Toshihiko Masui

Changes in Nature’s Balance Sheet: Model-based Estimates of Future Worldwide Ecosystem Services

Four quantitative scenarios are presented that describe changes in worldwide ecosystem services up to 2050-2100. A set of soft-linked global models of human demography, economic development, climate, and biospheric processes are used to quantify these scenarios. The global demand for ecosystem services substantially increases up to 2050: cereal consumption by a factor of 1.5 to 1.7, fish consumption (up to the 2020s) by a factor of 1.3 to 1.4, water withdrawals by a factor of 1.3 to 2.0, and biofuel production by a factor of 5.1 to 11.3. The ranges for these estimates reflect differences between the socio-economic assumptions of the scenarios. In all simulations, Sub-Saharan Africa continues to lag behind other parts of the world. Although the demand side of these scenarios presents an overall optimistic view of the future, the supply side is less optimistic: the risk of higher soil erosion (especially in Sub-Saharan Africa) and lower water availability (especially in the Middle East) could slow down an increase in food production. Meanwhile, increasing wastewater discharges during the same period, especially in Latin America (factor of 2 to 4) and Sub-Saharan Africa (factor of 3.6 to 5.6) could interfere with the delivery of freshwater services. Marine fisheries (despite the growth of aquaculture) may not have the ecological capacity to provide for the increased global demand for fish. Our simulations also show an intensification of present tradeoffs between ecosystem services, e.g., expansion of agricultural land (between 2000 and 2050) may be one of the main causes of a 10%-20% loss of total current grassland and forest land and the ecosystem services associated with this land (e.g., genetic resources, wood production, habitat for terrestrial biota and fauna). The scenarios also show that certain hot-spot regions may experience especially rapid changes in ecosystem services: the central part of Africa, southern Asia, and the Middle East. In general, the scenarios show a positive balance of increasing services, especially in developing countries, and a negative balance of increasing risks and tradeoffs of services. The challenge, then, is dealing with these risks so as to avoid a future curtailment of ecosystem services.

Economic Impacts from PM2.5 Pollution-Related Health Effects in China: A Provincial-Level Analysis

This study evaluates the PM2.5 pollution-related health impacts on the national and provincial economy of China using a computable general equilibrium (CGE) model and the latest nonlinear exposure-response functions. Results show that the health and economic impacts may be substantial in provinces with a high PM2.5 concentration. In the WoPol scenario without PM2.5 pollution control policy, we estimate that China experiences a 2.00% GDP loss and 25.2 billion USD in health expenditure from PM2.5 pollution in 2030. In contrast, with control policy in the WPol scenario, a control investment of 101.8 billion USD (0.79% of GDP) and a gain of 1.17% of Chinas GDP from improving PM2.5 pollution are projected. At the provincial level, GDP loss in 2030 in the WoPol scenario is high in Tianjin (3.08%), Shanghai (2.98%), Henan (2.32%), Beijing (2.75%), and Hebei (2.60%) and the top five provinces with the highest additional health expenditure are Henan, Sichuan, Shandong, Hebei, and Jiangsu. Controlling PM2.5 pollution could bring positive benefits in two-thirds of provinces. Tianjin, Shanghai, Beijing, Henan, Jiangsu, and Hebei experience most benefits from PM2.5 pollution control as a result of a higher PM2.5 pollution and dense population distribution. Conversely, the control investment is higher than GDP gain in some underdeveloped provinces, such as Ningxia, Guizhou, Shanxi, Gansu, and Yunnan.

Local air pollutant emission reduction and ancillary carbon benefits of SO2 control policies: Application of AIM/CGE model to China

While a great deal of literature has been published in recent years on the ancillary benefits of greenhouse gas mitigation (e.g., reductions in local air pollution), less attention has been focused on the climate benefits of local air pollution strategies themselves. Local air pollution is, however, a more immediate issue now faced by developing countries. This study assesses the impacts on local air pollutant emission reduction and ancillary CO2 emission reduction of SO2 control policies in China, such as a sulphur tax, SO2 total emissions control (TEC), and improvement of energy efficiency, based on the Asia-Pacific Integrated Model (AIM)/Computable General Equilibrium (CGE) country model. The simulation period is from 1997 to 2020. Major conclusions include the following: an SO2 emission cap will help to control SO2 emissions, but will result in a large GDP loss; the role of a SO2 emission tax at the present level is very limited; and an ancillary carbon reduction benefit can be achieved through the introduction of SO2 control policies in China.

