The Kyoto Protocol was finally put into practice on 16 February 2005. Developed countries, including Japan, are now anticipated to reinforce and promote their domestic CO₂ reduction measures by complementarily utilizing Kyoto mechanisms such as emissions trading and the clean development mechanism in order to achieve their reduction goals during the first commitment period (from 2008 to 2012). On the other hand, the impacts of global warming are becoming increasingly apparent all around the world and there is growing concern about these impacts, as exemplified by both the recent frequent occurrences of extreme weather phenomena and the measures taken to adapt to these phenomena.

　The scientific symposium “Avoiding Dangerous Climate Change” held in Exeter, UK in February 2005 revealed that global warming is worsening more rapidly than researchers thought and is having some extremely serious effects. This is something that may have been overlooked by researchers and their studies, and therefore further cooperation between climate system and model studies, and effect and adaptation studies is definitely necessary.

　As provided in Article 2 of the United Nations Framework Convention on Climate Change, the basic policy for prevention of global warming aims to stabilize both temperatures and greenhouse gas concentrations in the atmosphere. Consequently, we need to judge what constitutes a dangerous rise in temperature and the level of effect that this may have, and we need to judge “What constitutes danger?” in order to decide on a dangerous effect level. Science must always separate itself from politics, and policymakers have been assumed to be responsible for deciding “what constitutes danger.” However, in regard to the global warming issue, policymakers should not only be responsible for providing research data on its effects and our possible adaptation strategies, but they should also show us what level of effects is dangerous. To this end, we have an urgent task ahead of us to identify the dangerous effect level by promoting studies of effects and adaptations and integrating the knowledge obtained from individual fields and regions, and furthermore to promote research in cooperation with stakeholders, including policymakers.

　For this special issue of Global Environmental Research, the latest achievements in research on global warming effects and adaptations have been summarized by front-line researchers. Part I will introduce the latest research developments on future climate forecasting, which are the basis for predictions and assessments of the effects of global warming. Although there is a time lag (1–2 years) when the results of climate model-based prediction are used for studies on effect and adaptation, thanks to the global warming research initiative by the Council for Science and Technology Policy, cooperation between climate model-based studies and effect-related studies has grown increasingly close, and impact studies are now able to use the latest climate-prediction as climate scenarios. In parts II, III and IV, the latest research achievements in effects and adaptations in different fields will be summarized. These fields include ecosystems, agriculture and fisheries, water resources and drought risk. Part V is a summary of the latest studies on the effects on civil life, including human life and an evaluation from an economic point of view, none of which have been studied much so far. Part VI and Part VII summarize adaptation to global warming and studies on the dangerous impacts level and stability concentration, respectively. More advanced studies that will be useful for the prevention of global warming, including ones on dangerous effect levels, are expected to be conducted into effects and adaptations on the basis of accumulated past results.

　Recent advancements in the spatial resolution of climate models enable us to provide detailed future climate change scenarios including changes in regional climate and extreme events for impact assessment research. However, impact researchers should be aware that climate models are still burdened with sizable and inherent uncertainty caused by the incompleteness in the representation of physical processes, or “parameterizations.” The prediction of the quantitative amplitude of climate change, such as “climate sensitivity,” remains uncertain because it depends more on physical parameterizations than on resolution. However, some qualitative characteristics of projected climate change, such as geographical patterns, can be regarded as relatively reliable, though they remain at the level of “expert judgment” by climate researchers rather than fact. Criteria for determining the reliable aspects of projections include: a. statistical significance, b. inter-model consistency, c. interpretability, and d. the validity of key processes. It is difficult for impact researchers alone to judge whether these criteria are met by the projected climate change in question for their impact assessments. Therefore, active mutual communication between climate researchers and impact researchers is highly desirable to improve the overall reliability of impact assessment based on the results of high-resolution climate modeling.

