Volcanoes have a big impact. The ocean warming and sea level would have risen much more if it weren't for volcanoes.
We can't rely on future volcanic eruptions slowing ocean warming and sea level rises.
These results are suggesting that an eruption such as Pinatubo temporarily slows down the warming but it is only temporary, and in the future we can't rely on eruptions as a way of slowing the warming because we have no idea when or where they're going to occur.