"...we determine the global volcanic aerosol forcing since 2000 to be −0.19 ± 0.09 W/m2. This translates into an estimated global cooling of 0.05 to 0.12°C. We conclude that recent volcanic events are responsible for more post-2000 cooling than is implied by satellite databases that neglect volcanic aerosol effects below 15 km."The study examined the years 2000-2013, so the reduction in the trend would be 0.04 to 0.09°C/decade of cooling. That's could be up tonearly half the expected (from models, with no natural variability) 0.2°C/decade.
Here's their time series of the stratospheric aerosol optical depth (SAOD) since shortly after the 1991 large eruption of Mount Pinatubo washed out of the atmosphere:
After putting this all together, they get the following impacts on total radiative forcing and on temperature: