Volcanic eruptions produce dust and aerosols that act to provide short term cooling, however seems unclear as to whether there is any long term warming effect from the gasses emitted and also the effect of different aerosols and the interactions between them is unclear.
Most aerosols are of natural origin and key groups include sea salt, nitrates, sulfates, organic carbon, black carbon & mineral dust and they often clump together and form complex mixes. Sea salt, dust and volcanic ash are common types of aerosol, only about 10% of aerosols are of anthropogenic origin.
Different aerosols reflect or absorb sunlight depending on their make up. Large volcanic eruptions can cool the earth for a year or more while sulfate aerosols remain in the atmosphere, black carbon deposited on ice or snow can contribute to global warming by altering the albedo (reflectivity) of the planet. It is a complex area and potential impacts are not fully understood. It certainly makes me worry about potential Geoengineering solutions to climate change….