CL3.2.8
Orals: Wed, 26 Apr | Room 0.49/50
Managing extreme weather events of unprecedented magnitude is one of the main challenges facing climate risk management and climate adaptation. Because of the unprecedented nature of these events, some authors have questioned the use of probabilistic approaches in this context. As an alternative, they introduced the so-called climate storylines approach. Climate storylines do not aim at predicting system states; rather, their focus is on revealing plausible chains of events whose impact might undermine the performance of the system.
Conceptually, climate storylines relate to - but are separate from – downward counterfactual histories. Downward counterfactual histories are plausible alternative realizations of historical events that could have turned to the worse. By constructing downward counterfactual histories in a disaster risk reduction context, some authors showed that many disasters that took societies by surprise could have in fact been anticipated.
This talk will introduce a decision-support framework to build climate storylines based on downward counterfactual histories. The framework is event-oriented, it focuses on impact and it is designed to be applied in a participatory fashion. By following the framework, the user first constructs climate storylines based on an iterative analysis of what (combinations of) counterfactuals are deemed critical (i.e., downward). Then, the user analyzes the future impact of the constructed storylines under climatic and socio-economic scenarios. Finally, the user explores the effects on the estimated impacts of the value-laden choices involved in the construction of the storylines.
The framework is applied to study the impact of tropical cyclones hitting the European Union’s outermost regions on the stability of the European Union Solidarity Fund (EUSF), a public fund that provides financial relief to Member States affected by large disasters. Contrary to what historic evidence would suggest, it is found that extreme - yet plausible - tropical cyclones might deplete the EUSF capital if they happen concurrently with large events in mainland Europe, and that a substantial recapitalization of the fund might be required to cope with future climatic and socio-economic changes.
How to cite: Ciullo, A.: A decision-support framework to construct climate impact storylines using downward counterfactuals, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-15450, https://doi.org/10.5194/egusphere-egu23-15450, 2023.
In late June 2021 a heatwave of unprecedented magnitude impacted the Pacific Northwest (PNW) region of Canada and the United States. Many locations broke all-time maximum temperature records by more than 5°C, and the Canadian national temperature record was broken by 4.6°C, with the highest recorded temperature 49.6°C. Local records were broken by large margins, even when compared to local records broken during the infamous heatwaves in Europe 2003, and Russian in 2010. A region of high pressure that became stationary over the region (an atmospheric block) was the dominant cause of this heatwave; however, trajectory analysis finds that upstream diabatic heating played a key role in the magnitude of the temperature anomalies. Weather forecasts provided advanced notice of the event, while sub-seasonal forecasts showed an increased likelihood of a heat extreme with 10-20 day lead times, with an increased likelihood of a blocking event seen in forecasts initialized 3 weeks prior to the heatwave peak. The impacts of this event were catastrophic. We provide a summary of some of these impacts, including estimates of hundreds of attributable deaths across the PNW, mass-mortalities of marine life, reduced crop and fruit yields, river flooding from rapid snow and glacier melt, and a substantial increase in wildfires—the latter contributing to devastating landslides in the months following. These impacts provide examples we can learn from, and a vivid depiction of how climate change can be so devastating.
How to cite: White, R., Anderson, S., Booth, J. F., Braich, G., Draeger, C., Fei, C., Harley, C. D. G., Henderson, S. B., Jakob, M., Lau, C.-A., Mareshet Admasu, L., Narinesingh, V., Rodell, C., Roocroft, E., Weinberger, K. R., and West, G.: The Unprecedented Pacific Northwest Heatwave of June 2021: Causes and Impacts, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-10709, https://doi.org/10.5194/egusphere-egu23-10709, 2023.
From mid-June until the end of August 2022, a sequence of torrential rains and deluges pummeled Pakistan, displacing more than 30 million residents with a death toll of near 2000. The accumulated amount exceeds the centennial average of 126 mm by about 7 standard deviations (50 mm), reaching a value of 487 mm and breaking its record over a century. The extraordinary extremity underscores the urgency for understanding the physical drivers of the event and the relations with human-induced climate change.
Here, we find that distinctive from the historical floods which tend to occur over the relatively wet northern mountains, the 2022 rainfall took place over arid southern Pakistan. Unlike the floods over northern mountains which had closer associations with extratropical westerly troughs, the heavy downpours in 2022 were primarily initiated by the synoptic low-pressure systems (LPS). The longevity and intensity of LPS were sustained and enhanced by the cross-equatorial monsoon flow, which has trended upward since the 1970s and is at a historical high. In combination with the zonal inflow of moisture induced by La Niña, a corridor of heavy rainfall extending from the Bay of Bengal toward southern Pakistan formed.
The signal of greenhouse-gas-forced changes in the heavy rainfall over Pakistan and the cross-equatorial monsoon flow is detectable in climate models, confirming that the likelihood of such extreme events would increase under future warming.
How to cite: You, Y. and Ting, M.: Climate change contributes to the record-shattering 2022 Pakistan rainfall , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4544, https://doi.org/10.5194/egusphere-egu23-4544, 2023.
