Figure 2.9: (a) to (d) Annual
surface temperature trends for the periods 1901 to 2000, 1910 to 1945, 1946 to
1975, and 1976 to 2000, respectively (°C/decade), calculated from combined
land-surface air and sea surface temperatures adapted from Jones et al. (2001).
The red, blue and green circles indicate areas with positive trends, negative
trends and little or no trend respectively. The size of each circle reflects the
size of the trend that it represents. Trends were calculated from annually averaged
gridded anomalies with the requirement that annual anomalies include a minimum
of 10 months of data. For the period 1901 to 2000, trends were calculated only
for those grid boxes containing annual anomalies in at least 66 of the 100 years.
The minimum number of years required for the shorter time periods (1910 to 1945,
1946 to 1975, and 1976 to 2000) was 24, 20, and 16 years, respectively.