Dr Paul Ritchie
Postdoctoral Research Fellow
I'm currently a postdoc on the ECCLES project led by Prof. Peter Cox studying connections between emergent constraints and early-warning signals used to detect the approach of a tipping point. A system is often described to pass a tipping point when gradual changes made to input levels or rates cause the output to suddenly change state. Whilst Emergent Constraints are a method for reducing uncertainties in climate change projections. Other current work involves studying the possibility of briefly overshooting tipping thresholds, and the stability of methane hydrates in the sediment beneath the ocean floor.
In my previous postdoc position, supervised by Prof. Tim Lenton and Dr. Anna Harper, 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.