　This paper illustrates studies on impacts of climate change on buna (Fagus crenata) forests in Japan and discusses issues for further study. The occurrence probability of buna forests was predicted by tree-based models. In the models, the response variable was presence/absence data on actual distribution of buna forests derived from the Third Mesh Vegetation Database (MVDB). Predictor variables comprised four climatic ones, i.e., the Warmth Index (WI), the mean minimum daily temperature of the coldest month (TMC), the precipitation in the warm season (PRS) and that in the cold season (PRW); and five non-climatic variables, i.e., topography, surface geology, soil, slope aspect and inclination. According to the models developed, DWS values, which evaluate the contribution of each predictor variable to a model, were the highest for PRW, followed by WI and TMC. They were low for PRS as well as for the non-climatic variables. The models showed climatic conditions for varying occurrence probability for buna forests, indicating that the variables controlling buna forest distribution and their thresholds vary among regions. Suitable habitats for buna forests, defined as the areas with over 0.5 in occurrence probability, cover 26,220 km² under the current climate. The area of suitable habitats is predicted to decrease to 9% of the current area under the CCSR/NIES climate change scenario and 37% under the RCM20 scenario. Under both scenarios, suitable habitats disappear in Kyushu, Shikoku and the Pacific Ocean side of Honshu, and decline greatly even in the Tohoku area of northern Honshu with the most extensive suitable habitats. The vulnerability index, which indicates the degree to which climatic conditions become worse for buna with climate change, is defined as the reciprocal of the occurrence probability, and its map was depicted. Buna forests in the areas which become unsuitable after climate change may gradually decline along with the death of the buna trees. This method is useful for predicting distributions of plants and vegetation on large spatial and temporal scales. The MVDB provides distribution data for vegetation types but not for plant species. It is necessary to construct databases on plant species distributions in Japan in order to predict habitats for various plant species.

　This paper introduces the results of our research projects for the Ministry of the Environment and discusses the possibility of using alpine vegetation to monitor global warming impacts in Japan. We plotted the trend of air temperature in the Japanese alpine zone, and then collected information on possible global warming impacts there, some of which we studied in detail. We elucidated the relationships between these impacts and meteorological factors. From these relationships and common future climate scenarios, we estimated potential global warming impacts in the Japanese alpine zone. We devised a measuring system that could operate properly in the alpine zone, where conditions are very severe. The system operates unmanned, runs on solar power and is small and lightweight. This paper discusses the possibility of monitoring global warming impacts using alpine vegetation in Japan.

　We analyzed the relationships between a long-term trend of rising air temperature and the lives of three species of creatures: red-cheeked starlings, paleotropical migratory birds that breed in Japan, small white butterflies and cherry trees (Somei-Yoshino cherry). We studied the egg-laying dates of the starlings in Niigata City located in the central part of Honshu, the largest of the four main islands of Japan. We obtained the first appearance dates of imagoes of small whites and the blooming dates of Somei-Yoshino cherry trees in Niigata from the Japan Meteorological Agency. Red-cheeked starlings had a significant tendency to start their egg-laying earlier each year; over the course of 28 years the laying date became 15.3 days earlier. Their progressively earlier egg-laying dates were significantly correlated with the rise in early spring temperatures in Niigata City, their breeding ground, and with the temperature of Naha City in Okinawa Prefecture, which is a migration stopover area in southern Japan. Since temperatures of both areas rose significantly during the period, it is likely that the temperature rise was the cause of the advanced egg-laying dates. The cherries’ blooming date also tended to become earlier year-by-year, showing a strong negative correlation with the temperature of early spring. The first appearance date of small whites showed no tendency to become earlier year-by-year, but showed a significant negative correlation with the temperature of early spring. We think that the reason for the cherry trees’ blooming date showing a stronger correlation with the temperature of early spring than the laying date of the starlings is because, unlike migratory birds, cherry trees grow in the same region for the entire year. Thus they are greatly influenced by the temperature of our investigation area (Niigata City). Also, unlike small whites whose chrysalises pass the winter close to the surface of the earth covered with snow, cherry buds are exposed to the air and so might have been more influenced by the long-term warming trend in early spring air temperatures.