The Murray Darling Basin, located in southeast Australia, is an agriculturally rich area, providing one-third of the country’ food supply. In 2017-2019 the region experienced one of its worst droughts since 1900. Rainfall in the Murray Darling Basin was consistently below average for three consecutive cool seasons, an unprecedented event on record. The drought set the extreme conditions that led later to the 2019-2020 Black Summer Bushfires. Previous studies suggest that the strong 2019 positive Indian Ocean Dipole intensified the conditions of the drought, however the state of the climate drivers cannot fully explain the onset and development of the Murray Darling Basin drought. In this study, we investigate processes other than remote climate drivers that may have triggered the drought. Using a Lagrangian model to backtrack moisture sources to southeast Australia, we show that local processes were crucial in explaining the onset and development of the drought. We identify the sources of moisture to the cool season precipitation over the Murray Darling Basin and show for the first time that the moisture supply from the Tasman Sea declined in 2017 and 2018. We further show that the expected moisture was instead transported northward by an anomalous anticyclonic circulation. Our results provide an explanation for the moisture and rainfall deficit that caused the 2017-19 drought. Understanding the processes that led to the 2017-2019 Murray Darling Basin drought is important for predicting and planning future multi-year droughts in Australia.
How to cite: Taschetto, A. S., Stojanovic, M., Holgate, C., Drumond, A., Evans, J., Gimeno, L., and Nieto, R.: Reduced moisture sources contributed to the 2017-2019 southeast Australian drought, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4681, https://doi.org/10.5194/egusphere-egu23-4681, 2023.
In the summer of 2022 unprecedented weather conditions in the UK lead to wildfires in many regions. Record breaking temperatures – above 40 °C for the first time - and prolonged dry conditions led to exceptional fire weather severity. On July 19th London Fire Brigade declared a major incident as firefighters battled several significant wildfires across the city. We investigate if climate change is enhancing summertime wildfire risk in the UK.
We use reanalysis data from 1960 to the present day to analysis trends in the climatic indicators that influence the fire weather index. A large ensemble of initialised climate model simulations from the same time period are used to support the findings and identify as-yet-unrealised possible fire weather index situations in the UK.
In the UK the term ‘wildfire’ is not limited to fires in wildland, but to any uncontrolled vegetation fire which requires action regarding suppression. Wildfires in the UK are considered a semi-natural hazard due to their close link with human activity. Though we investigate only meteorological influences, these are not the sole cause of wildfires – for example fuel availability plays a large role.
Better understanding of the trends in the fire weather severity and chance of exceptional conditions for the UK will enable improved understanding of the risks. This information can feed into relevant policy and contingency planning, allowing society to become better prepared for the future as the planet continues to warm.
How to cite: Thompson, V., Mitchell, D., Bloomfield, H., Dunstone, N., and Kay, G.: Increasing chances of summer wildfires in the UK? , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2330, https://doi.org/10.5194/egusphere-egu23-2330, 2023.
It comes as no surprise that the future holds record-breaking weather and climate events. As global warming continues, temperature records will continue to be broken. Also heavy precipitation records are likely to be broken due to the increased water holding capacity of the atmosphere, in combination with changing atmospheric stability and circulation patterns. Improved estimates on the range of possible record-breaking precipitation events – now and in the future – are a first step to inform adequate adaptation policies for heavy precipitation. Of particular interest are events that break records by large margins – record-shattering events –, since these are likely to incur most damage and losses.
In order to improve estimates of record shattering precipitation events in the present and future climate we use initial condition large ensemble simulation data (CESM2, SSP370) and statistical models. We evaluate record-shattering events in Rx1d (day with most precipitation per chosen time period (year or season)). In a stationary climate, the probability of Rx1d record-breaking is known to decrease with the number of data points since the start of measurements (inversely proportional). We find, however, that in our nonstationary climate, the decay in Rx1d record breaking and shattering probability is slowed down and even reversed in most world regions. Regional changes in record shattering probability are attributable to a changing underlying probability distribution of Rx1d, which also is region specific. We elucidate the contributions of changes in mean (distribution shift), and in variability (distribution widening/narrowing) to increasing record shattering probability by using a statistical model to create counterfactual realities representative of the regions of interest.
We focus on regions of a size relevant for national and cross-border policy that show differently driven changes in record shattering precipitation probabilities. For example, the annual probability of a record shattering precipitation event somewhere in the Benelux-Germany region which was hit by severe floods in summer 2021 increases from ~2% now to ~4.5% at the end of the century in CESM2. This increase results from a non-linear interaction between mean and variability increases, and is primarily driven by increasing variability. At lower latitudes, for example in Central America, the effect of variability is even stronger, where we find increasing record shattering probability despite a negative long-term trend in Rx1d levels.
Very unlikely events are, paradoxically, arguably the most important to know about, since their unimaginability often means that critical infrastructure is not sized to withstand these events. Our results may thus prove invaluable for regional policy.
How to cite: de Vries, I., Sippel, S., Fischer, E., Zeder, J., Humphrey, V., and Knutti, R.: Increasing probability of extreme records in heavy precipitation , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14539, https://doi.org/10.5194/egusphere-egu23-14539, 2023.
