Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Glaciers between Little Ice Age and Anthropocene:
causes of the global meltdown
Ben Marzeion, J. Graham Cogley, Kristin Richter, David Parkes,
Alexander H. Jarosch
23.01.2015
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Conclusions
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
A few examples: Lower Grindelwald Glacier
Zumbühl et al. (2008)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Conclusions
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
A few examples: Mer de Glace
Zumbühl et al. (2008)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
A few examples: Pasterze
Gletscherarchiv/Gesellschaft für ökologische Forschung e.V.
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
Little Ice Age: northern hemisphere temperatures
Masson-Delmotte et al. (2013)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
Little Ice Age: causes
Jansen et al. (2007)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
Is the retreat obviously anthropogenic?
Leclercq et al. (2011)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
Is the retreat obviously anthropogenic?
The problem: glaciers respond lagged to climate change
Oerlemans (2008)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
Effect of lagged response: committed future mass loss
Marzeion et al. (2014)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Is the retreat obviously anthropogenic?
The problem: glaciers respond lagged to climate change
Response time:
longer for bigger glaciers
shorter for glaciers with high turnover
Magnitude:
mid-latitude glaciers (e.g., Alps, Southern Scandinavia):
∼10-100 years
dry, high latitude glaciers; ice caps :
∼100-1000 years
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Conclusions
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
Is the retreat obviously anthropogenic?
The problem: glaciers respond lagged to climate change
Response time:
longer for bigger glaciers
shorter for glaciers with high turnover
Magnitude:
mid-latitude glaciers (e.g., Alps, Southern Scandinavia):
∼10-100 years
dry, high latitude glaciers; ice caps :
∼100-1000 years
−→ on the global scale, glaciers are still responding to the end of the Little Ice
Age
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Detection & Attribution
Can we detect an anthropogenic signal in the observed glacier mass balances?
model glaciers with and without anthropogenic forcing of the climate
are modeled mass balances consistent with observations?
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Conclusions
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Detection & Attribution
Can we detect an anthropogenic signal in the observed glacier mass balances?
model glaciers with and without anthropogenic forcing of the climate
are modeled mass balances consistent with observations?
If detection was successful:
Which part of mass loss is attributable to anthropogenic forcing of the
climate system?
How does this part evolve over time?
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Conclusions
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
Is the anthropogenic signal detectable?
12 reconstructions of climate from global, coupled models
each of the 12 reconstructions twice: once including only natural (nat), once
all (full) forcings
use these climate reconstructions to reconstruct each of the world’s glaciers
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
Is the anthropogenic signal detectable?
updated from Marzeion et al. (2014)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
Is the anthropogenic signal detectable?
updated from Marzeion et al. (2014)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
How big is the anthropogenic fraction?
updated from Marzeion et al. (2014)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
But this is old news...
Humble Oil (now Exxon, Life Magazine Februar 2nd, 1962)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Conclusions
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
But this is old news...
Could be literally true:
Each day humanity is
melting 650±200
million tons of glacier!
Humble Oil (now Exxon, Life Magazine Februar 2nd, 1962)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
Projected global mass loss
updated from Marzeion et al. (2012)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
Projected regional mass loss
updated from Marzeion et al. (2012)
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt
Global retreat of glaciers
Past climate
Cause and effect?
Results
Projections
Conclusions
Conclusions
the evidence for anthropogenic glacier mass loss is strong
more than half of the mass loss during the past 30 years is likely
anthropogenic
more than half of the mass loss during the 20th century is likely natural
regional attribution is difficult because of greater model errors, stronger
variability, and greater uncertainty in observations
we are already committed to strong glacier mass loss during the 21st century
on the regional scale, diversity and uncertainty of projections is large
Ben Marzeion, University of Innsbruck
Causes of the global glacier melt