The Rhone Glacier is changing rapidly. Since the first annual survey in 1874, the glacier has receded 1.9 km, which is an annual average rate of 13 ma⁻¹.

 The photograph to the left was taken in August 1900 by J.P. Fruh, the first geography professor of E.T.H., Switzerland. The image shows the lowest part of the ablation area descending a steep rock wall and forming an icefall. A side-moraine is forming at the left side of the glacier (orographic right-hand side), which dates to the last stage of the Little Ice Age. Further to the left, at the middle, a trace of an older side-moraine is visible, which dates back to the Egesen-Stadium, 12,000-11,000 aBP, indicating the end of the Last Ice Age (Würm in the Alps).

 The image to the right shows the Rhone Glacier in 2004, approximately 100 years later, by late Dr. U. Moser of the author's institute. The rate of retreat has accelerated in recent years to 20 ma⁻¹. A small lake appeared in 2004 between the rock wall and the glacier front. Since the lake appears to be permanent, the Swiss Topographic Office (Swisstopo) has given it an official geographic name, Rhonesee (Rhone Glacier Lake). The temperature change between the two images at high-altitude stations (above 2,000 m a.s.l.) in the Alps is 0.15 K per decade, with an accelerating trend. The change became especially prominent after 1980, and in the most recent 45 years, the rate has been 0.42 K per decade.

 Besides the changes to the glacier, the two images show how much the vegetation has changed during the last 100 years. Most visible is an invasion of Swiss Pine (Pinus cembra), which is now common in the upper Rhone Valley. If the climate continues to change at the present rate, the glacier is expected to lose 85% of its surface area by the end of the present century, surviving as a small mountain glacier with its front at about 3,000 m a.s.l.

(Atsumu OHMURA)

 The International Union of Geological Sciences (IUGS) has subdivided the Holocene into 3 stages, defining Stage boundaries at 8200 and 4200 years B.P. The basis for such a division is reviewed and it is concluded that while there is a good argument for a stage boundary at 8200 B.P., this is not the case for a boundary at 4200 B.P. The evidence for a globally significant event is insufficient to justify the use of the term Meghalayan stage (or age) to refer to the period after 4200 B.P. The decision of the International Commission on Stratigraphy to define the Meghalayan stage should be rescinded.

 The Holocene is the current geological era, which started 11,700 years before present and is divided into three stages: 8, 200, and 4,200 years before present. The early stage is the Greenlandian, the middle stage is the Northgrippian, and the late stage is the Meghalayan. According to proxy-based climate reconstructions, the global mean surface temperature during the Greenlandian and the Northgrippain was warmer than the Pre-industrial (PI). However, most model-based reconstructions, including those used by the Intergovernmental Panel on Climate Change (IPCC), indicate it was colder than PI. This is known as the Holocene temperature conundrum (HTC), which raises concerns regarding the model's ability to predict future climate change. The HTC is introduced, current knowledge is reviewed, and future direction of research is discussed.

 Contemporary land surface air temperature (SAT) change rate is a key issue in studies of climate change or global change. This article reviews the research progress on global land and regional climate warming rates, with a focus on the main results and findings of our own research group in the last two decades. It also discusses uncertainties and scientific questions currently facing researchers in this field and prospects for future research directions. Global land, Asian, Chinese, and smaller regional scale studies have consistently shown significant warming of surface climate over the past century, especially over the past half century. However, there is significant uncertainty in the existing researches regarding the magnitude and rate of the warming. The biggest uncertainty comes from the urbanization bias in the observation data series, followed by the heterogeneity of data spatial coverage and its change over time, and the maximum and minimum temperature average method in calculating daily, monthly and annual mean SAT. These issues need to be further investigated in future in order to obtain more solid and reliable research conclusions.

