely dominated over RCPs, nitrogen rates, and soils for the projections of wheat yield at drier locations. However, at wetter sites, the largest share of uncertainty was nitrogen, followed by GCMs, soils, and RCPs. In addition, the soil types at two northern sites in the study area had greater effects on yield change uncertainty probably due to the interaction effect of seasonal rainfall and soil water storage capacity. We concluded that the relative contributions of different uncertainty sources are dependent on climatic location. Understanding the share of uncertainty in climate impact assessment is important for model choice and will provide a basis for producing more reliable impact assessment.     

Quantifying the sensitivity of simulated climate change to model configuration

This study used “factor separation” to quantify the sensitivity of simulated present and future surface temperatures and precipitation to alternative regional climate model physics components. The method enables a quantitative isolation of the effects of using each physical component as well as the combined effect of two or more components. Simulation results are presented from eight versions of the Mesoscale Modeling System Version 5 (MM5), one-way nested within one version of the Goddard Institute for Space Studies Atmosphere-Ocean Global Climate Model (GISS AOGCM). The MM5 simulations were made at 108 km grid spacing over the continental United States for five summers in the 1990s and 2050s. Results show that the choice of cumulus convection parameterization is the most important “factor” in the simulation of contemporary surface summer temperatures and precipitation over both the western and eastern USA. The choice of boundary layer scheme and radiation package also increases the range of model simulation results. Moreover, the alternative configurations give quite different results for surface temperature and precipitation in the 2050s. For example, simulated 2050s surface temperatures by the scheme with the coolest 1990s surface temperatures are comparable to 1990s temperatures produced by other schemes. The study analyzes the spatial distribution of 1990s to 2050s projected changes in the surface temperature for the eight MM5 versions. The predicted surface temperature change at a given grid point, averaged over all eight model configurations, is generally about twice the standard deviation of the eight predicted changes, indicating relative consensus among the different model projections. Factor separation analysis indicates that the choice of cumulus parameterization is the most important modeling factor amongst the three tested contributing to the computed 1990s to 2050s surface temperature change, although enhanced warming over many areas is also attributable to synergistic effects of changing all three model components. Simulated ensemble mean precipitation changes, however, are very small and generally smaller than the inter-model standard deviations. The MM5 versions therefore offer little consensus regarding 1990s to 2050s changes in precipitation rates.     

Relative roles of climate sensitivity and forcing in defining the ocean circulation response to climate change

The response of the ocean’s meridional overturning circulation (MOC) to increased greenhouse gas forcing is examined using a coupled model of intermediate complexity, including a dynamic 3-D ocean subcomponent. Parameters are the increase in CO₂ forcing (with stabilization after a specified time interval) and the model’s climate sensitivity. In this model, the cessation of deep sinking in the north “Atlantic” (hereinafter, a “collapse”), as indicated by changes in the MOC, behaves like a simple bifurcation. The final surface air temperature (SAT) change, which is closely predicted by the product of the radiative forcing and the climate sensitivity, determines whether a collapse occurs. The initial transient response in SAT is largely a function of the forcing increase, with higher sensitivity runs exhibiting delayed behavior; accordingly, high CO₂-low sensitivity scenarios can be assessed as a recovering or collapsing circulation shortly after stabilization, whereas low CO₂-high sensitivity scenarios require several hundred additional years to make such a determination. We also systemically examine how the rate of forcing, for a given CO₂ stabilization, affects the ocean response. In contrast with previous studies based on results using simpler ocean models, we find that except for a narrow range of marginally stable to marginally unstable scenarios, the forcing rate has little impact on whether the run collapses or recovers. In this narrow range, however, forcing increases on a time scale of slow ocean advective processes results in weaker declines in overturning strength and can permit a run to recover that would otherwise collapse.     

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.     

Adjusting water resources management to climate change

The nature of climate impacts and adjustment in water supply and flood management is discussed, and a case study of water manager response to climate fluctuation in California's Sacramento Basin is presented. The case illuminates the effect on climate impact and response of traditional management approaches, the dynamic qualities of maturing water systems, socially imposed constraints, and climate extremes. A dual pattern of crisisresponse and gradual adjustment emerges, and specific mechanisms for effecting adjustment of water management systems are identified. The case study, and broader trends in U.S. water development, suggest that oversized structural capacity, the traditional adjustment to climate variability in water resources, may prove less feasible in the future as projects become smaller and new facilities are delayed by economic and environmental concerns.     

