Studying the fingerprints of Human Actions over the Extreme Climatic Events of 2013. AMS Report (by Diego Fdez-Sevilla)

Studying the fingerprints of Human Actions over the Extreme Climatic Events of 2013. AMS Report (by Diego Fdez-Sevilla)

In September 2014 the American Meteorological Society has published a special report presenting assessments of how climate change may have affected the strength and likelihood of individual extreme events.

DiegoFdezSevilla Front Report Explaining Extreme Events 2013 BAMS

Front Cover from “Explaining Extreme Events of 2013”. Special Supplement to the Bulletin of the American Meteorological Society Vol. 95, No. 9, September 2014

This publication has already found echo in the news media in which different points from the report are highlighted. It is a matter of concern how biased can be the information being fed into the debate about the impact of anthropogenic development on planetary environmental evolution. Therefore, here I just present from the report the Abstract, Summary and Broader Context followed by the Table of Contents. You can always access the original report following this link.

This report has been selected based on the adding value that represents in the study of the potential impact from anthropogenic development on planetary environmental evolution, altogether with previous “related posts” (at the bottom).


Attribution of extreme events is a challenging science and one that is currently undergoing considerable evolu­tion. In this paper, 20 different research groups explored the causes of 16 different events that occurred in 2013. The findings indicate that human-caused climate change greatly increased the risk for the extreme heat waves assessed in this report. How human influence affected other types of events such as droughts, heavy rain events, and storms was less clear, indicating that natural vari­ability likely played a much larger role in these extremes. Multiple groups chose to look at both the Australian heat waves and the California drought, providing an opportu­nity to compare and contrast the strengths and weak­nesses of various methodologies. There was considerable agreement about the role anthropogenic climate change played in the events between the different assessments. This year three analyses were of severe storms and none found an anthropogenic signal. However, attribution as­sessments of these types of events pose unique challenges due to the often limited observational record. When human-influence for an event is not identified with the scientific tools available to us today, this means that if there is a human contribution, it cannot be distinguished from natural climate variability.

DiegoFdezSevilla Location and type of events analyzed in this paper.

Climatic Events Studied

  1. CALIFORNIA                                      DROUGHT                                                   3 studies
  2. NORTHEAST COLORADO              EXTREME RAINS                                          1 study
  3. A U.S. FOCUSED ANALYSIS           PRECIPITATION EXTREMES                    1 study
  4. WESTERN SOUTH DAKOTA          BLIZZARD                                                        1 study
  5. AUSTRALIA AND PACIFIC             EXTREME WARM ANOMALIES                4 studies
  6. AUSTRALIA                                        BIG DRY                                                           1 study
  7. NORTH ISLAND, NZ                        DROUGHT                                                         1 study
  8. KOREA                                                 HEAT WAVE                                                     1 study
  9. JAPAN                                                  HEAT WAVES                                                   1 study
  10. CENTRAL EASTERN CHINA         HOT SUMMER                                                   1 study
  11. NORTHERN INDIA                          SEVERE PRECIPITATION                              1 study
  12. WESTERN EUROPE                         DRY SUMMER                                                   1 study
  13. SOUTHERN EUROPE                      WET WINTER                                                    1 study
  15. SPANISH PYRENEES                       EXTREME SNOW ACCUMULATION           1 study
  17. UNITED KINGDOM                         COLD SPRING                                                   1 study


We acknowledge that these reports represent a small and nonrandom sampling of extreme events from around the world. However, with 22 studies looking at 16 events, a few interesting patterns emerge. Examining Table 24.1 reveals that the nine analyses of extreme heat events overwhelmingly showed that human-caused climate change is having an influence. In some cases, events have become as much as 10 times more likely due to the current cumulative effects of human-induced climate change, as found for the Korean heat wave of summer 2013. These individual examples are consistent with the broader trends captured in the latest IPCC (Stocker et al. 2014) statement, “it is likely that the frequency of heat waves has increased in large parts of Europe, Asia and Aus­tralia.” At the other end of the temperature distribu­tion, the one analysis of a cold event found that such events were becoming much less likely.

DiegoFdezSevilla Table Report Explaining Extreme Events 2013 BAMS

Summary of results for Explaining Extreme Events of 2013 from a Climate Perspective, with the role of anthropogenic climate change (increased, decreased, no evidence) noted for each event. Specific papers examining the event are noted in parenthesis.