 For investigating climate changes, the use of meteorologically observed data was delayed. The reason for this delay was partly due to the belief that observational records were of too short duration, and the ranges of the change too small to detect climate changes. During the last half a century, meteorological records started to be used, especially for temperature and precipitation. The use of radiation was further delayed, owing to the belief that radiation is a stable component, lacking in temporal changes. Radiation, like other climatic elements, has measurable variations, whose ranges are sufficiently large to play a role in climate changes. The present article reviews the way in which shortwave (solar) global radiation was integrated into the research of climate changes. The developing process toward a realistic radiation balance of the atmosphere and the earth's surface was presented. The earlier faulty belief that the atmosphere absorbs only about 17% of the primary radiation from the space, giving unnaturally large solar radiation to the earth's surface has been systematically explained and the way to remedy this error is presented. Further, the solar global radiation was found to change in a decadal time scale as much as 8 Wm⁻². The first Global Brightening was experienced in early middle 20^th century, followed by the Global Dimming of the thirty years from 1960 to 1990, which was followed by a steep recovery to present. Aerosol was found as the main cause for the variation in solar radiation. These changes significantly affected other earth's surface processes, such as temperature and glacier mass balance. These discoveries were accomplished by the direct observation of radiation at the earth's surface.

 Recently, flood and drought disasters have been rapidly increasing due to global warming. In order to accurately predict changes in the water cycle, it is necessary to understand its multidecadal variability in nature through collaborations in the fields of meteorology and paleoclimatology. During the last decade, the summer climate in central Japan over the past 2600 years has been successfully reconstructed using the tree-ring cellulose oxygen isotope ratio, a proxy for summer relative humidity, in many wood samples obtained from living trees, old buildings, archaeological remains, and natural buried logs. Given that there are various periodicities of variations, including the multidecadal time scale, in the 2600-year time-series of tree-ring oxygen isotope ratios, it is worth investigating the meteorological and paleoclimatological characteristics of the time-series in detail. By analyzing modern observational data, it is found that summer relative humidity in central Japan is not only affected by regional air temperature, but is also controlled by sea surface temperature around Japan through changes in water vapor pressure. Moreover, during the past 2,000 years, relative humidity in central Japan reconstructed from the tree-ring oxygen isotope ratio has changed roughly in sync with the land surface temperature in Northern Hemisphere, and discrepancies between the two are entirely due to variations in sea surface temperature. In this way, it can be concluded that variations in the summer water cycle of central Japan are controlled explicitly by two factors, continental air temperature and oceanic water temperature, at every time scale including the multidecadal time scale. This means that collaborations in the fields of meteorology, oceanography, paleoclimatology, and paleoceanography are critical for accurately predicting climate change in the near future.

 Long-term variations of snowfall ratio during winter/early spring in the Sea of Japan side area of north-eastern Japan since 1665 are analyzed. Two long-term historical daily weather documents and instrumental meteorological data are used for this analysis. A time series of snowfall ratios from 1665 to 2005 is reconstructed. It is revealed that multi-decadal scale variations prevailed from the 17th to the early 20th century. In particular, the 1780s and the 1830s are characterized by high snowfall ratios, which coincide with periods of prolonged famines and unusually cool summers. Abrupt decreases of snowfall ratio are observed in the mid-1940s and from the 1970s to the 1990s. These abrupt decreases are unprecedented during the study period. It is revealed that these abrupt decreases were due to a recent rapid warming of the surface air temperature.

 Biologically, human beings are termed Homo sapiens. The first was born in Africa about 200,000 years ago. Some groups migrated from there about 60,000 years ago under a humid climate. The first ancestors of the modern Japanese arrived in the Japanese archipelago about 37,500 years ago. The ancestors of the most of modern Japanese experienced 10 innovative events: (1) First immigration of Homo sapiens to Japan during the Paleolithic period, (2) Invention of the world's oldest pottery and stone arrowheads (16,500 years ago, start of the Jomon period), (3) Human migration in Hokakido associated with the 8.2 ka event, (4) Beginning of Sannai Maruyama site, (5) Its collapse following an event at 4.2 ka, (6) Beginning of Yayoi period, (7) Transition from Yayoi period to Kofun period, (8) Beginning of aristocratic culture, (9) Transition from Imperial court to Feudal society, (10) Transition from Feudal to Modern society. These innovative transitions basically occurred under severe cold climates. (1) and (2) occurred during the cold Dansgaard-Oeschger and Heinrich events, respectively. (3) and (5) corresponded to global cooling events at the early/middle and middle/late boundaries of the Holocene, respectively. (4) (6) (8) (10) were related to global cold periods of the Holocene Bond events. (7) and (9) were influenced by regional cold extreme events associated with large volcanic eruptions and ENSO. Innovative events in Japan were accompanied by cold events on regional and global scales, although causality has not been clearly proven as yet.