Estimated global (land area only) mean temperatures during 1996 (determined from station data received over the GTS and computed relative to the 1961-90 base period means) were the coolest in the past 11 yr, and only the 19th warmest out of 46 years dating back to 1951 (Fig. 1a). The anomaly for 1996 (0.06°C above the 1961-90 mean of 11.5°C) was the lowest since 1985 (0.11°C). The decrease from 1995 to 1996 is the largest since that observed between 1981 and 1982.
There was relatively little intermonthly variability in the global land-only surface temperatures during 1996 (not shown), with all months averaging within 0.30°C of the long-term mean. Each of the four seasons [December-February (DJF), March-May (MAM), June-August (JJA), and September-November (SON)] during 1996 were cooler than the corresponding 1995 season. MAM (0.03°C) and SON (0.08°C) averaged below the 1961-90 base period mean, while DJF (0.12°C) and JJA (0.19°C) averaged above the mean. Only May and December were warmer than their 1995 counterparts. June 1996 (although cooler than June 1995) was still the sixth warmest June dating back to 1951 (June 1995 was fourth).
Much of the relative decrease in global temperature during 1996 occurred in the Northern Hemisphere extratropics, where mean land temperature anomalies decreased from 0.42°C in 1995 to 0.04°C in 1996 (Fig. 1c). This was the first time that mean Northern Hemisphere land temperatures averaged below normal since 1985.
In contrast, mean temperature anomalies in the Southern Hemisphere extratropics increased from 0.08°C in 1995 to 0.13°C in 1996 (Fig. 1d), while anomalies decreased slightly in the tropical belt from 0.41°C in 1995 to 0.38°C above normal in 1996 (Fig. 1b). Mean land temperatures in the global Tropics have been above normal since the beginning of the decade, coincident with the beginning of a long period of warm [El Niño-Southern Oscillation (ENSO)] episode conditions in the tropical Pacific. Despite the weak cold episode conditions that prevailed during much of 1996 in the tropical Pacific, land surface temperatures in the Tropics continued to be much above normal, with the 1996 value surpassed only in 1983, 1987, and 1995. During previous cold episodes (e.g., 1975-76, 1988-89) land temperatures throughout the global Tropics were often colder than the longterm mean.
The estimated global mean surface temperature for land and marine areas combined (Fig. 2a) is derived from observations at over 1000 land stations and from sea surface temperatures (SSTs) measured by ships and buoys. The time series also indicates a cooling during 1996 relative to the record warm year of 1995 previously measured by the land and marine data. However, the anomaly for 1996 (0.21°C) is still among the 10 highest since 1860. The 1996 annual anomaly in both the Northern and Southern Hemispheres was also 0.21°C. In the Northern Hemisphere this value represents a significant decrease from the record value of 0.54°C observed in 1995 (Fig. 2b). In the Southern Hemisphere, mean temperatures have averaged near 0.2°C above normal for the past decade (Fig. 2c).