Societally relevant weather impacts typically result from compound events, which are rare combinations of weather and climate drivers. For example, compound hot-dry events frequently cause damage to human and natural systems, often exceeding separate impacts from heatwaves and droughts. Focussing on four event types arising from different combinations of climate variables across space and time, we illustrate that robust analyses of compound events – such as frequency and uncertainty analysis under present-day and future conditions, event attribution, and exploration of low-probability-high-impact events – require very large sample sizes. In particular, the required sample is much larger than that needed for routinely considered univariate extremes. We demonstrate how large ensemble simulations from multiple climate models are crucial for advancing our assessments of compound events and for constructing robust model projections. For example, among the case studies, we focus on compound hot-dry events and show that large ensemble model simulations allow for identifying plausible extremely dry climates that, if occurring in a warmer world, would be associated with high risk from compound hot-dry events. Overall, combining large ensemble simulations with an improved physical understanding of compound events will ultimately provide practitioners and stakeholders with the best available information on climate risks.
How to cite: Bevacqua, E., Suarez-Gutierrez, L., Jezequel, A., Lehner, F., Vrac, M., Yiou, P., Zappa, G., and Zscheischler, J.: Advancing research on compound weather and climate events via large ensemble model simulations, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2376, https://doi.org/10.5194/egusphere-egu23-2376, 2023.
The UK is committed to substantially increasing offshore wind capacity in its drive to decarbonise electricity production and achieve net zero. If low wind episodes – or “wind drought” events – occur during high energy demand periods, energy security may be threatened without alternative supply. To ensure resilience of the power system now and in the coming years as offshore wind generation grows, better understanding of the severity, frequency and duration of low wind episodes would be useful. Variability in winds is likely to dominate over trends in the next few decades, and hence having improved information on present day characteristics of wind drought is valuable.
Here we focus our attention on the North Sea as a centre of current and planned offshore wind resource for the UK and a number of other European countries, and on the winter season, given the occurrence of weather patterns that risk security of supply. We use a large ensemble of initialised climate model simulations to provide a synthetic but realistic event set that greatly increases the sample size of extreme events compared with that available from reanalysis data, and gives more robust information about their likelihood and properties. Using the basic unit of a week of low winds as the timescale of analysis, we report on the frequency and duration of wind drought events. In addition, we examine the wider conditions associated with wind drought events to investigate what remote factors may contribute to prolonged wind drought.
How to cite: Kay, G., Dunstone, N., Maidens, A., Scaife, A., Smith, D., Thornton, H., Dawkins, L., and Belcher, S.: Variability in North Sea wind energy and the potential for prolonged winter wind drought, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-13309, https://doi.org/10.5194/egusphere-egu23-13309, 2023.
Extreme wind events are among the costliest natural disasters in Europe. Significant effort is dedicated to understanding the risk of such events, usually analysing observed storms in the modern era. However, it is likely that some historical windstorms were more extreme and/or followed different tracks from those in the modern era. Producing plausible reanalyses of such events would improve the quantification of current and future windstorm risks.
Billions of historical climatological observations remain unavailable to science as they exist only on paper, stored in numerous archives around the world. We demonstrate how the rescue of such paper observations has improved our understanding of an extreme windstorm that occurred in February 1903 and its significant impacts. By assimilating newly rescued atmospheric pressure observations into the 20th Century Reanalysis system, the storm is now credibly represented in an improved reanalysis of the event. In some locations this storm produced stronger winds than any event during the modern era. As a result, estimates of risk from severe storms, based on modern period data, may need to be revised. Simulations of the storm surge resulting from this storm show a large coastal surge of around 2.5m, comparing favourably with newly rescued tide gauge observations and increasing our confidence in the quality of the reconstruction.
In addition, we use novel reanalysis experiments to translate this windstorm into a warmer world to quantify how it might be different both in the present and in the future. We find that the same storm produces more intense rainfall and stronger winds in a warmer climate, providing a new approach to quantifying how extreme weather events will change as the world is warming.
How to cite: Hawkins, E., Brohan, P., Burgess, S., Burt, S., Compo, G., Gray, S., Haigh, I., Hersbach, H., Kuijjer, K., Martinez-Alvarado, O., McColl, C., Schurer, A., Slivinski, L., and Williams, J.: Quantifying windstorm risks by translating historical extreme events into the future, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9290, https://doi.org/10.5194/egusphere-egu23-9290, 2023.
The 2021 summer flooding was an extremely rare event, driven by precipitation extremes that exceed Dutch design levels for flood protection in regions away from the main rivers and coastline. However, similar events in neighboring locations cannot be ruled out even in the near future. The implications of such extreme rainfall amounts will vary by region, subject to local topography, hydraulic flow patterns, water management, and societal exposure. We explore the geographic distribution of potential flood impacts induced by a similar event by constructing impact-oriented event storylines for different subregions in the Netherlands. The plausibility of the storylines is underlined by using physical evidence, proven impact-modelling concepts, and expert judgment successfully assessing the (sometimes unexpected) outcomes. The approach supports impact assessment for extraordinary events.
