mt, galunggungIt will be interesting to see how much impact the ongoing Icelandic volcanic activity has on regional climates.

The 1822 eruption of Mount Galunggung in Indonesia influenced weather in Northwest England based on the detailed diary of a farmer at that time. So the Icelandic activity around that time may have only contributed to other stronger volcanic events (or solar activity).

Thus significant climate anomalies are found in the 2 years following the Tambora 1815 eruption and to a lesser extent 1 year following another major eruption, Galunggung in 1822. As well as colder and wetter summers, other indicators such as optical phenomena, which are not routinely included in climate records, are recorded. There is no evidence that the diarist was aware of the Tambora and Galunggung eruptions at the time of writing.

The main points
are that "sulphur-rich gases (principally SO2) emitted during an eruption are the most important" and "Once injected to the stratosphere, these can cause the largest perturbation on climate in the form of cooling of the earth's surface as well as providing a nucleus for various chemical reactions that can even lead to the stratospheric ozone depletion."

and Higher latitude volcanic eruptions have their own signature:

High latitude eruptions in the Northern Hemisphere, while also producing global cooling, do not have the same impact on atmospheric dynamics. They weaken the Indian and African summer monsoon, and the effects can be seen in past records of flow in the Nile and Niger Rivers.

and an interesting fact about Benjamin Franklin and volcanoes:

Benjamin Franklin was one of the first to recognize the connections between volcanic eruptions and climate. Shortly after the 1783-1784 Laki eruption, he postulated that the dry fog over much of Europe was likely caused by a volcanic eruption in Iceland, that the winds would have transported the gas and aerosol over much of the Northern Hemisphere, and that the cold winter of 1783-84 was caused by this dry fog. We used the NASA Goddard Institute for Space Studies ModelE climate model to examine the chemical conversion and transport of SO2 gas from the Laki eruption (64.10°N, 17.15°W) and used the resulting aerosol concentrations to model the climate response. Using our calculated aerosol distribution, we conducted a 10-member ensemble simulation with ModelE coupled to a q-flux mixed-layer ocean. The mean of these runs reproduced the extensive radiative cooling (-1 to -3°C) that occurred during the summer of 1783 across much of Asia, Canada, and Alaska and produced a strong dynamical effect in summer as the Laki eruption forces a significant weakening of the African and India monsoon circulations. This is seen in cloud cover and precipitation anomalies and resulted in significant warming (1 to 2°C) from the Sahel of Africa to northern India. This is a very robust result and has been observed after the last 3 large high-latitude volcanic eruptions, Eldgjá (939), Katmai (1912), and Laki, all of which produced large reductions in the flow of the Nile River. In the winter of 1783-1784 our model reproduced the significant negative temperature anomalies over the Northeastern United States, and smaller cooling produced over Europe. That winter was one of the coldest on record over these areas and our model results confirm that Laki could have been partially responsible for these anomalies.


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