The results of observations and analyses made by the JMA until the end of year 2005 with regard to the atmospheric and marine greenhouse gases, the ozone layer, ultraviolet radiation, atmospheric turbidity, precipitation and dry deposition, and marine pollution are as follows.
Carbon Dioxide (CO2)
| Yearly mean concentration in 2005
(ppm) | The difference from previous year's concentration
(ppm) |
| Japan | Ryori | 382.5 | +2.2 |
| Minamitorishima | 380.7 | +2.5 |
| Yonagunijima | 382.5 | +2.5 |
| Global | 379.1 | +2.0 |
| Ocean | The area along 137°E
in winter
（7～33°N）
| Mean concentration in 2005 (ppm) | 381.2（atmosphere）
341.1（seawater） |
| The difference from previous year's concentration (ppm) | +1.1（atmosphere）
+0.4（seawater） |
| Mean annual growth rate（ppm/year, 1984～） | 1.7（atmosphere）
1.6（seawater） |
| Subtropical region in the western North Pacific
（130～165°E, 11～30°N）
| Ocean uptake in 2005 （Estimation, PgC） | 0.064 |
| Ocean uptake in 2005 （Estimation, PgC） | -0.002 |
- The all growth rates in three Japanese stations exceeded 2 ppm/year in 2005. In general, CO2 growth rates are large during El Niño event, however, the El Niño event did not occur in 2005. The large growth rates in 2005 may be ascribed to increase of CO2 emission from the biosphere due to record-breaking high temperature (the highest record in the Northern Hemisphere) in 2005.
- The Global mean concentration of CO2 in 2005 was 379.1 ppm from archive data in the World Data Centre for Greenhouse Gases, which has increased by 35.4% compared with mean concentration (280 ppm) before the industrial age (1750).
- Growth rates in atmospheric CO2 for each 30° latitude zone had the highest peak from 1997 to 1998. The increase of CO2 emission in the tropical land area due to the global high temperature anomaly from the large El-Niño event in 1997/1998 is considered to cause this increase of growth rates. Growth rates in atmospheric CO2 in the middle and high Northern latitudes had a peak exceeding 3 ppm/year from 2002 to 2003 corresponding to the occurrence of the 2002/2003 El-Niño event. The mean annual growth rates in atmospheric CO2 was 1.9 ppm/year in the last 10 years.
- The differences in the CO2 partial pressure （⊿pCO2） between the sea water and the air along 137°E were lower between 11° and 16°N in January - February 2005 and were higher at 12°N and between 27° and 28°N in July 2005. The CO2 concentrations in the ocean between the 142°E and 165°E along the equator were close to that in the atmosphere in February and July 2005.
- The mean annual growth rate of the oceanic CO2 concentration averaged between 7°N-33°N along 137°E from 1984 to 2005 was 1.6±0.3 ppm/year, which was almost equal to those of atmospheric CO2 concentration, 1.7±0.1 ppm/year.
- The annual CO2 uptake estimated in the western subtropical North Pacific (11°N-30°N, 130°E-165°E) was 0.064 PgC in 2005. The uptake in 2005 was 0.002 PgC lower than that in 2004 and was similar to 0.058 PgC/year which is the mean from 1996 to 2005.
Methane (CH4)
| Yearly mean concentration in 2005 (ppb) | The difference from previous year's concentration
(ppb) |
| Japan | Ryori | 1,860 | -2 |
| Minamitorishima | 1,800 | -7 |
| Yonagunijima | 1,824 | -2 |
| Global | 1,783 | 0 |
- Based on the data archived at the WDCGG, the global mean concentration of atmospheric CH4 in 2005 was 1,783 ppb, which has increased by 154.7% compared with mean concentration (700 ppb) before the industrial age (1750).
- The growth rates of atmospheric CH4 in 1990s were generally less than those in 1980s, but the growth rate in 1998 was globally large except in low latitudes. The growth rates decreased afterward, but the growth rates increased again in 2002/2003 corresponding to the occurrence of the 2002 /2003 El-Niño event. The mean annual growth rates in atmospheric CH4 was 2.8 ppb/year in the last 10 years.