In contrast, the role of human influences on ex­treme precipitation events observed in 2013 is decid­edly mixed (Table 24.1). The analysis of the extreme June monthly averaged precipitation in northern India found evidence suggesting an increase of the event probability in the present climate compared to preindustrial climate (see “Severe Precipitation in Northern India in June 2013: Causes, Historical Context, and Changes in Probability” in this report), whereas analyses of seasonal and annual precipita­tion extreme values over the north-central and east­ern United States (see “Seasonal and Annual Mean Precipitation Extremes Occurring During 2013: A U.S. Focused Analysis” in this report) showed an an­thropogenic contribution. The high profile and high impact extreme rainfall event in northeast Colorado in early September happened despite global warming making the event less likely according to this analysis (see “Northeast Colorado Extreme Rains Interpreted in a Climate Change Context” in this report). Two additional heavy precipitation analyses did not find anthropogenic influences.

Of the four analyses of drought, the one focused on New Zealand drought found global warming contributed to the severity of that event. However, the three papers that looked at the California drought did not find a clear anthropogenic influence. “Examining the Contribution of the Observed Global Warming Trend to the California Droughts of 2012/13 and 2013/14” and “Causes of the Extreme Dry Conditions Over Califor­nia During Early 2013” looked directly at the precipi­tation deficits associated with the California drought and their link to SSTs and found no appreciable effect from long-term SST warming. “The Extraordinary California Drought of 2013/14: Character, Context, and the Role of Climate Change” took a different ap­proach and focused on particular circulation patterns that contributed to the drought, rather than examin­ing precipitation directly. While they found global warming to increase the probability of certain large-scale atmospheric circulations, the implications for extremely low precipitation over California were found to be uncertain. This comparison of three studies for the same extreme event, each using different methods and metrics, strengthened the attribution evidence (in this case, against a substantial effect of global warming on the severe precipitation deficits), and revealed the sources of uncertainty more deeply than might have been evident from a single study alone.

This year, we also had a few very exciting additions that looked at different types of extreme events: an as­sessment of a blizzard that hit South Dakota, Cyclone “Christian” that caused significant damage in north­western Europe, and an extreme snowfall event in the Pyrenees Mountains. None of these analyses found an anthropogenic signal, in part because attribution assessments of storm events such as these pose unique challenges due to the often limited observational record. As stated earlier, this failure to find anthro­pogenic signals does not prove anthropogenic climate change had no role to play in these events. Rather, a substantial anthropogenic contribution to these events cannot be supported by these analyses.

Broader context of attribution research. As we conclude our third annual report on explaining extreme events, the dialog around the value of attribution science is intensifying (Kerr 2013). Perhaps the most evident and widely applicable value of event attribution is to interpret what an event occurrence means for the fu­ture. The annual State of the Climate report (Blunden and Arndt 2014) puts current conditions into historical perspective, while our report also seeks to explain the events in the context of the future as well by identify­ing how our changing climate system is currently influencing events.

In addition to interpreting how the risk of an extreme event may be changing, event attribution is also valuable to the overall scientific enterprise of im­proving predictions and projections. As stated in the World Climate Research Program Grand Challenges white paper for Science Underpinning the Prediction and Attribution of Extreme Events, “There are strong links between the development of routine event attri­bution methods and those used to make sub-seasonal to interannual predictions” (Karoly et al. 2012). The physical understanding of extreme events is valuable in determining if models are capable of representing and simulating those processes and events realistically. Assessments of extremes can, therefore, elucidate strengths and limitations of models. The ultimate goal is to develop new prediction products relating to extremes that better meet the needs of the public and decision makers, who must make choices about how to prepare for extremes.

Beyond the science, there is an ongoing public dialog around climate change and its impacts. It is clear that extreme events capture the public’s atten­tion. And, indeed, they should because “people, plants and animals tend to be more impacted by changes in extremes compared to changes in average climate” (Peterson et al. 2008). And, with or without the avail­ability of a robust scientific analysis, the public often associates extreme events such as these with climate change. Scientific event attribution can help inform the public’s understanding of our changing environ­ment.

