Rainfall across the state of Victoria in Australia exhibits a strong climatological gradient from north to south and from east to west. In general, the highland areas in eastern Victoria receive the highest rainfall, followed by the southern coastal regions and substantially less rainfall occurs over the north-west of Victoria. The latter two regions show a pronounced annual cycle with winter maxima while rainfall over eastern Victoria is more uniform throughout the year. These distinct variations in rainfall arise from the fact that the different regions of Victoria are influenced by different weather systems and large-scale climate drivers and they also respond differently to external forcing. Many of the previous studies on rainfall changes were derived using all-Victoria area-averaged rainfall. However, there is a strong interest of stakeholders, both within and beyond the climate science community in Australia, about the role of climate change on the decline in local rainfall since the beginning of the Millennium Drought in 1997.

In this study, we used both observations and climate models to provide comprehensive and robust information on past and future rainfall changes on three sub-regions of Victoria (Murray Basin Victoria: MBVic, southeast Victoria: SEVic, and southwest Victoria: SWVic) during the cool season (April – October) due to climate change. Our results show that the percentage decline of rainfall for the 1997-2018 period, relative to the 1900-1959 period average, is more pronounced over the MBVic and SEVic regions of Victoria and least pronounced over the SWVic region. However, the fractional contribution of external forcing is estimated to be about 30% to the observed drying over SWVic which is about 1.5 times higher than the other two regions. Equivalently, the external forcing contribution to the observed trend for the 1900-2018 period are 56%, 17% and 24% for SWVic, MBVic and SEVic, respectively. These numbers suggest that the recent drying across Victoria, while primarily driven by internal rainfall variability, was reinforced by external forcing.  We are currently investigating the time of emergence of the external forcing signal beyond its pre-industrial and historical range and the expected combined impact of both external forcing and internal variability on rainfall over different sub-regions of Victoria for coming decades.

How to cite: Rauniyar, S., Hope, P., and Power, S.: The role of external forcing and natural processes on past and future changes in rainfall over sub-regions of Victoria, Australia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10927, https://doi.org/10.5194/egusphere-egu23-10927, 2023.

It has been established that the variations/trends in large-scale precipitation over land since the mid-twentieth century can be attributed to forcing changes due to anthropogenic greenhouse gas emissions (Eyring et al.). The detection and attribution (D&A) of changes in regional precipitation regimes, however, remains challenging due to issues such as larger influences from internal variability, as well as larger uncertainty in observed and simulated data (Doblas-Reyes et al.). This study is aimed at exploring the feasibility of attributing the quantile trends in daily precipitation over China to natural and anthropogenic influences, aided by the latest CMIP6 GCM data. The quantile trends in observed and modeled daily precipitation are derived through quantile regression (Koenker and Bassett). The scenarios considered are the historical, natural, anthropogenic greenhouse gas, and anthropogenic aerosol forcings, and the control simulations are employed to reflect natural variability. The D&A is undertaken through the regularized optimal fingerprinting (Ribes et al.). The results show that the increasing trends in winter precipitation at high and extremely high quantile levels, as well as the increasing trends in spring precipitation at all quantile levels, can be attributed to the effects of historical forcing. The effect of anthropogenic greenhouse gas forcing is evident over the domain, to which the increasing precipitation trends at all quantile levels in all seasons can be attributed; this effect can be separated from that of anthropogenic aerosol forcing for winter precipitation trends at high and extremely high quantile levels, and for spring, summer, and autumn trends at low quantile levels. Findings of this research can help improve our knowledge of anthropogenic processes on the climate system, which can further support climate modeling and projections.

Reference

Doblas-Reyes, F. J., et al. “Linking Global to Regional Climate Change.” Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, edited by V. Masson-Delmotte et al., Cambridge University Press, 2021.

Eyring, V., et al. “Human Influence on the Climate System.” Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change, edited by V. Masson-Delmotte et al., Cambridge University Press, 2021, pp. 423–552, https://doi.org/10.1017/9781009157896.005.

Koenker, Roger, and Gilbert Bassett. “Regression Quantiles.” Econometrica, vol. 46, no. 1, Jan. 1978, p. 33, https://doi.org/10.2307/1913643.

Ribes, Aurélien, et al. “Application of Regularised Optimal Fingerprinting to Attribution. Part I: Method, Properties and Idealised Analysis.” Climate Dynamics, vol. 41, no. 11–12, Dec. 2013, pp. 2817–36, https://doi.org/10.1007/s00382-013-1735-7.

How to cite: Lu, C., Huang, G., Wang, X., and Coppola, E.: Anthropogenic influence on precipitation quantile trends over China, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8136, https://doi.org/10.5194/egusphere-egu23-8136, 2023.

