Search

Variability of the North Atlantic Oscillation (NAO) drives wintertime temperature anomalies in the Northern Hemisphere. Dynamical seasonal prediction systems can skilfully predict the winter NAO. However, prediction of the NAO‐dependent air temperature anomalies remains elusive, partially due to the low variability of predicted NAO. Here, we demonstrate a hidden potential of a multi‐model ensemble of operational seasonal prediction systems for predicting wintertime temperature by increasing the variability of predicted NAO. We identify and subsample those ensemble members which are close to NAO index statistically estimated from initial autumn conditions. In our novel multi‐model approach, the correlation prediction skill for wintertime Central Europe temperature is improved from 0.25 to 0.66, accompanied by an increased winter NAO prediction skill of 0.9. Thereby, temperature anomalies can be skilfully predicted for the upcoming winter over a large part of the Northern Hemisphere through increased variability and skill of predicted NAO. Plain Language Summary: Wintertime temperature in the Northern Hemisphere is regulated by the variations of atmospheric pressure, represented by the so‐called North Atlantic Oscillation (NAO). The NAO's phase—negative or positive—is associated with the pathways of cold and warm air masses leading to cold or warm winters in Europe. While the NAO phase can be predicted well, predictions of the NAO‐dependent air temperature remain elusive. Specifically, it is challenging to predict the strength of the NAO, the most important requirement for the accurate prediction of wintertime temperature. Here, we improve wintertime temperature prediction by increasing the strength of the predicted NAO. We use observation based autumn Northern Hemisphere ocean and air temperature, as well as ice and snow cover for statistical estimation of the first guess NAO for the upcoming winter. Then, we sub‐select only those simulations from the multi‐model ensemble, which are consistent with our first guess NAO. As a result, based on these selected members, the wintertime temperature prediction is substantially improved over a large part of the Northern Hemisphere. Key Points: Amplitude and skill of predicted North Atlantic Oscillation (NAO) improve significantly by subsampling of ensemble of existing seasonal prediction systemsAmplified NAO variability leads to significant improvement in predicting the upcoming winter temperature anomalies in the Northern Hemisphere [ABSTRACT FROM AUTHOR]

We use the 100-member Max Planck Institute Grand Ensemble (MPI-GE) to disentangle the contributions from colocated dynamic atmospheric conditions and local thermodynamic effects of moisture limitation as drivers of variability in European summer heat extremes. Using a novel extreme event definition, we find that heat extremes with respect to the evolving mean climate increase by 70% under a moderate warming scenario during the twenty-first century. With a multiple regression approach, we find that the dynamical mechanisms representing blocking and anticyclonic conditions are the main driver of variability in extreme European summer temperatures, both in past and future climates. By contrast, local thermodynamic drivers play a secondary role in explaining the total variability in extreme temperatures. We also find that considering both dynamical and thermodynamical sources of variability simultaneously is crucial. Assessing only one type of drivers leads to an overestimation of their effect on extreme temperatures, particularly when considering only thermodynamical drivers. Lastly, we find that although most past and future heat extremes occur under favorable dynamical atmospheric conditions; this occurs 10–40% less frequently over Central Europe in the twenty-first century. By contrast, heat extremes over Central Europe occur 40% more frequently under concurrent extreme moisture limitation in the twenty-first Century. Our findings highlight a new type of neutral-atmosphere, moisture-driven heat extremes, and confirm that the increase in European heat extremes and associated variability increase are dominated by the local thermodynamic effect of moisture limitation. [ABSTRACT FROM AUTHOR]

