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The data presented in this report are preliminary. Ranks and anomalies may change as more complete data are received and processed. The most current data may be accessed via the Global Surface Temperature Anomalies page.
Temperature anomalies for December 2007 are shown on the dot maps below. The dot map, below left, provides a spatial representation of anomalies calculated from the Global Historical Climatology Network (GHCN) data set of land surface stations using a 1961-1990 base period. The dot map, below right, is a product of a merged land surface and sea surface temperature anomaly analysis developed by Smith and Reynolds (2005). Temperature anomalies with respect to the 1961-1990 mean for land and ocean are analyzed separately and then merged to form the global analysis. Additional information on this product is available.
Throughout the year, anomalously warm temperatures have covered much of the globe. The January-December 2007 map of temperature anomalies shows the presence of warmer-than-average temperatures across all land areas, with the exception of the western and southern countries in South America. Warmer-than-average Sea Surface Temperatures (SSTs) occurred in the Atlantic, Indian, and the Northwest Pacific oceans. Cooler-than-average conditions were observed in the Niño 1+2 and 3 regions, the northeastern Pacific and some areas in the southern oceans.
During December, there were above average temperatures across Mexico, Alaska, Scandinavia, Argentina, most of the eastern and western states of the contiguous U.S., and most of Asia. Cooler-than-average conditions occurred in central Europe, western Australia and parts of the east coast, the Middle Eastern region, the western countries of South America, and much of the central contiguous U.S. Meanwhile, SST anomalies in the Niño 3.4 region continued to decrease in December, indicating the strengthening of an ENSO cold event (La Niña). Please see the latest ENSO discussion for additional information.
The mean 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 map) are generally reflected by areas of positive and negative temperature anomalies at the surface, respectively. For other Global products see the Climate Monitoring Global Products page.
Images of sea surface temperature conditions are available for all weeks during 2007 at the weekly SST page.
Effective with the February 2006 report, NCDC transitioned from the use of the Operational Global Surface Temperature Index (Quayle et al. 1999) to the blended land and ocean dataset developed by Smith and Reynolds (2005). The differences between the two methods are discussed in Smith et al. (2005).
December 2007 ranked as the thirteenth warmest December since records began in 1880 for combined global land and ocean surface temperatures. The December land surface temperature ranked eighth warmest on record, while the ocean surface temperature ranked eighteenth warmest in the 127-year record. The global surface temperature for the combined January-December period was the fifth warmest year on record, while the global land surface temperature ranked warmest on record for the year.
| December | Anomaly | Rank | Warmest (or Next Warmest) Year on Record |
|---|---|---|---|
GlobalLandOcean Land and Ocean |
+0.81°C (+1.46°F) +0.25°C (+0.45°F) +0.40°C (+0.72°F) |
8th warmest 18th warmest 13th warmest |
1999 (+1.35°C/2.43°F) 1997 (+0.56°C/1.01°F) 2006 (+0.71°C/1.28°F) |
Northern HemisphereLandOcean Land and Ocean |
+0.98°C (+1.76°F) +0.30°C (+0.54°F) +0.56°C (+1.01°F) |
10th warmest 10th warmest 7th warmest |
1939 (+1.82°C/3.28°F) 2006 (+0.55°C/0.99°F) 2003 (+0.91°C/1.64°F) |
Southern HemisphereLandOcean Land and Ocean |
+0.27°C (+0.49°F) +0.21°C (+0.38°F) +0.22°C (+0.40°F) |
24th warmest 31st warmest 26th warmest |
1972 (+0.79°C/1.42°F) 1997 (+0.60°C/1.08°F) 1997 (+0.62°C/1.12°F) |
| January- December |
Anomaly | Rank | Warmest (or Next Warmest) Year on Record |
|---|---|---|---|
GlobalLandOcean Land and Ocean |
+1.02°C (+1.84°F) +0.38°C (+0.68°F) +0.55°C (+0.99°F) |
warmest 9th warmest 5th warmest |
2005 (+0.97°C/1.75°F) 2003 (+0.48°C/0.86°F) 2005 (+0.60°C/1.08°F) |
Northern HemisphereLandOcean Land and Ocean |
+1.19°C (+2.14°F) +0.42°C (+0.76°F) +0.71°C (+1.28°F) |
warmest 7th warmest 2nd warmest |
2005 (+1.03°C/1.85°F) 2005 (+0.54°C/0.97°F) 2005 (+0.72°C/1.30°F) |
Southern HemisphereLandOcean Land and Ocean |
+0.50°C (+0.90°F) +0.35°C (+0.63°F) +0.37°C (+0.67°F) |
8th warmest 10th warmest 10th warmest |
2005 (+0.82°C/1.48°F) 1998 (+0.50°C/0.90°F) 1998 (+0.53°C/0.95°F) |
The most current data may be accessed via the Global Surface Temperature Anomalies page.
