Volcanic eruptions contribute largely to cooling of the planet, not warming.   You may want to educate yourself on   history of past eruptions and the dramatic shor term effect they've had on climate, particularly the massive eruption of Mt. Tambora in 1815.   The following year was considered "the year with no summer" and crops failed around the globe.   Fossil fuel emissions have the opposite effect, C02 and methane gasses trapping heat rather than reflecting sunlight.