scholarly journals Bringing physical reasoning into statistical practice in climate-change science

2021 ◽  
Vol 169 (1-2) ◽  
Author(s):  
Theodore G. Shepherd
Keyword(s):  
Climate Change ◽  
Extreme Event ◽  
Scientific Practice ◽  
Statistical Significance ◽  
Physical Reasoning ◽  
Event Attribution ◽  
Climate Change Science ◽  
Normative Standard ◽  
Warming Hiatus ◽  
Sampling Statistics

AbstractThe treatment of uncertainty in climate-change science is dominated by the far-reaching influence of the ‘frequentist’ tradition in statistics, which interprets uncertainty in terms of sampling statistics and emphasizes p-values and statistical significance. This is the normative standard in the journals where most climate-change science is published. Yet a sampling distribution is not always meaningful (there is only one planet Earth). Moreover, scientific statements about climate change are hypotheses, and the frequentist tradition has no way of expressing the uncertainty of a hypothesis. As a result, in climate-change science, there is generally a disconnect between physical reasoning and statistical practice. This paper explores how the frequentist statistical methods used in climate-change science can be embedded within the more general framework of probability theory, which is based on very simple logical principles. In this way, the physical reasoning represented in scientific hypotheses, which underpins climate-change science, can be brought into statistical practice in a transparent and logically rigorous way. The principles are illustrated through three examples of controversial scientific topics: the alleged global warming hiatus, Arctic-midlatitude linkages, and extreme event attribution. These examples show how the principles can be applied, in order to develop better scientific practice.“La théorie des probabilités n’est que le bon sens reduit au calcul.” (Pierre-Simon Laplace, Essai Philosophiques sur les Probabilités, 1819).“It is sometimes considered a paradox that the answer depends not only on the observations but on the question; it should be a platitude.” (Harold Jeffreys, Theory of Probability, 1st edition, 1939).

scholarly journals Attributing compound events to anthropogenic climate change

2021 ◽  
pp. 1-45
Author(s):  
Jakob Zscheischler ◽  
Flavio Lehner
Keyword(s):  
Climate Change ◽  
South Africa ◽  
Climate Model ◽  
Extreme Event ◽  
Synthetic Data ◽  
Anthropogenic Climate Change ◽  
Anthropogenic Influence ◽  
Western Cape ◽  
Event Attribution ◽  
Compound Events

AbstractExtreme event attribution answers the question whether and by how much anthropogenic climate change has contributed to the occurrence or magnitude of an extreme weather event. It is also used to link extreme event impacts to climate change. Impacts, however, are often related to multiple compounding climate drivers. Because extreme event attribution typically focuses on univariate assessments, these assessments might only provide a partial answer to the question of anthropogenic influence to a high-impact event. We present a theoretical extension to classical extreme event attribution for certain types of compound events. Based on synthetic data we illustrate how the bivariate fraction of attributable risk (FAR) differs from the univariate FAR depending on the extremeness of the event as well as the trends in and dependence between the contributing variables. Overall, the bivariate FAR is similar in magnitude or smaller than the univariate FAR if the trend in the second variable is comparably weak and the dependence between both variables is moderate or high, a typical situation for temporally co-occurring heatwaves and droughts. If both variables have similarly large trends or the dependence between both variables is weak, bivariate FARs are larger and are likely to provide a more adequate quantification of the anthropogenic influence. Using multiple climate model large ensembles, we apply the framework to two case studies, a recent sequence of hot and dry years in the Western Cape region of South Africa and two spatially co-occurring droughts in crop-producing regions in South Africa and Lesotho.

scholarly journals Media Representation of Extreme Event Attribution: A Case Study of the 2011–17 California Drought

2020 ◽  
Vol 12 (4) ◽  
pp. 847-862 ◽  
Author(s):  
Shannon Osaka ◽  
James Painter ◽  
Peter Walton ◽  
Abby Halperin
Keyword(s):  
Climate Change ◽  
Media Coverage ◽  
Extreme Event ◽  
Climate Impacts ◽  
Media Representation ◽  
Extreme Weather Events ◽  
Weather Events ◽  
Event Attribution ◽  
The Media

