Relatively little change in the mid latitude ozone losses has been observed in the last half-decade. The smaller increases of UV-B radiation at mid latitudes, while expected, have not yet been detected unambiguously. Cloud transmission depends somewhat on wavelength. Liu et al. The net effects on biota from such changes in direction of incidence are not well understood.
Stratospheric aerosols are usually too sparse to have any effect on atmospheric UV transmission.
The heavier ash sedimented out of the stratosphere relatively quickly and its optical effects were of limited geographical extent. Higher stratospheric sulfate aerosol loadings were observed for several years after the eruption, during which time these particles were distributed on global scales. A less direct but more important UV-related consequence of stratospheric aerosols is their effect on stratospheric ozone itself.