Climate change is leading to alterations in the dynamic climate systems worldwide. The Indian Summer Monsoon (ISM) is one such climate system that supports more than a billion population and drives the Indian economy. The ISM is governed by intra-annual to inter-decadal variabilities. However, anthropogenic climate change is inducing unprecedented transformations in this natural system, such as the increased probability of precipitation extremes (dry and wet), changes in their frequency and duration, spatial variabilities, etc. These changes, in turn, impact the human and ecological systems due to droughts, floods, and prolonged dry spells. In such scenarios, it is essential to gain insights into the projected precipitation extremes (PEs) changes. The velocity of climate change (VoCC) or climate velocity can help us project the temporal and spatial shift of PEs especially in terms of their intensities. VoCC is a regional metric of climate change, defined as the ratio of the temporal gradient of a particular climate variable (temperature, precipitation, humidity, etc.) with its spatial gradient, and the resultant units are in km/year. In the current study, the climate velocities of 50^th, 75^th, 95^th, 99.5^th, and 99.9^th percentiles of precipitation for the JJAS season are projected over India and its different biogeographic zones for the four time periods: historical (1976-2000), near-future (2025-2049), mid-future (2050-2074) and far-future (2075-2099). ROM, a regional earth system model over the CORDEX-South Asia domain was used in the study. It was found that ROM showed a better resemblance with observation in simulating the PEs over other regional climate models (RCMs). The intense rainfall (95th percentile: R95) is expected to be enhanced over most of the study region in mid future and far future. Interestingly, very intense rainfall (99.9th percentile: R99) showed robust increases in the near and mid-future as compared to the far future. The PEs also exhibited higher velocities as compared to the median values. The detailed results will be discussed further in the presentation.

How to cite: Sachan, D., Kumari, A., and Kumar, P.: Shifting Velocity of Precipitation Extremes over India under Climate Change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16818, https://doi.org/10.5194/egusphere-egu23-16818, 2023.

In the context of climate change, assessing how likely a particular change or event has been caused by human influence is important for mitigation and adaptation policies. Disturbances, such as increases in the frequency and intensity of extreme precipitation have been observed at continental to global scales. In this work we present an Extreme Event Attribution methodology for yearly maxima records that takes into consideration the temporal non-stationarity of climate variables and allow us to quantify record probability at a global scale in a transient setup. We apply our methodology to study records of yearly maxima of daily precipitation issued from the numerical climate model IPSL-CM6A-LR and the scenario rcp8.5 at a global scale. Focusing on decadal records, we detect a clear anthropogenic signal from the 2020's, even thought decadal record probability increases in most parts of the world, we observe a decrease of records probability in the subtropics.

How to cite: Gonzalez, P., Naveau, P., Thao, S., and Worms, J.: Analysis of precipitation records from climate models in a non-stationary context, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13786, https://doi.org/10.5194/egusphere-egu23-13786, 2023.

The impact of climate change on typhoon is of great concern in the East Asia. In particular, typhoon heavy rainfall has a destructive impact on our society and economy since they are many megacities along the coastal regions. Although observations suggest significant changes in typhoon heavy rainfall, the contribution of anthropogenic forcing has not been determined.

In this study, we show that anthropogenic global warming has a substantial impact on the observed changes in typhoon heavy rainfall in the western North Pacific region. Observational data show that, in general, typhoon heavy rainfall has increased (decreased) in coastal East Asia (tropical western North Pacific) during latter half of 20^th Century and onward. A similar spatial distribution is found in the “Anthropogenic fingerprint”, difference between Earth systems with and without human-induced greenhouse gas emission, from a set of large ensemble climate simulations. This provides evidence to support that the significant increase in the frequency of typhoon heavy rainfall along coastal East Asia is not explained solely by natural variability. Further, the results show that since mid-1970s, the signal of “Anthropogenic fingerprint” has been increasing rapidly and departs from natural variability in early-2000s.

Reference:
Utsumi, N., & Kim, H. (2022). Observed influence of anthropogenic climate change on tropical cyclone heavy rainfall. Nature Climate Change, 12(5), 436–440. https://doi.org/10.1038/s41558-022-01344-2

How to cite: Kim, H. and Utsumi, N.: Anthropogenic Fingerprint on Recent Changes in Typhoon Heavy Rainfall beyond Tipping-Point, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5392, https://doi.org/10.5194/egusphere-egu23-5392, 2023.

A thunderstorm system formed during the night of August 17 to 18 over the northern Balearic Islands and moved rapidly to the northeast, causing widespread damage over Corsica, Northern Italy and Austria due to the production of strong surface wind gusts (>200 km/h over Corsica) and severe hail. The intensity of this phenomenon can be classified in the category of derechos: this is a classification of very violent storms that takes into account the wind gusts (more than 94km/h with maxima of more than 120km/h) and the extent of the affected territory (major axis longer than 400 kilometers). Here we analyse recent derechos event in France in the satellite era and assess the role of climate change in modifying their characteristics. We identify eleven events in the past and provide their tracks retrieved using the ERA5 reanalysis dataset. To detect climate change signal, we compare  analog cyclonic atmospheric circulations that can lead to derechos in the distant past (1950-1979) and in the recent past (1992-2022). Two of the events, the derechos which affect the Northern regions are unprecedented, that is no good analogues can be found and attribution statements cannot be made on the basis of the present analysis. For the other events, instead, we find a significant signal of increased precipitation in the recent period which, without change in circulation, is explained by the higher temperatures of the Bay of Biscay and the Mediterranean Sea. For these events there is also not a clear change in depth of the pressure minimum which triggered the convective system. Finally, we can exclude the role of the climate variability of El Nino (ENSO) in most of the events, while we cannot rule out the influence of the Atlantic Multidecadal Oscillation (AMO) in favoring low pressure systems possibly leading to derechos.

How to cite: Fery, L., Dubrulle, B., and Faranda, D.: Climate change has increased the intensity of documented Derecho storms in France, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15502, https://doi.org/10.5194/egusphere-egu23-15502, 2023.

