Adapting temperature-attribution methodologies to understand industrial-era glacier retreat

Observed glacier melt is a hallmark of modern climate change, yet a comprehensive attribution of industrial-era glacier retreat to human-caused warming remains to be settled. This challenge stems from difficulties in accurately simulating individual glacier behavior, which depends on poorly constrained factors like local geometry and historical climate conditions.  Here, we adapt methodologies that have previously been applied to industrial-era temperature attribution, and apply them towards climate metrics of specific relevance to glacier mass balance. We use historical and natural-forcing-only simulations from the CMIP5 and CMIP6 climate-model archives, along with observational products of near-surface temperature (e.g. Berkeley Earth) to create a global map of anthropogenic melt-season temperature change. These temperature changes are translated into shifts in equilibrium line altitude (ELA), the boundary between a glacier’s accumulation and ablation zones.  By applying these ELA shifts to example glacier profiles that match known Little Ice Age extents, we estimate the changes in ablation area and rates resulting from anthropogenic activity.  This approach offers fresh insights on quantifying the impact of anthropogenic emissions on modern glacier retreat globally.