The Role of Natural Variability and Anthropogenic Climate Change in the 2017/18 Tasman Sea Marine Heatwave

Perkins‐Kirkpatrick, Sarah E.; King, Andrew D.; Cougnon, Eva A.; Grose,; Oliver, Eric C. J.; Holbrook, Neil J.; Lewis, Sophie C.; Pourasghar, Farnaz

doi:10.1175/bams-d-18-0116.1

Cited by 72 publications

(66 citation statements)

References 11 publications

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“…Due to taking averages over large areas, the signal-to-noise ratio is high for such events, and we could exclude that it could have occurred as part of natural variability. To our knowledge, so far only for marine heat waves, it could be concluded that their occurrence would not have been possible without climate change (Oliver et al, 2018;Perkins-Kirkpatrick et al, 2019). Thus, the GCWH18 event possibly constitutes the first climate phenomenon on land that has been uniquely attributed to human-induced global warming.…”

Section: Discussionmentioning

confidence: 93%

“…To our knowledge, so far only for marine heat waves, it could be concluded that their occurrence would not have been possible without climate change (Oliver et al, 2018;Perkins-Kirkpatrick et al, 2019). Due to taking averages over large areas, the signal-to-noise ratio is high for such events, and we could exclude that it could have occurred as part of natural variability.…”

Section: Discussionmentioning

confidence: 94%

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Concurrent 2018 Hot Extremes Across Northern Hemisphere Due to Human‐Induced Climate Change

et al. 2019

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Extremely high temperatures pose an immediate threat to humans and ecosystems. In recent years, many regions on land and in the ocean experienced heat waves with devastating impacts that would have been highly unlikely without human‐induced climate change. Impacts are particularly severe when heat waves occur in regions with high exposure of people or crops. The recent 2018 spring‐to‐summer season was characterized by several major heat and dry extremes. On daily average between May and July 2018 about 22% of the populated and agricultural areas north of 30° latitude experienced concurrent hot temperature extremes. Events of this type were unprecedented prior to 2010, while similar conditions were experienced in the 2010 and 2012 boreal summers. Earth System Model simulations of present‐day climate, that is, at around +1 °C global warming, also display an increase of concurrent heat extremes. Based on Earth System Model simulations, we show that it is virtually certain (using Intergovernmental Panel on Climate Change calibrated uncertainty language) that the 2018 north hemispheric concurrent heat events would not have occurred without human‐induced climate change. Our results further reveal that the average high‐exposure area projected to experience concurrent warm and hot spells in the Northern Hemisphere increases by about 16% per additional +1 °C of global warming. A strong reduction in fossil fuel emissions is paramount to reduce the risks of unprecedented global‐scale heat wave impacts.

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Section: Discussionmentioning

confidence: 93%

Section: Discussionmentioning

confidence: 94%

Concurrent 2018 Hot Extremes Across Northern Hemisphere Due to Human‐Induced Climate Change

et al. 2019

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“…As the impacts of MHWs will likely continue in the future (Darmaraki et al, ; Frölicher et al, ), it is important to improve our knowledge of both the local and remote processes that lead to MHW conditions in the ocean and to, ultimately, predict these conditions. Three‐dimensional ocean models are a valuable tool to explore key mechanisms that lead to MHW conditions, aiding our overall understanding of these extremes (e.g., Behrens et al, ; Oliver et al, ; Perkins‐Kirkpatrick et al, ).…”