Parts of western North America experienced a heatwave in late June 2021that many would have conceived impossible based on observations so far. In Lytton, Canada, temperatures peaked at 49.6°C, and the area-average daily maximum temperature record across the Pacific Northwest was broken by nearly 5°C. Given the exceptional intensity of the eventsome media outlets and scientists raised the questions whether heat extremes intensify faster than previously projected based on climate models, or whether current generations of climate models miss crucial processes and are thus unable to even reproduce such an event.^. Here I address these questions and highlight some of the challenges for widely methods in model evaluation and attribution.

First, I review some of the recent literature detailing the key physical mechanisms driving the Pacific Northwest heatwave. I address some of the key scientific challenges regarding the quantification of return periods, event attribution, model evaluation and near-term projections. Widely used methods estimating stationary return periods based on the observational record up to the year before imply that such an event had an infinite return period, i.e., that it would never happen. Even when taking into account the non-stationarity of a warming climate, the exceedance probability would be zeroor nearly zero depending on the estimation of the confidence intervals, the duration of the event and whether the event itself is included in the fit^.

I discuss some potential ways forward in addressing the above challenges and in quantifying the potential intensity of record-shattering events in the near future.  

How to cite: Fischer, E.: The record-shattering 2021 Pacific Northwest heatwave – challenges and opportunities for attribution and event storylines, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11732, https://doi.org/10.5194/egusphere-egu23-11732, 2023.

Extreme winter cold temperatures in Europe have huge societal impacts. Being able to simulate worst-case scenarios of such events for present and future climates is hence crucial for adaptation. Rare event algorithms have been applied to simulate extreme heat waves. They have emphasized the role of atmospheric circulation in such extremes. The goal of this study is to test such algorithms for extreme cold spells.

We focus first on winter cold temperatures that have occurred in France from 1950 to 2021 and then on winter cold spells that could occur in the future according to different emissions pathways. We investigate winter mean temperatures in France (December, January, and February) and identify a record-shattering event in 1963. We find that, although the frequency of extreme cold spells decreases with time, their intensity is stationary.

We applied a stochastic weather generator approach with importance sampling, to simulate the coldest winters that could occur every year since 1950. We hence simulated ensembles of worst winter cold spells that are consistent with observations. Only some of the simulations reach colder temperatures than the record-shattering event of 1963, and the ensembles do not yield the trend that is observed in the mean temperature. The atmospheric circulation that prevails during those events is analyzed and compared to the observed circulation during the record-breaking events.

How to cite: Cadiou, C. and Yiou, P.: Simulating extreme cold winters in France with empirical importance sampling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-233, https://doi.org/10.5194/egusphere-egu23-233, 2023.

As climate changes to likely a warmer mean state by the end of this century than any time during the existence of humans, the world population has rapidly increased from about 1.3 billion in 1850 to 8 billion in November 2022. The latest IPCC AR6 reports attests that extreme events (e.g., heatwaves, floods, droughts, etc.) are occurring in many parts of the world at an increasing frequency and/or intensity due to global climate change, and are threatening human health, Earth’s biosphere, and the socio‐economic fabric of our rapidly expanding and resource‐hungry civilisation. On 19 July 2022 England, Wales and Scotland all experienced the hottest days on the record reaching 40.3 deg.C, 37.1 deg.C and 34.8 deg.C, respectively, and London Fire Brigade received the highest number of emergency calls since World War II. While in Dublin near-surface air temperature reached 33.0 deg.C on 18 July – the highest in the Ireland’s record. Furthermore, the annual mean temperature in 2022 was highest on the record in the UK and Ireland. This study uses a set of observations and reanalysis products combined with large ensembles of CMIP5/6 simulations to examine the structure of atmospheric circulation and the role of anthropogenic drivers leading to these extreme events on annual timescale. We also use large ensembles of specifically designed historical/factual and natural/counterfactual simulations of EC-Earth3 coupled climate model at the standard resolution and weather@home2 climate simulations performed by citizen scientists around the world to assesses to what extent anthropogenic forcing modified the probability and magnitude of this event. Moreover, we involve conditional perspective of the atmospheric circulation in our attribution estimates. The preliminary results points to a pronounced role of the global climate change in modifying likelihood and intensity of these annual extreme events.

How to cite: Fuckar, N., Allen, M., and Obersteiner, M.: On the nature and attribution of the 2022 annual record temperature in the UK and Ireland, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16087, https://doi.org/10.5194/egusphere-egu23-16087, 2023.

Because they are rare, extreme weather events inevitably attract public and scientific attention. The most unusual events are regularly documented as part of routine climate monitoring by meteorological services, and put into the perspective of climate change by attribution studies through quantities such as a probability ratio. However, it is often recognized that (i) the selection of studied events is geographically uneven, and (ii) the definition of a given event, in particular its spatio-temporal scale, is subjective, which may impact the results.

In previous work, we proposed an objective method of event definition, consisting in the automatic selection of the spatio-temporal window maximizing the event rarity. Importantly, we showed that maximizing the event rarity does not bias attribution statements, in the sense that it does not systematically maximize (or minimize) the probability ratio. Here we present how this method can be used to compare several events occurring on different years, seasons, regions, etc. Our objective research procedure works both over time, which can be useful for routine climate monitoring, and over space, which can resolve the geographical selection bias of attribution studies. Ultimately, we provide a selection of the most extreme hot and cold events that have occurred worldwide in the recent past, among which are iconic heat waves such as that seen in 2021 in Canada or 2003 in Europe.

