State of the Climate
Global Analysis
December 2004

National Oceanic and Atmospheric Administration

National Climatic Data Center

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Global Highlights:

Based on preliminary data, global average combined land and sea surface temperature was fifth warmest on record for December 2004
December temperatures were above average across Scandinavia, Japan, Alaska and the majority of the U.S., with below average temperatures over eastern Canada, the Middle East and the majority of Siberia
Precipitation during December was above average over the western coast of Alaska, the southwestern U.S. and Japan, with drier than average conditions in parts of Southeast Asia, the central portions of the U.S., and the majority of Europe
Sea Surface Temperatures (SSTs) continued to be above normal in the central equatorial Pacific

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.

Introduction

Temperature anomalies for December are shown on the two maps* below. The dot map on the left uses anomalies that were calculated from the Global Historical Climatology Network (GHCN) data set of land surface stations using a 1961-1990 base period. The map on the right is a blended product which uses satellite and surface anomaly values of measured land and ocean temperatures as well as SSTs with the base period of 1988-2004. Both maps reflect conditions during December 2004, indicating above average temperatures in Alaska, parts of West Africa, Norway, western and southern Australia, Japan and the majority of eastern Europe, with cooler than average temperatures over most of Siberia, the Middle East, Mexico, parts of Southeast Asia and the eastern half of Canada.

*The two maps below utilize different base periods and may reflect different anomaly values of land surface temperatures.

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Current month's Temperature blended SSMI map

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Above average sea surface temperatures are also evident in the blended product, above right. Warmer than average conditions covered large parts of the central and eastern Pacific in association with weak El Niño conditions. Sea surface temperatures were also warmer than average in much of the northern Pacific.

The mean position of upper level ridges of high pressure and troughs of low pressure (depicted by positive and negative 500 millibar height anomalies on the December 2004 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.

Temperature Rankings and Graphics

Current Month / Year-to-date

December	Anomaly	Rank	Warmest Year on Record
Global Land Ocean Land and Ocean	+0.41°C (+0.74°F) +0.50°C (+0.90°F) +0.47°C (+0.85°F)	23rd warmest 2nd warmest 5th warmest	1939 (+1.09°C/1.96°F) 1997 (+0.62°C/1.12°F) 1997 (+0.62°C/1.12°F)
Northern Hemisphere Land Ocean Land and Ocean	+0.34°C (+0.61°F) +0.57°C (+1.03°F) +0.48°C (+0.86°F)	32nd warmest warmest 8th warmest	1939 (+1.61°C/2.90°F) 2nd - 1997 (+0.57°C/1.03°F) 2003 (+0.66°C/1.19°F)
Southern Hemisphere Land Ocean Land and Ocean	+0.68°C (+1.22°F) +0.40°C (+0.72°F) +0.45°C (+0.81°F)	6th warmest 8th warmest 6th warmest	1972 (+0.79°C/1.42°F) 1997 (+0.61°C/1.10°F) 1997 (+0.64°C/1.15°F)

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January-December	Anomaly	Rank	Warmest Year on Record
Global Land Ocean Land and Ocean	+0.83°C (+1.50°F) +0.42°C (+0.76°F) +0.54°C (+0.97°F)	4th warmest 3rd warmest 4th warmest	1998 (+0.98°C/1.76°F) 1998 (+0.47°C/0.85°F) 1998 (+0.63°C/1.13°F)
Northern Hemisphere Land Ocean Land and Ocean	+0.90°C (+1.62°F) +0.50°C (+0.90°F) +0.66°C (+1.19°F)	3rd warmest warmest 2nd warmest	1998 (+1.03°C/1.85°F) 2nd - 1998 (+0.49°C/0.88°F) 1998 (+0.71°C/1.28°F)
Southern Hemisphere Land Ocean Land and Ocean	+0.56°C (+1.01°F) +0.37°C (+0.67°F) +0.40°C (+0.72°F)	4th warmest 7th warmest 6th warmest	1998 (+0.77°C/1.40°F) 1998 (+0.47°C/0.85°F) 1998 (+0.53°C/0.95°F)

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The most current data may be accessed via the Global Surface Temperature Anomalies page.

