Units is a wonderful program; don't be afraid to use their definitions (/usr/share/units/definitions.units):

  $ units -t '24816400 GWh / (1347000000 km^3) / waterdensity / water_specificheat'
  1.5851925e-05 K

There's even definitions like `oceanarea`, etc ;-)

And if there's 7.62 gigapersons on earth, that's about 3.2MWh/year per person or 271 kWh/month per person.

Since that's the same order of magnitude as, say, a US household, that does seem credible.

So that is to say, all the worlds energy production directed toward heating the oceans, could increase global oceanic temperature by 0.00001 degree C in a year.

Looking again, I think I got caught off by the "." being used as a decimal separator in some places.