The maps below represent anomaly values based on the GHCN data set of land surface stations using a base period of 1961-1990. During December 2007, above average precipitation fell over areas that include the midwestern and eastern states of the contiguous U.S. and parts of South America and Australia. Drier-than-average conditions were observed in the south central states of the contiguous U.S, Uruguay, eastern Argentina, parts of Europe and India. Additional details on flooding and drought can also be found on the December Global Hazards page.
Sea Surface Temperature (SST) anomalies continued to decrease across the eastern and central equatorial Pacific during December with cooler anomalies extending further east of the International Date Line. Meanwhile, warmer-than-normal anomalies were observed in the far western equatorial Pacific. These conditions are indicative of a strengthening ENSO cold event (shown in the adjacent animation of weekly SST anomalies). A comprehensive summary of December 2007 ENSO conditions can be found on the ENSO monitoring page. For the latest advisory on ENSO conditions go to NOAA's Climate Prediction center (CPC) and the CPC ENSO Diagnostic Discussion.
Images of sea surface temperature conditions are available for all weeks since 2003 at the weekly SST page.
As shown in the time series to the right, mean Northern Hemisphere snow cover extent during December 2007 was above average. Much of this can be attributed to a series of snow storms that struck much the Northern Hemisphere during the month of December. The December 2007 snow cover extent was the 9th largest extent over the 41-year historical record. The mean Northern Hemisphere December snow cover extent for the 1967-2007 period of record is 43.5 million square kilometers.
Snow cover for December 2007 across North America was much above average, being the 3rd largest extent, behind 1983 and 1985, since records began in 1967. During the month of December, much of the contiguous U.S. experienced severe winter storms that wreaked havoc causing transportation delays and leaving thousands of residents without electricity. The mean North America December snow cover extent is 16.6 million square kilometers for the 1967-2007 period of record.
As depicted in the time series to the right, Eurasia's snow cover extent in December was slightly below average and was the 18th lowest extent over the 41-year historical period. On average, Eurasian December snow cover extent is 26.9 million square kilometers for the 1967-2007 period of record.
Data were provided by the Global Snow Laboratory, Rutgers University.
Temperatures above the Earth's surface are measured within the lower troposphere, middle troposphere, and stratosphere using in-situ balloon-borne instruments (radiosondes) and polar-orbiting satellites (NOAA's TIROS-N). The radiosonde and satellite records have been adjusted to remove time-dependent biases (artificialities caused by changes in radiosonde instruments and measurement practices as well as changes in satellite instruments and orbital features through time).
These temperatures are for the lowest 8 km (5 miles) of the atmosphere. Information on the UAH and RSS sources of troposphere data is available.
| December | Anomaly | Rank | Warmest (or Next Warmest) Year on Record | Trend |
|---|---|---|---|---|
| UAH low-trop | +0.11°C/0.20°F | 13th warmest | 2003 (+0.47°C/0.85°F) | +0.14°C/decade |
| *RSS low-trop | -0.05°C/-0.08°F | 20th warmest | 2003 (+0.46°C/0.83°F) | +0.14°C/decade |
*Version 03_0
| January- December |
Anomaly | Rank | Warmest (or Next Warmest) Year on Record | Trend |
|---|---|---|---|---|
| UAH low-trop | +0.28°C/0.51°F | 4th warmest | 1998 (+0.51°C/0.93°F) | +0.14°C/decade |
| *RSS low-trop | +0.16°C/0.29°F | 9th warmest | 1998 (+0.58°C/1.04°F) | +0.17°C/decade |
*Version 03_0
These temperatures are for the atmospheric layer centered in the mid-troposphere (approximately 3-10 km (2-6 miles) above the Earth's surface), which also includes a portion of the lower stratosphere. (The MSU channel used to measure mid-tropospheric temperatures receives about 25 percent of its signal above 10 km (6 miles)). Because the stratosphere has cooled due to increasing greenhouse gases in the troposphere and losses of ozone in the stratosphere, the stratospheric contribution to the tropospheric average, as measured from satellites, may create an artificial component of cooling to the mid-troposphere temperatures. The University of Washington (UW) versions of the UAH and RSS analyses attempt to remove the stratospheric influence from the mid-troposphere measurements, and as a result, the UW versions tend to have a larger warming trend than either the UAH or RSS versions. For additional information, please see NCDC's Microwave Sounding Unit page.
The radiosonde data used in this global analysis were developed using the Lanzante, Klein, Seidel (2003) ("LKS") bias-adjusted dataset and the First Difference Method (Free et al. 2004). Additional details are available. Satellite data have been adjusted by the Global Hydrology and Climate center at the University of Alabama in Huntsville (UAH). An independent analysis is also performed by Remote Sensing Systems (RSS) and a third analysis has been performed by Dr. Qiang Fu of the University of Washington (UW) (Fu et al. 2004)** to remove the influence of the stratosphere on the mid-troposphere value. Global averages from radiosonde data are available from 1958 to present, while satellite measurements began in 1979.
