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Dr Paul Ritchie

Dr Paul Ritchie

Research Fellow
Mathematics and Statistics

I am a postdoctoral research fellow on the OptimESM project working with Prof. Tim Lenton and Dr. Chris Boulton to find evidence of early warning preceding tipping points that have been detected in the latest generation of climate models. This includes testing generic early warning signals such as increasing autocorrelation and variance and developing system specific early warning signals. 

 

In previous positions I've worked on the ECCLES project led by Prof. Peter Cox studying tipping points of strongly forced systems. This includes the concept of briefly overshooting tipping thresholds and still avoiding tipping and researching rate-induced tipping. I have also worked on a Valuing Nature project, supervised by Prof. Tim Lenton and Dr. Anna Harper, where I studied potential tipping points in UK ecosystem services from future land-use and climate change projections. This project involved used the Joint UK Land Environment Simulator (JULES) a land-surface model to look for tipping events in carbon stocks, greenhouse gas emissions and frehwater fluxes.

 

During my PhD (also here at Exeter) I studied the underlying dynamics behind tipping points, supervised by Prof. Jan Sieber and Prof. Peter Cox. In particular my work studied a more recent concept of tipping known as rate-induced tipping. For classical tipping events such as a slow passage through a fold bifurcation, so-called early-warning indicators (increase in autocorrelation and variance) have been developed to detect the approach of a tipping point. However, for rate-induced tipping the dynamics are different and thus it is unclear if these early-warning indicators can still be used for rate-induced tipping events. However, we were able to show that there exists both a delay in the time of tipping from when one would expect to see tipping and in the early-warning indicators. Furthermore, these delays are consistent such that we conclude that early-warning indicators can be used for rate-induced tipping events.

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