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NOAA illustration of Earth and sun.Jan. 30, 2006 Scientists at the NOAA National Climatic Data Center in Asheville, N.C., today said the 2005 global temperature was statistically indistinguishable from the standing record set in 1998. Using two global data sets developed at NCDC, scientists determined that the 2005 average temperature was part of a string of very warm years—nine of the 10 warmest years on record have occurred since 1995. (Click NOAA illustration for larger view of Earth and sun. Click here for high resolution version. Please credit “NOAA.”)

In 1998, under the influence of an extremely strong El Niño episode, the annual global temperature surged beyond every other year on record. In the years after this El Niño event, annual global temperatures remained below the record established in 1998. In some years, the temperature was depressed by the presence of La Niña conditions in the equatorial Pacific. In other years, neutral or weak El Niño conditions were present. But in the span of seven years, the global temperature for 2005 returned to 1998 levels, without the warming influence of a very strong El Niño episode.

When calculating global temperatures, NCDC scientists, as well as those at NASA and in the United Kingdom, use methods that address areas of the globe with sparse observations or differences in measurement. The various methodologies result in very small differences (on the order of a few hundredths of a degree Celsius) between the global temperature estimates. However, these differences can affect individual yearly rankings.

One data set, in use at NCDC since the late 1990s, produced a global annual temperature for 2005 that was slightly below 1998. Another data set, which will become NCDC's operational version in February 2006, results in 2005 being slightly warmer than 1998.

Based on NCDC's current operational data set, the 2005 global temperature was 1.04 degrees F (0.58 degrees C) above the 1880-2004 long-term mean, compared to the 1998 global temperature of 1.12 degrees F (0.62 degrees C) above the long-term mean. The new data set indicates the 2005 global temperature was 1.12 degrees F (0.62 degrees C) above the mean, while 1998 was 1.06 degrees F (0.59 degrees C) above average.

The new data set also provides for the calculation of uncertainties in global temperature attributable to factors, such as sampling errors and biases from changes in observational instruments and measurement techniques through time. The uncertainties associated with the various factors and methodologies used in data set development make 2005 statistically indistinguishable from 1998.

During the past century, global surface temperatures have increased at a rate of near 1.0 degrees F/century (0.6 degress C/century), but the trend has been three times larger since 1976, with some of the largest temperature increases occurring in the high latitudes.

NOAA, an agency of the U.S. Department of Commerce, is dedicated to enhancing economic security and national safety through the prediction and research of weather and climate-related events and providing environmental stewardship of the nation's coastal and marine resources.

Through the emerging Global Earth Observation System of Systems (GEOSS), NOAA is working with its federal partners and nearly 60 countries to develop a global monitoring network that is as integrated as the planet it observes.

Relevant Web Sites
NOAA Climate of 2005 in Historical Perspective

NOAA National Climatic Data Center

Media Contact:
John Leslie, NOAA Satellite and Information Service, (301) 457-5005