SCENARIO NERC DTP - A storyline approach to explaining changes in precipitation seasonality in the Mediterranean during the Holocene

Climate scenarios suggest that the Mediterranean region will be increasingly subject to prolonged droughts over the 21st century, with consequent impacts on water availability, biodiversity, and human health and well-being. These model-based projections are highly uncertain because they reflect changes in atmospheric circulation that are poorly described even under modern conditions. The reliability of the projections is also questionable because state-of-the-art climate models do not reproduce known changes in precipitation regimes in the Mediterranean region in the past. For example, pollen evidence shows a shift from evergreen to deciduous woody vegetation in southern Europe during the mid-Holocene. Such vegetation cannot be supported if the rainfall occurs predominantly in winter, as it does today, and there must therefore have been considerably more rainfall in the spring and summer. The cause of this fundamental change in rainfall patterns is unknown, but model simulations of the mid-Holocene do not show an increase in growing-season rainfall in the Mediterranean region.

The recent development of a “storyline” approach to explaining climate changes offers a novel way of tackling this problem. The storyline approach is a regression-type analysis that can be used to identify the synoptic changes that give rise to particular local climate phenomena, such as rainfall in spring or summer, and relate these synoptic changes to large-scale forcings, e.g. teleconnections from remote regions. By applying this analysis to either modern meteorological data or climate model simulations, it is possible to identify rare but physically plausible events that produce a specific change in climate, and determine what changes in large-scale forcings might increase the frequency of such events. The storyline approach has already been used successfully to explain recent changes and describe scenarios for future changes in wintertime precipitation in the Mediterranean (see figure), both in terms of proximate circulation changes and remote drivers, but has not been applied to summertime precipitation or palaeoclimate regimes.

Training opportunities:
The project involves a diverse set of tasks, which will build a well-rounded set of skills including:
• Analytical and programming skills through the manipulation and analysis of complex palaeoenvironmental data sets and model outputs;
• Statistical skills through the development of error matrices and the propagation of uncertainty.

The student will be able to attend various MSc courses in the Department of Meteorology, covering climate change, tropical/extratropical meteorology, and statistics. They will also be able to attend the Swiss Climate Summer School (run by the Oeschger Centre, Bern) which has a focus on both present-day and palaeoclimate, as well as the NCAS Climate Modelling Summer School.

The project is highly relevant to the Palaeoclimate Modelling Intercomparison Project (PMIP), which is responsible for palaeoclimate simulations and their analysis within the framework of the Coupled Model Intercomparison Project which directly contributes to the Intergovernmental Panel on Climate Change. The student will be able to attend PMIP meetings and workshops, including workshops of the various projects that are developing data syntheses for model evaluation.

The project is designed as a thesis-by-papers, which will allow the student to develop science communication skills as well as training in publication and project management.


To read more about this project please follow the link: http://www.met.reading.ac.uk/nercdtp/home/available/desc/entry2018/SC201809.pdf