In this study the latest version of the MiKlip decadal hindcast system is analyzed, and the effect of an increased horizontal and vertical resolution on the prediction skill of the extratropical winter circulation is assessed. Four different metrics – the storm track, blocking, cyclone and windstorm frequencies – are analyzed in the North Atlantic and European region. The model bias and the deterministic decadal hindcast skill are evaluated in ensembles of five members in a lower-resolution version (LR, atm: T63L47, ocean: 1.5 ∘ L40) and a higher-resolution version (HR, atm: T127L95, ocean: 0.4 ∘ L40) of the MiKlip system based on the Max Planck Institute Earth System model (MPI-ESM). The skill is assessed for the lead winters 2–5 in terms of the anomaly correlation of the quantities' winter averages using initializations between 1978 and 2012. The deterministic predictions are considered skillful if the anomaly correlation is positive and statistically significant. While the LR version shows common shortcomings of lower-resolution climate models, e.g., a storm track that is too zonal and southward displaced as well as a negative bias of blocking frequencies over the eastern North Atlantic and Europe, the HR version counteracts these biases. Cyclones, i.e., their frequencies and characteristics like strength and lifetime, are particularly better represented in HR. As a result, a chain of significantly improved decadal prediction skill between all four metrics is found with the increase in the spatial resolution. While the skill of the storm track is significantly improved primarily over the main source region of synoptic activity – the North Atlantic Current – the other extratropical quantities experience a significant improvement primarily downstream thereof, i.e., in regions where the synoptic systems typically intensify. Thus, the skill of the cyclone frequencies is significantly improved over the central North Atlantic and northern Europe, the skill of the blocking frequencies is significantly improved over the Mediterranean, Scandinavia and eastern Europe, and the skill of the windstorms is significantly improved over Newfoundland and central Europe. Not only is the skill improved with the increase in resolution, but the HR system itself also exhibits significant skill over large areas of the North Atlantic and European sector for all four circulation metrics. These results are particularly promising regarding the high socioeconomic impact of European winter windstorms and blocking situations. [ABSTRACT FROM AUTHOR]

We improve seasonal hindcast skill of European summer climate in an ensemble based coupled seasonal prediction system by selecting individual ensemble members based on their respective consistent chain of processes that describe a physical mechanism. This mechanism is associated with the second mode of seasonal climate variability in the North-Atlantic-European sector and is contrary to the summer North Atlantic Oscillation. We initially analyse the mechanism in the ERA-Interim reanalysis and then test the influence of the mechanism on European hindcast skill in an initialised coupled seasonal climate model. We show that the mechanism originates in the tropical North Atlantic in spring, where either warm or cold sea surface temperature anomalies (SSTs) are connected with the European climate by an upper-level wave-train. This wave-train is accompanied by a zonal pressure gradient, that in turn influences the climate over central Europe in the following summer. We analyse the seasonal summer hindcast skill in a mixed resolution hindcast ensemble simulation generated by MPI-ESM, with 30 members starting every year in May. While the mean over the full ensemble shows no seasonal hindcast skill in summer, we achieve significant hindcast skill through forming a new mean over subselected ensemble members. For this selection, we test every ensemble member for the proposed consistent chain of connections between the wave-train, the zonal pressure gradient and their impact on European summer temperatures, and find that the processes that describe the mechanism are not represented in every ensemble member. Due to its influence on European summer climate, we use the condition of the persistent spring SSTs to anticipate the phase of the mechanism in each considered year. We thus use statistical relations to select ensemble members generated by a dynamical prediction system. With this approach, we significantly enhance the seasonal hindcast skill and the reliability of the hindcasts in the North-Atlantic-European sector, especially in the areas where the mechanism is showing a prominent signal. Since we only use knowledge that would be available in a real forecast set-up, this approach can potentially be applied in operational ensemble prediction systems. [ABSTRACT FROM AUTHOR]

The Atlantic multidecadal variability (AMV) is known to affect the central to eastern (C–E) European summer climate through an associated atmospheric baroclinic response called North-Atlantic-European East West mode as demonstrated in the twentieth century reanalysis (20CRv2). Here, using the atmospheric model ECHAM6.3, we perform sensitivity experiments with prescribed sea surface temperature (SST) anomalies that are representative of the observed positive and the negative AMV phases and investigate the model response to the observed AMV pattern for European summer climate. The results from the experiments reveal that in the negative phase of AMV, the North-Atlantic-European (NAE) climate is mainly governed by the extra-tropical branch of the AMV through a baroclinic-like response. This response brings negative surface air temperature (SAT) anomalies over C–E Europe. The response and its influence are similar to what is found in the 20CRv2. In contrast, in the positive phase of the AMV, the NAE climate in the model experiments is mainly influenced by the tropical branch of the AMV. A stationary Rossby wave response excited in the tropics is associated with negative SAT anomalies over C–E Europe, which is opposite to what is found in the 20CRv2. The model response from the tropical part of the AMV SST is unlikely to be realistic due to the lack of coupled air–sea interaction, when SST is specified. Hence, the results demonstrate that ECHAM6.3 can simulate the observed linear baroclinic response, but only in the negative phase of the AMV. For the positive phase, in agreement with the previous findings, the model response is very sensitive to the tropical branch of the AMV and unrealistic. [ABSTRACT FROM AUTHOR]

