Sea Surface Temeprature anomolies in the Indian Ocean in 1998.  Colour, and scale bar on left, shows amount temperature was raised above the man value for that time and place over the preceeding 10 years (not absolute temperature).  Band of colour can be seen to track northwards with the northward passage of the sun, from Jan to June, before fading in July.  The rise of 1.5 or 1.75 degrees above normal was enough to cause widespread mortality of corals throughout the Indian Ocean.
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