- In the western North Pacific, the subtropical and the equatorial region in January - February 2005 and the subarctic and subtropical region in June - July 2005 acted as CH4 sources. The CH4 concentrations in the atmosphere were about 1.8 ppm (1.73 - 1.88 ppm) and those in the ocean were 1.88 - 2.83 ppm.
Halocarbons
| Yearly mean concentration in 2005 (ppt) |
| Ryori | CFC-11 | 257 |
| CFC-12 | 551 |
| CFC-113 | 80 |
- The decreasing trends of CFC-11 and CH3CCl3 were seen in Japan (Ryori), while the increases of CFC-12 and CFC-113 were almost ceased. These trends result from the regulation under the Montreal Protocol on Substances that Deplete the Ozone Layer after the Vienna Convention for the Protection of the Ozone Layer.
Nitrous Oxide (N2O)
| Yearly mean concentration in 2005 (ppb) |
| Ryori | 320.0 |
| Global | 319.2 |
- The global mean concentration of N2O is gradually increasing. The mean concentration in Japan (Ryori) in 2005 was 320.0 ppb. The mean annual growth rate in the last 10 years was 0.6 ppb/year.
- Based on the data archived at the WDCGG, the global mean concentration of N2O in 2005 was 319.2 ppb. The mean annual growth rate in atmospheric N2O was 0.74 ppb/year in the globe in the last 10 years.
Carbon Monoxide (CO)
| Yearly mean concentration in 2005 (ppb) | The difference from previous year's concentration (ppb) |
| Japan | Ryori | 158 | -10 |
| Minamitorishima | - | - |
| Yonagunijima | 158 | -1 |
| Global | 95 | +1 |
(Data at Minamitorishima is missing due to a trouble of instrument.）
- Based on the data archived at the WDCGG, the global mean concentration of CO in 2005 was about 95 ppb.
- The enhanced CO concentrations from 1997 to 1998 were resulted from the large biomass-burning events that occurred in Southeast Asia and Siberia. The significant increase of CO growth rate in the Northern Hemisphere from 2002 to 2003 was possibly attributed to large forest fires due to high temperature anomaly from the El Niño event.
Tropospheric Ozone (O3)
| Yearly mean concentration in 2005 (ppb) | The difference from previous year's concentration (ppb) |
| Japan | Ryori | 39 | -2 |
| Minamitorishima | 29 | -2 |
| Yonagunijima | 36 | -6 |
- A gradual increase of O3 concentration has been observed at Ryori since 1990. The concentrations at Yonagunijima show a negative trend after mid-2003.
- The seasonal variation with low concentration in summer was obvious at Japanese three stations, being accounted for by summer dominating oceanic air mass around Japan with a low concentration of ozone. Ozone sonde observation showed a similar seasonal variation in the tropospheric O3 concentration, but sporadic increases of concentration were found in summer in the lower troposphere at Tsukuba, which might be resulted from photochemical production of ozone.
Ozone Layer
- In 2005, monthly mean total ozone values were almost normal throughout the year at Sapporo and Tsukuba. On the other hand, the highest monthly mean values since the beginning of monitoring (1974) were observed in January and March at Naha. Yearly variation of the total ozone over Japan is considered to be caused by the atmospheric flow fluctuations including QBO.
- The total ozone over Japan decreased in the 1980s except Naha. Since the mid-1990s, although the total ozone varies year by year, no significant trends or slight increasing trends have appeared the total ozone over Japan. Slight increasing trends since the beginning of monitoring are seen in the total ozone at Naha.
- In 2005, although the total ozone over the Syowa station from August to November were relatively low level, it rapidly increased around the end of November. The ozone hole in 2005 expanded rapidly in early August (earlier than normal), reached its annual maximum area 2,673 million km2, which was average size in the past 10 years, on 11 September. It shrank rapidly in mid-November and subsequently disappeared on 14 December.
- The decreasing trends in the global total ozone are significant except in the tropics. Generally, the decreasing trend is larger with increasing latitudes. Decreasing trends are large in the springtime in both hemispheres.