The presentation will illustrate the development of the storylines, and its uptake and interpretation by governing authorities responsible for water safety, civil protection and water management.
How to cite: Van Den Hurk, B., de Bruijn, K., Slager, K., Hegnauer, M., and Rongen, G.: Storylines of the impacts in the Netherlands of alternative realizations of the Western Europe July 2021 floods, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-1212, https://doi.org/10.5194/egusphere-egu23-1212, 2023.
Posters on site: Wed, 26 Apr, 16:15–18:00 | Hall X5
Climate strongly impacts socio-ecologic systems. Increasing the intensity and frequency of heatwaves is one of its major consequences. Heatwaves are periods of consecutive days when temperatures are much hotter than normal. Cities are especially affected because their impact is usually aggravated by the Urban Heat Island (UHI), an intrinsic phenomenon that increases urban temperatures compared to surrounding rural areas. Extreme hot temperatures affect urban areas causing health problems, increasing energy requirements, and altering water supplies, among others.
Heatwaves have been studied in Argentina but this has not been updated for the whole country recently. Due to these impacts on people’s well-being, infrastructure, and ecosystem functioning, this work proposes to study changes in spatial distribution and frequency of heatwaves in Argentina.
We use the ERA5 LAND dataset and the HeatWaver R package to identify heatwaves over mainland Argentina. For the purpose of this study, we define heatwaves as periods where maximum and/or minimum temperatures are above the 90th percentile of the WMO standard reference period (1961-1990) during five or more consecutive days. We inspect the temporal and spatial extent of the phenome and monitor its changes over time. In agreement with global warming tendencies, heatwaves are more frequent, and a larger portion of the country has been under stress in recent years. We also inspect the heterogeneous impact over the territory and large cities.
To understand the impact of heatwaves in cities, it is crucial to evaluate the risk, which is the conjunction of hazards, exposure and vulnerability. As a first step, this work studies heatwaves as hazards while those other aspects will be incorporated into future research. Our final objective is to reach an urban heatwave risk index, combining meteorological, environmental, urban, and social aspects. This indicator would liaise climate science with local and regional policies and offer information for adaptation and mitigation policies to face climate variability and change.
Keywords: heatwaves, cities, climate change, Argentina.
How to cite: Cimolai, C., Aguilar, E., Zaragozí, B., Olano Pozo, J., and Boqué Ciurana, A.: Is Argentina hotter? Understanding heatwaves temporal and spatial behavior using the ERA5-LAND dataset (1950-2022) , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-428, https://doi.org/10.5194/egusphere-egu23-428, 2023.
There is a dearth of information regarding prehistoric foraging societies from the intermontane longitudinal valleys of the South-Central Andes. Due to the intense anthropization of the landscape or the scarce research efforts on prehistoric populations of hunter-gatherers in the intermontane valleys of the Andes, occupation sites have been found on very few occasions. However, new perspectives in the Abra del Toro rock shelter in the Yocavil Valley (Catamarca province, Argentina) have opened up from recent and ongoing excavations. This rock shelter is the first archaeological case in which it is possible to analyze the relationship between a large-scale natural catastrophe and the prehistoric populations living in the Andean intermontane valleys of the southern Central Andes. This rock shelter's stratigraphy and archaeological remains contain the record of interactions between human communities and volcanism. The stratigraphic record of the rock shelter shows a 1-m-thick volcanic ash deposit formed by aeolian transport from primary outer ashfall deposits. Geomorphological and sedimentological context, texture, glass and mineral content, whole-rock chemical composition, and radiocarbon dating prove that the tephra was derived from the 4.2 ka BP eruption of the Cerro Blanco Volcanic Complex in southern Puna (NW Argentina). This volcanic eruption is the largest documented in the world in the last five thousand years and covered the surroundings of the archaeological site with an ash layer of approximately 1 meter thick. The stratigraphic sequence of the Abra del Toro rock shelter allows us to hypothesize that there were three main occupational moments: two hunter-gatherer moments, separated by the record of the large volcanic eruption, and a subsequent agro-pottery period (Carbonelli et al. 2022. J. Archaeol. Sci. Rep. 45, 103629). The rock shelter after the eruption remained in the memory of the hunter-gatherer groups. Good visibility, accessibility, and proximity to water were attributes of this space that made it possible for it to be re-occupied after the eruptive event. Our next objective is to reconstruct, using proxy analysis, how the paleoenvironment was in the intermontane valleys before and after the eruption. The evidence of this Mid-Holocene catastrophic volcanic event in the Abra del Toro rock shelter opens the possibility of knowing its impact on the contemporary hunter-gatherer community and drawing conclusions for similar future volcanic crises.
This work was supported by the National Scientific and Technical Research Council (Grant PIP 112-201301-00178), the University of Buenos Aires (Grant UBACyt 20020170100318BA) (University of Buenos Aires), the National Agency for the Promotion of Research, Technological Development and Innovation (Grant 2019-01229) and the QUECA Project (MINECO, Grant CGL2011-23307).
