How much data do we really have?

Hurricane modelling following the active years of 2004 and 2005 was enlivened by the recognition of - and arguments around - the decadal see-sawing of the sea-surface temperatures in Atlantic Basin and its possible influence on hurricane frequency. However I'm not here to discuss this rather thorny issue given recent reductions in landfall activity, but rather use it as an example that highlights the uncertainty around the data we use, even in a "landfall-rich" area such as Florida where we would expect to have fairly good confidence around catastrophe model output. The most commonly-used index to highlight the warm and cold fluctuations of sea-surface temperature in the Atlantic hurricane r