A compound event framework for understanding extreme impacts

Leonard, Michael; Westra, Seth; Phatak, Aloke; Lambert, Martin F.; Hurk, Bart van den; McInnes, Kathleen L.; Risbey, James S.; Schuster, Sandra; Jakob, Dörte; Smith, Mark S.

doi:10.1002/wcc.252

Cited by 569 publications

(480 citation statements)

References 63 publications

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“…To differentiate between the effects of univariate extremes and the possibility of different impacts of simultaneous extremes of heat and drought, the following types of extreme events were differentiated: (1) single variable extreme events irrespective 10 of the possible extremeness of other variables (denoted T/WAI min ), (2) single variable extreme events without other variables being extreme (denoted T/WAI min,s ) and (3) concurrent extremes (Seneviratne et al, 2012;Leonard et al, 2014), i.e. coupled extreme events with multiple variables being extreme (T max + WAI min ) (Tab.…”

Section: Climate Datamentioning

confidence: 99%

Impacts of droughts and extreme temperature events on gross primary production and ecosystem respiration: a systematic assessment across ecosystems and climate zones

Buttlar¹,

Zscheischler²,

Rammig³

et al. 2017

Preprint

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Abstract.Extreme climatic events, such as droughts and heat stress induce anomalies in ecosystem-atmosphere CO 2 fluxes, such as gross primary production (GPP) and ecosystem respiration (R eco ), and, hence, can change the net ecosystem carbon balance.However, despite our increasing understanding of the underlying mechanisms, the magnitudes of the impacts of different types of extremes on GPP and R eco within and between ecosystems remain poorly predicted. Here we aim to identify the major 5 factors controlling the amplitude of extreme event impacts on GPP, R eco , and the resulting net ecosystem production (NEP).We focus on the impacts of heat and drought and their combination. We identified hydrometeorological extreme events in consistently downscaled water availability and temperature measurements over a 30 year time period. We then used FLUXNET eddy-covariance flux measurements to estimate the CO 2 flux anomalies during these extreme events across dominant vegetation types and climate zones. Overall, our results indicate that short-term heat extremes increased respiration more strongly than 10 they down-regulated GPP, resulting in a moderate reduction of the ecosystem's carbon sink potential. In the absence of heat stress, droughts tended to have smaller and similarly dampening effects on both GPP and R eco , and, hence, often resulted in neutral NEP responses. The combination of drought and heat typically led to a strong decrease in GPP, whereas heat and drought impacts on respiration partially offset each other. Taken together, compound heat and drought events led to the strongest C sink reduction compared to any single-factor extreme. A key insight of this paper, however, is that duration matters most: 15 for heat stress during droughts, the magnitude of impacts systematically increased with duration, whereas under heat stress without drought, the response of R eco over time turned from an initial increase to a down-regulation after about two weeks.This confirms earlier theories that not only the magnitude but also the duration of an extreme event determines its impact. Our study corroborates the results of several local site-level case studies, but as a novelty generalizes these findings at the global scale. Specifically, we find that the different response functions of the two antipodal land-atmosphere fluxes GPP and R eco can 20 also result in increasing NEP during certain extreme conditions. Apparently counterintuitive findings of this kind bear great potential for scrutinizing the mechanisms implemented in state-of-the-art terrestrial biosphere models and provide a benchmark for future model development and testing.

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Section: Climate Datamentioning

confidence: 99%

Impacts of droughts and extreme temperature events on gross primary production and ecosystem respiration: a systematic assessment across ecosystems and climate zones

