Can volcanos change the climate?
Can volcanos really change the climate so relatively (geological timescale speaking) fast, up to the abnormal levels that we are seeing today?


Even more so.

You wrote about the 1815 eruption of Mount Tambora. While that was an extremely large eruption in terms of written human history, it was rather tiny compared to the absolutely colossal volcanic events whose histories have been written in the rocks. Multiply the Tambora eruption by a factor of 10000 or more and you'll get things like the Deccan Traps and Siberian Traps.

A number of geologists think that it was the formation of the Deccan Traps rather than the Chicxulub impact event that killed the dinosaurs. A much larger fraction think the combination of the two dealt a one-two punch that ended the reign of the dinosaurs.

The Siberian Traps are still deemed by many, if not most, geologist as the leading contender for the cause of the Permian–Triassic extinction event. This was by far the most severe extinction event ever, much greater in impact than the Cretaceous–Tertiary extinction event that killed the dinosaurs. The lava released by the Siberian Traps covered an area the size of Europe (or larger, depending on who you read). It may have triggered massive fires in coal deposits, significantly adding to the greenhouse gases.



That said, what's happening to the Earth's atmosphere now is not a result of volcanic activity. It's us. (That of course is assuming that the massive amounts of hot air that comes out of the mouths of politicians is not classified as volcanic.)