Global Analysis - December 2009
Note: GHCN-M Data Notice
An omission in processing a correction algorithm led to some small errors on the Global Historical Climatology Network-Monthly dataset (GHCN-M v3.2.0). This led to small errors in the reported land surface temperatures in the October, November, December and Annual U.S. and global climate reports. On February 14, 2013, NCDC fixed this error in its software, included an additional improvement (described below), and implemented both changes as GHCN-M version 3.2.1. With this update to GHCN-M, the Merged Land and Ocean Surface Temperature dataset also is subsequently revised as MLOST version 3.5.3.
The net result of this new version of GHCN-M reveals very small changes in temperature and ranks. The 2012 U.S. temperature is 0.01°F higher than reported in early January, but still remains approximately 1.0°F warmer than the next warmest year, and approximately 3.25°F warmer than the 20th century average. The U.S. annual time series from version 3.2.1 is almost identical to the series from version 3.2.0 and that the 1895-2012 annual temperature trend remains 0.13°F/decade. The trend for certain calendar months changed more than others (discussed below). For the globe, ranks of individual years changed in some instances by a few positions, but global land temperature trends changed no more than 0.01°C/century for any month since 1880.
NCDC uses two correction processes to remove inhomogeneities associated with factors unrelated to climate such as changes in observer practices, instrumentation, and changes in station location and environment that have occurred through time. The first correction for time of observation changes in the United States was inadvertently disabled during late 2012. That algorithm provides for a physically based correction for observing time changes based on station history information. NCDC also routinely runs a .pairwise correction. algorithm that addresses such issues, but in an indirect manner. It successfully corrected for many of the time of observation issues, which minimized the effect of this processing omission.
The version 3.2.1 release also includes the use of updated data to improve quality control and correction processes of other U.S. stations and neighboring stations in Canada and Mexico.
Compared to analyses released in January 2013, the trend for certain calendar months has changed more than others. This effect is related to the seasonal nature of the reintroduced time-of-observation correction. Trends in U.S. winter temperature are higher while trends in summer temperatures are lower. For the globe, ranks of individual years changed in some instances by a few positions, but global temperature trends changed no more than 0.01°C/century for any month since 1880.
More complete information about this issue is available at this supplemental page.
NCDC will not update the static reports from October through December 2012 and the 2012 U.S and Global annual reports, but will use the current dataset (GHCN-M v. 3.2.1 and MLOST v. 3.5.3) for the January 2013 report and other comparisons to previous months and years.
Contents of this Section:
- The combined global land and ocean average surface temperature for December 2009 was 0.49°C (0.88°F) above the 20th century average of 12.2°C (54.0°F). This is the eighth warmest December on record.
- The global land surface temperature for December 2009 was 0.35°C (0.63°F) above the 20th century average of 3.7°C (38.7°F)—the coolest December anomaly since 2002—and tied with 1915 as the 31st warmest December on record.
- The worldwide ocean surface temperature for December 2009 was the second warmest—behind 1997—on record for December, 0.54°C (0.97°F) above the 20th century average of 15.7°C (60.4°F). This could be attributed to the strengthening El Niño across the equatorial Pacific Ocean. According to NOAA's Climate Prediction Center (CPC), El Niño is expected to continue through the Northern Hemisphere spring 2010.
- The persistent El Niño in the equatorial Pacific Ocean contributed to the warmth observed in the tropical belt and of the overall ocean temperature. According to NOAA's Climate Prediction Center (CPC), El Niño is expected to continue through the Northern Hemisphere spring 2010.
- For the year to date, the combined global land and ocean surface temperature of 14.5°C (58.0°F) tied with 2006 as the fifth-warmest calendar year on record. This value is 0.56°C (1.01°F) above the 20th century average.
Please Note: The data presented in this report are preliminary. Ranks and anomalies may change as more complete data are received and processed. Effective with the July 2009 State of the Climate Report, NCDC transitioned to the new version (version 3b) of the extended reconstructed sea surface temperature (ERSST) dataset. ERSST.v3b is an improved extended SST reconstruction over version 2. For more information about the differences between ERSST.v3b and ERSST.v2 and to access the most current data, please visit NCDC's Global Surface Temperature Anomalies page.
Temperature anomalies for December 2009 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 (GHCN) 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 combined global land and ocean surface temperature for December 2009 was the eighth warmest December on record since records began in 1880. The combined global land and ocean temperature anomaly was 0.49°C (0.88°F) above the 20th century average. Sea surface temperatures (SST) during December 2009 were warmer than average across much of the world's oceans, with cooler-than-average conditions across the higher-latitude southern oceans and the northern parts of the Atlantic and eastern Pacific oceans. The December 2009 worldwide ocean SST ranked as the second warmest—behind 1997— on record, 0.54°C (0.97°F) above the 20th century average of 15.7°C (60.4°F).