In this study the latest version of the MiKlip decadal hindcast system is analyzed and the effect of different horizontal and vertical resolutions on the prediction skill of the northern hemisphere extra-tropical atmospheric circulation is assessed. Four metrics – the stormtrack, blocking frequencies, cyclone frequencies and windstorm frequencies – are analyzed with respect to the anomaly correlation of their winter averages. The model bias and hindcast skill are evaluated in both, a lower resolution version (LR, atm: T63L47, ocean: 1.5° L40) and a higher resolution version (HR, atm: T127L95, ocean: 0.4° L40) of the MPI-ESM system, for the lead years 2–5 using initializations between 1978 and 2012. While the LR version shows common shortcomings of lower resolution climate models, e.g. a too zonal stormtrack and a negative bias of blocking frequencies over the eastern North Atlantic and Europe, the HR version works against these biases. As a result, a functional chain of significantly improved decadal prediction skill between all four metrics is found with the increase of the spatial resolution. While the stormtrack, is significantly improved primarily over the main source region of synoptic activity – the North Atlantic Current, the other extra-tropical measures experience a significant improvement downstream thereof. Thus, the skill of the cyclone frequencies is significantly improved over the central North Atlantic and Northern Europe, the skill of the blocking frequencies is significantly improved over the Mediterranean, Scandinavia and Eastern Europe and the skill of the windstorms is significantly improved over Newfoundland and Central Europe. Not only is the skill improved with the increase in resolution, but the HR system itself exhibits significant skill over large areas of the North Atlantic and European sector for all four circulation metrics. These results are particularly promising regarding the high socio-economic impact of European winter windstorms and blocking situations. [ABSTRACT FROM AUTHOR]

The current state of development and the prospects of the regional MiKlip decadal prediction system for Europe are analysed. The MiKlip regional system consists of two 10-member hindcast ensembles computed with the global coupled model MPI-ESM-LR downscaled for the European region with COSMO-CLM to a horizontal resolution of 0.22 ∘ (∼25 km). Prediction skills are computed for temperature, precipitation, and wind speed using E-OBS and an ERA-Interim-driven COSMO-CLM simulation as verification datasets. Focus is given to the eight European PRUDENCE regions and to lead years 1–5 after initialization. Evidence of the general potential for regional decadal predictability for all three variables is provided. For example, the initialized hindcasts outperform the uninitialized historical runs for some key regions in Europe, particularly in southern Europe. However, forecast skill is not detected in all cases, but it depends on the variable, the region, and the hindcast generation. A comparison of the downscaled hindcasts with the global MPI-ESM-LR runs reveals that the MiKlip prediction system may distinctly benefit from regionalization, in particular for parts of southern Europe and for Scandinavia. The forecast accuracy of the MiKlip ensemble is systematically enhanced when the ensemble size is increased stepwise, and 10 members is found to be suitable for decadal predictions. This result is valid for all variables and European regions in both the global and regional MiKlip ensemble. The present results are encouraging for the development of a regional decadal prediction system. [ABSTRACT FROM AUTHOR]

The current state of development and prospects of the regional MiKlip decadal prediction system for Europe are analysed. The Miklip regional system consists of two 10-member hindcast ensembles computed with the global coupled model MPI-ESM-LR downscaled for the European region with COSMO-CLM to a horizontal resolution of 0.22° (∼25 km). Prediction skills are computed for temperature, precipitation, and wind speed using E-OBS and an ERA-Interim driven COSMO-CLM simulation as verification datasets. Focus is given to the eight European PRUDENCE regions and to lead 20 years 1-5 after initialization. Evidence of the general potential for regional decadal predictability for all three variables is provided. For example, the initialized hindcasts outperform the uninitialized historical runs for some key regions in Europe and for some variables both in terms of accuracy and reliability. However, forecast skill is not detected in all cases, but it depends on the variable, the region, and the hindcast generation. A comparison of the downscaled hindcasts with the global MPI-ESM-LR runs reveals that the MiKlip prediction system may distinctly benefit from regionalization, in particular for 25 parts of Southern Europe and for Scandinavia. The forecast accuracy and the reliability of the MiKlip ensemble is systematically enhanced when the ensemble size is stepwise increased, and a number of 10 members is found to be suitable for decadal predictions. This result is valid for all variables and European regions in both the global and regional MiKlip ensemble. The predictive skill improves distinctly, particularly for temperature, when retaining the long-term trend in the time series. The present results are encouraging towards the development of a regional decadal prediction system. [ABSTRACT FROM AUTHOR]

