Observed long-term trends of the surface air temperature are treated, comparing with the results of numercal experiment for increase of greenhouse gases. Global mean of the marine surface air temperature, which is not suffered from the local effect of urbanization, is estimated from 1900 to 1986 using COADS . Linear regression of the annual mean temperature gives a trend of about + 0.32°C/86 years, that is consistent with the results of numerical experiment by upwelling-diffusion climate model. After the 1960s with remarkable increase of carbon dioxide, significant warming is seen in Southern Hemisphere while no appreciable warming for Northern Hemisphre. This interhemispherical asymmetry of the temperature trend is opposite to the results of numerical simulation by atmosphere-ocean coupled model . This discrepancy between observation and numerical simulation should be possibly dissolved by taking account of the effect of sulphate aerosols on albedo for insolation. In the northernmost zone of the Atlantic Ocean, significant cooling appears after the 1960s together with noticeable decrease of salinity and temperature of the water in the surface layer. These facts suggest some variation of the thermohaline circulation.
