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Climate bulletin - September 2014

Temperature anomalies relative to the 1961 - 1990 average.

Summary of the world's climate in September 2014.

The global average temperature for September 2014 as estimated from the HadCRUT4 data set was 0.59 ± 0.19 °C above the 1961-1990 average. Although the central estimate of 0.59 °C for September 2014 suggests that it was the warmest September on record, the difficulties of measuring global average temperature are such that it is not possible to provide a definitive ranking. Other very warm Septembers were comparable within the estimated margin of error. Other global temperature data sets maintained by NASA GISS and NOAA NCDC also show that September was a very warm month globally. Sea-surface temperatures in the tropical Pacific were close to or above average in September, but did not exceed El Niño thresholds. They were particularly high (relative to average) in the western Pacific.

During September, the global average air temperature over land was warmer than the long term average (0.82 ± 0.29 °C). Cooler than average land surface temperatures were recorded in eastern and northern Canada, and central Russia. In central Russia, temperatures fell below the 10th percentile. Except for northern Australia and New Guinea, most other land areas were warmer than average, with significant warmth - exceeding the 90th percentile of occurrence - extending from the UK down to north Africa and across from there to western Pakistan. Coastal areas of Alaska and the western US as well as large areas of South America, Madagascar, western Australia and parts of south east Asia were also unusually warm.

Sea-surface temperatures were generally warmer than average in September. The global mean sea-surface temperature was 0.57 ± 0.08 °C above the long term average. The northern hemisphere was particularly warm, with the northern hemisphere average being 0.89 ± 0.07 °C above the 1961-1990 average. Unusually high sea-surface temperatures were widespread in September 2014 as they were in August. Large areas of both the North Atlantic and Pacific were above the 98th percentile. There were only limited areas of below average temperatures in the northern hemisphere. In the southern hemisphere, cooler than average sea-surface temperatures were observed in the east Pacific, parts of the South Atlantic and along the southern edge of the Indian Ocean. Large areas of the Southern Ocean were also cooler than average. Warmer than average sea-surface temperatures were observed in the eastern and south-western Indian Ocean and around the southern fringes of Australia.

According to figures from the US National Snow and Ice Data Center, Arctic sea-ice extent was 5.28 million square kilometres. September is the month which has the lowest long term average ice extent. 2014 was nominally the 6th least extensive September on record. Southern hemisphere sea ice extent was 20.03 million square kilometres. September 2014 was nominally the most extensive September on record. This continues a series of record high extents for Antarctic sea ice starting with April 2014.

Last updated: Nov 26, 2014 2:12 PM