during 1951–2015 is 0.7 °C (0.11 °C/decade), while the
TIO SST has risen by about 1.0 °C on average (0.15 °
C/decade) (high confidence) (Fig. 10.1). A 138-year (1870–
2007) monthly observed SST time series averaged along the
ship track extending from the Gulf of Aden through the
Malacca Strait also reveals a warming of 1.4 °C during the
entire period (Chowdary et al. 2012). Coherently, historical
simulations by climate models participating in the Coupled
Model Inter-comparison Project (CMIP5), with CO 2 forcing
at observed rates, show warming trends of 0.1–0.18 °C per
decade during 1976–2005 (Fig. 10.1b), with maximum
warming trends over the northern Arabian Sea.
Fig. 10.1 SST trend (
o
C/decade) from: a observed Extended Reconstructed Sea Surface Temperature, version 4 (ERSST v4) during 1951–
2015, b CMIP5 historical simulations for 1976–2005 and c Time series
of SST anomalies (solid lines) and their linear trends (°C/decade; dotted
line) over the tropical Indian Ocean (TIO, blue), central equatorial
Indian Ocean (CEIO, 60 °E:90 °E; 10 °S:10 °N, green) and global
tropics (GT, 0°:360°; 30 °S:30 °N, red)
10 Indian Ocean Warming
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