Figure 9: Attribution of New Zealand glacier mass balance to natural and human causes.

Standard mass balance model run (black line, all glaciers) is plotted alongside modelled New Zealand glacier mass balance output from a global-scale glacier attribution study³. Mass balance units are metres of water equivalent per year (m w.e.a⁻¹). ‘Full forcings’ (red) show the ensemble mean-specific mass balance and model range for New Zealand glaciers, calculated from 12 models that include both natural and anthropogenic forcings from the Coupled Model Intercomparison Project phase 5 (CMIP5). ‘Natural forcings’ (green) show the same for CMIP5 models that include natural and omit anthropogenic forcings on climate. The standard run derived here shows a larger degree of interannual variability than either the ‘full forcing’ or ‘natural forcing’ runs. The standard run, however, is more consistent with ‘full forcing’ mass balance simulation (Supplementary Table 6), suggesting that New Zealand glacier mass balance was influenced by anthropogenic climate change between 1980 and 2005.