Global Analysis - September 2011
Contents of this Section:
- The combined global land and ocean average surface temperature for September 2011 was the eighth warmest on record at 15.53°C (59.95°F), which is (0.53°C) 0.95°F above the 20th century average of 15.0°C (59.0°F). The margin of error associated with this temperature is +/- 0.11°C (0.20°F).
- Separately, the global land surface temperature was 0.87°C (1.57°F) above the 20th century average of 12.0°C (53.6°F), making this the fourth warmest September on record. The margin of error is +/- 0.24°C (0.43°F). Warmer-than-average conditions occurred across Europe, northern and western Africa, the Middle East, western Russia, the western and northeastern United States, and Mexico. Cooler-than-average regions included much of eastern Asia, western Canada and southeastern Alaska, and part of the central United States.
- Separately, the global land surface temperature was 0.87°C (1.57°F) above the 20th century average of 12.0°C (53.6°F), making this the fourth warmest September on record. The margin of error is +/- 0.24°C (0.43°F).
- The September global ocean surface temperature was 0.40°C (0.72°F) above the 20th century average of 16.2°C (61.1°F), making it the 14th warmest September on record. The margin of error is +/- 0.04°C (0.07°F). The warmth was most pronounced across the north central and northwest Pacific Ocean and within about the 30°N–40°N latitude belt across the Atlantic.
- The September global ocean surface temperature was 0.40°C (0.72°F) above the 20th century average of 16.2°C (61.1°F), making it the 14th warmest September on record. The margin of error is +/- 0.04°C (0.07°F).
- The United Kingdom marked its warmest September since 2006 and sixth warmest in the last 100 years, at 1.5°C (2.7°F) above the 1971–2000 average.
- Spain had its warmest September since 1990 for the and fifth warmest over the past 50 years, at 1.8°C (3.2°F).
- The combined global land and ocean average surface temperature for the January – September period was 0.51°C (0.92°F) above the 20th century average of 14.1°C (57.5°F), making it the 11th warmest such period on record. The margin of error is +/- 0.10°C (0.18°F).
- The January – September worldwide land surface temperature was 0.80°C (1.44°F) above the 20th century average — the 7th warmest such period on record. The margin of error is +/- 0.20°C (0.36°F). The global ocean surface temperature for the year to date was 0.41°C (0.74°F) above the 20th century average and was the 12th warmest such period on record. The margin of error is +/- 0.04°C (0.07°F).
- La Niña conditions strengthened during September 2011. According to NOAA's Climate Prediction Center, La Niña is expected to gradually strengthen further and continue into the Northern Hemisphere winter 2011/12.
- Arctic sea ice reached its annual minimum extent on September 9th at 4.33 million square km (1.67 million square miles), marking the second smallest extent on record. In September 2007, the sea ice extent dipped to 4.17 million square km (1.61 million square miles). According to the University of Washington's Polar Science Center, Arctic sea ice volume, which depends on ice thickness and extent, dropped to 4,000 cubic km (960 cubic miles) on September 10th, the smallest volume on record.
- The average Arctic sea ice extent during September was 34.5 percent below average, ranking as the second smallest September extent since satellite records began in 1979. The extent was 2.43 million square kilometers (938,000 square miles) below average and 310,000 square kilometers (120,000 square miles) above the record low September extent set in 2007.
- On the opposite pole, sea ice extent typically reaches its annual maximum extent during September, but environmental conditions extended the ice growth season into October. The September Antarctic monthly average extent was 0.9 percent above the 1979–2000 average, the 14th largest on record.
Temperature anomalies for September 2011 are shown on the dot maps below. The dot map on the left provides a spatial representation of anomalies calculated from the Global Historical Climatology Network-Monthly (GHCN-M) version 3 dataset of land surface stations using a 1961–1990 base period. The dot map on the right is a product of a merged land surface and sea surface temperature (SST) anomaly analysis developed by Smith et al. (2008). For the merged land surface and SST analysis, temperature anomalies with respect to the 1971–2000 average for land and ocean are analyzed separately and then merged to form the global analysis. For more information, please visit NCDC's Global Surface Temperature Anomalies page.
The return of La Niña conditions in the central equatorial Pacific Ocean in August brought slightly cooler temperature anomalies than in previous months where ENSO-neutral conditions prevailed. As would be expected for such conditions, temperature anomalies were lower across the globe—although still well above the 20th century average—compared with recent months. According to NOAA's Climate Prediction Center, La Niña conditions strengthened across the eastern half of the equatorial Pacific during September and are predicted to gradually continue to strengthen through the Northern Hemisphere winter 2011/12.
