The estimate for the climate sensitivity was 1.5 to 4.5 Â C ; and the average temperature was predicted to increase by 1.4 to 5.8 Celsius degrees between 1990 and 2100 , and the sea level was predicted to rise between 0.1 and 0.9 meters . The TAR estimate for the climate sensitivity is 1.5 to 4.5 Â C ; and the average surface temperature is projected to increase by 1.4 to 5.8 Celsius degrees over the period 1990 to 2100 , and the sea level is projected to rise by 0.1 to 0.9 meters over the same period .