Global mean temperature 1860-2001

E. Linacre and B. Geerts


The global mean temperature over the last 137 years (1, 2) shows two periods of rapid warming: between 1915-1942, and between 1974-1998. Figure 1 shows a rise of about 0.6 K since 1910 and no trend between 1940-75. Observe the rapid rise from 1975 to 1995: global mean temperature anomalies in the last decade were about 0.5 K, several times larger than the interannual variation. The 20th century temperature trend is largely explained by observed changes in greenhouse gas and aerosol concentrations in the atmosphere.


Fig 1. Global and annual mean temperatures from 1860 to 1996, as measured in situ at weather/climate stations. The temperatures are expressed as an anomaly from the average over 1961-90 (1). (Source: Climate Research Unit, Univ. of East Anglia, UK)

 Figure 2 shows that the global sea-surface temperature, also, has gradually increased, especially since 1910 (3). A rise from 1910 to 1940, and from 1980 until recently, as well as a stagnation between 1940-75, are apparent in both surface and sea-surface temperature data. The magnitude of the changes are also similar.

Fig 2. Global and annual mean sea-surface temperatures from 1860 to 1992, as estimated, measured in situ, or measured remotely (from satellite). The temperatures are expressed as an anomaly from the average over 1951-80. The curve has been smoothed to show the trend more clearly (3).

A 1998 release by the US National Climate Data Center in Asheville, North Carolina reported that 1997 was the warmest year this century over the globe as a whole (4). It was 0.42 K warmer than the normal, i.e. the 1961-1990 average. The warmest year previously was 1990, which was 0.34 K warmer than the normal. Nine of the past 11 years have been warmer than the warmest on record prior to 1980.

However, the situation was different in Australia, for instance, where the average temperature in 1997 was 22.0° C, i.e. 0.2 K above the 1961-90 norm there. This was cooler than 1988, when the annual average was 0.7 K above normal. Daily minimum temperatures in Australia in 1997 averaged 15.5° C, i.e. 0.3 K above the normal, whilst the maxima (averaging 28.5° C) were only 0.1 K above the corresponding norm.

Globally 1998 was by far the warmest on record, with a temperature anomaly (between January-May) of 1.4K. This is in part due to a very strong El Niņo. So it appears that 1998 will set another record.



  1. Halpert, M.S. and G.D. Bell, 1997. Climate assessment for 1996. Bull. Amer. Meteor. Soc., 78, 1-49.
  2. Manabe, S. and R.J. Stouffer, 1997. Climate variability of a coupled-atmosphere-land surface model. Bull. Amer. Meteor. Soc., 78, 1177-85.
  3. Folland, C.K. & D.E. Parker 1995. Correction of instrumental biases in historical sea-surface temperature data. Quart. J. Roy. Meteor. Soc., 121, 319-67.
  4. See Bull. Aust. Meteor. Ocean. Soc. 79, 113.