　The current and latest works on the impacts of global climate change on agricultural production throughout the Asian region are introduced from the viewpoint not only of changes in natural environment (meteorological and water resources) but also of soil environment changes and increased insect pests. The results involve a model simulation of rice yields at different locations in Asia under increased CO₂ and temperature conditions. How the impact of global warming on the agro-ecosystem may influence food security in Japan and around the world is also discussed.

　We evaluated the vulnerability of Cryptomeria japonica (Japanese cedar) forests to global warming in Japan, using two indexes of plant water balance. One was an index of the water supply available to plants: the effective water-holding capacity of forest soils. The other was an index of plant dryness: the ratio of the annual transpiration of C. japonica forests to annual precipitation (Tr/P ratio). The effective water-holding capacities of four types of soil were estimated from soil-water retention curves calculated from soils’ physical properties. Tr/P ratios were calculated from the leaf gas exchange characteristics of C. japonica and climatic data. Both indexes were projected on nationwide maps using a grid-square system. Forestlands in areas with low effective water-holding capacity were found mainly in the Mikawa and Kinki regions, and in coastal areas of the Setouchi and Shikoku regions. We predict that the decline of C. japonica forests will accelerate if droughts occur frequently in these areas because of climate change. Under current climatic conditions, high Tr/P ratio areas were recognized around the Tone River in the Kanto Plain, in the Kou-shin region, and in coastal areas of the Kansai and Setouchi regions, where declines of C. japonica have been observed already. To evaluate future declines in C. japonica forests, we calculated Tr/P ratios using predicted climatic data (average of 2081-2100) based on a global warming scenario. The area of declining C. japonica forests may expand in the Kanto Plain and the eastern part of Aomori Prefecture in the future.

　The IPCC report published in April 2001, predicted sea surface water temperatures to increase by 3°C or so by 2100. This rise in seawater temperature is expected to have a significant impact on marine organisms distributed around Japan. In order to estimate the influence of warmer water, we performed a simulation study based on the assumption that sea surface water temperatures will increase by 1.0°C in 30 years (short-term), 1.4°C in 50 years (medium-term), and 2.9°C in 100 years (long-term). Data on the range of water temperatures marine organisms can inhabit were collected from previous studies and reports, and those data were applied to maps of seawater temperatures predicted over the short, medium, and long-term to study the changes in the distribution of areas of inhabitation.

　The results showed that a shift in the 29°C isothermal line (i.e., the line at which the maximum annual sea water temperature is 29°C) significantly influences the distribution of marine organisms, because the line coincides with the boundary between the zone of temperate marine organisms and that of sub-tropical ones. Though the isothermal line currently stays south of the island of Kyushu, it will supposedly move north as global warming proceeds, reaching the coasts of the Chugoku district and the island of Shikoku in 50 years, and those of the Kanto and Hokuriku districts in 100 years. The north-ward-shift of the 29°C isothermal line will not affect pelagic fish, such as mackerel, bonito, and Pacific saury, because they have strong swimming abilities, although their catch and fishing seasons will have to change somewhat, Demersal organisms like Alaska pollock and tanner crab will also not be influenced because water temperatures will rise only slightly in water deeper than 100 m.

　However, our simulation showed that the number of coastal marine organisms such as bastard halibut, red sea bream, abalone, and sea urchin will decrease significantly and the cultivation of Japanese amberjack, puffer, and seaweeds will also be impacted, especially in southern Japan, where these bad influences will be observed early in the future. These results indicate that we must urgently consider plans to protect fishery resources against global warming.

　This paper introduces examples of influences of global warming on water resources, and means of adaptation. Problems regarding water resources widely and complexly interact with each other. Therefore current technologies for coping with these influences and making integrated assessments include much uncertainty and are difficult to perform. Many researchers have done their best, however, to develop numerical simulation techniques which can evaluate each interaction and the integrated influences. Numerical simulations with GCM data are elucidating problems on floods and droughts. They also help us understand the impact of fresh water resource loss and human activities in coastal regions due to sea level rise. Although no models of water quality under the influence of global warming have been established yet, there is some qualitative understanding of the influence on water quality. Even though research and discussions for adaptation of water resources have already started, no predictions of social and climatic changes have been made yet. Therefore it is necessary to develop numerical models expressing the relationship between water resources and social conditions.

