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Recent unprecedented extremes such as the 2023 New Year’s winter warm spell in Europe, the 2022 summer heat and dryness in China and Europe, the 2021 Pacific Northwest heatwave, the 2021 floods in northwestern Germany and the 2020 Siberian heat anomaly broke previous observed record intensities by large margins. Based on the observations up to the year before the event, some of these record-shattering extremes were inconceivable. Could the scientific community have better quantified the potential for such unseen events based on the current generation of climate models?Here, we demonstrate how a new ensemble boosting approach can be used to generate physically coherent storylines of such unseen events. In ensemble boosting a fully-coupled free-running climate model (CESM2) is used to develop physical storylines of very rare extremes. To this end, the most extreme events in an initial-condition large ensemble for the near future are re-initialized with slightly perturbed atmospheric initial conditions to efficiently generate events with magnitudes unprecedented in the observational record.We demonstrate that, with this approach, CESM2 can simulate events that e.g. substantially exceed the magnitude of the 2021 Pacific Northwest (PNW) heatwave anomaly. Even though the most extreme ensemble members were only selected based on the local temperature anomaly over the PNW region, they show a very similar temporal evolution and spatial pattern as the observed event. The associated 500hPa geopotential height anomaly is remarkably similar to the observed event with a strong anticyclone over PNW that is part of a wave pattern extending over much of the Northern Hemisphere. We further show that in some of the storylines pre-conditioning dry soils strongly contributed to the heatwave intensity, whereas in others, heatwaves of similar magnitude occur even at average land surface conditions.We further develop storylines for heatwaves in the Greater Paris and Chicago regions of much greater intensities than ever observed. Particularly the US Midwest, where no intensification of heatwaves has been observed in recent decades, has not experienced anything close to the heatwave intensities possible in the coming years.Finally, we demonstrate examples how ensemble boosting can also be used to generate storylines for multi-year drought events and large-scale heavy precipitation extremes and compare the findings to other storyline approaches. Event storylines based on ensemble boosting can be used in impact studies that require physical consistency across variables, e.g., for the evaluation of humid heatwaves or compound events, for assessing wildfire risks or for ecosystem modelling.

Heat waves such as the one in Europe 2003 have severe consequences for the economy, society, and ecosystems. It is unclear whether temperatures could have exceeded these anomalies even without further climate change. Developing storylines and quantifying highest possible temperature levels is challenging given the lack of long homogeneous time series and methodological framework to assess them. Here, we address this challenge by analysing summer temperatures in a nearly 5000-year pre-industrial climate model simulation, performed with the Community Earth System Model CESM1. To assess how anomalous temperatures could get, we compare storylines, generated by three different methods: (1) a return-level estimate, deduced from a generalized extreme value distribution, (2) a regression model, based on dynamic and thermodynamic heat wave drivers, and (3) a novel ensemble boosting method, generating large samples of re-initialized extreme heat waves in the long climate simulation.All methods provide consistent temperature estimates, suggesting that historical exceptional heat waves as in Chicago 1995, Europe 2003 and Russia 2010 could have been substantially exceeded even in the absence of further global warming. These estimated unseen heat waves are caused by the same drivers as moderate observed events, but with more anomalous patterns. Moreover, altered contributions of circulation and soil moisture to temperature anomalies include amplified feedbacks in the surface energy budget. The methodological framework of combining different storyline approaches of heat waves with magnitudes beyond the observational record may ultimately contribute to adaptation and to the stress testing of ecosystems or socio-economic systems to increase resilience to extreme climate stressors.

