Radiative effects of ozone on the climate of a Snowball Earth

Abstract

Abstract. Some geochemical and geological evidence suggests that the concentration of atmospheric oxygen was only 1–10% of the present level in the time interval from 750 to 580 million years ago when several nearly global glaciations or Snowball Earth events occurred. This low concentration of oxygen would have been accompanied by lower ozone concentration than present. Since ozone is a greenhouse gas, this change in ozone concentration would alter surface temperature, and thereby could have an important influence on the climate of the Snowball Earth. Previous works for either initiation or deglaciation of the proposed Snowball Earth have not taken the radiative effects of ozone changes into account. We address this issue herein by performing a series of simulations using an atmospheric general circulation model with various ozone concentrations. Our simulation results demonstrate that as ozone concentration is uniformly reduced from 100% to 50%, surface temperature decreases by approximately 0.8 K at the equator, with the largest decreases located in the middle latitudes reaching as high as 2.5 K, primarily due to a strengthened snow-albedo feedback. When ozone concentration is reduced and its vertical and horizontal distribution is simultaneously modulated, surface temperature decreases by 0.4–1.0 K at the equator and by 4–7 K in polar regions. These results suggest that ozone has significant effects on the climate during the Neoproterozoic glaciations.