How to cite: Cattiaux, J. and Ribes, A.: Searching for the most extreme temperature events in recent history, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13745, https://doi.org/10.5194/egusphere-egu23-13745, 2023.

The field of extreme event attribution (EEA) seeks to quantify how recent extreme events are directly exacerbated by ongoing climate change. As this is a relatively new field in climate science, there is a noticeable knowledge gap in EEA analysis in mountain areas. Precisely, this work performs an attribution to climate change of the two greatest heatwaves (HWs) occurred during June and July 2022, both hitting the Iberian Peninsula and southern France, and therefore, the Pyrenees Mountain range. We used the analogues technique on 500 hPa geopotential height composites to identify the 30 days closer to the dynamical structure of both heatwaves for the counterfactual (1950-1985) and factual (1986-2021) period, using ERA5 daily data. Results showed that factual HWs analogues in the factual period have a spatial structure closer to the 2022 HWs events than those analogues extracted from the counterfactual period. At the Pyrenean scale, we observed that 2-meter air temperature differences consisted of a positive non-uniform pattern in a factual world, with a significant increase in the southern slope of the mountain range and in the nearby depressed areas. However, most of the mountain range exhibited a small increase of the HW air temperature in a factual world. We also provided an explanation of the physical process involving the abovementioned 2-meter air temperature differences. In this study, we revealed the complexity of conducting the attribution of extreme heatwaves to climate change in mountain areas, both because of the scarcity of in-situ data, as well as due to the physical processes involved during these extreme events in an area of complex terrain.

How to cite: Lemus-Canovas, M., Gonzalez-Herrero, S., Trapero, L., Albalat, A., Insua-Costa, D., Senande-Rivera, M., and Miguez-Macho, G.: Attributing heatwaves to climate change in mountainous areas. An analysis of the summer 2022 heatwaves in the Pyrenees, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11234, https://doi.org/10.5194/egusphere-egu23-11234, 2023.

Heat extremes show the fastest warming trend over western Europe (WEU) and a weak cooling trend over the Midwest United States (MUS). We use observations and Earth System Model (ESM) large ensemble simulations to understand why the observed trends over these two regions are opposite. Based on the dynamical adjustment method we provide observational and model evidence that circulation changes greatly amplify the warming trends over WEU and weaken the trends over MUS in the last four decades. We find that circulation-driven changes in heat extremes cause ~0.2°C/decade cooling over MUS that reverses the weaker warming effects of all other forcings combined and thus leads to very small overall trends. In contrast, it causes an additional ~0.2°C/decade warming over WEU, which accounts for ~35% of the warming rate that is caused by forced thermodynamic changes. Although ESMs represent the forced thermodynamic warming well over WEU, they underestimate the circulation-induced warming that further reveals why ESMs underestimate the observed warming rate over WEU.

Overall, these findings imply that if the circulation changes represent a forced response WEU continues to experience a severe intensification of heat extremes conditions in future as circulation-induced amplification of heat extremes may further intensify in the warmer world. Conversely, if the circulation-induced trend were due to internal variability, and thus would reverse in the coming decades, this would imply a somewhat slower rate of warming of heat extremes. Moreover, heat extremes over MUS continue to warm more slowly if circulation keeps dampening the warming effects in the coming decades, but potentially increase rapidly if the circulation trend reverses.

How to cite: Singh, J., Sippel, S., and Fischer, E.: Observed intensification of heat extremes amplified by circulation over western Europe and dampened over the US Midwest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12990, https://doi.org/10.5194/egusphere-egu23-12990, 2023.

The intensification of the global hydrological cycle has significantly altered the behaviour of climate extremes. Lately, compound extremes i.e. simultaneous occurrence of two or more extremes, have received substantial emphasis because of their larger impact than individual extremes. Therefore, this study evaluates compound dry-hot extremes in summer monsoon season in India for the past and future using advanced statistical (variance transform method and REA- reliability ensemble averaging) and probabilistic methods (copulas). Monthly projections of precipitation/temperature are obtained from multi-modal ensembles of 21 CMIP5 GCMs, constructed using the REA technique. Furthermore, the frequency and spatial extent of monsoonal compound dry-hot events are assessed using a Standardized Compound Event Indicator (SCEI), based on monthly precipitation/temperature, for past (1975-2015)  and future (2025-2095 under RCP8.5). Moreover, vegetation loss estimates (using NDVI-Normalized Difference Vegetation Index) are evaluated under multiple dry-hot conditions (using SCEI) during 1982-2013 using bivariate copulas. Further, the teleconnections (Nino3.4, PDO, AMO and DMI) with SCEI are assessed using the variance transformation method. The results indicate a rise in dry-hot extremes in the monsoon season during 1975-2015. Due to the adverse impact of such extremes on vegetation, vegetation vulnerability assessment indicate that around 65.70% of the country’s area is prone to vegetation loss under extreme dry-hot conditions. And, it is also found that Nino3.4 (ENSO) is the dominant climate indice influencing SCEI (4 monthly scale), in > 50% of the country. Furthermore, the results show that the frequency and spatial extent of dry-hot extremes are projected to increase in the future (2055-2095), relative to past (1975-2015) across the country. Our study gives an enhanced understanding of dry-hot extremes in monsoon season and can further facilitate an effective adaptation strategy.

