Tsuneyuki Morita

Scenario analysis of global warming using the Asian Pacific Integrated Model (AIM)

Abstract The Asian Pacific Integrated Model (AIM) is a large-scale model for scenario analyses of green-house gas (GHG) emissions and the impacts of global warming in the Asian Pacific region. The AIM comprises two main models — the AIM/emission model for predicting GHG emissions and the AIM/impact model for estimating the impacts of global warming — which are linked by the global GHG cycle and the climate change models. This paper categorizes the scenarios that have been written so far in relation to global warming, and then, given fixed inputs, simulates the effects of global warming taking into account various uncertainties. Several recent outcomes from the AIM/impact model are then described. Assuming climate change scenarios deduced from AIM/emission and GCM experiments, primary impacts on water resources and natural vegetation are assessed.

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.

Overview of mitigation scenarios for global climate stabilization based on new IPCC emission scenarios (SRES)

This paper provides an overview of new emission mitigation scenarios that lead to stabilization of atmospheric CO2 concentrations, presented in this Special Issue. All of these scenarios use as their baselines the new IPCC scenarios published in the IPCC Special Report on Emission Scenarios (SRES), which quantify a wide range of future worlds. This means the new mitigation and stabilization scenarios are based on a range of future development paths that have fundamental implications for future emissions reduction strategies. Here, we refer to these new scenarios as “Post-SRES” mitigation scenarios. In addition to providing an overview of these new scenarios, this paper also assesses the implications that emerge from a range of alternative development baselines for technology and policy measures for reducing future emissions and stabilizing atmospheric CO2 concentrations. Nine modeling teams have participated in this joint effort to quantify a wide range of mitigation and stabilization scenarios. The nine modeling approaches involve different methodologies, data, regional aggregations and other salient characteristics. This pluralism of approaches and alternative baselines serves to cover some of the uncertainties embedded across a range of different mitigation and stabilization strategies. At the same time, several common trends and characteristics can be observed across the set of Post-SRES scenarios. First, the different baseline “worlds” described in the SRES scenarios require different technology/policy measures to stabilize atmospheric CO2 concentrations at the same level. Second, no one single measure will be sufficient for the timely development, adoption and diffusion of mitigation options to achieve stabilization. Third, the level of technology/policy measures in the beginning of the 21st century that would be needed to achieve stabilization would be significantly affected by the choice of development path over next one hundred years. And finally, several “robust policy options” across the different worlds are identified for achieving stabilizations.

Emissions Scenarios Database and Review of Scenarios

This paper reviews and analyzes more than 400 scenarios of global and regional greenhouse gas emissions and their main driving forces - population, economy, energy intensity, and carbon intensity - drawn from an extensive literature survey and summarized in a database. This new and growing database is available online, which makes summary statistics on these scenarios widely available. The scenarios in the database were collected from almost 200 different literature sources and other scenario evaluation activities. The ultimate objective of the database is to include all relevant global and regional emissions scenarios. This paper shows how the database can be utilized for the analysis of greenhouse gas emissions ranges across the scenarios in the literature and for the analysis of their main driving forces. The scenarios in the database display a large range of future greenhouse gas emissions. Part of the range can be attributed to the different methods and models used to formulate the scenarios, which include simple spreadsheet models, macroeconomic models and systems-engineering models. However, most of the range is due to differences in the input assumptions for the scenarios, in particular of the main scenario driving forces. Special emphasis is given to an analysis of medians and ranges of scenario distributions and the distributions of the main scenario driving forces in the database. The analysis shows that the range for projected population increase in the world, across the scenarios in the database, is the smallest of all main driving forces (about a factor of 3 in 2100). The range of economic growth, measured by the gross world product, and the range of primary energy consumption vary by a factor of 10 in 2100. Carbon intensity of energy, an indicator of the degree of technological change, varies by nearly two orders of magnitude in the year 2100. In addition, this paper presents the first attempt to analyze the relationships among the main scenario driving forces. Subsequent papers in this special issue give further analyses of the relationships among the main scenario driving forces and their other relevant characteristics.

The AIM/end-use model and its application to forecast Japanese carbon dioxide emissions

Abstract The Asian-Pacific Integrated Model (AIM) has been developed for predicting greenhouse gas emissions and evaluating policy measures to reduce them. Two socioeconomic scenarios were assumed and CO 2 emissions were predicted based on these scenarios and policy intervention assumptions. It is found that mitigating CO 2 emissions by 6% to the 1990 level is possible without scaling back productive activities or living standards in Japan. However, this cannot be achieved by relying on the market mechanism alone. Our analysis shows that it is indispensable to introduce new policies and measures such as a carbon tax and subsidies.