The observed prominent multidecadal variations in the central to eastern (C-E) European summer temperature are closely related to the Atlantic multidecadal variability (AMV). Using the Twentieth Century Reanalysis project version 2 data for the period of 1930-2012, we present a mechanism by which the multidecadal variations in the C-E European summer temperature are associated to a linear baroclinic atmospheric response to the AMV-related surface heat flux. Our results suggest that over the north-western Atlantic, the positive heat flux anomaly triggers a surface baroclinic pressure response to diabatic heating with a negative surface pressure anomaly to the east of the heat source. Further downstream, this response induces an east-west wave-like pressure anomaly. The east-west wave-like response in the sea level pressure structure, to which we refer as North-Atlantic-European East West (NEW) mode, is independent of the summer North Atlantic Oscillation and is the principal mode of variations during summer over the Euro-Atlantic region at multidecadal time scales. The NEW mode causes warming of the C-E European region by creating an atmospheric blocking-like situation. Our findings also suggest that this NEW mode is responsible for the multidecadal variations in precipitation over the British Isles and north-western Europe. [ABSTRACT FROM AUTHOR]

We outline a comprehensive research program on institutional reforms in European parliaments. Original data show that parliamentary rules in Western European parliaments have been changed frequently and massively during the period from 1945 to 2010 suggesting that actors use institutional reforms as a distinct strategy to pursue their substantive goals. We discuss how institutional instability affects existing theoretical and empirical arguments about institutional effects. Furthermore, we present four ideal-typical approaches to analyzing rule changes, present new software tools for identifying and coding changes in large text corpora, and demonstrate their usefulness for valid measurement of the overall change between subsequent text versions. [ABSTRACT FROM AUTHOR]

Multiparty government in parliamentary democracies entails bargaining over the payoffs of government participation, in particular the allocation of cabinet positions. While most of the literature deals with the numerical distribution of cabinet seats among government parties, this article explores the distribution of individual portfolios. It argues that coalition negotiations are sequential choice processes that begin with the allocation of those portfolios most important to the bargaining parties. This induces conditionality in the bargaining process as choices of individual cabinet positions are not independent of each other. Linking this sequential logic with party preferences for individual cabinet positions, the authors of the article study the allocation of individual portfolios for 146 coalition governments in Western and Central Eastern Europe. The results suggest that a sequential logic in the bargaining process results in better predictions than assuming mutual independence in the distribution of individual portfolios. [ABSTRACT FROM AUTHOR]

Predictability on seasonal time scales over the North Atlantic-Europe region is assessed using a seasonal prediction system based on an initialized version of the Max Planck Institute Earth System Model (MPI-ESM). For this region, two of the dominant predictors on seasonal time scales are El Niño-Southern Oscillation (ENSO) and sudden stratospheric warming (SSW) events. Multiple studies have shown a potential for improved North Atlantic predictability for either predictor. Their respective influences are however difficult to disentangle, since the stratosphere is itself impacted by ENSO. Both El Niño and SSW events correspond to a negative signature of the North Atlantic Oscillation (NAO), which has a major influence on European weather. This study explores the impact on Europe by separating the stratospheric pathway of the El Niño teleconnection. In the seasonal prediction system, the evolution of El Niño events is well captured for lead times of up to 6 months, and stratospheric variability is reproduced with a realistic frequency of SSW events. The model reproduces the El Niño teleconnection through the stratosphere, involving a deepened Aleutian low connected to a warm anomaly in the northern winter stratosphere. The stratospheric anomaly signal then propagates downward into the troposphere through the winter season. Predictability of 500-hPa geopotential height over Europe at lead times of up to 4 months is shown to be increased only for El Niño events that exhibit SSW events, and it is shown that the characteristic negative NAO signal is only obtained for winters also containing major SSW events for both the model and the reanalysis data. [ABSTRACT FROM AUTHOR]

