The Tolstoy paper that you referenced detailed a mechanism for, and the timing of tectonic activity influencing climate over very long (millennial) periods. That influence is not new knowledge. Tectonic activity has always been responsible for moving carbon from Earth to atmosphere. But this process is slow, and affects climate over very long durations. It is not responsible for current climate change. Underwater volcanoes do not effectively heat the ocean, and they emit only a tiny fraction of the CO₂ emitted by humans.

We know from mass balance accounting and isotopic analysis that the origin of the increase in the atmospheric mixing ratio of CO₂ is us. And it is that increase in CO₂ that has caused modern warming.

http://onlinelibrary.wiley.com/doi/10.1002/2014GL063015/abstract