Since we regularly get questions about this type of thing, I wanted to repost this excellent post from Erik Klemetti's blog 'Eruptions.'
"I recently read a post about how humans couldn't be to blame for the warming of the oceans. The "logic" of their post was this:
We see water getting warmed by magma at volcanoes worldwide, like Taal andRuapehu. The bottom of the ocean is covered in volcanoes, whether it be seamounts or the mid-ocean ridge system. Volcanoes at the bottom of the ocean must heat up the ocean water (like in crater lakes), so humans aren't to blame. There are a number of ways to attack this poor reasoning, but I'll try to go with the ones I think are most convincing.