河南省稻麦类作物对气候变化的响应

小麦和水稻是世界最重要的粮食作物。利用河南省小麦和水稻的历史观测资料,结合DSSAT-CERES 小麦和ORYZA2000水稻模拟模型,分析和模拟河南省稻麦类作物在历史气候变化条件下发育期和产量的变化。结果表明：冬小麦全育期长度呈缩短趋势,但播种-越冬天数平均每10年增加1.7天,开花到乳熟天数平均每10年增加2-4天,返青后各发育期均表现出不同程度的提前;水稻各发育期均有不同程度的提前,尤其是拔节期以前,分蘖前的发育期间隔天数以缩短为主,拔节后以延长为主。雨养小麦模拟产量和水氮增产潜力均呈减少趋势;随着播种期的提前,水稻减产趋势逐渐减弱。     

Optimal growth with adaptation to climate change

We find that approximately a quarter of the world’s productive capital could be sensitive to climate; therefore, this capital faces the risk of accelerated obsolescence in a world warming by an average of 0.2 °C per decade. We examine the question of optimal adaptation to climate change in a vintage capital growth model without uncertainty. Along the optimal pathway, adaptation is proactive with an anticipation period of approximately twenty years. While there is additional investment in this scenario compared with a no-climate-change baseline, the overall cost to adapt is low relative to the potential losses from maladaptation. Over-investment in protection capital allows the economy to be consistently well-adapted to climate; thus, such a policy prevents transient maladaptation costs. Sensitivity analysis with an integrated assessment model suggests that costs could be ten times larger if adaptation only begins after vulnerable sectors are impacted.     

Impact of climate change on corrosion and damage to concrete infrastructure in Australia

The durability of concrete is determined largely by its deterioration over time which is affected by the environment. Climate change may alter this environment, causing an acceleration of deterioration processes that will affect the safety and serviceability of concrete infrastructure in Australia, U.S., Europe, China and elsewhere. This investigation of concrete deterioration under changing climate in Australia uses Monte-Carlo simulation of results from General Circulation Models (GCMs) and considers high greenhouse gas emission scenarios representing the A1FI schemes of the IPCC. We present the implications of climate change for the durability of concrete structures, in terms of changes in probability of reinforcement corrosion initiation and corrosion induced damage at a given calendar year between 2000 and 2100 across Australia. Since the main driver to increased concrete deterioration is CO₂ concentration and temperature, then increases in damage risks observed in Australia are likely to be observed in other concrete infrastructure internationally. The impact of climate change on the deterioration cannot be ignored, but can be addressed by new approaches in design. Existing concrete structures, for which design has not considered the effects of changing climate may deteriorate more rapidly than originally planned.     

Unpacking multilevel adaptation to climate change in the Great Barrier Reef,Australia

Multilevel governance is regarded as a promising approach to deal with the multidimensional nature of climate change adaptation. However, the policy context in which it is implemented is very often complex and fragmented, characterised by interacting climate and non-climate strategies. An understanding of multilevel decision-making and governance is particularly important, if desired adaptation outcomes are to be achieved. This paper examines how climate change adaptation takes place in a complex multilevel system of governance, in the context of Australia's Great Barrier Reef (GBR) region. It examines over one hundred adaptation strategies at federal, state, regional and local levels in terms of type, manifestation, purposefulness, drivers and triggers, and geographic and temporal scope. Interactions between strategies are investigated both at the same level of governance and across governance levels. This study demonstrates that multilevel approach is a necessary, but not a sufficient condition in responding to complex multiscale and multisector issues, such as climate change adaptation. Short-term adaptation measures; a predominant incremental, sectoral, top-down approach to adaptation; and the lack of a framework for managing interactions are major threats to effective climate adaptation in the GBR region. Coping with such threats will require long-term transformative action, establishing enabling conditions to support local adaptation, and, most important, creating and maintaining strategic interactions among adaptation strategies. Coordinating and integrating climate and non-climate strategies across jurisdictions and policy sectors are the most significant and challenging tasks for multilevel governance in the GBR region and elsewhere.