How to cite: Kumar, N. and Kumar Goyal, M.: Evaluation of compound dry-hot extremes in summer monsoon in India: Past and Future, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1722, https://doi.org/10.5194/egusphere-egu23-1722, 2023.

Attributing extreme weather events to human-induced climate change has been a topic of interest for decades. In recent years where unprecedented and high-impact events have occurred all over the world, it is all the more important to not just understand how human influence on the climate system has changed the probability or magnitude of the weather events, but also how it has changed the impacts of these events on human life. In this talk, I will review the climate-epidemiology literature on attributing adverse human health impacts to climate change, with a focus on heat-related mortality, as it is well-established that high temperatures are associated with increased mortality risks. I will include notable heat-mortality events in history such as the 1995 Chicago heatwave, 2006 UK summer, and the 2003 European heatwave. I will also discuss the use of large ensembles of future climate projections to ‘attribute’ heat-related mortality that could occur if global mean warming reached certain levels, keeping other factors unchanged. Finally, I will discuss the use of climate-health attribution information in engaging with the media and communicating with policymakers.

How to cite: Lo, E., Mitchell, D., Vicedo-Cabrera, A. M., and Perkins-Kirkpatrick, S.: Attributing human health impacts to climate change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5612, https://doi.org/10.5194/egusphere-egu23-5612, 2023.

In recent decades, anthropogenic climate change has led to significant increases in heat wave length and intensity. Many of these heat waves have resulted in substantial impacts on human health. In 2009, the state of Victoria, Australia, experienced several days with maximum temperatures rising 12-15°C above the climatological mean and a marked rise in the human death toll. This study attempts to directly quantify the heat-related human fatalities of the 2009 heatwave attributable to anthropogenic climate change.

We focus on changes in return values of heat wave-related mortality. Furthermore, we combine two types of modeling tools. The first is a set of large initial-condition ensembles of simulations from atmosphere-only models from the weather@home/ANZ and C202C+ D&A projects, and large initial-condition ensembles of simulations from atmosphere-ocean models from CMIP6.  We compare factual outcomes from year-2009 era periods from historical simulations against counterfactual outcomes from either naturalised (non-anthropogenic) simulations or pre-industrial times. The second tool is an empirical model linking heat-related mortality to exceedance of temperature percentile thresholds from daily climate simulation output. This mortality model categorizes heat waves based on three consecutive percentile windows starting at the 95th, 97.5th, and the 99th percentile.

Our analysis shows considerable agreement among the climate-mortality model combinations indicating significant increases in human fatalities during conditions comparable to the 2009 Victoria heat wave under anthropogenic climate change. Most models attribute approximately one third to one half of excess heat-related deaths to anthropogenic greenhouse gas emissions. These findings demonstrate that unless significant climate change mitigation and adaptation efforts are undertaken, further increases in heat-related mortality risk can be expected.

How to cite: Aglas-Leitner, P., Perkins-Kirkpatrick, S., Lansbury, N., Selvey, L., Osborne, N., and Stone, D.: Attribution of excess heat-related death toll during 2009 heat wave in Victoria, Australia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6412, https://doi.org/10.5194/egusphere-egu23-6412, 2023.

Extreme Event Attribution (EEA) aims to answer the question of whether and to what extent the intensity and likelihood of an observed extreme weather event have changed due to climate change. This approach has been applied to different types of weather extremes such as heatwaves, droughts, or extreme rainfall, but has only rarely been used to assess the role of climate change on health impacts caused by extreme weather events.

In this study, we focus on the short-term effects of extreme heat events on human mortality in Europe. We first apply an epidemiological model to estimate the lagged association between temperatures and mortality counts. We use ERA5-Land temperature data and a mortality database including 92.612.620 counts of death from 823 contiguous regions in 35 European countries, representing a population of over 534 million people. We estimate the number of deaths attributable to heat and then compute the death count caused by climate change by applying EEA methods. Here, we apply a conditional extreme value distribution to estimate how the likelihood of selected heat-attributable mortality events has changed from a pre-industrial climate to present-day conditions (1.2ºC global warming).

We show that in all regions of Europe, a climate change signal in heat-attributable mortality can be detected. This climate change contribution to mortality differs between geographical locations in Europe and is also influenced by demographic, and socioeconomic factors, e.g., we identify differences in climate impacts in gender-specific mortality.

This study shows that epidemiological models can be combined with EEA methodologies and it opens the door to conducting further EEA studies, including rapid attribution, on other health impacts and beyond.

How to cite: Beck, T., Gudmundsson, L., Seneviratne, S. I., Achebak, H., Schumacher, D., and Ballester, J.: Quantifying the contribution of climate change to heat-attributable mortality in Europe: Interfacing epidemiology and Extreme Event Attribution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14521, https://doi.org/10.5194/egusphere-egu23-14521, 2023.

How to cite: Colón-González, F. J., Fletcher, I., Annan-Callcott, G., and Mateen, B.: Challenges and opportunities for detection and attribution of climate change impacts on health, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17514, https://doi.org/10.5194/egusphere-egu23-17514, 2023.