We investigate European summer (July-August) precipitation variability and its global teleconnections using the NCEP/NCAR reanalysis data (1950-2010) and a historical Coupled Model Intercomparison Project climate simulation (1901-2005) carried out using the ECHAM6/MPIOM climate model. A wavelike pattern is found in the upper tropospheric levels (200 hPa) similar to the summer circumglobal wave train (CGT) extending from the North Pacific to the Eurasian region. The positive phase of the CGT is associated with upper level anomalous low (high) pressure over western (eastern) Europe. It is further associated with a dipole-like precipitation pattern over Europe entailing significantly enhanced (reduced) precipitation over the western (eastern) region. The anomalous circulation features and associated summer precipitation pattern over Europe inverts for the negative CGT phase. Accordingly, the global teleconnection pattern of a precipitation index summarizing summer precipitation over Western Europe entails an upper level signature which consists of a CGT-like wave pattern extending from the North Pacific to Eurasia. The imprint of the CGT on European summer precipitation is distinct from that of the summer North Atlantic Oscillation, despite the two modes of variability bear strong similarities in their upper level atmospheric pattern over Western Europe. The analysis of simulated CGT features and of its climatic implications for the European region substantiates the existence of the CGT-European summer precipitation connection. The summer CGT in the mid-latitude therefore adds to the list of the modes of large-scale atmospheric variability significantly influencing European summer precipitation variability. [ABSTRACT FROM AUTHOR]

Tularemia outbreaks in humans have recently been reported in many European countries, but data on the occurrence in the animal population are scarce. In North America, seroconversion of omnivores and carnivores was used as indicator for the presence of tularemia, for the European fauna, however, data are barely available. Therefore, the suitability of wild boars ( Sus scrofa) and red foxes ( Vulpes vulpes) as indicators for the circulation of F. tularensis in Germany was evaluated. Serum samples from 566 wild boars and 457 red foxes were collected between 1995 and 2012 in three federal states in Central Germany (Hesse, Saxony-Anhalt, and Thuringia). The overall rate of seropositive animals was 1.1% in wild boars and 7.4% in red foxes. In conclusion, serological examination of red foxes is recommended, because they can be reliably used as indicator animals for the presence of F. tularensis in the environment. [ABSTRACT FROM AUTHOR]

Marked changes in human dispersal and development during the Middle to Upper Paleolithic transition have been attributed to massive volcanic eruption and/or severe climatic deterioration. We test this concept using records of volcanic ash layers of the Campanian Ignimbrite eruption dated to ca. 40,000 y ago (40 ka B.P.). The distribution of the Campanian Ignimbrite has been enhanced by the discovery of cryptotephra deposits (volcanic ash layers that are not visible to the naked eye) in archaeological cave sequences. They enable us to synchronize archaeological and paleoclimatic records through the period of transition from Neanderthal to the earliest anatomically modern human populations in Europe. Our results confirm that the combined effects of a major volcanic eruption and severe climatic cooling failed to have lasting impacts on Neanderthals or early modern humans in Europe. We infer that modern humans proved a greater competitive threat to indigenous populations than natural disasters. [ABSTRACT FROM AUTHOR]

By mid-2003, the legal orders (the entire bodies of legislation in force) of three EU member states – Austria , Denmark, and The Netherlands – contained between 10.5 and 14.2 per cent of rules devoted to the transposition of EU directives. Only a few ministerial jurisdictions contain more than 20 per cent of Europeanized rules. The member states show remarkable differences in the use of parliamentary versus delegated legislation as a means of transposition. The comparison of the three cases tentatively suggests that different legal traditions and the parliamentary involvement in EU affairs are important factors that account for cross-national differences. [ABSTRACT FROM AUTHOR]

This article addresses the scope of legal Europeanization with regard to Austria, a 1995 accession country. Depending on the choice among several plausible indicators of legal Europeanization, the relative impact of the EU varies greatly. The share of EU-related legislation peaked in the pre-accession period when most of the acquis communautaire needed to be adopted. In the membership period, legislation that relates to the EU accounts for almost 25 per cent of the enactments. Although government decrees outnumber laws as the means of transposition, EU-related rules constitute a much smaller share of delegated legislation. Collectively, EU-related rules constitute a tenth of Austrian legislation. Yet by mid-2003, 42 per cent of Austria's original laws—the core of its legislation—were related to EU rules. While falling short of some inflated expectations, legal Europeanization is indeed a major feature of Austrian legislation. The article confirms expectations derived from the political controversy of EU affairs, federalism, and legal traditions. When we refer to ‘legal orders' in the article we mean the entire body of legislation in force; we use the term ‘legislation’ to refer to recent additions to the body of legislation. [ABSTRACT FROM AUTHOR]

