STATE OF THE CLIMATE IN 2004
Abstract From a global perspective, the annual average surface temperature in 2004 was the fourth highest value observed since regular instrumental records began in 1880. Global surface air temperatures in 2004 were 0.44°C (0.79°F) above the 1961–90 mean, according to both the U.S. and U.K. archives. Observations of the global annual mean temperature in 2004 from the combined lower and middle troposphere was 0.38°C (0.68°F)—the fourth warmest year in the 47-yr archive of worldwide radiosonde observations, and the ninth warmest year out of the past 26 based on satellite measurements. The average precipitation anomaly over global land areas in 2004 was 10.7 mm above average, which was ∼1% above the 1961–90 mean, and the first year since 2000 that the global mean value was wetter than average. Northern Hemisphere sea ice extent was the third lowest on record for the year, dating back to 1973. The annual snow cover extent over Northern Hemisphere land areas was 25.1 million km2, which was the 25th most extens...