Climate change is increasingly affecting the health of vulnerable populations, including pregnant women, the developing foetus and newborns. Despite growing epidemiological evidence on the effects of ambient temperatures on adverse birth outcomes and child survival, the role of climate change in the burden of temperature-related adverse birth outcomes has been insufficiently investigated. We combine data from the Demographic Health Survey (DHS) for 29 low- and middle-income countries with factual temperature data from the ISIMIP3a simulation round to quantify the non-linear association between daily mean temperature and stillbirths and neonatal deaths. We estimate the associations using a time-stratified case-crossover design. Based on the derived exposure-response functions and counterfactual temperature data we estimate the burden of stillbirths and neonatal deaths between 2001-2019 that can be attributed to climate change. The results both for stillbirths and neonatal deaths indicate a U-shaped curve, with risk of mortality increasing below and above an optimum temperature. We find that climate change has increased the burden of heat-related stillbirths across 28 of the countries (from 0.6% in Albania and Tajikistan to 4.1% in Philippines) and the burden of heat-related neonatal deaths – across 20 of the countries (from 0.2% in India to 1% in Philippines and Haiti). For 21 of the included countries climate change has also led to a reduction in the burden of cold-related stillbirths (from 0.2% in Tajikistan to 4.4% in Uganda) and neonatal deaths (from 0.5% in Tajikistan to 3.5% in the Philippines).

How to cite: Dimitrova, A., Dimitrova, A., Mengel, M., Gasparrini, A., Gabrysch, S., and Lotze-Campen, H.: The burden of temperature-related stillbirths and neonatal deaths attributable to climate change – a global analysis across 29 Low- and Middle-income countries, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17253, https://doi.org/10.5194/egusphere-egu23-17253, 2023.

Heatwaves are increasing in frequency, intensity, and duration, and represent the category of extreme event that is most easily attributable to anthropogenic warming. Yet how the spatiotemporal patterns of attribution outcomes link to population dynamics is still poorly understood.  Here we show that children and young people are already being affected by a disproportionately greater number of attributable heatwaves, especially in the Global South. Using observations, reanalysis, and simulations of temperature changes available through the ISIMIP3b and CMIP6 projects in combination with demographic data, we show that temperature extremes emerge more clearly and consistently from the noise across low-income countries in lower latitudes, which have some of the youngest populations. Our findings have important implications for children and young people seeking redress from climate harms, for example through climate lawsuits.

How to cite: Pietroiusti, R. and Thiery, W.: Children disproportionally exposed to attributable heatwaves at low-latitude low-income countries, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7528, https://doi.org/10.5194/egusphere-egu23-7528, 2023.

In climate change attribution, unprecedented magnitudes of extreme events can be defined on the basis of thresholds in the pre-industrial distributions of event magnitudes. This notion of unprecedented levels of climate change impacts has been extended toward the lifetime exposure to extreme events by evaluating exposure frequency. Unprecedented exposure to extreme events is assessed by comparing average lifetime exposure under different climate scenarios to an upper percentile of exposure in a pre-industrial climate. Here we combine simulations of climate change impacts under different climate forcing scenarios with country-level demography datasets to estimate the fraction of the global population experiencing unprecedented exposure to extreme events. This is done for 29 global mean temperature trajectories taken from the AR6 scenario explorer and multiple extreme event categories such as heatwaves, floods and droughts. Further, we assess the age of emergence at which birth cohorts reach unprecedented levels of exposure.

How to cite: Grant, L., Thiery, W., Vanderkelen, I., Gudmundsson, L., Fischer, E., and Seneviratne, S.: The evolution of the global population experiencing unprecedented exposure and its age of emergence., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7716, https://doi.org/10.5194/egusphere-egu23-7716, 2023.

Weather and climate extreme indicators are useful tools in the assessment and quantification of climate change induced alterations of key climate variables and extreme events. However, capturing both the main change aspects and the total extremity of such extreme events remains a challenging task.

Climate change can affect multiple characteristics of weather and climate extremes. Most indices, such as annual maximum temperature or number of hot days, focus on only one aspect of extreme events. While annual maximum temperature aims at describing the magnitude, the number of hot days is used for assessing the frequency of an extreme. The consideration of only one characteristic is a common limitation of such metrics. Since the total severity of extremes is the result of a combination of frequency, duration, magnitude and areal extent changes, however, the extremity is more than the sum of these parts and compound indices are hence required to fully capture the overall change.

Here we introduce Threshold-Exceedance-Amount (TEA) indicators as a new class of metrics that capture changes in event frequency, duration, magnitude, and spatial extent both in isolation and in total. Using a high-percentile-based threshold in a key climate variable that describes extreme magnitudes, the TEA metrics work in a cascaded manner up to expressing the total extremity of events, optionally also as an amplification vs. a suitable reference period.

Besides a detailed definition, we also show example applications for heat and heavy precipitation extremes (using daily maximum temperature and precipitation amount as key variables), from local- to country-scale regions in Austria to resolving and covering the entire European land region. We discuss amplifications and climate change detection vs. the 1961-1990 reference period and natural variability.

The TEA indicators are applicable for different types of extremes also beyond temperature and precipitation, making them a useful and versatile tool for the climate change-related investigation of extreme events and their impacts on natural and socio-economic systems, while also helping to fulfill the need for compound indices.