The Pacific Northwest heat wave is one of a series of record-shattering heat extremes that, based on the previous observational record, may have been deemed impossible. Here we address the question of whether the potential for such an extreme heat wave could have been foreseen using simulated physical climate storylines.We use a novel approach, called ensemble boosting, in which a fully-coupled free-running climate model (CESM2) is used to develop physical storylines of very rare heat extremes under present-day conditions. In ensemble boosting, the most extreme events in an initial-condition large ensemble for the near future are re-initialized with slightly perturbed atmospheric initial conditions to efficiently generate events that are even more extreme, with the goal of sampling events with magnitudes that have not been seen before.We demonstrate that, with this approach, CESM2 can efficiently simulate events that reach or even exceed the magnitude and duration of the 2021 Pacific Northwest heatwave anomaly. The atmospheric circulation anomalies associated with the most extreme simulated heat waves in the boosted ensemble are remarkably similar to the observed event. We further evaluate the anomalies in the surface energy and water budgets that contribute to the most intense simulated events. We conclude that based on this approach, heat waves unseen in the observational record can be simulated in models, at least in some regions. After probing this approach for the Pacific Northwest heatwave, we apply it to other mid-latitude regions where extreme heat events of much higher magnitude than has been observed are plausible in the near future.The ensemble boosting approach is computationally efficient, and it preserves physical consistency both in time, in space and across variables. This has the major advantages that the drivers can be directly evaluated against observed events and the generated storylines can be used in impact studies that require physical consistency, e.g. for the evaluation of humid heatwaves or compound events, for assessing wildfire risks or for ecosystem modelling.

Heavy precipitation events as the one in western Germany and the Benelux countries in July 2021 destroy the local infrastructure and numerous fatalities. Due to the lack of long homogenous climate data and methodological framework, it is uncertain how intense precipitation extremes could get. We address these questions by developing storylines of the rarest precipitation events. We here generate large samples of reinitialized heavy rainfall events starting from the most extreme events in an initial condition large ensemble for the near future, carried out with CESM2. In an approach referred to as ensemble boosting, we first reinitialize the most extreme 3-day precipitation events to estimate how anomalous they could get. We find that the most extreme precipitation events can be substantially exceeded in the boosted ensembles for different regions across the world. Second, we evaluate whether the model can reproduce analogues of the precipitation event in July 2021 and re-initialize these events to analyze how this event type could have evolved and whether it could have become even more intense. In doing so, the ensemble boosting method provides storylines of heavy rainfall development beyond the observational record, which can be used to generate worst-case scenarios and stress test the socioeconomic system.

In recent years, unprecedented temperature and precipitation extremes have been observed across the world. With further global warming, climate models project extreme events to get even more intense and likely break observational records by large margins. It is challenging to estimate how extreme climate events could get and to quantify the contribution of physical drivers in the future or even in the present climate? To address these questions, we introduce the ensemble boosting method, a model-based method that generates large samples of re-initialized extreme events in climate simulations. In doing so, the method provides physically consistent storylines of climate extremes that can be used to analyse the driving factors and estimate the very high return levels for the event type beyond observational records. We apply ensemble boosting to heat waves in the millennial pre-industrial control run, made with CESM1 and to heavy precipitation in the large ensemble near future simulations, carried out with CESM2. We find that individual members of the boosted ensembles can substantially exceed the most extreme heat and precipitation events over Europe and North America in the respective climatology. Furthermore, we show that estimated upper bounds of heat correspond to the statistical estimates by the generalized extreme value (GEV) distribution and regression models. Therefore, the framework of ensemble boosting might ultimately contribute to adaption and the stress testing of ecosystems or socioeconomic systems, increasing the resilience to extreme climate stressors.

