Global Analysis - Annual 1998
Note: The data presented in this report are preliminary. Ranks and anomalies may change as more complete data are received and processed. Effective September 2012, the GHCN-M version 3.2.0 dataset of monthly mean temperature replaced the GHCN-M version 3.1.0 monthly mean temperature dataset. Beginning with the August 2012 Global monthly State of the Climate Report, released on September 17, 2012, GHCN-M version 3.2.0 is used for NCDC climate monitoring activities, including calculation of global land surface temperature anomalies and trends. For more information about this newest version, please see the GHCN-M version 3.2.0 Technical Report.
*The GHCN-M version 3.1.0 Technical Report was revised on September 5, 2012 to accurately reflect the changes incorporated in that version. Previously that report incorrectly included discussion of changes to the Pairwise Homogeneity Algorithm (PHA). Changes to the PHA are included in version 3.2.0 and described in the version 3.2.0 Technical Report. Please see the Frequently Asked Questions to learn more about this update.
PLEASE NOTE: The ranks and temperature anomalies in this report represent the values known at the time the report was issued. The actual ranks will change as subsequent years are added to the dataset. The anomalies themselves may change slightly as missing or erroneous data is resolved. Also, in 2009, NCDC switched to ERSST version 3b (from version 2) as a component of its global surface temperature dataset. Because the versions have slightly different methodologies, the calculated temperature anomalies will differ slightly. For more information about this switch please see the Global Surface Temperature Anomalies FAQ .Global Mean Temperature Anomalies - 1998
The above time series shows the combined global land and ocean temperature anomalies from 1880 to 1998 with respect to an 1880-1997 base period. The largest anomaly occurred in 1998, making it the warmest year since widespread instrument records began in the late Nineteenth Century. The second warmest year was 1997, and seven of the ten warmest years have occurred in the 1990s.
A map of surface temperature anomalies for 1998, derived by merging both sea and land surface temperatures, shows the extent of the anomolously warm temperatures. This map product is based on both satellite and surface measurements. The anomalies from both data sets are with respect to a 1992 - 1998 base period, itself a warm period in global temperature history.
While anomolously warm temperatures are found throughout the tropics, the warmest anomalies occurred over North America and northern Asia. Most of China averaged above normal for the year, as did Australia and the mideast. The areas of extensive cold anomalies occurred over the mid latitudes of the eastern Pacific Ocean, and along the west equatorial central Pacific. The coldest anomalies existed in far eastern Siberia and the adjoining ocean.
The following time series shows the global land and sea surface combined mean temperature anomalies as well as the sea surface and land surface components separately for the 1880 - 1998 period, with respect to the base period 1880-1997.
Both the sea and land surfaces set record high anomalies in 1998, although the magnitude of the sea surface anomaly is smaller than the 'land only' anomaly. There is still a high correspondence between the independent land and ocean time series. These two surfaces generally have temperature anomalies that vary in concert with one another.
The land surface generally has larger anomalies, compared the ocean surface, because the ocean can store heat through a greater volume and water has a higher heat capacity. As a result, sea surface temperatures have a smaller interannual variability.
Much of the positive global temperature anomaly during 1998 can be attributed to the zonal band between 30°S-30°N, where anomalies were close to 1°C for the year, setting a new record. Widespread positive sea surface temperature anomalies in low latitudes contributed to the overall warm anomalies in this low latitude belt.
Record warmth was also generally observed over the mid- and high latitudes of the Northern Hemisphere. The warmth was most notable in North America, and eastern Asia. Much of Europe and western Asia also recorded warmer than normal temperatures for the year, but the anomalies were smaller than those observed elsewhere.
Temperatures from the Southern Hemisphere band 30°S - 90°S, while not record-breaking, were also above normal. South Africa and Australia generally were anomalously warm during the majority of the year, whereas northern Argentina averaged cooler than normal.
The mean global precipitation anomaly for land areas in 1998 was 27.9 mm (1.1 in) above the 1900 - 1997 average. Considerable differences were evident in precipitation departures across latitude bands. Much of the Northern Hemisphere received above average precipitation, while land areas in the Southern Hemisphere were, on average, drier than the 1900 - 1997 mean.
Record precipitation occurred in both the 85°N - 55°N and the 55°N - 30°N latitude bands. Precipitation over land areas between 30°N and 55°N averaged 3.1 inches (79.2 mm) above normal. This anomaly was more than 26 mm above the previous record set in 1979.
Precipitation also averaged above normal in the Northern Hemisphere high latitudes (55°N-85°N). Precipitation was 2.3 inches (58.7 mm) above the 1900 - 1997 average in this latitude band. This exceeded the previous record set in 1990 by 5 mm.
Precipitation in the 30°N - 10°N latitude band was also above the long term mean (1.8 inches,45.1 mm), but was much lower than the previous record anomaly of 3.9 inches (99.1 mm) recorded in 1956.
While precipitation amounts in high and mid-latitude land areas increased to record levels, the trend of much below normal precipitation continued in equatorial regions. Precipitation in the equatorial zone (10°S - 10°N) averaged 7.18 inches (182.4 mm) below the long-term mean.
Below average precipitation was also recorded throughout many land areas of the Southern Hemisphere. Precipitation was 1.1 inches (28.4 mm) below the 1900 - 1997 average in the Southern Hemisphere (figure not shown). The drier than average conditions south of 10°N were in contrast to the very wet conditions in the mid and high latitudes of the Northern Hemisphere and resulted in a globally averaged precipitation anomaly that was near the long term mean.