Section: Introductionmentioning

confidence: 99%

Sensitivity of Marine Heatwave Metrics to Ocean Model Resolution

Pilo

Holbrook

Kiss

et al. 2019

Geophysical Research Letters

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Sustained extreme temperature events in the ocean, referred to as marine heatwaves (MHWs), generate substantial ecological, social, and economic impacts. Ocean models provide insights to the drivers, persistence, and dissipation of MHWs. However, the sensitivity of MHW metrics to ocean model resolution is unknown. Here, we analyze global MHW metrics in three configurations of a global ocean-sea ice model at coarse (1 • ), eddy-permitting (0.25 • ), and eddy-rich (0.1 • ) resolutions. We show that all configurations qualitatively represent broad-scale global patterns of MHWs. These simulated MHWs are, however, weaker, longer-lasting, and less frequent than in observations. The 0.1 • configuration, despite local biases, performs best both globally and regionally. Based on these results, model projections of future MHW metrics using coarse-resolution models are expected to be biased toward weaker and less frequent MHWs, when compared with results using an eddy-rich model. Plain Language SummaryMarine heatwaves (MHWs) are persistent extreme temperatures in the ocean. They have a negative impact on marine life, fisheries, and tourism, and are becoming more frequent and more intense. One way to understand how MHWs form, intensify, and decay is by analyzing results from computer simulations of the ocean. However, these simulations are a simplification of reality, and depending on how they are designed they represent different aspects of the ocean circulation. It is still unknown how much the resolution of an ocean simulation matters when representing MHWs. In this work, we compare the performance of three ocean simulations-with low, medium, and high resolutions-when representing MHWs. We find that, regardless of their resolution, all simulations have weaker, longer, and less-frequent MHWs, when compared with the real world. Despite these differences, we find that simulations with medium and high-resolutions realistically represent global spatial patterns of MHWs. However, the ocean simulation with high resolution is preferable when studying regional patterns of MHWs. These results show how simulated MHWs differ from the real world, helping us to improve ocean simulations to be more realistic. In addition, we now better understand how computer simulations of future oceans, under climate change conditions, represent these extreme events. Key Points:• Marine heatwaves are weaker, longer-lasting, and less frequent in models than in observations • The higher the model resolution, the less biased the marine heatwave metrics • Eddy-permitting models can be used for global marine heatwave analyses, but eddy-rich models are optimal for regional analyses

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“…This evolution includes in the number of studies, their scope and applied methodologies, and the certainty of results. For some temperature extremes, studies (Imada et al, 2018;Knutson et al, 2018;Lewis & Karoly, 2014b;Perkins-Kirkpatrick et al, 2019;Walsh et al, 2018) have identified events that do not occur (infinite RRs or FAR values of one) in the model frameworks used within simulations run without anthropogenic influences (e.g., greenhouse gases). In specific cases, this trend includes increasingly large anthropogenic influences determined for events, as measured through risk ratio (RR) or fraction of attributable risk (FAR) values.…”

Section: Introductionmentioning

confidence: 99%

“…For example, the first quantitative examination of the 2003 record hot European summer found that the risk of such an event was doubled (RR of 2) due to climate change (Stott et al, 2004), while a study revisiting this event found a dramatically increased risk of extreme summers of the 2003 magnitude occurring in the decade since (Christidis et al, 2015). For some temperature extremes, studies (Imada et al, 2018;Knutson et al, 2018;Lewis & Karoly, 2014b;Perkins-Kirkpatrick et al, 2019;Walsh et al, 2018) have identified events that do not occur (infinite RRs or FAR values of one) in the model frameworks used within simulations run without anthropogenic influences (e.g., greenhouse gases). This saturation of RR values for temperature extremes for certain events has been explored in depth elsewhere (Harrington et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Toward Calibrated Language for Effectively Communicating the Results of Extreme Event Attribution Studies

et al. 2019

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Extreme event attribution studies attempt to quantify the role of human influences in observed weather and climate extremes. These studies are of broad scientific and public interest, although quantitative results (e.g., that a specific event was made a specific number of times more likely because of anthropogenic forcings) can be difficult to communicate accurately to a variety of audiences and difficult for audiences to interpret. Here, we focus on how results of these studies can be effectively communicated using standardized language and propose, for the first time, a set of calibrated terms to describe event attribution results. Using these terms and an accompanying visual guide, results are presented in terms of likelihood of event changes and the associated uncertainties. This standardized language will allow clearer communication and interpretation of probabilities by the public and stakeholders.

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The Role of Natural Variability and Anthropogenic Climate Change in the 2017/18 Tasman Sea Marine Heatwave

Cited by 72 publications

References 11 publications

Concurrent 2018 Hot Extremes Across Northern Hemisphere Due to Human‐Induced Climate Change

Concurrent 2018 Hot Extremes Across Northern Hemisphere Due to Human‐Induced Climate Change

Sensitivity of Marine Heatwave Metrics to Ocean Model Resolution

Toward Calibrated Language for Effectively Communicating the Results of Extreme Event Attribution Studies

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