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Precipitation

The maps below represent anomaly values based on the GHCN data set of land surface stations using a base period of 1961-1990. The map to the left is precipitation anomalies measured in millimeters, the map to the right is the percentage of average (1961-1990) precipitation. During December 2004, above average precipitation fell in Alaska, the southwestern U.S., South Africa, parts of Scandinavia and Italy. Below average precipitation was observed in India, the southeastern U.S., Brazil, southeastern Asia, Portugal and Turkey.

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The maps below were produced from SSM/I satellite data using a base period of 1988-2004. The map on the left reflects surface liquid wetness conditions, while the map on the right reflects snow cover conditions for the month. Snow covered areas that are normally snow-free during this month will appear drier than average on the wetness image since a wetness value cannot be determined for regions that are snow covered. This is due to the snow crystalline structure which produces a considerable amount of scatter and makes it difficult for the SSM/I to accurately detect the surface conditions. Data in these areas that are normally snow covered are displayed as missing. The SSM/I products are experimental and are under continuing review and development.

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ENSO SST Analysis

Last week of the month's ENSO condtions Map

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Sea Surface Temperatures (SSTs) continued to be above normal in the central equatorial Pacific during December (as shown in the adjacent animation of weekly sea surface temperature anomalies), suggesting ENSO is in a weak warm phase. A comprehensive summary of December 2004 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 months during 2004 at the weekly SST page

Troposphere

Current Month
The tables below summarize mid-tropospheric conditions for December 2004. These temperatures are for the atmospheric layer centered in the mid-troposphere (approximately 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 6 miles.) Analysis of the satellite record that began in 1979 indicates that global temperatures are increasing in the mid-troposphere, but the magnitude of the trend differs based on the analysis methods used in adjusting for factors such as orbital decay and inter-satellite differences. The 1979-2004 trend for December is 0.02°C/decade based on data from the University of Alabama at Huntsville (UAH). Based on data provided by Remote Sensing Systems (RSS) the trend for December is 0.10°C/decade. The base period used in both data sets is 1979-1998.

December	Anomaly	Rank	Warmest Year on Record
UAH mid-troposphere	-0.02°C (0.04°F)	13th coolest	1987 (+0.36°C/0.65°F)
RSS mid-troposphere	+0.09°C (+0.16°F)	10th warmest	1987 (+0.38°C/0.68°F)

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Stratosphere

Current Month
The tables below summarize stratospheric conditions for December 2004. The stratosphere is located between 10-14 miles above the Earth's surface. Over the last decade, stratospheric temperatures have been below average in large part due to the depletion of ozone. The large increase in temperature in 1982 was caused by the volcanic eruption of El Chichon in Mexico, and the increase in 1991 was a result of the eruption of Mt. Pinatubo in the Philippines. Therefore the base period used in both data sets is 1984-1990 which was chosen to avoid contamination by these eruptions.

December	Anomaly	Rank	Warmest Year on Record
UAH stratosphere	-0.51°C (-0.92°F)	8th coolest	1982 (+1.24°C/2.23°F)
RSS stratosphere	-0.48°C (-0.86°F)	7th coolest	1982 (+1.08°C/1.94°F)

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Mid-tropospheric and lower stratospheric temperature data are collected by NOAA's TIROS-N polar-orbiting satellites and adjusted for time-dependent biases by NASA and 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).

For additional details on precipitation and temperatures in December, see the Global Hazards page .

References:

Peterson, T.C. and R.S. Vose, 1997: An Overview of the Global Historical Climatology Network Database. Bull. Amer. Meteorol. Soc., 78, 2837-2849.

Questions?

For questions on technical or scientific content of this report, please contact:

Ahira Sánchez-Lugo:
Ahira.Sanchez-Lugo@noaa.gov

For general climate monitoring questions, please contact:

CMB.Contact@noaa.gov

For climate data orders, please contact the National Climatic Data Center's Climate Services and Monitoring Division:

NCDC.Orders@noaa.gov

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State of the ClimateGlobal AnalysisDecember 2004

National Oceanic and Atmospheric Administration

National Climatic Data Center

Global Highlights:

Contents of this Section:

Introduction

Temperature Rankings and Graphics

Precipitation

ENSO SST Analysis

Troposphere

Stratosphere

Questions?

State of the Climate
Global Analysis
December 2004