　In order to implement policy measures on practical water management related to floods to combat the influences of variations in rainfall characteristics arising from global warming, there is a need for quantitative indicators of future regional-based flood risk. In this study, changes in regional-based flood risk arising from global warming were analyzed based on records of observed precipitation obtained in Japan over the past 100 years. The effectiveness of the risk assessment was then evaluated using the results of projection of regional climate change over the next 50 and 100 years by the RCM20 regional climate model developed by the Japan Meteorological Agency (JMA) and the Meteorological Research Institute (MRI). Based on that changes in regional-based flood risk were forecasted. This study was based on a joint study between the National Institute for Land and Infrastructure Management (NILIM) and JMA/MRI under the Global Warming Research Initiative of the Council for Science and Technology Policy, Cabinet Office of Japan.

　Global warming is progressing, and its direct and indirect influences on various fields and in various regions have come to the surface. Although there have been few studies of the effect of global warming on civil life, I have summarized the effects that have been detected so far and those that are predicted to occur in the future. Effects on the natural environment, the atmosphere and the water environment have also become apparent, and this situation will presumably become more serious in the future. Also, there is a growing worldwide tendency for the frequency and intensity of extreme climate events and other unusual phenomena to increase, and once extreme weather events occur they often cause heavy and extensive damage. Therefore, I have summarized both our existing knowledge of the effects of heat waves and devastating rain events and our future predictions.

　In economic evaluation of the impacts of global warming on non-marketed goods or services, generally the Hedonic Price Method, Travel Cost Method or Contingent Valuation Method are used. However, because of the huge costs involved in applying these methods, utilization of the results of established research is recommendable on the basis of consideration of benefit transfer. There is no guarantee at all, however, of adjustability between individual values and overall values in measuring the economic value of plural impact items, because the economic value of each impact item is measured individually in the results of established research. This research aims to calculate a control total for managing adjustability between individual values and overall values in each field, and attempts to classify residential environments into four large fields and sixteen sub-fields and apply a conjoint analysis based on a questionnaire survey.

　The Kyoto Protocol, which became effective in February 2005, has been promoting a series of countermeasures against global warming on an international scale under the UN Framework Convention on Climate Change (UNFCCC). As a result of overwhelming impacts of the heat wave in Europe in 2003 and Hurricane Katrina that devastated the city of New Orleans in August 2005, there has been a growing concern over widespread climatic anomalies. This in turn has triggered increased interest in adaptation as a long-term countermeasure against the effects of global warming. In particular, developing countries, including small islands in tropical and subtropical zones, are vulnerable to climate change and variability, though they emit only small amounts of greenhouse gases. Therefore, adaptation is widely recognized as a primary countermeasure against global warming in these countries. In this paper, we attempt to draw a picture of the current understanding of the role and scope of adaptation by examining its purposes, nature and tools, as well as gaps in implementation and the social capacity for adaptation.

　Measures in response to global warming can be divided into two strategies: mitigation, which reduces climate change itself by the reduction of greenhouse gases, and adaptation, which reduces the impacts of climate change. Interest in the adaptation approach, in particular, has recently been rising both in Japan and internationally. Agricultural production is expected to be greatly impacted by future climate change, and enhanced knowledge through research on adaptation will be required in order to reduce these impacts. Against such a background, this paper summarizes the concept of adaptation and describes some existing studies on the impacts of global warming on agricultural production and studies on adaptation. With this as a basis, the paper discusses the crucial issue of studies concerning adaptation in the agricultural sector and presents suggestions. From a policy standpoint, the significances of studies differ between those that quantitatively estimate the impacts of global warming, taking adaptation measures into consideration and using climate scenarios as assumptions on the one hand, and studies aimed at selecting, promoting and implementing adaptation measures suitable for reducing impact damage on the other. While proceeding with these two types of studies in a balanced manner, it is necessary to promote close cooperation between both research communities. An important task with regard to the former type of study is further refinement of methods for assessing impacts on agricultural production taking extreme weather phenomena such as typhoons, continuous dry periods, etc., into consideration. For the latter type, important tasks include estimation of adaptation costs, clarification of factors that inhibit implementation of individual adaptations, and accordingly, grasping of the limitations that can be expected with regard to future adaptations.