How to cite: Fernandez-Turiel, J.-L., Carbonelli, J. P., and Belotti López de Medina, C.: The hunter-gatherers of Abra del Toro rock shelter, northwestern Argentina, suffered the effects of the large 4.2 ka Cerro Blanco eruption, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-862, https://doi.org/10.5194/egusphere-egu23-862, 2023.
Historical extreme flooding events in Central European river catchments caused high socioeconomic impacts. Previous studies investigated single events in detail but did not focus on an analysis of the underlying extreme precipitation events in general as historical events are too rare for a robust assessment of their generic dynamical causes. This study attempts to fill this gap by analyzing a set of realistic daily 100-year large-scale precipitation events over five major European river catchments with the help of operational ensemble prediction data from the ECMWF. The dynamical conditions during such extreme events are investigated and compared to those of more moderate extreme events (20- to 50-year). 100-year precipitation events are generally associated with an upper-level cut-off low over Central Europe in combination with a surface cyclone southeast of the specific river catchment. The 24 hours before the event are decisive for the exact location of this surface cyclone, depending on the location and velocity of the upper-level low over Western Europe. The differences between 100-year and more moderate extreme events vary from catchment to catchment. Dynamical mechanisms such as an intensified upper-level cut-off low and surface cyclone are the main drivers distinguishing 100-year events in the Oder and Danube catchments, whereas thermodynamic mechanisms such as a higher moisture supply in the lower troposphere east of the specific river catchment are more relevant in the Elbe and Rhine catchments. For the Weser/Ems catchment, differences appear in both dynamical and thermodynamic mechanisms.
How to cite: Pfahl, S. and Ruff, F.: What distinguishes 100-year precipitation extremes over Central European river catchments from more moderate extreme events?, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-2390, https://doi.org/10.5194/egusphere-egu23-2390, 2023.
Wheat yield in Australia is highly dependent on year-to-year climate variability. Prolonged droughts and anomalously high temperatures have been considered as causes of agricultural failures in recent years. However, the origins of these climate extremes and their impacts on yield remain under study. Here, we use a Lagrangian trajectory model driven by atmospheric reanalysis data to delineate the source regions of moisture and heat over Australia’s largest rainfed agricultural region. In particular, we focus on extreme crop failure years (1994, 2002, 2006) and analyze the impact of upwind droughts on heat and moisture imports into the region. Our results indicate that low-yield years are often associated with stable high-pressure systems that lead to a decreased import of moisture from the surrounding oceans. Within the breadbasket, however, this caused higher-than-usual surface sensible heating. Moreover, the analyzed low-yield years coincide with widespread droughts over the Australian continent. We find that upwind droughts can further influence moisture and heat imports to the region. During the initial phase of the Millennium Drought in 2002, crop failure over the breadbasket exceeded 50% and only around 9% of the precipitation over the region originated from (upwind) land — this constitutes a decrease of 5.0% compared to the climatological average. Simultaneously, the heat import from remote land regions increased from an average of 22.8% to 24.7% in 2002. While our findings suggest that upwind droughts played only a minor role for Australia's largest breadbasket due to the influence of oceanic contributions in the region, other agricultural areas that show a larger dependency on moisture and heat imports from the land would be more susceptible to upwind climate anomalies.
How to cite: Li, H., Keune, J., Gou, Q., Holgate, C., and Miralles, D.: Understanding the origins of climate anomalies during low-yield years in Australia’s largest breadbasket, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3832, https://doi.org/10.5194/egusphere-egu23-3832, 2023.
Recent extreme temperature and precipitation events such as the dry and heat events in summer 2022 in Europe and China, the New Year’s warm spell 2022/23 across Europe, the 2021 heavy rainfall extremes in northwestern Germany, Belgium and the Netherlands and the 2021 Pacific Northwest heatwave broke previous observed record levels by large margins. The probability of such unprecedented record-shattering extremes increases with the rapid rate of warming. Thus, there is a crucial need for analyzing the underlying processes leading to these events and quantifying potential intensities of events possible in the coming decades.
Here, we evaluate how ensemble boosting (Gessner et al. 2021 and Gessner et al. 2022) can help assess the tail of climate distributions and generate climate model-based storylines more resource-efficiently. In ensemble boosting the most extreme simulated events in an intermediate-size initial condition ensembles are re-initialized in targeted experiments in order to efficiently sample very extreme states of the model climatology. Here, we evaluate different ensemble design choices including lead time, ensemble size and potential iteration choices to most efficiently allocate computational resources to simulate events of very extreme intensity.
The resulting boosted events are analyzed through a storyline approach, thus helping to interpret the underlying mechanisms of each physically consistent unfolding extreme event and its consequences. The Pacific Northwest heatwave in June 2021 will be used as a starting point; but ensemble boosting and storylines can be powerful tools for understanding extremes beyond heat. We further discuss how ensemble boosting can also be applied to compound extremes and future climate scenarios.
How to cite: Bloin-Wibe, L., Fischer, E., and Knutti, R.: Developing storylines for unprecedented extreme events using ensemble boosting, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7134, https://doi.org/10.5194/egusphere-egu23-7134, 2023.