Introdução: A síndrome de hipersensibilidade a drogas com eosinofilia e sintomas sistêmicos (DRESS) incide em 1/1.000 a 1/10.000 pacientes expostos a anticonvulsivantes, com mortalidade de 10%, e morbidade significativa em curto e longo prazo. Para tratamento o indicado é a combinação entre medicação sistêmica e produtos tópicos. A emulsão com óleo de andiroba tem sido usada em lesões cutâneas principalmente causadas por queimaduras térmicas, depilação e por radioterapia. Objetivo: Verificar e analisar a eficácia e a resposta clínica da lesão por DRESS com o uso tópico de emulsão com óleo de andiroba (Tegum®). Material e métodos: O estudo será um relato de caso retrospectivo, as informações foram obtidas por meio de revisão do prontuário, entrevista com a paciente, registro fotográfico dos métodos diagnósticos aos quais o paciente foi submetido e revisão da literatura, no período entre os meses de outubro e novembro de 2019, com assinatura do Termo de Consentimento Livre e Esclarecido (TCLE). Resultados: Paciente do sexo feminino, 42 anos, procurou o pronto socorro apresentando rash cutâneo pruriginoso, após ser admitida no setor de internação, nos primeiros três dias fez uso de antibioticoterapia e prednisona dose não-imunossupressora, foi suspenso o antibiótico e mantido a corticoterapia e iniciou os cuidados de enfermagem no terceiro dia de internação apresentando a lesão no membro superior esquerdo (MSE) com rubor, dor, calor, edema e flictemas em toda extensão, foi utilizado no curativo com emulsão com óleo andiroba por 8 dias com trocas diárias pós banho pela equipe de enfermagem, apresentou diminuição das lesões, dor e prurido. Paciente teve alta no decimo segundo dia com lesões cicatrizadas. Conclusão: A lesão em MSE apresentou cicatrização completa, reduzindo os sintomas da paciente em um curto período, sendo assim a cobertura escolhida foi efetiva.

During the last decades, Europe has experienced intense dry and hot spells, which seriously impact socio-economic sectors and the ecosystem by shortages of water in the summer season. The occurrence of two exceptional consecutive dry summers 2018/2019 let a multi-year drought become a conceivable scenario. In order to implement adaptation strategies for such a natural hazard, stakeholders raise the questions, how dry and hot a worst-case drought scenario would turn out and how long it would take to fully recover from those climate anomalies?We address these concerns through the generation of storylines, describing the driest plausible multi-year droughts over western Europe. By repeatedly resampling the occurrence of precipitation in the climate simulation, using 100-member ensembles, we inhibit rainfall and dehydrate the soils in western Europe. These storylines and a millennial climate control simulation are carried out with CESM1.2 under pre-industrial forcing.In doing so, local precipitation is reduced by 80% and local soil moisture falls far below the 1st percentile of the climatology. Even compared to the present and future climate scenarios, still, the number of dry days is very rare in our drought storyline, i.e. we describe a hazardous but unlikely scenario. Moreover, these storylines are associated with the hottest spring, summer and fall temperatures, but also the coldest winter temperatures. Starting large ensembles from each summer of the multi-year drought scenario, i.e. under exceptional dry initial soil conditions, we find that summertime hot and dry spells have a twenty-fold chance to occur plus their persistence extents by about 1.5 days. After strong precipitation deficits in the summer months, the precipitation increases again. Nevertheless, the local soil moisture does not fully recover within the next year so that the following spring and summer season may be affected by re-occurring droughts, aggravating the damage through water deficits for the vegetation growth and the economy.

Seasonal prediction is one important element in a seamless prediction chain between weather forecasts and climate projections. After several years of development in collaboration with Universität Hamburg and Max Planck Institute for Meteorology, the Deutscher Wetterdienst performs operational seasonal forecasts since 2016 with the German Climate Forecast System, now in Version 2 (GCFS2.0). Here, the configuration of the previous system GCFS1.0 and the current GCFS2.0 are described and the performance of the two systems is compared over the common hindcast period of 1990–2014. In GCFS2.0, the forecast skill is improved compared to GCFS1.0 during boreal winter, especially for the Northern Hemisphere where the Pearson correlation has increased for the North Atlantic Oscillation index. Overall, a similar performance of GCFS2.0 in comparison to GCFS1.0 is assessed during the boreal summer. Future developments for climate forecasts need a stronger focus on the performance of interannual variability in a model system., Journal of Advances in Modeling Earth Systems, 13 (2), ISSN:1942-2466