AbstractExtreme event attribution (EEA) is a relatively new branch of climate science combining weather observations and modeling to assess and quantify whether and to what extent anthropogenic climate change altered extreme weather events (such as heat waves, droughts, and floods). Such weather events are frequently depicted in the media, which enhances the potential of EEA coverage to serve as a tool to communicate on-the-ground climate impacts to the general public. However, few academic papers have systematically analyzed EEA’s media representation. This paper helps to fill this literature gap through a comprehensive analysis of media coverage of the 2011–17 California drought, with specific attention to the types of attribution and uncertainty represented. Results from an analysis of five U.S. media outlets between 2014 and 2015 indicate that the connection between the drought and climate change was covered widely in both local and national news. However, legitimate differences in the methods underpinning the attribution studies performed by different researchers often resulted in a frame of scientific uncertainty or disagreement in the media coverage. While this case study shows substantial media interest in attribution science, it also raises important challenges for scientists and others communicating the results of multiple attribution studies via the media.

scholarly journals Projected Changes in the Atmospheric Dynamics of Climate Extremes in France

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1440
Author(s):  
Pascal Yiou ◽  
Davide Faranda ◽  
Soulivanh Thao ◽  
Mathieu Vrac
Keyword(s):  
Climate Change ◽  
Atmospheric Circulation ◽  
Climate Models ◽  
Extreme Event ◽  
Global Climate ◽  
Climate Extremes ◽  
Atmospheric Dynamics ◽  
Event Attribution ◽  
The Subject ◽  
Projected Changes

Extremes of temperature, precipitation and wind have caused damages in France, in the agriculture, transportation and health sectors. Those types of events are largely driven by the atmospheric circulation. The dependence on the global climate change is not always clear, and it is the subject of extreme event attribution (EEA). This study reports an analysis of the atmospheric circulation over France for seven events that struck France in the 21st century, in various seasons. We focus on the atmospheric dynamics that leads to those extremes and examine how the probability of atmospheric patterns and their predictability responds to climate change. We analyse how the features of those events evolve in simulations following an SSP585 scenario for future climate. We identify how thermodynamical and dynamical changes of the atmosphere affect the predictability of the atmospheric circulation. Those using a range of CMIP6 simulations helps determining uncertainties linked to climate models.

scholarly journals Climate change increases the probability of heavy rains like those of storm Desmond in the UK – an event attribution study in near-real time

2015 ◽  
Vol 12 (12) ◽  
pp. 13197-13216 ◽  
Author(s):  
G. J. van Oldenborgh ◽  
F. E. L. Otto ◽  
K. Haustein ◽  
H. Cullen
Keyword(s):  
Climate Change ◽  
Climate Model ◽  
Extreme Event ◽  
Initial Assessment ◽  
Model Simulations ◽  
Event Attribution ◽  
Climate Model Simulations ◽  
Using Data ◽  
The Uk ◽  
Precipitation Events

Abstract. On 4–6 December 2015, the storm "Desmond" caused very heavy rainfall in northern England and Scotland, which led to widespread flooding. Here we provide an initial assessment of the influence of anthropogenic climate change on the likelihood of one-day precipitation events averaged over an area encompassing northern England and southern Scotland using data and methods available immediately after the event occurred. The analysis is based on three independent methods of extreme event attribution: historical observed trends, coupled climate model simulations and a large ensemble of regional model simulations. All three methods agree that the effect of climate change is positive, making precipitation events like this about 40 % more likely, with a provisional 2.5–97.5 % confidence interval of 5–80 %.

scholarly journals Can the Issuance of Hazardous-Weather Warnings Inform the Attribution of Extreme Events to Climate Change?