The Northeast United States (NEUS) has faced the most rapidly increasing occurrences of extreme precipitation within the US in the past few decades. Understanding the physics leading to long-term trends in regional extreme precipitation is essential to adaptation and mitigation planning. Simulating regional extreme precipitation, however, remains challenging, partially limited by climate models’ horizontal resolution. Our recent work shows that a model with 25 km horizontal resolution facilitates a much more realistic simulation of extreme precipitation than comparable models with 50 or 100 km resolution, including frequency, amplitude, and temporal variability, based on ensembles generated by GFDL (Geophysical Fluid Dynamics Laboratory) SPEAR (Seamless System for Prediction and EArth System Research) models. The 25-km GFDL-SPEAR ensemble also simulates the trend of NEUS extreme precipitation quantitatively consistent with observed trend over recent decades, as the observed trend is within the ensemble spread. We therefore leverage multiple ensembles and various simulations (with historical radiative forcing and projected forcing following the SSP2-4.5 and SSP5-8.5 scenarios) to detect and project the trend of extreme precipitation. The 10-ensemble member GFDL-SPEAR 25-km simulations project unprecedented rainfall events over the NEUS, driven by increasing anthropogenic radiative forcing and distinguishable from natural variability, by the mid-21st century. Furthermore, very extreme events (99.9th percentile events) may be six times more likely by 2100 than in the early 21st century.
We further conduct a process-oriented study, assessing the physical factors that have contributed to the increasing extreme precipitation over the NEUS. We categorize September to November extreme precipitation days based on daily cumulative precipitation over the NEUS into weather types, including atmospheric river (AR), tropical cyclone (TC), and others. In observations, the most precipitation days were AR days or/and TC days. The number of extreme precipitation days related to pure AR events (without any TC-related event in the vicinity) had increased slightly from 1959 to 2020. The greater contribution to the increasing extreme precipitation was caused by TC-related events, especially the influences from extratropical transitions. The extreme precipitation days related to extratropical transitions were 2.5 times more frequent for the 1990 to 2020 period compared to the 1959 to 1989 period. We apply the same analysis to the GFDL-SPEAR 25-km simulations. Similar to observations, the increasing extreme precipitation days were mainly caused by TC-related events, with a smaller influence from pure AR events. However, the increasing number of TC-related days was dominated by hurricane and tropical storm events, while the number of extratropical transitions near the NEUS changed very little from 1959 to 2020. These results are different from the observational results. Ongoing work focuses on the discrepancy between observations and SPEAR simulations. For example, we are assessing whether the prominent increasing extratropical transitions since the 1990s in observations were the results of limited sample size or caused by decadal variability.
How to cite: Jong, B.-T., Delworth, T., and Murakami, H.: Increases in Extreme Precipitation over the Northeast United States using High-resolution Climate Model Simulations, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-7329, https://doi.org/10.5194/egusphere-egu23-7329, 2023.
According to the IPCC AR6 report, the frequency and intensity of high temperatures and precipitation extremes, such as heat waves, and extreme rainfall events that can lead to flash floods have increased in recent decades and are projected to keep increasing. These extreme events, which can occur in separate or as compound events can lead to droughts and flooding, causing severe economic and health impacts including loss of lives. Especially when such events occur shortly or directly in sequence, they can cause more severe impacts than in isolation. Understanding their compound behavior and timing in current and future climates can help to better estimate associated risks and require protection and adaptation planning.
In this study, the frequency and intensity of the compound events of heat waves and extreme precipitation over Sicily, Italy were analyzed and characterized for the present (1980-2010) and near future (2030-2050) periods. We used high resolution gridded datasets from observations (E-OBS) and from the EURO-CORDEX ensemble of regional climate change simulations. Heat waves were defined using a daily maximum temperature threshold persistent for at least three consecutive days while the extreme precipitation events were defined using the 95th percentile threshold of daily data. Results showed that the highest frequency of heat waves occured near the coastal regions of Sicily, while the extreme rainfalls were located in the west of Sicily. We identified the areas where heat waves and extreme rainfall events have occurred in the past and we demonstrate how they are expected to change in the future, separately and as compound events. The results of this study will be used to develop a workflow for estimating climate risks in the region, which is part of the “risk workflow for CAScading and COmpounding hazards in COastal urban areas” (CASCO) project, and can be combined with other workflows on geophysical risks (earthquakes and tsunamis) to characterize overall natural hazard risks for the island of Sicily.
How to cite: Remedio, A., Sirisena, J., and Bouwer, L.: Estimating compounding heat waves and rainfall extremes under projected climate change over the island of Sicily, Italy, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-9277, https://doi.org/10.5194/egusphere-egu23-9277, 2023.
The heat dome that Portland experienced in 2021 with temperatures up to 46 °C was unprecedented and unexpectedly severe, leading to the death of dozens of people. What if such an exceptional event were to occur somewhere else?
The Netherlands seems to be sensitive to such 'record-shattering' hot events, but luckily has not yet experienced them. Here, we show how to qualitatively connect the increasing scientific understanding of plausible record-shattering hot events with potential impacts and necessary responses for the city of Amsterdam. The expected impacts and potential responses of record-shattering hot events are identified through expert judgement with professionals from various disciplines.
