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Research interests

My main research interest is on physical and bio-geochemical climate feedbacks and their role in shaping future projections of climate change. The question of quantifying and constraining projection uncertainty is a central aspect of my work, with a focus on climate sensitivity, permafrost-carbon feedback, and runaway climate conditions.


Reducing Uncertainty in Climate Sensitivity

Uncertainty in Climate sensitivity - the equilibrium change in global mean temperature following a doubling of atmospheric CO2 content - crucially affects projections of future climate warming. Recent studies have shown that (up to now) it has not been possible to satisfactorily constrain Climate Sensitivity by focusing on historical data of past warming (~last 100 years) or on present day climatology.

In my work I investigate which constraints prove especially promising in putting effective bounds on climate sensitivity - such as information of regional differences in the observed warming, or information stemming from paleo data archives (such as the reconstructed cooling during the last  glacial maximum, LGM, 21kyrs B.P.).

 

 Permafrost-carbon feedbacks

 How strongly will permafrost degradation affect future global temperature rise and atmospheric greenhouse gas levels?

For investigating this aspect of uncertainty in the terrestrial carbon cycle I developed a new and simplified module which calculates the thawing of permafrost and subsequent decomposition of soil carbon. This module was coupled to MAGICC-6, an efficient climate-carbon cycle model which allows running large ensembles for scenario-based probabilistic climate predictions.

 

Runaway climate conditions

Can climate feedbacks increase strongly enough with global warming to lead to a limited self-amplified warming of the Earth-climate system?

 

Analysis of climate model feedbacks

A physical interpretation of Climate Sensitivity estimates can be achieved by quantifying and analysing the key model feedbacks (water vapour, clouds, lapse rate, albedo). I use an offline-calculation scheme to extract those information from a large set of different models versions (based on a model of Intermediate Complexity, CLIMBER-2). Especially the question of asymmetry in the feedback strength between a colder (e.g. LGM) and a warmer climate (e.g. 2CO2) is subject of my investigations.

 

Further research areas
  • Analysis of radiative forcing
  • Impact of dynamical ocean changes on Climate Sensitivity
  • Probabilistic projections of future climate change
  • Emission targets for climate policies
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