In particular, the values given in the Fourth Assessment Report (AR4), published in 2007, are relatively low. This is the major reason for the changes in the projected rise in mean sea level. 2– 5) In each of the assessments, the IPCC used different climate models and scenarios for greenhouse gas (GHG) emissions. The future sea-level rises by 2100 projected in the First to Fourth Assessment Reports are 31–110 cm (Business as usual scenario), 13–94 cm, 9–88 cm and 18–59 cm, respectively. The IPCC has published four major assessment reports since its establishment in 1988. The latest scientific understanding has been assessed in a systematic way by the Intergovernmental Panel on Climate Change (IPCC).

Finally, planned responses to the adverse impacts will be discussed. Then this paper will examine the impacts of sea-level rise along with other factors of climate change, from both global and Japanese perspectives. First, the present status of observed sea-level rise, analyses of its causes, and future projections are summarized. This paper aims to give answers to these questions, based on a review of recent research in the relevant areas. They include: To what extent did climate change contribute to GMSL rise in the past? How much will GMSL increase in the future due to climate change? How serious are the impacts of the expected sea-level rise, and can human society respond properly to them? Given its potential significant effects, there are many questions which scientific research is expected to answer. Among such a wide range of fluctuations, climate change-related sea-level change has its own unique characteristics. There are also much shorter-term fluctuations in sea level, such as tide, waves and tsunamis. This fluctuation of mean sea level reached about 120 m. It is well known that the mean sea level has repeatedly had a large fluctuation due to the alternation of glacial and interglacial periods for the past several hundred thousand years in the Holocene. The causes of changes in sea level are not limited to those related to climate change. A specific word such as “global (local) sea-level rise” is used to denote the increase in global (local) mean sea level, where it is necessary to distinguish the two terms. When we refer to sea-level change (rise) in this paper, it means the change (increase) in mean sea level, including both global and local, in a general sense. The changes in local mean sea level usually differ from that of GMSL, because phenomena dominating in regional and local scales modify the global mean change. The mean sea level averaged over the global oceans is called global mean sea level (GMSL). 1) Mean sea level has also spatial distribution in the world. Mean sea level at a given position is defined as the height of the sea surface averaged over a period of time, such as a month or a year, long enough that fluctuations caused by tide and waves are largely removed. The level of the sea varies with time and space due to physical processes, such as tide and waves. Therefore, this issue has resulted in heightened attention internationally, as the effects of climate change become apparent. Particularly, countries which are located in low-lying areas as well as small islands are concerned that their land areas would be decreased due to inundation and coastal erosion and, at worst, a large proportion of their population may be forced to migrate to other countries. High projected rates of future sea-level rise have captured the attention of the world. Sea-level rise is one of the most significant effects of climate change. Finally, responses to adverse impacts will be discussed in order to clarify the implications of the sea-level rise issue for human society. Then the impacts are examined along with other consequences of climate change, from both global and Japanese perspectives. To what extent did climate change contribute to sea-level rise in the past? How much will global mean sea level increase in the future? How serious are the impacts of the anticipated sea-level rise likely to be, and can human society respond to them? This paper aims to answer these questions through a comprehensive review of the relevant literature. There are questions associated with sea-level rise which science needs to answer. It has drawn international attention, because higher sea levels in the future would cause serious impacts in various parts of the world. Sea-level rise is a major effect of climate change.

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