“…Previous modelling efforts (Townsend et al, 2003(Townsend et al, , 2006(Townsend et al, , 2013Stephens et al, 2005;Thomas et al, 2007Thomas et al, , 2011Rodger et al, 2008;Calisto et al, 2012Calisto et al, , 2013Norman et al, 2014) on the effects of an extreme, Carrington-like, SPE fitted their primary spectrum to the E > 30 MeV fluence (F30) estimated by McCracken et al (2001a,b) from ice-core nitrate data. Ice core nitrate deposits have, however, now been shown to not offer a reliable index of energetic particle fluence hitting the upper atmosphere, and the nitrate spike seen in the ice core data presented by McCracken et al (2001a,b) is most likely mis-dated and due to biomass burning plumes rather than SEP. (Wolff et al, 2012;Cliver and Dietrich, 2013;Kovaltsov et al, 2014).…”