IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group I: The Physical Science Basis Indian Ocean

Based on the MMD ensemble mean the annual temperature is projected to increase by about 2.1°C, somewhat below the global average, with individual models ranging from 1.4°C to 3.7°C and at least half of the models giving values quite close to the mean. All models show temperature increases in all months with no significant seasonal variation (Supplementary Material Figure S11.31). Evidence of temperature increases from 1961 to 1990 in the Seychelles is provided by Easterling et al. (2003), who find that the percentage of time when the minimum temperature is below the 10th percentile is decreasing, and the percentage of time where the minimum temperature exceeds the 90th percentile is increasing. Similar results were obtained for the maximum temperatures. This is consistent with general patterns of warming elsewhere (see Chapter 3).

The annual precipitation changes projected by individual MMD models varied from –2 to 20% with a median of 4% and 50% of the models projecting changes between 3 and 5%. Thus, there is some level of confidence in the precipitation results although not as high as for temperature. Figure 11.24 shows that the annual increase is restricted mainly to the north Indian Ocean, where the model consensus is greatest, especially in the vicinity of the Maldives. In DJF, some increases are noted in the south. Model agreement on increases is greatest for the Seychelles in DJF and for the Maldives in JJA. There is also strong agreement on decreases in the vicinity of Mauritius in JJA. Sections 10.3.5 and 11.4 discuss changes in monsoon behaviour in a warmer climate. There is an emerging consensus that the effect of enhanced moisture convergence in a warmer atmosphere will dominate over possible weaker monsoonal flows and tropical large-scale circulation in global warming simulations, resulting in increased monsoonal precipitation. Easterling et al. (2003) find evidence that extreme rainfall tended to increase from 1961 to 1990 (see also Section 11.4.3, South Asia projections).

Figure 11.24

Figure 11.24. As for Figure 11.23 but for the Indian Ocean.