The relationship between soot aerosol and warming is complex.
Black Soot may dim the sunlight,but may increase the warming by warming the snow.
"A new study found that emissions of soot, or black carbon, alters the way sunlight reflects off snow and may be responsible for as much as 25 percent of observed global warming over the past century."
"A new study found that emissions of soot, or black carbon, alters the way sunlight reflects off snow and may be responsible for as much as 25 percent of observed global warming over the past century."
https://www.nasa.gov/vision/earth/lookingatearth/Black_Soot....
Ash from the volcanoes on the other hand,can cause cooling depending on,among other factors,their composition.
https://climate.nasa.gov/blog/183/
For example, the cooling observed due to Mount Pinatubo is due to Sulphuric Acid aerosol particles.
https://earthobservatory.nasa.gov/images/1510/global-effects...