Climate and weather extremes in early instrumental records, mechanisms and consequences

This PhD project is one of two PhD projects arising from the NERC-funded consortium GloSAT. GloSAT will extend the observed surface temperature record back into the 18th century, and extend the coverage of historical climate change data using historical ship data, logbooks and other sources. The student will identify past extreme seasonal and monthly events over both land and ocean, making use of multiple data sources including climate model data and palaeoclimatic data. The physical mechanisms and spatial extent of early extremes will be analysed where possible, using historical weather analysis data and early observations of sea level pressure, many of which are now becoming available. Climate models output will be used to identify mechanisms and possible causes of these events.

The student will determine if the probability of individual events has been affected by external drivers such as volcanic eruptions, and changes in the sun, building on techniques used to interpret recent extreme weather events. They will also determine the extent to which the events are influenced by large-scale climate variability, such as the North Atlantic Oscillation (NAO), Atlantic Multidecadal Variability (AMV) or El Nino, drawing on GloSAT project results. For example, the hypothesis will be explored if record cold winters tend to occur during solar minima in Europe (Lockwood et al., Env. Res. Let. 2010), and to what extent anomalously warm and wet winters follow volcanic eruptions.

Analysis of temperature extremes over the ocean will investigate what drives marine heat waves and cold spells. This is necessary for understanding to what extent extreme marine heat waves might superimpose on the warming trend in the future, with potentially devastating consequences for marine life such as corals. This will help place possible future events into the context of rare past events, for example, by addressing the question 'what would this event be like if it occurred today'.

The student will be part of the interdisciplinary UK-wide project team comprising researchers from the National Oceanography Centre, the Met Office and the Universities of Edinburgh, Reading, East Anglia, Southampton and York. He or She will be supervised by Hegerl, supported by Ed Hawkins (Reading) and Andrew Schurer (Edinburgh). Hawkins will be consulted at least quarterly, either adjacent to a project meeting, or through a visit. The student will be connected to the newly funded and vibrant Edinburgh Earth, Ecology and Environment DTP (18 students/year) and will join Hegerl's research group. The student will be trained by the NERC DTP (transferrable skills, writing, computing and presentation skills) and apply for external training in suitable summer schools. Scientifically, the student will learn scientific data analysis, mechanisms of climate variability and extreme events, extreme value statistics, climate modelling, climate model analysis and gain an understanding of quantitative and rigorous analysis approaches.

The most recent Climate Change Public Attitude Tracking Survey in the UK found that
74% of respondents were either 'very' or 'fairly' concerned about climate change. Global political concern over the issue is reflected by the Paris Agreement negotiated by 196 parties at the 21st Conference of Parties in 2015. The UK has committed to reducing greenhouse emissions by 80% by 2050. Clean growth is a key element of the government's industrial strategy.

The most visible measure of climate change for both policymakers and the public is the historical temperature record, which measures how global temperatures have changed over the past 170 years, and shows periods of rapid warming in the early 20th century and for the whole of the last 50 years. However the record is not long enough to give a complete picture of temperature change since before the start of the industrial revolution, or how exceptional recent temperature change is in comparison to pre-industrial conditions. The current historical temperature record mixes air and water temperatures in a way which creates confusion when comparing with climate model predictions.

This project will produce a new global surface air temperature dataset starting in around 1780 - at least 70 years longer than any other and stretching back almost to the start of the industrial revolution. The length of the record, the use of air temperatures for both land and oceans, and improvements to our understanding of the historical measurements will make this new dataset the benchmark for the understanding human impact on the climate for both policymakers and the general public.

Temperature data underpins national and international policy on climate change. The UN Framework Convention on Climate Change (UNFCCC) process will benefit from improved quantification of temperature change since the pre-industrial period to feed into their regular 'global stocktake' which will monitor progress towards achieving the aims of the Paris Agreement to limit global temperature change to 1.5 or 2C above pre-industrial levels.

A range of datasets with differing spatial and temporal resolutions will be produced to represent improving data coverage over time, and incorporating new analyses of the level of confidence in the data at any point in time. This information will feed into national & international climate assessments, such as the annual State of the Climate Report, the UK Climate Change Risk Assessments, and future Intergovernmental Panel on Climate Change reports. The climate science community will also benefit from an improved understanding of natural climate variations, such as those due to volcanic eruptions and internal ocean-atmosphere interactions: the new dataset will be widely used to compare to other observational datasets, weather model reanalyses and climate model simulations. This will improve our understanding of past climate change and weather extremes, and implications for future change, providing data for risk management in both government and industry.

An important part of GloSAT will be the digitisation of historical observations from their current paper or scanned image formats. Much of this will be achieved through public engagement and citizen science digitisation, building on the highly successful WeatherRescue.org project, which has already rescued more than 2.5 million weather observations using thousands of volunteers. The rescued observations will be added to international weather observation databases such as ICOADS, ISTI, ISPD and the Copernicus Climate Data Store for the entire climate community to use. The use of citizen science for digitisation will also be exploited as an opportunity to engage the public in science and to communicate climate science.