In modem democracies political parties exist because (1) they reduce transaction costs in the electoral, parliamentary and governmental arenas and (2) help overcome the dilemma of collective action. In Western Europe political parties are the central mechanism to make the constitutional chain of political delegation and accountability work in practice. Party representatives in public office are ultimately the agents of the extra-parliamentary party organization. In order to contain agency loss parties rely on party-internal mechanisms and the institutionalisation of party rights in public rules and, in contrast to US parties, they apply the full range of ex ante and ex post mechanisms. Generally, the role of party is weaker the further down the chain of delegation. [ABSTRACT FROM AUTHOR]

The article presents the authors' views on political parties in European democracies since 1960-1990. According to them, there has been an organizational decline and a loss of organizational links which tie parties to electors. They say that raw membership count is one of the principal measures by which party membership strength can be assessed across national boundaries. They note that the pattern of party membership among the traditional liberal parties has also been erratic.

In this white paper, we describe the founding of a new ELIXIR Community - the Systems Biology Community - and its proposed future contributions to both ELIXIR and the broader community of systems biologists in Europe and worldwide. The Community believes that the infrastructure aspects of systems biology - databases, (modelling) tools and standards development, as well as training and access to cloud infrastructure - are not only appropriate components of the ELIXIR infrastructure, but will prove key components of ELIXIR's future support of advanced biological applications and personalised medicine. By way of a series of meetings, the Community identified seven key areas for its future activities, reflecting both future needs and previous and current activities within ELIXIR Platforms and Communities. These are: overcoming barriers to the wider uptake of systems biology; linking new and existing data to systems biology models; interoperability of systems biology resources; further development and embedding of systems medicine; provisioning of modelling as a service; building and coordinating capacity building and training resources; and supporting industrial embedding of systems biology. A set of objectives for the Community has been identified under four main headline areas: Standardisation and Interoperability, Technology, Capacity Building and Training, and Industrial Embedding. These are grouped into short-term (3-year), mid-term (6-year) and long-term (10-year) objectives., Competing Interests: No competing interests were disclosed., (Copyright: © 2022 Martins dos Santos V et al.)

Mobility of people and goods during the Upper Paleolithic has proven difficult to reconstruct given the relative rareness of remains. Nevertheless, archaeological contexts like the Late Pleistocene horizon of Borsuka Cave (Southern Poland) represent a unique opportunity to explore patterns of objects' transportation across Central Europe. We investigated the origin of four ornaments made of European elk (Alces alces L.) incisors recovered at Borsuka Cave - the oldest known burial site in Poland, possibly a child grave. Laser-ablation plasma source mass spectrometric analyses of trace elements and Sr isotopic compositions revealed that one elk was roaming within a geologically uniform area while the others changed their pastures during their lifetimes. The non-local origin of the elk teeth is inferred from their exotic Sr isotopic compositions and the lack of evidence for the presence of elk in this territory during the Pleistocene. Instead, the elks' Sr isotopic composition show good agreement with sites near the Austria-Slovakia border region and northern Hungary, ~250 km away from the study site. We argue that the artefacts were most likely brought to Borsuka Cave by humans or by a network of exchange, so far never reported in the time range 32.5-28.8 ka cal BP for Southern Poland.

Although more than a century of radiation research has provided a lot of insight into radiation risk, there are still fields that need clarification. This is particularly true for the low dose range, meaning doses up to ∼100 mSv. One can detect biological effects in that dose range, but it is unclear whether these biological effects like mutations or chromosomal aberrations translate into health effects like cancer, cataracts or circulatory diseases. Thus, for radiation protection purposes, assumptions have to made that must be reappraised on the basis of new findings from time to time. Affected by new insights are currently the DDREF (dose and dose-rate effectiveness factor), cataracts and circulatory diseases. If the new findings are very convincing, dose limits have to be changed at short notice. If there are only weak indications, stability of the radiation protection system is more important than changing limits all the time., (© The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.)