Geographical Distributions of Temperature Change for Scenarios of Greenhouse Gas and Sulfur Dioxide Emissions

Time-dependent geographical distributions of surface–air temperature change relative to year 2000 are constructed for four scenarios of greenhouse gas (GHG) and sulfur dioxide (SO2) emissions, and are compared to the IS92a scenario. The four new scenarios have been developed by four different modeling teams. The four scenarios are noninterventionist, in that they do not include abatement of GHG emissions for the purpose of climate-change mitigation. The time evolution of the changes in global-mean surface-air temperature and sea level are calculated for each scenario by our energy-balance-climate/upwelling-diffusion-ocean model. The temperature changes individually and jointly for the radiative forcing by the GHGs and by the sulfate aerosol, which is formed in the atmosphere from the emitted SO2. These GHG- and SO2-induced global-mean temperature changes are used to scale in time the geographical distributions of surface–air temperature simulated by our University of Illinois at Urbana–Champaign (UIUC) atmospheric-general-circulation/mixed-layer-ocean model, respectively for a doubling of the CO2 amount and for a 10-fold increase in present-day SO2 emission—the latter from the entire earth as well as individually from Europe, Siberia, North Africa, Asia, North America, and the Southern Hemisphere—each geographical distribution having been normalized by its respective global-mean surface–air temperature change. It is found that: (1) the global-mean surface–air temperature changes are not distinguishable among the four scenarios presented here until near the middle of the 21st century; (2) in 2100, the warming and sea level rise range from 1.2°C and 27 cm for the B1 scenario, with a temperature sensitivity of ΔT2x = 1.5°C to 4.9°C and 72 cm for the A2 scenario, with ΔT2x = 4.5°C, with 62 and 69% of these 3.7°C and 45 cm ranges respectively resulting from the uncertainty in ΔT2x, and 38 and 31% from the scenario uncertainty; (3) the scenario uncertainty in future noninterventionist CO2 emissions translates into a large uncertainty about the geographical distribution of the warming, particularly in the Arctic; (4) the reduction in regional SO2 emissions of the four scenarios compared to IS92a results in a significant warming of Europe, Asia, and North America, as well as either a reduction or reversal of the cooling elsewhere, thereby showing that mitigation of the acid-rain problem exacerbates the greenhouse-warming problem; and (5) sulfate aerosol reduces the GHG-induced warming in the Arctic for IS92a, but increases the Arctic warming for the four scenarios.

Climate Change Impact and Adaptation Assessment on Food Consumption Utilizing a New Scenario Framework

We assessed the impacts of climate change and agricultural autonomous adaptation measures (changes in crop variety and planting dates) on food consumption and risk of hunger considering uncertainties in socioeconomic and climate conditions by using a new scenario framework. We combined a global computable general equilibrium model and a crop model (M-GAEZ), and estimated the impacts through 2050 based on future assumptions of socioeconomic and climate conditions. We used three Shared Socioeconomic Pathways as future population and gross domestic products, four Representative Concentration Pathways as a greenhouse gas emissions constraint, and eight General Circulation Models to estimate climate conditions. We found that (i) the adaptation measures are expected to significantly lower the risk of hunger resulting from climate change under various socioeconomic and climate conditions. (ii) population and economic development had a greater impact than climate conditions for risk of hunger at least throughout 2050, but climate change was projected to have notable impacts, even in the strong emission mitigation scenarios. (iii) The impact on hunger risk varied across regions because levels of calorie intake, climate change impacts and land scarcity varied by region.