Buttlar¹,

Zscheischler²,

Rammig³

et al. 2017

Preprint

View full text Add to dashboard Cite

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mentioning

confidence: 99%

“…Environmental hazards often result from a combination of climatic events (13,14) over a range of spatial and temporal scales (15,16). A wildfire, for example, may occur on a hot, dry, and windy day, although each of these individual conditions may not necessarily be extreme by themselves (16). In the Intergovernmental Panel on Climate Change special report on managing the risks of extreme events and disasters, the combination of multiple climate extreme events is termed a compound event (14,16).…”

mentioning

confidence: 99%

“…A wildfire, for example, may occur on a hot, dry, and windy day, although each of these individual conditions may not necessarily be extreme by themselves (16). In the Intergovernmental Panel on Climate Change special report on managing the risks of extreme events and disasters, the combination of multiple climate extreme events is termed a compound event (14,16). Most analyses of climate and weather extremes typically tend to focus on a single climatic condition; however, this univariate approach may underestimate the effects of concurrent and compound extremes (16).…”

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confidence: 99%

“…Heatwaves concurrent with droughts can intensify individual impacts of heatwaves or drought on society, the environment, and the global economy (19,20). Studies suggest that changes in the relationship between precipitation and temperature may be more important than the changes in each of the variables individually (16,21). This study investigates changes in concurrent droughts and heatwaves in the United States using several different statistical techniques.…”

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confidence: 99%

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Substantial increase in concurrent droughts and heatwaves in the United States

Mazdiyasni

AghaKouchak

2015

Proc. Natl. Acad. Sci. U.S.A.

534

311

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A combination of climate events (e.g., low precipitation and high temperatures) may cause a significant impact on the ecosystem and society, although individual events involved may not be severe extremes themselves. Analyzing historical changes in concurrent climate extremes is critical to preparing for and mitigating the negative effects of climatic change and variability. This study focuses on the changes in concurrences of heatwaves and meteorological droughts from 1960 to 2010. Despite an apparent hiatus in rising temperature and no significant trend in droughts, we show a substantial increase in concurrent droughts and heatwaves across most parts of the United States, and a statistically significant shift in the distribution of concurrent extremes. Although commonly used trend analysis methods do not show any trend in concurrent droughts and heatwaves, a unique statistical approach discussed in this study exhibits a statistically significant change in the distribution of the data.

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Impact of large‐scale climate extremes on biospheric carbon fluxes: An intercomparison based on MsTMIP data

Zscheischler

Michalak

Schwalm

et al. 2014

Global Biogeochemical Cycles

231

150

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Understanding the role of climate extremes and their impact on the carbon (C) cycle is increasingly a focus of Earth system science. Climate extremes such as droughts, heat waves, or heavy precipitation events can cause substantial changes in terrestrial C fluxes. On the other hand, extreme changes in C fluxes are often, but not always, driven by extreme climate conditions. Here we present an analysis of how extremes in temperature and precipitation, and extreme changes in terrestrial C fluxes are related to each other in 10 state-of-the-art terrestrial carbon models, all driven by the same climate forcing. We use model outputs from the North American Carbon Program Multi-scale Synthesis and Terrestrial Model Intercomparison Project (MsTMIP). A global-scale analysis shows that both droughts and heat waves translate into anomalous net releases of CO 2 from the land surface via different mechanisms: Droughts largely decrease gross primary production (GPP) and to a lower extent total respiration (TR), while heat waves slightly decrease GPP but increase TR. Cold and wet periods have a smaller opposite effect. Analyzing extremes in C fluxes reveals that extreme changes in GPP and TR are often caused by strong shifts in water availability, but for extremes in TR shifts in temperature are also important. Extremes in net CO 2 exchange are equally strongly driven by deviations in temperature and precipitation. Models mostly agree on the sign of the C flux response to climate extremes, but model spread is large. In tropical forests, C cycle extremes are driven by water availability, whereas in boreal forests temperature plays a more important role. Models are particularly uncertain about the C flux response to extreme heat in boreal forests.

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A compound event framework for understanding extreme impacts

Cited by 569 publications

References 63 publications

Impacts of droughts and extreme temperature events on gross primary production and ecosystem respiration: a systematic assessment across ecosystems and climate zones

Impacts of droughts and extreme temperature events on gross primary production and ecosystem respiration: a systematic assessment across ecosystems and climate zones

Substantial increase in concurrent droughts and heatwaves in the United States

Impact of large‐scale climate extremes on biospheric carbon fluxes: An intercomparison based on MsTMIP data

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