Evaluating ENSO teleconnections using observations and CMIP5 models

Bias correction of global and regional climate models is essential for credible climate change projections. This study examines the bias of the models of the Coupled Model Inter-comparison Project Phase 5 (CMIP5) in their simulation of the spatial pattern of sea surface temperature (SSTs) in different phases of the El Niño Southern Oscillation (ENSO) and their teleconnections—highlighting the strengths and weaknesses of the models in different oceanic sectors. The comparison between the model outputs and the observations focused on the following three features: (i) the typical horseshoe pattern seen in the Pacific Ocean during ENSO events with anomalies in SSTs opposite to the warm/cool tongue, (ii) different signature in the tropical Pacific Ocean from that of the North and tropical Atlantic Ocean, and (iii) spurious signature in the southern hemisphere beyond 45° S. Using these three cases, it was found that the model simulations poorly matched the observations, indicating that more attention is needed on the tropical/extratropical teleconnections associated with ENSO. More importantly, the observed SST coupling between the tropical Pacific Ocean and the Atlantic Ocean is missing in almost all models, and differentiating the models between high/low top did not improve the results. It also found that SSTs in the tropical Pacific Ocean are relatively well simulated when compared with observation. This work has improved our understanding of the simulation of ENSO and its teleconnections in the CMIP5 models and has raised awareness of the bias existing in the models, which requires further attention by climate modellers. © 2018 The Author(s

How do models give us knowledge? The case of Carnot's ideal heat engine.

Our concern is to explain how and why models give us useful knowledge. We argue that if we are to understand how models function in the actual scientific practice the representational approach to models proves either misleading or too minimal—depending on how representation is defined. By ‘representational approach’ we mean one that attributes the epistemic value of models to the representational relationship between a model and some real target system. In contrast we propose turning from the representational approach to the artefactual, which also implies a new unit of analysis: the activity of modelling. Modelling, we suggest, could fruitfully be approached as a scientific practice in which concrete artefacts, i.e., models, are constructed with specific representational means and used in various ways, for example, for the purposes of scientific reasoning, theory construction and design of experiments and other artefacts. Furthermore, we propose that in the activity of modelling the construction of models is intertwined with the construction of new phenomena, concepts, and theoretical principles. We will illustrate these claims by studying the construction of the ideal heat engine by Sadi Carnot