Extended scenarios for glacier melt due to anthropogenic forcing

The IPCC Third Assessment Report (TAR) developed a formula for the global meltwater contribution to sea level rise from Glaciers and Small Ice Caps (GSICs) that is applicable out to 2100. We show that, if applied to times beyond 2100 (as is necessary to assess sea level rise for concentration‐stabilization scenarios), the formula imposes an unrealistic upper bound on GSIC melt. A modification is introduced that allows the formula to be extended beyond 2100 with asymptotic melt equal to the initially available ice volume (V0). The modification has a negligible effect on the original TAR formulation out to 2100 and provides support for the IPCC method over this time period. We examine the sensitivity of GSIC melt to uncertainties in V0 and mass balance sensitivity, and give results for a range of CO2 concentration stabilization cases. Approximately 73–94% of GSIC ice is lost by 2400