We asked what could possibly happen in Amsterdam if the temperature rises to 45 degrees, in particular what kind of problems and bottlenecks are expected and what possible solutions are. The results of this exercise provided additional insights to heat plans based on lived experiences. As such, this case study may prove a useful example for governments and private sectors wishing to prepare for future exceptional heat waves.
How to cite: Klok, L., Kelder, T., van Vessem, E., and Hondema, L. S.: How to prepare for record-shattering hot events, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-11435, https://doi.org/10.5194/egusphere-egu23-11435, 2023.
Coastal flooding can be regarded as the most damaging extreme weather event. Careful
planning of mitigation and adaptation strategies requires a deep understanding of the event’s
likelihood and intensity.
This project provides a framework for assessing those changing statistics of coastal floods in
the future. We use historical records of coastal floods on the coasts of the UK historical
weather variables data (sea surface temperature, sea-level pressure, zonal and meridional
wind speeds and daily precipitations) from remote sensing sources, reanalysis data and
global climate models and future predictions of those weather variables from global climate
models. The method consists of using machine learning models to classify days as being
either ‘flooded’ (i.e. containing a coastal flood event) or ‘non-flooded’, at tide gauge
locations in the past 2 decades; both ‘out-of-the-box’ and more complex machine learning
models are trained on historical data. The models are then further used to assess the future
statistics of coastal flooding, by classifying days with or without flooding in the future
decades, from global climate models data. Currently, the method is showing promising
results on predicting the future number of ‘flooding days’, while the models used and trained
still show gradual improvement.
Using the same intensity scale as in the dataset of historical records of floods, it can be
assessed whether those events are becoming stronger or not. As well, the frequency, or the
return period, for the upcoming decades can be inferred from this project. This framework
produces an actionable set of information, that can be used by policy-makers, businesses,
governments and people, to plan accordingly for future floods.
How to cite: Suciu, T., Shuckburgh, E., and Lane, N.: Future Extreme Weather: a Data and AI driven approach to Understand Future Coastal Flooding, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-17463, https://doi.org/10.5194/egusphere-egu23-17463, 2023.
Compound drought-heatwave (CDHW) events are one of the worst climatic stressors for global sustainable development. However, the physical mechanisms behind CDHW and their impacts on socio-ecosystem productivity remain poorly understood. Here, by combining satellite observations, field measurements and reanalysis, we show that terrestrial water storage and temperature are negatively coupled, likely driven by similar atmospheric conditions (e.g., water vapor deficit and energy demand). Using simulations from a large climate-hydrology model ensemble of 111 members, we demonstrate that the frequency of extreme CDHWs is projected to increase by ten-fold globally under the highest emissions scenario, along with a disproportionate negative impact on vegetation and socioeconomic productivity by the late 21st century. Limits on water availability are likely to play a more important role in constraining the terrestrial carbon sink than temperature extremes, and over 90% of the global population and GDP could be exposed to increasing CDHW risks in the future, with more severe impacts in poorer or rural areas. Our results provide crucial insights towards assessing and mitigating adverse effects of compound hazards on ecosystems and human well-being.
How to cite: Yin, J., Gentine, P., Slater, L., Gu, L., Pokhrel, Y., and Guo, S.: Future socio-ecosystem productivity threatened by compound drought-heatwave events, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-3277, https://doi.org/10.5194/egusphere-egu23-3277, 2023.
We present the CMIP6 version of the Max Planck Institute-Grand Ensemble (MPI-GE CMIP6) with 30 realisations for the historical period and five emission scenarios. The power of MPI-GE CMIP6 goes beyond its predecessor ensemble MPI-GE by providing high-frequency model output, the full range of emission scenarios including the highly policy relevant scenarios SSP1-1.9 and SSP1-2.6, and the opportunity to compare the ensemble to high resolution simulations of the same model version. We demonstrate with six novel application examples how to use the power of MPI-GE CMIP6 to better quantify and understand present and future extreme events in the Earth system, to inform about uncertainty in approaching Paris Agreement global warming limits, and to combine large ensembles and artificial intelligence. For instance, MPI-GE CMIP6 allows us to show that the recently observed Siberian and Pacific North American heat waves are projected to occur every year in 2071-2100 in high-emission scenarios, that the storm activity in most tropical to mid-latitude oceans is projected to decrease, and that the ensemble is sufficiently large to be used for infilling surface temperature observations with artificial intelligence.
How to cite: Olonscheck, D., Brune, S., Suarez-Gutierrez, L., Beobide-Arsuaga, G., Baehr, J., Fröb, F., Hellmich, L., Ilyina, T., Kadow, C., Krieger, D., Li, H., Marotzke, J., Plésiat, É., Schupfner, M., Wachsmann, F., Wieners, K.-H., and Milinski, S.: A new Max Planck Institute-Grand Ensemble with CMIP6 forcing and high-frequency model output, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-14556, https://doi.org/10.5194/egusphere-egu23-14556, 2023.
