Volcanic activity / plate tektonics drive the climate over very long periods of time - absolutely nothing to do with human induced climate change!
They don't have any connection with AGW, but volcanic eruptions can have relatively quick impacts on the global climate, although the changes are short-lived, and are almost universally of a cooling effect.
When Tambora erupted in 1815, the following year heralded extremely poor weather, predominantly in the northern hemisphere. This was the result of the ejection of millions of tons of ash and sulphur into the atmosphere then carried around the world on jet streams.
1816 became known as 'the year without a summer' as typical winter and early spring conditions perpetuated across Europe, North America and Asia. The impacts included widescale crop failures, frosts and snow recorded in July, changes to the monsoon season in Asia (a lot of flooding) and the resultant hundreds of thousands of deaths through not just starvation and famine, but typoid and cholera.
Some unexpected social and cultural side-effects:
A shortage of animal feed led German inventor Karl Drais to invent the velocipede as a form of horseless transport, the forerunner of the bicycle
The tefra in the atmosphere led to extremely vivid sunsets, which were captured in the paintings of JMW Turner and Caspar Freidrich
A group of Aristocratic friends spending the summer in a villa on the shores of Lake Geneva were kept inside by rain, cold and often perpetual dusk. To pass the time, they organised a writing competition to create the scariest story. Mary Shelley wrote Frankenstein, and John Polidori (expanding on host Lord Byron's 'A Fragment') wrote The Vampyre, which was an inspiration for Bram Stoker to write Dracula.
The 1817 winter was one of the coldest in history across the Americas, Britain and Europe.
Much smaller - but definitely noticeable - climatological impacts occurred after the eruptions of Mt St Helens (1981) and Mt Pinatubo (1991).
Tambora had a Volcanic Explosivity Index (VEI) of 7 (St Helens was a 5; Pinatubo a 6. For comparison, Cumbre Vieja on La Palma was a 3). The Hunga Tonga–Hunga Haʻapai eruption is expected to be a VEI5, but not expected to impact global climates due to the composition of the ash (very low levels of sulphur).