Climate variability and climate change

The verification of climate change as a real phenomenon, and the quantification of its progress, is an extremely difficult challenge in terms of processing information from multiple locations and of widely different types. So, for example, over a period of several years, new record summer temperatures may be observed at a range of European locations, along with an increased prevalence of serious flooding across all seasons, while the annual arrival times of the first migrant birds, and the first-flowering times of certain plants, may be observed to drift steadily forward.

While a comprehensive analysis of all available information represents an unattainable ‘holy grail’ for climatologists, the idea motivates a range of more focussed problems at different levels, representing steps in the right direction.

Hence, possible research topics for a PhD programme may be outlined by more well-defined questions about specific aspects of climate change. For example:

• increased variability is anticipated in the UK rainfall climate, producing more extremes in both directions – i.e. more flooding, and more droughts. An analysis of UK rainfall data focussing specifically on both types of extremes would be a novel starting point for a project;

• rainfall data collected over a network of approximately 200 sites in the UK strongly suggest an upward trend in the magnitude of the most extreme (large) rainfall events when the sites are considered as providing independent records. The records are not independent however. In order to verify/quantify any upward trend in extremes, appropriate models are needed, incorporating the dependence structure between sites. A starting point for a project would be to employ and build on existing multivariate methods, with the aim of realistically assessing the evidence provided by the UK rainfall data;

• the identification of a key set of variables for the quantification of future climate change is a valued aim for climatologists, and one with a strong component of statistical modelling required. A climatologist might ask, for example, what events would have to be observed over the next ten years to help assess whether perceived climate variability represents change rather than chance. Hence, an objective of a PhD project might be the identification of an ensemble of key target variables for observation, perhaps drawn from a wide range of possible candidates, with the aim of constructing a sensitive and objective tool for quantifying change.

As indicated by the suggested possibilities above, there is a wide scope for the student to choose and guide the topics of study in this project. The research would be likely to have an emphasis on Extreme Value Methodology and Bayesian Inference, and to involve a good deal of computational work. The aims are applied in nature, but can naturally lead to more theoretical work if the student is inclined to pursue this.