Cryo GL Marzeion 2014

Attribution of global glacier mass loss to anthropogenic and natural causes

What fraction of global ice mass is stored in glaciers?

What hazards are linked to glacial retreat in mountains?

Destabilization of slopes and formation of unstable meltwater lakes, increasing rockslide risk

What is the typical lag in glacier response to climate change?

A few decades

When did global glacier retreat begin?

Around the mid-19th century

What is the sign of modeled glacier mass balance (MB) in control runs?

Negative in both FULL and NAT runs

How do NAT runs change over time?

Become less negative as glaciers retreat, stabilising in the mid-20th century

How do FULL runs differ after mid-20th century?

Show a clear trend toward more negative glacier mass balance, consistent with observations

How does anthropogenic contribution to glacier mass loss change over time?

Increases from −6 ± 35% (1851–1870) to 69 ± 24% (1991–2010)

Is anthropogenic glacier signal detectable regionally?

Not always; detection varies by region

Where is anthropogenic glacier signal detected with high confidence?

Alaska, western Canada, and western USA

Where is model performance particularly poor?

Middle East (both FULL and NAT underestimate mass loss)

What regions show model overestimation of mass loss?

Svalbard and the Russian Arctic (FULL run overestimates loss)

Can glacier mass loss be fully separated into drivers?

No — cannot distinguish internal variability from natural forcing in some regions