Attribution of extreme events in developing countries poses a significant challenge. A primary hindrance is the lack of historical observations, which not only limits the appraisal of the extent of an extreme event, but also restricts benchmarking of climate models for the region. A secondary hindrance is that tropical climates, characteristic of developing countries, contain large uncertainties due to natural climate variability, which many climate models struggle to represent. As it is those countries and world regions where some of the most severe consequences of climate impacts emerge, addressing these challenges to robust climate attribution is critical to improve prospects of climate litigation in developing countries. In this study, we present a novel method for attribution using the Earth System Model (ESM) emulator for spatially resolved monthly temperatures, MESMER-M (Nath et al. 2022). We use a bootstrap method in calibrating MESMER-M, so as to also characterize its intrinsic parametric uncertainty. Attribution using MESMER-M is then demonstrated on the prolonged heat conditions of March/April 2022 over the Indo-Pakistani region. The outcomes of this study are twofold. Firstly, by calibrating MESMER-M on the BEST observational dataset, we are able to inflate observational records with observationally consistent natural climate variability estimates, enabling exploration of “possible pasts” and insofar characterization of the event and its likelihood under rising Global Mean Temperatures (GMTs). Secondly, by exploring the parametric uncertainty space of MESMER-M calibrated on both BEST and ESM data, we systematically disentangle the uncertainty surrounding the mean response of monthly temperatures to GMT from that surrounding the natural climate variability. Such allows robust appraisal of the uncertainty surrounding natural climate variability as present within ESMs/Observations for the region, so as to not over/understate the event’s likelihood under rising GMTs.
Nath, S., Lejeune, Q., Beusch, L., Seneviratne, S. I., & Schleussner, C. F. (2022) MESMER-M: an Earth system model emulator for spatially resolved monthly temperature. Earth System Dynamics, 13 (2), 851–877. doi: 10.5194/esd-13-851-2022
How to cite: Saeed, F., Nath, S., Candela, P., Lejeune, Q., Gudmundsson, L., Hauser, M., Schumacher, D., Seneviratne, S., and Schleussner, C.: Emulator-enhanced extreme event attribution for data scarce developing countries, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-16457, https://doi.org/10.5194/egusphere-egu23-16457, 2023.
Posters virtual: Wed, 26 Apr, 16:15–18:00 | vHall CL
The intensity and frequency of extreme storms have been increasing over time due to climate change, challenging sustainable stormwater management. This study examines the impacts of climate change on the precipitation patterns and extremes across the Cedar River Watershed in the Pacific Northwest under the Shared Socio-economic Scenario (SSP-585) obtained from CMIP6 models. Two global climate models (GCMs), namely MIROC6 and CMCC-ESM2, are considered in this study. Prior to generating future extreme storms for the selected GCMs and scenarios, the GCM simulated precipitation data was bias corrected relative to in-situ daily precipitation data. Precipitation data was bias corrected using three different statistical methods (please Named three method); among those Equidistant Quantile Mapping performed best. Bias corrected precipitation from the MIROC6 showed better performance compared to the CMCC-ESM2 in reproducing the observed precipitation statistics. Finally, the bias-corrected precipitation data from MIROC6 was used to develop non-stationary Intensity-Duration-Frequency curves (IDF) to identify the extreme storm events and their return periods. The results indicate that the storm intensities increase (ranging from 2.5% to 30%) over the future periods for all selected return periods, with relatively larger increase for higher return periods i.e., 50-year and 100-year storms. Further, we use the bias corrected precipitation projections and generate mean monthly perception maps of the Cedar River Watershed for the periods of 2020–2039 and 2040–2059.
How to cite: Salem, A. and Abduljaleel, Y.: Assessing the impact of climate change scenario for simulating nonstationary rainfall intensity and duration , EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4309, https://doi.org/10.5194/egusphere-egu23-4309, 2023.
Under the context of global warming, climate and weather extremes (e.g., droughts, high temperature extremes) take a heavy toll on natural and human systems. It has been reported that the concurrence of droughts and hot extremes (CDHEs) in summer 2022 in the Northern Hemisphere (NH) have led to reduced water resources/crop yield and increased health risks. While assessments of droughts and heatwaves in summer 2022 have been noted, the assessment of these extremes from a compound event perspective is still limited. In this study, we analyzed the rarity of CDHEs in summer 2022 across the NH, detected anthropogenic influence on CDHEs area, and projected the likelihood under different warming levels based on observations from ERA5 and simulations from the Sixth Phase of the Coupled Model Intercomparison Project (CMIP6). Our results illustrate that severe CDHEs in summer 2022 across the NH mainly occur in central North America, Europe, and south China. Event attribution analysis shows that CDHEs area in summer 2022 in the NH would not have occurred without anthropogenic global warming. The CDHEs area like 2022 is projected to occur more likely, particularly under SSP585 in a 4°C warming world. This study provides useful insights for advancing our understanding of compound extremes during summer 2022 across the NH.
How to cite: Meng, Y. and Hao, Z.: Attribution and projection of the summer 2022 compound dry and hot extreme in the Northern Hemisphere, EGU General Assembly 2023, Vienna, Austria, 24–28 Apr 2023, EGU23-4705, https://doi.org/10.5194/egusphere-egu23-4705, 2023.
