The atmospheric concentrations of CO₂ observed at Ryori, Minamitorishima and Yonagunijima show seasonal variations, with high values from winter to spring and low values from summer to autumn, and an increasing year-on-year trend. The mean growth rates over the last decade are 1.91 ppm, 1.94 ppm and (1.95) (*) ppm at Ryori, Minamitorishima and Yonagunijima, respectively.

The global mean concentration of CO₂ in 2008 was 385.2 ppm based on analysis using data reported to the World Data Centre for Greenhouse Gases (WDCGG). This represents an increase of 38% relative to the concentration (280 ppm) seen before the start of the industrial era in about 1750. The mean growth rate over the last decade was 1.93 ppm/year, which is larger than the growth rate of 1.5 ppm/year in the 1990s.

Model calculations using CO₂ observation data from around the world have estimated that CO₂ fluxes from land areas increased slightly following a number of El Niño events (1986–1988, 1997–1998 and 2002–2003), with the exception of the period of 1991–1992 when fluxes from land areas decreased significantly due to the eruption of Mt. Pinatubo.

CO₂ concentrations in the seawater in areas along 137°E and 165°E in the subtropical North Pacific (in comparison with those in the air above) were lower in January–February and nearly the same or higher in June–August 2007.

The average concentration of CO₂ in the air above the ocean along the 137°E line between 7°N and 33°N was 388.0 ppm in the winter of 2008. This is 3.3 ppm higher than the value of the previous year and represents an average rate of increase of 1.7 ± 0.1 ppm/year since 1984. In the seawater along the same line, the concentration was 345.2 ppm, representing an increase of 0.6 ppm on the previous year and an average growth rate of 1.6 ± 0.2 ppm since 1984.

The atmospheric concentrations of CH₄ observed at Ryori, Minamitorishima and Yonagunijima show an overall increasing trend with seasonal variation. The increasing trend seen up to 2003 was not clear in 2004–2006, but the concentrations have increased again since 2007. Levels of CH₄ should be watched carefully.

The global mean concentration of CH₄ in 2008 was 1,797 ppb based on analysis using data archived at the WDCGG, exceeding the value of the previous year by 7 ppb. The CH₄ concentration in 2008 was about 2.5 times as high as those seen before the industrial era (typically about 715 ppb). The concentration increased largely in two consecutive years, but it is not possible to tell at this stage whether a new increasing trend has started.

The equatorial, subtropical and subarctic regions of the western North Pacific were proven to be the major sources of CH₄ as seen before, based on analysis of CH₄ observations in seawater and air.

The concentrations of CFC-11, CFC-12 and CFC-113 observed at Ryori have decreased since peaking in 1993–1994, 2005 and 2004, respectively.

Based on analysis using data up to 2008 reported to the WDCGG, concentrations of CFC-11 have shown a slightly decreasing trend since 1992–1993 in the Northern Hemisphere and 1993–1994 in the Southern Hemisphere. The growth rates of CFC-12 have declined since the 1990s, while concentrations have recently remained almost constant. Concentrations of CFC-113 have decreased slightly since 1993–1994 in the Northern Hemisphere and about 1997 in the Southern Hemisphere.

The annual mean concentration of N₂O observed at Ryori in 2008 was 323.2 ppb, and the average growth rate over the last decade was 0.8 ppb/year.

The global mean concentration of N₂O in 2008 was 321.8 ppb based on analysis using data archived at the WDCGG. This represents an increase of 19% relative to the concentration seen before the industrial era. The average growth rate over the last decade was 0.78 ppb/year.

Concentrations of CO have shown a slightly decreasing trend over the long term at all stations in Japan, but the trend is not significant due to large interannual variations.

The global mean concentration of CO in 2008 was about 91 ppb based on analysis using data archived at the WDCGG. Deseasonalized concentrations are the highest in the mid-latitudes of the Northern Hemisphere and lower in the Southern Hemisphere. The concentrations decreased temporally in 1992–1993 and increased temporally in 1997–1998 and 2002–2003, mainly in the Northern Hemisphere.

The concentration of surface ozone at Ryori increased slightly in general after the 1990s, but the increase has been insignificant since 2007.