Back-casting analysis for 70% emission reduction in Japan by 2050

This article envisions a future in which advances in technology and urban development have transformed Japanese society by 2050, resulting in significant greenhouse gas reductions. Pathways leading Japan towards a low-carbon society are calculated using a scenario approach based on ‘back-casting’ techniques. It is possible to reach a 70% reduction in CO2 emissions through a combination of demand-side and supply-side actions. On the demand side, reductions of 40–45% are possible through efficiency improvements, decreased population and the more rational use of energy despite increased energy demands arising in certain sectors. On the supply side, CO2 emissions can be reduced through a combination of the appropriate choice of low-carbon energy sources (including carbon capture and storage) and improving energy efficiency. The estimated direct annual cost of technology to achieve this by 2050 is 6.7–9.8 trillion yen, approximately 1% of the estimated 2050 GDP. However, this excludes costs involved in infrastructure investments with aims other than climate policy (e.g. strengthening international competitiveness, improving security, enhancing urban development, and reinforcing energy). To avoid investing in its current high-carbon-emitting infrastructure, Japan must develop long-term strategies to create the necessary technological and societal innovations and to channel the appropriate financial resources for intensive economy-wide change, such as development of land, urban areas, and buildings, improvements in industrial structures, and new technologies.

Scenarios for the risk of hunger in the twenty-first century using Shared Socioeconomic Pathways

Shared socioeconomic pathways (SSPs) are being developed internationally for cross-sectoral assessments of climate change impacts, adaptation, and mitigation. These are five scenarios that include both qualitative and quantitative information for mitigation and adaptation challenges to climate change. In this study, we quantified scenarios for the risk of hunger in the 21st century using SSPs, and clarified elements that influence future hunger risk. There were two primary findings: (1) risk of hunger in the 21st-century greatly differed among five SSPs; and (2) population growth, improvement in the equality of food distribution within a country, and increases in food consumption mainly driven by income growth greatly influenced future hunger risk and were important elements in its long-term assessment.

Land use representation in a global CGE model for long-term simulation: CET vs. logit functions

Land use is one of the key elements in global computable general equilibrium models for food security and agricultural assessment. Constant elasticity transformation (CET) or logit functions have been used to allocate land. CET has the advantage that it is easily handled by modeling tools. However, it does not maintain area balance, whereas logit does. This article compares both functions in future scenarios and evaluates area balance violations of land use area made by CET. We found that agricultural goods production and land use were similar with CET and logit functions. The area balance violation generated by CET was large and heterogeneous across regions, but was small for the aggregated world total. In conclusion, the logit approach was preferable to the CET approach if any scenario assumption, such as consumption preference, changed by much from the base year, or if the main focus of the study was region-specific variables rather than global aggregates.

Consequence of climate mitigation on the risk of hunger.

Climate change and mitigation measures have three major impacts on food consumption and the risk of hunger: (1) changes in crop yields caused by climate change; (2) competition for land between food crops and energy crops driven by the use of bioenergy; and (3) costs associated with mitigation measures taken to meet an emissions reduction target that keeps the global average temperature increase to 2 °C. In this study, we combined a global computable general equilibrium model and a crop model (M-GAEZ), and we quantified the three impacts on risk of hunger through 2050 based on the uncertainty range associated with 12 climate models and one economic and demographic scenario. The strong mitigation measures aimed at attaining the 2 °C target reduce the negative effects of climate change on yields but have large negative impacts on the risk of hunger due to mitigation costs in the low-income countries. We also found that in a strongly carbon-constrained world, the change in food consumption resulting from mitigation measures depends more strongly on the change in incomes than the change in food prices.

Policy evaluations under environmental constraints using a computable general equilibrium model

Abstract In this paper, the AIM/Material model, a country-based computable general equilibrium model with recursive dynamics, is applied to Japan and simulations are carried out on various policies for the concurrent solution of CO2 reduction and solid waste management. To ensure the consistency of waste flows, the material balance is maintained in the model in addition to the monetary balance. Using this model, the GDP loss derived from the environmental constraints on CO2 reduction under the Kyoto Protocol and reduction of final disposal of solid wastes according to the target of the Japanese government is estimated to be 0.2% in 2010 compared to the business-as-usual case. On the other hand, the GDP loss in 2010 will be mitigated by 55% by introducing the following environmental policies: Enhancement of environmental investment, improvement of waste management technology, taxation reform for the introduction of waste power generation, and changes in consumption patterns.