2020 ◽  
Vol 101 (8) ◽  
pp. E1452-E1463
Author(s):  
Dale R. Durran
Keyword(s):  
Climate Change ◽  
Global Warming ◽  
Extreme Events ◽  
Weather Forecasting ◽  
Extreme Event ◽  
Probability Of Detection ◽  
False Alarms ◽  
Event Attribution ◽  
Hazardous Weather

Abstract When extreme weather occurs, the question often arises whether the event was produced by climate change. Two types of errors are possible when attempting to answer this question. One type of error is underestimating the role of climate change, thereby failing to properly alert the public and appropriately stimulate efforts at adaptation and mitigation. The second type of error is overestimating the role of climate change, thereby elevating climate anxiety and potentially derailing important public discussions with false alarms. Long before societal concerns about global warming became widespread, meteorologists were addressing essentially the same trade-off when faced with a binary decision of whether to issue a warning for hazardous weather. Here we review forecast–verification statistics such as the probability of detection (POD) and the false alarm ratio (FAR) for hazardous-weather warnings and examine their potential application to extreme-event attribution in connection with climate change. Empirical and theoretical evidence suggests that adjusting tornado-warning thresholds in an attempt to reduce FAR produces even larger reductions in POD. Similar tradeoffs between improving FAR and degrading POD are shown to apply using a rubric for the attribution of extreme high temperatures to climate change. Although there are obviously significant differences between the issuance of hazardous-weather warnings and the attribution of extreme events to global warming, the experiences of the weather forecasting community can provide qualitative guidance for those attempting to set practical thresholds for extreme-event attribution in a changing climate.

scholarly journals Pathways and pitfalls in extreme event attribution

2021 ◽  
Vol 166 (1-2) ◽  
Author(s):  
Geert Jan van Oldenborgh ◽  
Karin van der Wiel ◽  
Sarah Kew ◽  
Sjoukje Philip ◽  
Friederike Otto ◽  
...  
Keyword(s):  
Climate Change ◽  
Climate Model ◽  
Extreme Event ◽  
Climate Change Impacts ◽  
Climate Science ◽  
Companion Paper ◽  
Lessons Learned ◽  
Future Climate Change ◽  
Practical Applications ◽  
Event Attribution

AbstractThe last few years have seen an explosion of interest in extreme event attribution, the science of estimating the influence of human activities or other factors on the probability and other characteristics of an observed extreme weather or climate event. This is driven by public interest, but also has practical applications in decision-making after the event and for raising awareness of current and future climate change impacts. The World Weather Attribution (WWA) collaboration has over the last 5 years developed a methodology to answer these questions in a scientifically rigorous way in the immediate wake of the event when the information is most in demand. This methodology has been developed in the practice of investigating the role of climate change in two dozen extreme events world-wide. In this paper, we highlight the lessons learned through this experience. The methodology itself is documented in a more extensive companion paper. It covers all steps in the attribution process: the event choice and definition, collecting and assessing observations and estimating probability and trends from these, climate model evaluation, estimating modelled hazard trends and their significance, synthesis of the attribution of the hazard, assessment of trends in vulnerability and exposure, and communication. Here, we discuss how each of these steps entails choices that may affect the results, the common problems that can occur and how robust conclusions can (or cannot) be derived from the analysis. Some of these developments also apply to other attribution methodologies and indeed to other problems in climate science.

scholarly journals Singular Extreme Events and Their Attribution to Climate Change: A Climate Service–Centered Analysis

2020 ◽  
Author(s):  
Aglae Jezequel ◽  
Vivian Dépoues ◽  
Hélène Guillemot ◽  
Amélie Rajaud ◽  
Mélodie Trolliet ◽  
...  
Keyword(s):  
Climate Change ◽  
Extreme Event ◽  
Climate Science ◽  
Structured Interviews ◽  
European Climate ◽  
Weather Events ◽  
Event Attribution ◽  
Climate Service ◽  
Do So

<p>Extreme event attribution (EEA) proposes scientific diagnostics on whether and how a specific weather event is (or is not) different in the actual world from what it could have been in a world without climate change. This branch of climate science has developed to the point where European institutions are preparing the ground for an operational attribution service. In this context, the goal of this article is to explore a panorama of scientist perspectives on their motivations to undertake EEA studies. To do so, we rely on qualitative semi-structured interviews of climate scientists involved in EEA, on peer-reviewed social and climate literature discussing the usefulness of EEA, and on reports from the EUCLEIA project (European Climate and Weather Events: Interpretation and Attribution), which investigated the possibility of building an EEA service. We propose a classification of EEA’s potential uses and users and discuss each of them. We find that, first, there is a plurality of motivations and that individual scientists disagree on which one is most useful. Second, there is a lack of solid, empirical evidence to back up any of these motivations.</p>

scholarly journals “What’s Up with the Weather?” Public Engagement with Extreme Event Attribution in the UK

