Research interests

I use several climate models of different complexity, from intermediate complexity to general circulation models for my work. Below is a short summary on a few topics.

Process studies on the ocean thermohaline circulation

For my studies on the large-scale ocean thermohaline circulation, I use the Bern 2.5D Climate Model. This model is designed to study the role of the thermohaline circulation in the Earth climate system of the past, present and future. My early work focussed on the stability and dynamics of the thermohaline circulation on timescales of more than several decades and on spatial scales of more than a thousand kilometers. The simple parameterization of processes results in a computationally efficient climate model suitable for long-term integrations (up to millions of years) and large numbers of simulations not feasible with more complex models. This allows us to focus in detail on the mechanisms and processes of natural climate variability and on the potential anthropogenic climate change.

Probabilistic projections with very large model ensembles

The extreme efficiency of the zonally averaged climate model also allows to calculate ensemble simulations of several thousand members. This approach has recently been used to demonstrate a strategy of how probabilistic forecasts of climate change over the next century can be obtained. The idea is to run a model many times with different parameter combinations and then used observations to constrain the ensemble, i.e. give those model versions more weight that agree well with observations. Technically, these are Bayesian methods, and the result of this procedure is a probability density function of future warming given the observations of the past century.