Ultraviolet Radiation
- In 2005, monthly means of daily accumulations of erythemal UV radiation were higher than normal or almost normal at Sapporoa and Tsukuba throughout the year except in April at Sapporo where it was lower than normal. On the other hand, the monthly means were lower than normal or almost normal at Naha throughout the year except October and November. These observations may reflect mainly weather conditions at each station.
- Increasing trends are seen in erythemal UV radiation data at all stations in Japan since the beginning of its observation in the early 1990s. Because decreasing trends are not seen in the total ozone in the same period, the cause of the above increasing trends in erythemal UV radiation will be attributable to the decreasing trends of amount of cloud and aerosol overhead.
Aerosols
- In 2005, aerosol optical depth observations using sun photometers at Ryori, Minamitorishima, and Yonagunijima showed a seasonal variation with a maximum in spring. In the latter half of 2005, the monthly mean Angstrom exponents at Minamitorishima and Yonagunijima were sometimes large compared with the normal values. It indicates that aerosols with comparativery small particle frequently appeared. Most of monthly aerosol optical depths at Minamitorishima were smaller than those at two other stations, while the particle size was estimated to be relatively large. This large particle in Minamitorishima is presumed to be a sea salt particle.
- According to the observation of vertical distribution of aerosols by the Lidar of Ryori in 2005, the scattering ratio in the troposphere was large compared with that in the stratosphere, indicating that aerosol concentration in the troposphere is generally high. The scattering ratio was large in the middle troposphere in spring and in the lower troposphere in summer.
Kosa (Aeolian dust)
- In 2005, the total number of days of Kosa observation was 451 days.
- From April 20 to 23 in 2005, a Kosa event was observed in the large range from Nansei islands to Tohoku district.
- From November 7 to 10 in 2005, a Kosa event was observed in the large range from Nansei islands to Kinki district. It was the autumn event after 2002.
Atmospheric turbidity
- Atmospheric turbidity observations using pyrheliometers at 14 stations in Japan showed seasonal variation with a maximum in summer due to water vapor increases and fluctuations in spring that may be resulted from aeolian dust events (Kosa).
- While the total number of days of Kosa observation was larger, the atmospheric turbidities by Kosa were not particularly large compared with usual spring during the spring 2005. Atmospheric turbidities in Shionomisaki were larger than usual year from June and July.
- The interannual variation showed impermanent increases after the large-scale volcanic eruptions. The atmospheric turbidity largely increased after the eruption of Mt. Pinatubo in June 1991, but it decreased gradually afterwards. After 1995, the atmospheric turbidity further falled to the level of before the eruption of Mt. Agung in February/May 1963.
Precipitation and Dry Deposition
- For precipitation chemistry, the annual mean acidity was pH 4.5 at Ryori and pH 5.0 at Minamitorishima in 2005. At Ryori, the annual mean acidities were higher than pH 5.0 during 1976-1977, and have varied with range pH 4.4~5.0 afterwards. At Minamitorishima, the annual mean acidity had been pH 5.5~5.8 since the beginning of the observation in 1996, but it has lagely decreased in these years.
Marine Pollution
- In 2005, the mean concentrations of floating pollutants were 8.8 pieces/100 km in the seas adjacent to Japan, 3.2 pieces/100 km and 1.0 pieces/100 km in the area 20-30°N and 0-20°N along 137°E line, respectively. In the all area of the western North Pacific, the concentrations of floating pollutants are less than 10 pieces/100 km after 2000. In the seas adjacent to Japan, it has increased since 2000.
- In 2005, very small amount of floating tar was collected at the south of the Kuroshio Extension in spring and the south of Honshu in autumn. Floating tar collected in the seas adjacent to Japan and the western North Pacific after 1995 has been lower levels than the before.
- In 2005, the concentrations of cadmium in surface waters were high southeast of Hokkaido (16-79 ng/kg). At 1000 m depth, those are in the range of 47-126 ng/kg, which is the similar to the previous level. In 2005, the mean concentration of cadmium in surface waters south of 30°N was 1.8 ng/kg, which has been almost at the same level since 1997. The concentrations of mercury averaged in all stations were 4.6 ng/kg in surface waters and 6.4 ng/kg at 1000 m depth, which have been the same level since 1986.