Global and Regional Greenhouse Gas Emissions Scenarios

This article presents a set of 30 greenhouse gas (GHG) emissions scenarios developed by six modeling teams. The scenarios describe trajectories up to 2100 by four world regions. Today the distribution of both income and GHG emissions is very unbalanced between various world regions. Furthermore, the relative importance of individual gases and sources of emission differ from region to region. A feature shared by all scenarios is higher growth rates of population, income and GHG emissions in the current developing countries (DEV) than in industrialized countries (IND). Today the DEV regions account for about 46% of all emissions, but by 2100 no less they contribute 67–76% of the global total. By that same year the total income generated in the DEV regions reaches 58–71% from only 16% in 1990. As a result of these two developments, GHG emissions per unit of income converge over time. Carbon emitted from fossil fuel use remains the primary source of GHG emissions over the next century; by 2100 CO2 makes up 70 to 80% of total GHG emissions. The role of sulfur warrants special attention. Contrary to many earlier studies, all scenarios presented here assume that sulfur emissions are controlled in all regions sooner or later, and to various degrees. As sulfur plays a role in cooling of the atmosphere through formation of sulfate aerosols, a local effect, this abatement constitutes a relative local warming effect. The decrease of sulfur emissions is already observed the IND regions, and is expected also in ASIA after an initial rise.

Estimation of embodied CO2 emissions by general equilibrium model

Abstract This study estimates the extent to which embodied CO2 emissions are increased or reduced when a socioeconomic structural change occurs. Embodied CO2 emissions were estimated by Input–Output models (I–O models) and a General Equilibrium model (GE model), and the respective results were compared. The embodied CO2 emissions differ greatly depending on the assumptions of the total system. The embodied CO2 emissions obtained by I–O models are much larger than those obtained by the GE model. In some cases, the total CO2 emissions increase even if less intermediate inputs are required owing to technological improvement. It is shown that taking I–O type embodied emissions alone into consideration is insufficient for the estimation of policy effects. Careful consideration is necessary to effectively reduce emissions when production and consumption are interconnected in a complex way.

Long-Term GHG Emission Scenarios for Asia-Pacific and the World

Abstract Because the Asia-Pacific region has half of the world population and is experiencing very rapid economic growth, it is becoming more important in the global response to the climate change issue. However, the best way to respond to the issue depends largely on the development patterns of this region, and this region has a wide range of development path options. This article analyzes long-term greenhouse gas (GHG) emission scenarios depending on alternative development paths in the developing countries of this region (referred to hereafter as “the Developing Asia-Pacific”), as well as in the world. The Asian-Pacific Integrated Model, or AIM, is revised and applied to the quantification of narrative storylines into scenarios of socioeconomic development, and GHG emissions from energy use, land use change, and industrial production processes are simulated. The results show that GHG emissions from both the Developing Asia-Pacific and the world as a whole would rapidly increase in the first half of the next century, while the emission scenarios would diverge significantly in the latter half. The range of the Developing Asia-Pacific scenarios are wider than those of other regions, and include the possibilities of both keeping emissions low with high economic growth and also causing a rapid increase of emissions with low economic growth. The Developing Asia-Pacific, as well as the rest of the world, have to consider more sophisticated policies to reduce GHGs in the first half of next century, and also must consider a number of robust policies to prepare for the wide range of future development paths.

Development of an end-use model for analyzing policy options to reduce greenhouse gas emissions

An end-use energy model is presented for assessing policy options to reduce greenhouse gas emissions. This model evaluates the effects of imposing a carbon tax on various carbon-emitting technologies in order to reduce CO/sub 2/ emissions. It also estimates the effects of a carbon tax in combination with subsidies. The problem can be formulated in terms of two-level mathematical programming. An algorithm is proposed and applied to estimate Japanese CO/sub 2/ emissions. The conditions under which energy-saving technologies would be selected are analyzed using various carbon tax rates and subsidies, and the reduction of CO/sub 2/ emissions is calculated based on the introduction of such technologies. It is found that a low carbon tax such as 3000 yen per metric ton of carbon (tC) is insufficient to stabilize CO/sub 2/ emissions at the 1990 level in Japan, and that a tax of 30000 yen/tC would be necessary. However, the proposed algorithm shows that total emissions in Japan in the year 2000 can be stabilized at the 1990 level with a tax of 3000 yen/tC if the tax revenues are used to subsidize the introduction of energy-saving technologies.

Energy technology changes and CO 2 emission scenarios in China

With its recent rapid economic growth, China has become one of the foremost countries in terms of energy consumption and CO2 emission. The extent of future CO2 emission in China and how to reduce it are important issues. This paper presents the forecast results of CO2 emission studies for several cases and assesses the various policy options by using the AIM/end-use model and analyzing CO2 reduction costs for various sectors. The results shrued that CO2 emission will increase with the rapid economic development in China, but it is possible to slow down the CO2 emission growth rate by using technological progress, efficient markets, and by adopting policies for CO2 reduction.