2021 ◽  
Author(s):  
Joshua Ettinger ◽  
Peter Walton ◽  
James Painter ◽  
Shannon Osaka ◽  
Friederike E.L. Otto
Keyword(s):  
Climate Change ◽  
Extreme Event ◽  
Scientific Information ◽  
Extreme Weather ◽  
Extreme Weather Events ◽  
Scientific Uncertainty ◽  
Climate Change Communication ◽  
Change Communication ◽  
Event Attribution ◽  
The Uk

AbstractThe science of extreme event attribution (EEA) – which connects specific extreme weather events with anthropogenic climate change – could prove useful for engaging the public about climate change. However, there is limited empirical research examining EEA as a climate change communication tool. In order to help fill this gap, we conducted focus groups with members of the UK public to explore benefits and challenges of utilizing EEA results in climate change advocacy messages. Testing a range of verbal and visual approaches for communicating EEA, we found that EEA shows significant promise for climate change communication because of its ability to connect novel, attention-grabbing and event-specific scientific information to personal experiences and observations of extreme events. Communication challenges include adequately capturing nuances around extreme weather risks, vulnerability, adaptation and disaster risk reduction; expressing scientific uncertainty without undermining accessibility of key findings; and difficulties interpreting mathematical aspects of EEA results. Based on our findings, we provide recommendations to help address these challenges when communicating EEA results beyond the climate science community. We conclude that EEA can help catalyze important dialogues about the links between extreme weather and human-driven climate change.

scholarly journals Multi-method event attribution of 2015 OND drought in subtropical southern Africa

2020 ◽  
Author(s):  
Neven Fuckar ◽  
Friederike Otto ◽  
Flavio Lehner ◽  
Piotr Wolski ◽  
Emma Howard ◽  
...  
Keyword(s):  
Climate Change ◽  
Southern Africa ◽  
Carbon Dioxide Emissions ◽  
Extreme Event ◽  
High Surface ◽  
Risk Indicators ◽  
Intensity Change ◽  
Runoff Water ◽  
Austral Spring ◽  
Event Attribution

<p>The subtropical (south of 15deg.S) southern Africa experienced one of the most severe droughts in the record - accompanied with an exceptional heat wave – during the austral spring (October through December – the first half of the main rainy season) of 2015. The observed surface hydro-meteorological conditions led to substantial socio-economic impacts in the region - with mostly semi-arid climate and high spatial-temporal variability - where drought is the principal type of widespread natural disaster. More specifically, very low precipitation - compounded with very high surface air temperature (SAT) - caused low runoff, water shortages and restrictions, reduced electricity generation, and considerable loss of crops and livestock prompting Botswana, Namibia, Lesotho, Malawi, Swaziland and Zimbabwe to declare national drought emergencies. Every extreme event is the result of a combination of external drivers, natural (solar forcing and volcanos), and anthropogenic (carbon dioxide emissions, land use, etc.), and internal variability. The risk-based or probabilistic event attribution assesses to what extent anthropogenic forcing modifies the probability and magnitude, and hence the risk of an extreme event or a class of events to occur (i.e. to identify “the sharp edge” of climate change). This study utilises multiple long-term observations (CRU TS 4.03, GPCC v2018, NOAA PREC/L, etc.), and AGCM and CGCM historical simulations (12 models in total spread across CMIP3, CMIP5 and CMIP6 generations) to estimate risk indicators such as probability (risk) ratio (RR) and intensity change for the OND 2015 drought with respect to the beginning of the 20<sup>th</sup> century or pre-industrial conditions. Our multi-method approach indicates significant influence of climate change in total OND precipitation, e.g. RR = 1.48 (with 95% CI: 1.20, 1.85), and precipitation-temperature (mean OND SAT) ratio fields over the subtropical southern Africa, but uncertainty of risk indicators can be substantial. The crucial elements of atmospheric circulation and teleconnections (such as Angola Low and ENSO influence) associated with this extreme event are analysed and elaborated using the latest NOAA-CIRES-DOE 20<sup>th</sup> Century Reanalysis version 3.</p>

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