NOAA REPORTS 2005 GLOBAL TEMPERATURE SIMILAR TO 1998 RECORD WARM YEAR
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
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