EU FP7 Marie Curie Career Integration Grant (CIG)
Project lead: Dr Gregor C. Leckebusch
Meteorological and climatological extreme events have an extraordinarily high impact on financial, economic and social conditions in Europe and are one of the most dangerous triggers of failure in the administrative and infra-structural system of our society. Thus, according to figures of one of the largest re-insurance companies operating world-wide, the number of catastrophic events caused by natural hazards has increased during the course of the past few decades (Munich Re, 2011).
In relation to this, two main foci of scientific investigation have achieved high visibility so far. The first concerns the short-term prediction of extreme events, as is routinely carried out by operating weather forecasting providers. The second concentrates on the detection and attribution of anthropogenic climate modifications for the observed past and assessments of potential changes to extreme event behaviour, and characteristics for potential future climate developments.
Between the synoptic time scale (two to eight days) and potential future anthropogenic changes (more on the centennial scale) two distinct horizons should be recognized: on a shorter time scale the intra-seasonal and inter-annual variability and on a longer time scale the decadal-to-multi-decadal variability.
With respect to steering mechanisms for the occurrence of extreme events, the knowledge of natural decadal variability interacting with potential long-term anthropogenic climate change will be crucial to providing reliable information to stakeholders and end-users from industry and society. In particular, an estimation of possible variance of decadal variability features (as the observed past is from a statistical point of view only one of all possible realizations), giving evidence for possible maximum and minimum deviations from a mean climate state extreme value behaviour is missing. This information is crucial as it could be linked to longer-term anthropogenic forcing factors and will thus provide more realistic estimates of potential extreme event behaviour for the next few decades up to the middle of this century.
In order to be able, for example, to issue climate predictions on the scale of up to 30 years by the means of climate model simulations, it is necessary to learn more about the amount and the form of synoptic, seasonal and decadal scale variability in the coupled ocean-cryosphere-atmosphere system itself and its steering processes. Specific long-term variability modes may influence the frequency and intensity of extreme events on even synoptic scales. By increasing the understanding of processes involved in the modification of extreme event occurrence, it will be possible to identify, for example, the most important initial conditions to be reflected in the initial conditions of the decadal prediction, or to identify the most important processes which have to be captured correctly by the models physics in order to simulate realistically different kinds of variability of extremes.
A deeper understanding of decadal to multi-decadal scale variability of extremes and its reasons will also help to close the gap between observed or potential decadal variability and studies into potential future anthropogenic climate influences on a much longer scale but on a transient scenario basis. In fact, actual ACC studies are mainly based on IPCC-SRES scenarios assuming principally a monotonically increasing forcing in greenhouse gas concentrations and thus climate development due to this forcing.
In reality, however, decadal and multi-decadal variability will superpose any long-term trend. Consequently, it is of crucial interest to know about possible ranges of decadal variability and their interaction with the underlying ACC trend. This again will require a proper assessment of both, thus also of the ACC signal potential to the middle part of this century and of course beyond the time-scale of the next few decades.
In line with the IPCC 5th Assessment Report efforts, new coupled global climate model simulations are available for investigation. Within this project it is planned that these simulations will be analysed with respect to the occurrence of extremes (wind storm, heat waves) and that these will be compared with former scenarios; there is also planned analysis into the mechanisms of change within their generation on the long-term scale.
Consequently, EVE will work to the following five research objectives:
- Investigation of the synoptic scale event-to-event variability and assessment of reasons for different developments.
- Identification of mechanisms steering the seasonal variability of extreme events, thus leading to potential predictability and its related predictive skill
- Analysis of decadal to multi-decadal scale variability of extremes in relation to large-scale variability modes (AMO, AMM) dominant for the North-Atlantic and Europe.
- Identification of the potential anthropogenic climate change signal on extremes by means of the new IPCC RCP scenario simulations (CMIP3 data set).
- Assessment of the impact of decadal to long-term variability of extreme events in society and economy and its uncertainty.