How to cite: Kirchengast, G., Haas, S., and Fuchsberger, J.: New Compound Extreme Event Indicators for Detecting and Tracking Weather and Climate Extremes under Climate Change, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1279, https://doi.org/10.5194/egusphere-egu23-1279, 2023.

Recent long and intensive wildfire seasons in many regions have highlighted the urgency to understand the shift in worldwide fire regimes, raising the question if human induced climate change has played a role therein. However, attributing changes in fire to anthropogenic climate change is difficult, since possible signals are confounded by multiple drivers including fire weather, fuel availability and sources of ignition. Therefore, fire indices or individual input variables are often used as proxies. There have been some attempts to model drivers of recent trends in fire, though assessment of overall anthropogenic climate change is still lacking. Recent integration of fire models into ISIMIP now allow us to perform a fire impact attribution analysis using multiple coupled fire-vegetation models. Here, we combine both ISIMIP factual and counterfactual simulations with remote sensed observations to understand how burnt area has changed over the historical period due to a changing climate.

How to cite: Lampe, S., Burton, C., Burke, E., Chang, J., Christidis, N., Forrest, M., Gudmundsson, L., Huang, H., Hantson, S., Ito, A., Kelley, D., Kou-Giesbrecht, S., Lasslop, G., Li, F., Li, W., Nieradzik, L., and Thiery, W.: The Effect of Climate Change on Global Wildfire Activity, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14756, https://doi.org/10.5194/egusphere-egu23-14756, 2023.

The agriculture sector is sensitive to changes in weather and climate, notably extreme events. Extreme variations in weather conditions throughout a growing season led to changes in phenological features of vegetation and crops and cause variations in harvest, and, generally, the impact could be large in terms of production amounts and then food security in the region. The last version of the Intergovernmental Panel on Climate Change report (IPCC) highlighted the southern Mediterranean region as a hot spot and one of the most vulnerable regions in the world. While numerous studies have addressed changes in climate extremes throughout the world, very little research has been conducted in the southern Mediterranean region concerning the seasonal concurrence of climate extremes, and their evolutions in recent decades.  Moreover, understanding the impacts of these changes on vegetation phenology is crucial in the region, but this is yet to be studied.

This study evaluates the impact of climate extremes on vegetation phenology in the southern Mediterranean region over the last 40 years. Firstly, the trends of 15 phenological vegetation indicators (e.g., length of the growing season, maximum Normalized Difference Vegetation Index [NDVI] value/time, onset/offset times, green upslope, brown downslope, etc.) are examined using National Oceanic and Atmospheric Administration [NOAA] satellite images and the modified Mann-Kendall trend test. Secondly, we examine how recent trends in vegetation phenology compare with those observed in various heat-related indices (heat wave characteristics), water-related indices (Standard Precipitation Index [SPI], Standard Precipitation Evapotranspiration Index [SPEI], Extreme Precipitation, Wet/Dry spells), and compound indices (Dry-Cold, Dry-Hot, Wet-Cold, Wet-Hot events) calculated using the ERA5-land dataset. Finally, we examine the relative importance of each climate indicator in explaining multi-year changes in vegetation phenology. As such, this study not only identifies the areas with higher risk and vulnerability for vegetation and crops in the last years but also identifies potential predictors for seamless seasonal-to-decadal forecasts of agrometeorological risks across the region.

How to cite: Mirgol, B., Dieppois, B., Northey, J., Eden, J., Jarlan, L., Tramblay, Y., Mahé, G., El Hazdour, I., Khabba, S., Hanich, L., and Le Page, M.: Recent trends in vegetation phenology across the southern Mediterranean region, and potential climatic drivers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15331, https://doi.org/10.5194/egusphere-egu23-15331, 2023.

Weather extremes have multiple impacts on ecosystems, either through direct influence on plant functioning and health, or indirect and lagged impacts through disturbances such as fires, insects or pest outbreaks. Recent decades have seen an increase in high-impact extreme events, such as large-scale drought-induced mortality, crop failure, mega-fires, and widespread tree mortality events.

Understanding to which degree these events are already signs of human-driven climate change requires establishing a reference of natural climatic and ecological variability and formal attribution frameworks. Attribution of single weather extremes is challenging, but feasible through large ensembles of climate model simulations and by advanced statistical techniques. Attribution of high-impact ecological events is, however, complicated by the fact that impacts are not only driven by climate but also by internal ecological dynamics (mortality, gap dynamics, competition, succession) and human influence on the landscape and ecosystem composition (e.g., through land cover change, management, landscape fragmentation, etc.).

Here, we present a systemic framework that brings together climate risk and disturbance ecology perspectives to analyse the causal links between climate extremes, disturbances, and ecosystem dynamics. We propose an extended attribution approach that considers not only anthropogenic effects via climate change but also anthropogenic influences on ecological factors that modulate impacts. Based on this framework and on dedicated simulations by an Earth System Model, we exemplify how eco-climatic storylines can be used for robust attribution of high-impact events.

How to cite: Bastos, A., Sippel, S., Frank, D., Mahecha, M., Zaehle, S., Zscheischler, J., and Reichstein, M.: Challenges and ways forward in ecological impact attribution, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3412, https://doi.org/10.5194/egusphere-egu23-3412, 2023.