Extreme heat waves as in 2003 and 2010 can have severe consequences for the economy and society. This raises the question how anomalous they could have gotten. Addressing this question is challenging given the lack of long coherent reliably daily data. Multi-millennial GCM simulations and single-model initial condition large ensembles offer a new opportunity to investigate the very upper tail of temperature distribution. Here, we use a nearly 5,000-year long pre-industrial control run and a 84-member large initial condition ensemble performed with CESM1.2. Evaluations show that the simulated climate variability and temperature response to circulation anomalies agree well with the ERA5 reanalysis over large parts of the global land regions.We show that highest temperature extremes in the long pre-industrial control simulation exceed the temperature records of 2003 by several degrees in the related hotspot region over Western Europe. The anomalies are caused by large anticyclonic circulation anomalies and very dry land surface conditions, leading to amplifying feedbacks in the surface energy budget. Moreover, the simulation results reveal that summer temperature maxima as a function of return period have an asymptotic , suggesting an upper temperature limit.In a next step, we use a novel method of ensemble boosting to generate even more extreme temperatures. To that end, 100-member ensembles are reinitialized with perturbed atmospheric conditions weeks before the most intense events. Thereby, we gain insight into short-term mechanisms that underly these hot extremes. The result of the ensemble calculation shows that using this method even more extreme event anomalies can be generated, substantially exceeding highest values in the long pre-industrial control simulations. We investigate how the physical mechanisms of these rare and unseen simulated events differ from more moderate events. We further compare the simulated very rare events with maximum anomalies estimated based on statistical methods.

Anthropogenic increases of atmospheric greenhouse gas concentrations are the main driver of current and future climate change. The Integrated Assessment community quantified anthropogenic emissions for the Shared Socioeconomic Pathways (SSP) scenarios, each of which represents a different future socio-economic projection and political environment. Here, we provide the greenhouse gas concentration for these SSP scenarios – using the reduced complexity climate-carbon cycle model MAGICC7.0. We extend historical, observationally-based concentration data with SSP concentration projections from 2015 to 2500 for 43 greenhouse gases with monthly and latitudinal resolution. CO2 concentrations by 2100 range from 393 to 1135 ppm for the lowest (SSP1-1.9) and highest (SSP5-8.5) emission scenarios respectively. We also provide the concentration extensions beyond 2100 based on assumptions in the trajectories of fossil fuels and land use change emissions, net negative emissions, and the fraction of non-CO2 emissions. By 2150, CO2 concentrations in the lowest emission scenario are approximately 350 ppm and approximately plateau at that level until 2500, whereas the highest fossil-fuel driven scenario projects CO2 concentrations of 1737 ppm and reaches concentrations beyond 2000 ppm by 2250. We estimate that the share of CO2 in the total radiative forcing contribution of all considered 43 long-lived greenhouse gases increases from today 66 % to roughly 68 % to 85 % by the time of maximum forcing in the 21st century. For this estimation, we updated simple radiative forcing parameterisations that reflect the Oslo Line by Line model results. In comparison to the RCPs, the five main SSPs (SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0 and SSP5-8.5) are more evenly spaced in terms of their expected global-mean temperatures, extend to lower 2100 temperatures and sea level rise than the RCP set. Performing 2 pairs of 6-member historical ensembles with CESM1.2.2, we estimate the effect on surface air temperatures of applying latitudinally and seasonally resolved GHG concentrations. We find that the ensemble differences in the MAM season provide a regional warming in higher northern latitudes of up to 0.4 K over the historical period, latitudinally averaged of about 0.1 K, which we estimate to be comparable to the upper bound (∼ 5 % level) of natural variability. In comparison to the comparatively straight line of the last 2000 years, the greenhouse gas concentrations since the onset of the industrial period and this studies’ projections over the next 100 to 500 years unequivocally depict a ‘hockey-stick’ upwards shape – it is a collective choice whether the hothouse pathway is pursued or whether we manage climate damages to the SSP1-1.9 equivalent of around 1.5 °C warming.