Meanwhile, the worldwide land surface temperature tied with 1915 as the 31st warmest December on record. During December 2009, cooler-than-average conditions engulfed much of the contiguous United States, southwestern and south central Canada, northern Kazakhstan, Mongolia, northern China, and most of Russia. Temperature anomalies in most of these regions ranged from 2°C-6°C (4°F-11°F) below average. The anomalously cool conditions over much of northern Asia and North America may be associated with the record and near record December snow cover extent for Northern Hemisphere land areas. Other areas with below average conditions during December 2009 include New Zealand, Argentina, and southern Chile. The December 2009 worldwide land surface temperature anomaly was 0.35°C (0.63°F) above the 20th century average of 3.7°C (38.7°F)—the coolest December anomaly since 2002.
According to the U.K. Met Office, December 2009 was abnormally cool across the United Kingdom. Mean temperatures ranged from 1.5°C-3.5°C (2.7°F-6.3°F) below the 1971-2000 average. As a whole, the U.K. had its coolest December since 1995. Scotland and Northern Ireland each experienced their coolest December since 1981 and December 2009 ranked as the third and fourth coolest, respectively, since records began in 1914. The Irish Republic also experienced its coolest December in 28 years and December 2009 was the coolest of any month since February 1986 at a few stations, according to the Irish Meteorological Service.
Warmer-than-average conditions during December 2009 were observed across Alaska, eastern Canada, Australia, eastern Russia, southern Europe, southern Asia, and parts of northern Africa and northern South America. Alaska, eastern Canada, and eastern Russia had the warmest anomalies, ranging from 2°C-6°F (4°F-11°F) above average.
A vigorous upper-air pattern related to the Arctic Oscillation established very pronounced north-south bends in the jet stream, leading to the alternating regions of very warm and very cool conditions across North America, the northern Atlantic, Eurasia and the northern Pacific. However, just to the south of these areas, the tropical Northern Hemisphere (between the equator and 30°N) had its warmest December on record. The persistent El Niño in the equatorial Pacific Ocean contributed to the warmth observed in the tropical belt and of the overall ocean temperature. According to NOAA's Climate Prediction Center (CPC), El Niño is expected to continue through the Northern Hemisphere spring 2010.
In the Southern Hemisphere, the December 2009 average temperature for the Hemisphere as a whole (land and ocean surface combined) was 0.55°C (0.99°F) above the 20th century average—the second warmest December on record, behind 1997. The Southern Hemisphere ocean temperature during December 2009 also represented the second warmest December on record, with an anomaly of 0.54°C (0.97°F) above the 20th century average. The December 2009 Southern Hemisphere land temperature tied with 2003 as the eighth warmest on record.
The 2009 calendar year (January-December) map of temperature anomalies shows warmer-than-average conditions across most of the globe's surface area, with the exception of cooler-than-average conditions across central Russia, southern Canada, north central contiguous U.S., and the higher-latitude southern oceans, and along the eastern North Pacific Ocean. The combined global land and ocean surface temperature for the year tied with 2006 as the fifth warmest January-December period on record. This value is 0.56°C (1.01°F) above the 20th century average. For more information, please see our Annual Global report.
The average position of the upper-level ridges of high pressure and troughs of low pressure (depicted by positive and negative 500-millibar height anomalies on the December 2009 map, respectively) are generally reflected by areas of positive and negative temperature anomalies at the surface, respectively. For other Global products, please see the Climate Monitoring Global Products page.
Images of sea surface temperature conditions are available for all weeks during 2009 from the weekly SST page.
Temperature Rankings and Graphics
(out of 130 years)
|Warmest on Record|
|Land and Ocean||+0.49||+0.88||8th warmest||2006||+0.72||+1.30|
|Land and Ocean||+0.44||+0.79||15th warmest*||2006||+0.94||+1.69|
|Land and Ocean||+0.55||+0.99||2nd warmest||1997||+0.64||+1.15|
*Signifies a tie
(out of 130 years)
|Warmest on Record|
|Land and Ocean||+0.56||+1.01||5th warmest*||2005||+0.62||+1.12|
|Land and Ocean||+0.60||+1.08||8th warmest||2005||+0.71||+1.28|
|Land and Ocean||+0.53||+0.95||4th warmest||1998||+0.57||+1.03|
*Signifies a tie
The most current data may be accessed via the Global Surface Temperature Anomalies page.
The maps below represent anomaly values based on the GHCN dataset of land surface stations using a base period of 1961-1990. During December 2009, above-average precipitation fell over areas that included the south central and eastern contiguous United States, and across parts of South America, Europe, eastern Asia, and northeastern Australia. Drier-than-average conditions were present across parts of the northwestern contiguous United States, northern South America, the British Isles, Scandinavia, and the Pacific Islands, and much of Alaska.
Other notable precipitation extremes during December 2009 include copious rainfall across southern Brazil, prompting widespread floods and triggering deadly mudslides that claimed the lives of 26 people. The torrential downpours led to the overflow of rivers, forcing 180,000 residents to evacuate the area. Heavy rainfall caused floods and landslides in the city of Ayacucho, Peru, claiming nine lives and destroying homes and businesses. Additional details on flooding and drought can also be found on the December 2009 Global Hazards page.
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.