Coastal environments, in particular heavily populated semi-enclosed marginal seas and coasts like the Baltic Sea region, are strongly affected by human activities. A multitude of human impacts, including climate change, affects the different compartments of the environment, and these effects interact with each other.

As part of the Baltic Earth Assessment Reports (BEAR), we present an inventory and discussion of different human-induced factors and processes affecting the environment of the Baltic Sea region, and their interrelations. Some are naturally occurring and modified by human activities (i.e. climate change, coastal processes, hypoxia, acidification, submarine groundwater discharges, marine ecosystems, non-indigenous species, land use and land cover), some are completely human-induced (i.e. agriculture, aquaculture, fisheries, river regulations, offshore wind farms, shipping, chemical contamination, dumped warfare agents, marine litter and microplastics, tourism, coastal management), and they are all interrelated to different degrees.

We present a general description and analysis of the state of knowledge on these interrelations. Our main insight is that climate change has an overarching, integrating impact on all of the other factors and can be interpreted as a background effect, which has different implications for the other factors. Impacts on the environment and the human sphere can be roughly allocated to anthropogenic drivers such as food production, energy production, transport, industry and economy.

We conclude that a sound management and regulation of human activities must be implemented in order to use and keep the environments and ecosystems of the Baltic Sea region sustainably in a good shape. This must balance the human needs, which exert tremendous pressures on the systems, as humans are the overwhelming driving force for almost all changes we see. The findings from this inventory of available information and analysis of the different factors and their interactions in the Baltic Sea region can largely be transferred to other comparable marginal and coastal seas in the world.

This work is published as Open Access article in Earth System Dynamics (Earth Syst. Dynam., 13, 1–80, 2022; https://doi.org/10.5194/esd-13-1-2022)

How to cite: Reckermann, M. and the BEAR Human Impacts Author team: Human impacts and their interactions in the Baltic Sea region, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2776, https://doi.org/10.5194/egusphere-egu23-2776, 2023.

Changes in health and sustainability of the ocean that provide goods and services for human well-being are closely linked to climate change. However, the ocean is exposed to a range of climatic impact-drivers (CIDs, e.g., temperature increase, sea level rise, oxygen depletion, acidification etc.) from global to local scale concurrently. These multiple CIDs make the ocean environment shifting from the normal condition, posing either positive or detrimental effects to ocean ecosystems. Therefore, detecting and understanding the combined effect of different CIDs (named compound CIDs in this study) is critical to further unravel diverse and adverse impacts on the ocean ecosystems.

In this study, we analyzed compound CIDs from changes in the upper 2000m of the ocean temperature (T), salinity (S), and dissolved oxygen (DO) from 1960 to 2022, as well as surface pH changes from 1985 to 2021 by using several observation-based gridded products.

We used a time of emergence (ToE) approach to investigate the long-term change of  the compound CIDs. First, to quantify the ToE of each CID, we investigated when and where the long-term change (signal) is significantly larger than the background variability (noise). The long-term change is quantified by the 20 years of low-pass filtering of global time series, and the background variability is quantified by the magnitude of annual-interannual variability of the local time series. Additionally, the uncertainty of ToE is defined by using an ensemble approach. With the ToE of individual CID available, we defined the regions where ToE of the compound CIDs can be detected if the change of more than one CID has already emerged. The results we obtained provide a new insight on the 3D changing ocean properties. They differ from previous studies that were limited to a subset of individual CID (e.g., sea level rise, chlorophyll-a, net primary production) or to the ocean surface only (e.g., SST).

The analysis shows that, before 2021, for the upper 2000m, ~15% (±5%) of areas of global ocean has experienced the concurrent emergence of three CIDs (triple emergence), and ~30% (±8%) of global ocean has experienced concurrent emergence of two CIDs (double emergence) mainly in the Atlantic and northern Indian Ocean. Analyses at different depths reveal that ToE is stronger and starts earlier in deep layers (200-1300m) than in the upper ocean (0-200m) where the signal-to-noise ratio is lower (which may due to the strong interplay of the long-term change with natural variability).

As marine ecosystems rely on an environment determined by multiple drivers (T/S/oxygen etc.), the investigation of the compound CIDs provides a more complete description (and quantification) of their long-term exposure to the CIDs (multiple stressors).

How to cite: Tan, Z., von Schuckmann, K., Cheng, L., and Speich, S.: Global emergence of compound climatic impact-drivers, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3662, https://doi.org/10.5194/egusphere-egu23-3662, 2023.

We will present findings from a comprehensive review of the detection and attribution of climate change in the UK, including both recent and past events within the observation record. We will highlight where there are notable gaps, including those that can and cannot be closed with existing data and/or attribution techniques.

This systematic review of detection and attribution literature will feed into a report, with a database of supporting evidence, to inform the Climate Change Committee’s upcoming UK Climate Change Risk Assessment. The first part of the review will cover the detection and attribution of weather and climate changes in the UK, relevant to specific Climate Impact Drivers, while the second will cover societal, infrastructural, economic, and biodiversity impacts associated with these. As part of this, we will identify variables which are key drivers of multiple impacts, and, importantly, where further attribution analysis is needed, especially when the impacts are critical for UK risk.

How to cite: Betts, R., Mudhar, R., Mitchell, D., and Stott, P.: Gaps in Attribution for the Next UK Climate Change Risk Assessment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5385, https://doi.org/10.5194/egusphere-egu23-5385, 2023.