　To prevent global warming, as stated in Article 2 of the United Nations Framework Convention on Climate Change (UNFCCC), stabilization of greenhouse gas concentrations in the atmosphere and limitation of temperature increases to certain levels are required. Identification of the critical level of temperature increase (i.e., the level where danger occurs) in order to allow ecosystems to adapt, food to be produced and economies to develop is a fundamental issue, as is the implementation of reduction measures to ensure that temperatures do not exceed this level. However, to identify dangerous levels of temperature increase, we need to examine the factors that influence the target temperature so as to ensure it does not exceed the threshold, i.e., the border between danger and safety. For example, the European Union (EU) has accumulated scientific knowledge and decided that 550 ppm should be the stabilization concentration of greenhouse gases, and a temperature rise of 2°C or less should be the long-range target for preventing global warming. Examination has started of the framework stated in the Kyoto Protocol for beyond 2013. To set up a specific long-range target, scientific knowledge of related factors such as stabilization concentrations, level of temperature increase, and effect threshold plays an important role. On the basis of past impact studies, this paper considers levels of temperature rise and thresholds for the impacts caused by global warming.

　To mitigate the dangerous impacts of global warming to the greatest extent possible, various greenhouse gas stabilization scenarios have been proposed. Integrated studies are proceeding on emission pathways and the costs of achieving climate stabilization, as well as on the impact risks of global warming. This paper summarizes the existing knowledge on temperature rise, mitigation measures and impact threshold values, with a particular emphasis on climate stabilization scenarios. It also gives an outline of the AIM/Impact [Policy] policy support tool developed for integrated assessment of global warming, and reports on the results of analyses of global mean temperature increase, emission pathways, and global warming impacts under GHG concentration stabilization constraints.

　The year 2007 is a monumental year for Global Environmental Studies, because of the publication of the IPCC 4th Report. It is our great pleasure to publish this Special Issue in 2007, which contains the results of recent studies in Japan. Our journal “Global Environmental Research” has just passed the ten-year milestone, and we are very glad for the good reaction and encouragement to our journal from all over the world.

　Japanese researchers have been publishing their results in diverse international as well as national journals in English in various fields in recent years. It is not always easy, however, to approach their works from the standpoint of readers, because they are found in so many different journals, reports or proceedings from the respective fields of environmental studies. The present special issue is dedicated, therefore, to presentation of their new results under various themes to policy makers, media, other researchers, etc., who have an interest in the broad fields of global environmental problems.

　Japanese environmental studies have been developing mostly in association with the WCP, IGBP, HDP, etc., since the 1980s. The results presented in this special issue were obtained mainly in Japan during the last several years. Based on the results in these papers, it can be summarized that the following activities are important and should be planned in the near future:

(A) To organize a project for describing the past and present status under the influence of global warming,

(B) To strengthen cooperative studies by researchers in natural sciences and social, cultural and human sciences,

(C) To encourage closer communication internationally, inter-regionally and also among different fields of science,

(D) To examine the processes and structures of literature collection (study results), writing, editing, reviewing and refereeing, the systems of which have not always been ideal in the case of the IPCC and MA. This problem affects not only international bodies, but national ones as well, and Japan should examine these processes and structures for itself,

(E) To intensify the activities of the Science Council of Japan, a national correspondence body for the ICSU. The Council should commit itself more strongly to global environment researchers, and

(F) To help foster research on global environmental problems in developing countries. It is hoped that the present issue will be useful in carrying out the tasks and solving the problems mentioned above.

　Many of the articles in this special issue were translated from the Japanese Journal version of ‘Global Environmental Research’ (Chikyu Kankyo) Vol. 11 No. 1. In some articles, further information was added.