The aim of the TAR (Transient Aerosol Record) experiment is to investigate the relative contributions of volcanic and anthropogenic sources to the temporal evolution of the stratospheric aerosol layer between 1998 and 2012. Observations show that there is a transient increase in stratospheric aerosol loading, in particular after the year 2003, with small-to moderate-magnitude volcanic eruptions contributing significantly to this increase (e.g. Solomon et al., 2011, Vernier et al., 2011b; Neely et al., 2013; Ridley et al. 2014; Santer et al., 2015; Brühl et al., 2015). TAR model simulations will be performed using specified dynamics, prescribed sea surface temperature and time-varying SO2 emissions. The simulations are suitable for any general circulation or chemistry transport models that simulate the stratospheric aerosol interactively and have the capability to nudge meteorological parameters to reanalysis data. The TAR protocol covers the period from January 1998 to December 2012, when only volcanic eruptions have affected the upper troposphere and lower stratosphere (UTLS) aerosol layer with SO2 emissions about an order of magnitude smaller than Pinatubo. Time-varying surface emission datasets contain anthropogenic and natural sources of sulphur aerosol and their precursor species. The volcanic SO2 emission inventories contain information of all known eruptions that emitted SO2 into the UTLS during this period. It comprises the geolocation of each eruption, the amount of SO2 emitted, and the height of the emissions. SO2 emissions from continuously-degassing volcanoes are also included.

For further information and interactive visualization of TAR experiment see also TAR experiment webpage.