The concentrations of surface ozone at the three stations in Japan show a seasonal variation with low values in summer. This is due to the fact that an oceanic air mass with a low ozone concentration dominates Japan in summer. A similar seasonal variation is also seen in tropospheric observations from ozonesondes, but high ozone levels are observed around the surface at Tsukuba occasionally from spring to summer, which accounts for photochemical generation of ozone.

In 2008, higher total ozone values continued over Japan in August–October at Tsukuba, and in July–October at Naha. Meanwhile, spells of lower total ozone values were observed in February–March and December at Sapporo, and in February, May and December at Tsukuba.

Observed total ozone decreased from the 1980s to the mid-1990s, but has remained unchanged or increased slightly since then at Sapporo and Tsukuba. At Naha, it has shown a slow increase since the mid-1990s.

In 2008, the ozone hole appeared in late August and developed to its largest size for the year at 26,500,000 km² on 12 September. It was its fifth largest extent in the previous ten years since 1999.

Total ozone values were relatively low in most regions of the world in 2008. Decreasing trends are significant from north Europe to west Siberia in the Northern Hemisphere and from southern South America to southern Africa in the Southern Hemisphere. Decreasing trends are less significant from southern Australia to the Southern Pacific.

In 2008, the daily accumulation of erythemal UV radiation averaged over June to August was relatively high at all stations. It was particularly high in June at Sapporo and in July and August at Naha. The highest monthly values were recorded for the month in February and March at Sapporo and in July and December at Naha.

The annual accumulation of erythemal UV radiation at Sapporo, Tsukuba and Naha shows an increasing trend in the long term, although it is not statistically significant (95% confidence interval) except for Sapporo.

In 2008, aerosol optical depth observed using sun photometers was the largest on 23 April at Ryori and on 25 April at Yonagunijima, which are analyzed to originate from forest fires in Siberia and Kosa, respectively.

The vertical distribution of aerosols observed using lidar at Ryori in 2008 showed large scattering ratios from September at a height of 18 km in the troposphere. It has been reported that the large scattering ratios may relate to aerosols originating from the eruption of the Kasatochi volcano in the Aleutian islands in August 2008.

In 2008, the annual cumulative number of days on which stations observed Kosa was 113. From 2 to 4 March 2008, Kosa was observed at many stations over the wide area from southern Tohoku to the Nansei Islands.

The annual cumulatative number of Kosa observations has been relatively large since 2000, but no significant long-term trend is seen due to large interannual variations.

In 2008, monthly cumulative direct solar radiation was significantly above the normal at Sapporo and significantly below the normal at Ishigakijima in September. Otherwise it was generally normal. There has been an increasing long-term trend at a rate of about 1 MJ/m² per decade since about 1990.

The monthly mean atmospheric turbidity coefficient was almost normal in 2008, while it was above the normal in January at Fukuoka. Atmospheric turbidity increased significantly after the eruption of Mt. Pinatubo in 1991, followed by a decrease by 1995 to the level seen before the eruption of Mt. El Chichón in 1982. It subsequently decreased further, and has recently been as low as the level seen before the eruption of Mt. Agung in 1963.

In 2008, the annual mean acidity was pH 4.5 at Ryori and pH 5.2 at Minamitorishima. At Ryori, it exceeded pH 5.0 shortly after the start of observations in 1976, but has since been in the range of pH 4.4–5.0. At Minamitorishima, it remained in the range of pH 5.5–5.8 from 1996 to 2002, but has recently declined.

In 2008, the concentration of floating pollutants observed in the sea adjacent to Japan was 3.3 pieces per 100 km. This figure has been on an increasing trend since the beginning of the 2000s, but it dropped in 2008.

Small amounts of floating tarballs were collected in the waters from off Sanriku to the east of Kanto in the summer of 2008. Floating tarballs have scarcely been collected since 1996 in the western North Pacific.

In 2008, the concentrations of cadmium in surface waters were 29–38 ng/kg to the southeast of Hokkaido from spring to summer, and 32–62 ng/kg along the 165°E line north of 40°N in summer. The mean concentration of cadmium in surface waters south of 30°N was 0.7 ng/kg, and has remained almost the same since 1997. The concentrations of mercury averaged for all observations were 6.1 ng/kg in surface waters and 5.2 ng/kg at a depth of 1,000 m, and have remained almost the same since 1986.