The global monthly averaged land surface temperature was 0.87°C (1.57°C) above average, the fourth warmest September on record. This positive anomaly was the smallest for any month since May 2011, when the previous La Niña ended. The Northern Hemisphere land temperature, where the majority of land mass is located, had its third warmest September on record and the Southern Hemisphere tied with 1995 as the third warmest. Europe, northern and western Africa, western Russia, the western and northeastern United States, Canada, and Mexico observed the warmest anomalies, while it was cooler than average across much of eastern Asia, and parts of the central United States.
In Western Europe, the United Kingdom marked its warmest September since 2006 and sixth warmest in the last 100 years, at 1.5°C (2.7°F) above the 1971–2000 average, according to the UK Met Office.
It was also warmer than average in Southern Europe. AEMet, Spain's Meteorological Agency, reported that it was the warmest September since 1990 for the country and fifth warmest in the past 50 years, at 1.8°C (3.2°F) above the 1971–2000 average.
In the Southern Hemisphere, although not possible to decipher from these dot maps, Australia experienced a wider range of daily temperatures than normal. According to the country's Bureau of Meteorology (BoM), the average maximum temperature for September across Australia was 0.92°C (1.65°F) warmer than normal. However, the average minimum temperature was 0.57°C cooler than normal, which was the lowest minimum temperature since 1985.
The monthly averaged global ocean temperature was 0.40°C (0.72°F) above the 20th century average, the 14th warmest September in the 132-year period of record but the coolest since 1999. Monthly sea surface temperature anomalies were similar in both the Northern and Southern Hemispheres, ranking 13th and 14th warmest, respectively. Across the globe, the coolest anomalies occurred across the central and eastern equatorial Pacific (the region where ENSO conditions are measured), the northeastern Pacific, the southeastern Atlantic, and the parts of southern oceans. The warmest anomalies were observed in the north central and northwest Pacific Ocean and within about the 30°N–40°N latitude belt across the Atlantic.
Combined, the monthly averaged global land and ocean temperature was the eighth warmest September on record, at 0.53°C (0.95°F) above the 20th century average. The Northern Hemisphere had its sixth warmest September and the Southern Hemisphere, which is comprised of nearly 80 percent ocean and almost 20 percent land, had its ninth warmest September on record.
La Niña conditions have been present during all months to-date in 2011, with the exception of May, June, and July, when ENSO-neutral conditions briefly returned. These conditions impacted temperatures around the globe, making the January–September combined global land and ocean temperature the 11th warmest such period on record and the coolest since 2008, at 0.51°C (0.92°F) above average. The January–September 2011 map of temperature anomalies shows regions with anomalously warm and anomalously cool temperatures. Overall, the global land surface temperature anomaly (0.80°C / 1.44°F) was nearly twice as high as the global sea surface temperature anomaly (0.41°C / 0.74°F) for this period, ranking as 7th warmest and 12th warmest, respectively.
The maps below represent anomaly values based on the GHCN-M version 2 dataset of land surface stations using a base period of 1961–1990. Precipitation anomalies on a month-to-month basis are often highly variable across the globe and even within regions.
September brought a mix of wet and dry conditions around the globe. Tropical cyclones Talas and Roke impacted Japan and nearby regions with intense precipitation; Nesat brought extremely heavy rainfall to the Philippines; and Irene and Lee drenched the northeastern United States. Irene also dumped heavy rain over the Dominican Republic. The southwest Asian monsoon brought heavy precipitation to Pakistan and eastern India. Other regions with much higher-than-normal precipitation included Colombia in South America and part of southeastern Africa around Mozambique, Zimbabwe, and Tanzania. Below-average precipitation anomalies across the southern tier of the United States are indicative of ongoing major drought conditions. It was also exceptionally dry across the western United States, much of eastern and southern South America, particularly eastern Brazil, much of central Asia, including nearly all of Mongolia, and much of Australia.
The Bureau of Meteorology reported that Australia as a whole experienced 26 percent below-average rainfall for the month, with the two driest regions in separate parts of the country: the Northern Territory in the north (78 percent below average) and South Australia in the south (50 percent below average). New South Wales was the only state with above-average rainfall.
According to AEMet, it was much drier than normal in Spain, with average rainfall across the country (16 mm / 0.63 in) about one-third of normal, making this month the driest September since 1988.
Details on major flooding and drought events around the world are available in the September 2011 Global Hazards report.
Peterson, T.C. and R.S. Vose, 1997: An Overview of the Global Historical Climatology Network Database. Bull. Amer. Meteorol. Soc., 78, 2837-2849.
Quayle, R.G., T.C. Peterson, A.N. Basist, and C. S. Godfrey, 1999: An operational near-real-time global temperature index. Geophys. Res. Lett., 26, 333-335.
Smith, T.M., and R.W. Reynolds (2005), A global merged land air and sea surface temperature reconstruction based on historical observations (1880-1997), J. Clim., 18, 2021-2036.
Smith, et al (2008), Improvements to NOAA's Historical Merged Land-Ocean Surface Temperature Analysis (1880-2006), J. Climate., 21, 2283-2293.