The challenges in event attribution are high both from a technological perspective of improving sci­entific knowledge and from a communication per­spective of explaining what that science knowledge means. Observed events, such as those analyzed in this report, demonstrate the vulnerabilities of societ­ies to extremes of weather and climate. In the face of such vulnerabilities, citizens are faced with decisions in the presence of uncertainty, for instance whether climate change may be increasing their exposure to drought or flooding. Enhancing scientific knowledge through attribution helps build environmental intel­ligence, thereby enabling better decisions than would be possible without such understanding.

It remains that after an extreme event there is a window of opportunity to engage the public on climate change impacts and science more broadly (Peterson et al. 2008). Being able to deliver scientifically robust attribution statements about the event in a timely manner is an important first step in this dialog.

EXPLAINING EXTREME EVENTS OF 2013 FROM A CLIMATE PERSPECTIVE. Special Supplement to the Bulletin of the American Meteorological Society. Vol. 95, No. 9, September 2014

News media:


About Diego Fdez-Sevilla, PhD.

Citing This Site "Title", published online "Month"+"Year", retrieved on "Month""Day", "Year" from By Diego Fdez-Sevilla, PhD. More guidance on citing this web as a source can be found at NASA webpage:! DOIs can be generated on demand by request at email: d.fdezsevilla(at) for those publications missing at the ResearchGate profile vinculated with this project. **Author´s profile: Born in 1974. Bachelor in General Biology, Masters degree "Licenciado" in Environmental Sciences (2001, Spain). PhD in Aerobiology (2007, UK). Lived, acquired training and worked in Spain, UK, Germany and Poland. I have shared the outcome from my work previous to 2013 as scientific speaker in events held in those countries as well as in Switzerland and Finland. After 12 years performing research and working in institutions linked with environmental research and management, in 2013 I found myself in a period of transition searching for a new position or funding to support my own line of research. In the current competitive scenario, in order to demonstrate my capacities instead of just moving my cv waiting for my next opportunity to arrive, I decided to invest my energy and time in opening my own line of research sharing it in this blog. In March 2017 the budget reserved for this project has ended and its weekly basis time frame discontinued until new forms of economic and/or institutional support are incorporated into the project. The value of the data and the original nature of the research presented in this platform and at LinkedIn has proved to be worthy of consideration by the scientific community as well as for publication in scientific journals. However, without a position as member of an institution, it becomes very challenging to be published. I hope that this handicap do not overshadow the value of my achievements and that the Intellectual Property Rights generated with the license of attribution attached are respected and considered by the scientist involved in similar lines of research. **Any comment and feedback aimed to be constructive is welcome as well as any approach exploring professional opportunities to be part of.** In this blog I publish pieces of research focused on addressing relevant environmental questions. Furthermore, I try to break the barrier that academic publications very often offer isolating scientific findings from the general public. In that way I address those topics which I am familiar with, thanks to my training in environmental research, making them available throughout my posts. (see "Framework and Timeline" for a complete index). At this moment, 2017, I am living in Spain with no affiliation attachments. Free to relocate geographically worldwide. If you feel that I could be a contribution to your institution, team and projects don´t hesitate in contact me at d.fdezsevilla (at) or consult my profile at LinkedIn, ResearchGate and Also, I'd appreciate information about any opportunity that you might know and believe it could match with my aptitudes. The conclusions and ideas expressed in each post as part of my own creativity are part of my Intellectual Portfolio and are protected by Intellectual Property Laws. Licensed under Creative Commons Attribution-NonCommercial conditions. In citing my work from this website, be sure to include the date of access. (c)Diego Fdez-Sevilla, PhD, 2017. Filling in or Finding Out the gaps around. Publication accessed 20YY-MM-DD at
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3 Responses to Studying the fingerprints of Human Actions over the Extreme Climatic Events of 2013. AMS Report (by Diego Fdez-Sevilla)

  1. Pingback: Following the steps of water vapour in climatic events (By Diego Fdez-Sevilla) | diego fdez-sevilla

  2. Pingback: 2014 in review. One year trying to “Fill in” or “Find out” gaps of knowledge. (by Diego Fdez-Sevilla) | diego fdez-sevilla

  3. Pingback: Communication takes more than just publishing thoughts. (by Diego Fdez-Sevilla) | diego fdez-sevilla

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