Radiosonde measurements indicate that for the year 2007, temperatures in the mid-troposphere were 0.53°C (0.95°F) above average, resulting in the fourth warmest year since global measurements began in 1958. However, as shown in the table below, satellite measurements of the year 2007 middle troposphere temperatures varied from fifth to seventh warmest on record.
Depending on the source of analysis, December 2007 experienced either slightly cooler than average or slightly warmer than average mid-troposphere temperatures. Both, RSS and UAH analysis, show that December 2007 was slightly cooler than average. Adjustments provided by the UW suggest that December 2007 was slightly above average. Satellite measurement for the month ranked from fifthteenth to nineteenth warmest on record, depending on the analysis.
| December | Anomaly | Rank | Warmest (or Next Warmest) Year on Record | Trend |
|---|---|---|---|---|
| UAH mid-trop | -0.06°C/-0.11°F | 19th warmest | 1987 (+0.36°C/0.65°F) | +0.03°C/decade |
| *RSS mid-trop | -0.02°C/-0.04°F | 19th warmest | 2003 (+0.40°C/0.71°F) | +0.08°C/decade |
| **UW-UAH mid-trop | +0.05°C/0.09°F | 16th warmest | 2003 (+0.43°C/0.77°F) | +0.11°C/decade |
| **UW-*RSS mid-trop | +0.06°C/0.11°F | 15th warmest | 2003 (+0.50°C/0.90°F) | +0.13°C/decade |
*Version 03_0
| January- December |
Anomaly | Rank | Warmest (or Next Warmest) Year on Record | Trend |
|---|---|---|---|---|
| UAH mid-trop | +0.14°C/+0.25°F | 7th warmest | 1998 (+0.45°C/0.81°F) | +0.06°C/decade |
| *RSS mid-trop | +0.20°C/0.36°F | 5th warmest | 1998 (+0.50°C/0.90°F) | +0.12°C/decade |
| **UW-UAH mid-trop | +0.25°C/+0.44°F | 5th warmest | 1998 (+0.59°C/1.07°F) | +0.13°C/decade |
| **UW-*RSS mid-trop | +0.29°C/+0.53°F | 5th warmest | 1998 (+0.63°C/1.13°F) | +0.18°C/decade |
| RATPAC | +0.53°C/0.95°F | 4th warmest | 1998 (+0.74°C/1.33°F) | +0.15°C/decade |
*Version 03_0
The table below summarizes stratospheric conditions for December 2007. On average, the stratosphere is located approximately between 16-23 km (10-14 miles) above the Earth's surface. Over the last decade, stratospheric temperatures have been below average, in part due to the depletion of ozone. The large positive anomaly in 1982 was caused by the volcanic eruption of El Chichon in Mexico, and the sharp jump in temperature in 1991 was a result of the eruption of Mt. Pinatubo in the Philippines. In both cases the temperatures returned to pre-eruption levels within two years.
| December | Anomaly | Rank | Coolest Year on Record |
|---|---|---|---|
| UAH stratosphere | -0.58°C (-1.04°F) | 10th coolest | 2000 (-0.84°C/-1.51°F) |
| *RSS stratosphere | -0.41°C (-0.75°F) | 11th coolest | 2000 (-0.70°C/-1.25°F) |
*Version 03_0
For additional details on precipitation and temperatures in December, see the Global Hazards page.
Christy, John R., R.W. Spencer, and W.D. Braswell, 2000: MSU tropospheric Temperatures: Dataset Construction and Radiosonde Comparisons. J. of Atmos. and Oceanic Technology, 17, 1153-1170.
Free, M., D.J. Seidel, J.K. Angell, J. Lanzante, I. Durre and T.C. Peterson (2005) Radiosonde Atmospheric Temperature Products for Assessing Climate (RATPAC): A new dataset of large-area anomaly time series, J. Geophys. Res., 10.1029/2005JD006169.
Free, M., J.K. Angell, I. Durre, J. Lanzante, T.C. Peterson and D.J. Seidel(2004), Using first differences to reduce inhomogeneity in radiosonde temperature datasets, J. Climate, 21, 4171-4179.
Fu, Q., C.M. Johanson, S.G. Warren, and D.J. Seidel, 2004: Contribution of stratospheric cooling to satellite-inferred tropospheric temperature trends. Nature, 429, 55-58.
Lanzante, J.R., S.A. Klein, and D.J. Seidel (2003a), Temporal homogenization of monthly radiosonde temperature data. Part I: Methodology, J. Climate, 16, 224-240.
Lanzante, J.R., S.A. Klein, and D.J. Seidel (2003b), Temporal homogenization of monthly radiosonde temperature data. Part II: trends, sensitivities, and MSU comparison, J. Climate, 16, 241 262.
Mears, Carl A., M.C. Schabel, F.J. Wentz, 2003: A Reanalysis of the MSU Channel 2 tropospheric Temperature Record. J. Clim, 16, 3650-3664.
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.
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