Hurricanes themselves are vast thermometers. They tell you that the
temperature was 28oC or higher, and it was that hot 50 meters deep or
deeper. Unless both those things are true there are no hurricanes.

This years abundance of cat 5 hurricanes tells us more about the depth
of the heat related to the power, and related to pause over the hot
waters.

From facts of physics considerable forensic reconstruction of old sea
temperatures may be possible.