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14 February 2012 (JO-01/12)

Researcher in Climate & Computing

Climate Risk Analysis (CRA) is an expanding research company working on risk quantification of extreme climate/weather events.

CRA is seeking a computing scientist to work in an international, EU-funded Marie Curie project on interacting networks in climate.

Your qualifications

  • Degree (MS or equivalent) in computing, statistics or physics
  • Between four and five years full-time work experience in industry/academia after degree (PhD holders also less than four years)
  • Transnational (coming from outside of Germany) and intersectorial mobilities
  • Excellent communication skills (English)

Your work in the project

  • Industry-standard software development, including parallelization and GUIs
  • Adaptation of statistical algorithms (in collaboration with M. Mudelsee)
  • Support for statistics/computer course
  • Training of project partners (in-house and travel)

Position

  • Starting date: summer 2012
  • Duration: two years
  • Place: Hannover, Germany (part-time telework possible)
  • Gaining competence in climate time series and risk analysis, intersectorial work
  • Competitive salary (ca. 50 kEUR/year) plus bonuses
  • Extensive covering of research, training and relocation costs

Your application

  • Cover letter, CV, reference contacts, photo
  • PDF format (preferably one single file)
  • Send by 12 May 2012 to jobs@climate-risk-analysis.com under subject "JO-01/12" (later applications may be considered)
  • CRA guarantees confidentiality

Contact and more information

20 October 2011 (JO-01/11)

Position as Research Scientist

Climate Risk Analysis (CRA) is a research company working on risk quantification of extreme climate/weather events.

CRA is seeking a computing scientist/software designer to work in an international, EU-funded project on interacting networks in climate.

Your qualifications

  • Degree in computing, statistics or physics
  • PhD (or four years full-time work experience in industry/academia) in computing, statistics or physics
  • Less than five years full-time work experience (after degree) at the time of start of position
  • Transnational and intersectorial mobilities
  • Excellent communication skills (English)

Your work in the project

  • Industry-standard software development, including parallelization and GUIs
  • Adaptation of statistical algorithms (in collaboration with M. Mudelsee)
  • Support for statistics/computer course
  • Training of project partners (in-house and travel)

Position

  • Starting date: first half of 2012
  • Duration: two years
  • Place: Hannover, Germany (part-time telework possible)
  • Gaining competence in climate time series and risk analysis, intersectorial work
  • Competitive salary
  • Extensive covering of research and training costs

Your application

  • Cover letter, CV, references, photo
  • PDF format (preferably one single file)
  • Send by 23 December 2011 to jobs@climate-risk-analysis.com under subject "JO-01/11" (later applications may be considered)
  • CRA guarantees confidentiality

Contact and more information

31 May 2011 (PR-02/11)
Course on climate time series analysis

CRA offers this course from August 2011. For details please see under Courses.

About Climate Risk Analysis:

Climate Risk Analysis is a research company working on risk quantification of extreme weather or climate events.

Contact:

Dr. Manfred Mudelsee, CEO
Climate Risk Analysis
Phone +49-511-70032891
Fax +49-511-70032892
mudelsee@climate-risk-analysis.com
http://www.climate-risk-analysis.com

Copyright:

You are free to use this press release; please refer to Climate Risk Analysis and link to http://www.climate-risk-analysis.com.

10 February 2011 (PR-01/11)
Climate risk estimation software Caliza™ 2.0 (February 2011) released

CRA offers a demo version and a user manual. Please have a look at the Caliza™ page.

About Climate Risk Analysis:

Climate Risk Analysis is a research company working on risk quantification of extreme weather or climate events.

Contact:

Dr. Manfred Mudelsee, CEO
Climate Risk Analysis
+49-511-70032892
mudelsee@climate-risk-analysis.com
http://www.climate-risk-analysis.com

Copyright:

You are free to use this press release; please refer to Climate Risk Analysis and link to http://www.climate-risk-analysis.com.

21. Juni 2010 (PR-02/10g)
Abrupter Wechsel der Antarktischen Feuchtigkeitszufuhr-Quelle vor 128000 Jahren

Klimawissenschaftler erzielen neue Einsichten in den Wechsel von Eis- und Warmzeiten und deren Zusammenhang mit dem "Paläowetter" mit Hilfe von Eisbohrkerndaten und mathematischen Computersimulationsmethoden.

Hannover, Deutschland (www.climate-risk-analysis.com). Ein internationales Forscherteam aus Frankreich, Italien, Dänemark, USA, Japan, Großbritannien und Deutschland unter Führung von Dr. Valérie Masson-Delmotte vom Laboratoire des Sciences du Climat et de l’Environnement, Gif-sur-Yvette, Frankreich veröffentlichen Ihre Ergebnisse in der aktuellen Ausgabe des Wissenschaftsmagazins Proceedings of the National Academy of Sciences of the USA (PNAS, online Early Edition). Der sogenannte Deuterium-Exzess (Mengenverhältnis der schweren zu leichten Wasserstoffisotope) in polaren Eisbohrkernen dokumentiert vergangene Wechsel in den Quellen der Feuchtigkeitszufuhr.

Neue Daten aus der östlichen Antarktis (EPICA Dome C) erlauben Einblicke in den Ablauf der Ereignisse der "Termination II", dem Übergang von der vorletzten Eiszeit in die vorletzte Warmzeit vor ungefähr 128000 Jahren.

Dieser Übergang ist gekennzeichnet durch eine "Nord-Süd-Wippe", wobei zuerst ein langsamer Methankonzentrationsanstieg verbunden ist mit einer deutlichen antarktischen Erwärmung und einem langsamen Anstieg des Deuterium-Exzesses. Darauf, so die Befunde, folgte eine abrupte Erwärmung des nördlichen Atlantik, eine abrupte Aufnahme des Asiatischen Sommermonsuns, ein scharfer Methananstieg und schliesslich ein Überschießen der globalen Kohlendioxidkonzentration.

Die PNAS-Arbeit verdeutlicht, dass diese zweite Übergangsphase punktuiert wird von einem sehr scharfen, kurzzeiten Anstieg des Deuterium-Exzesses. Dies enthüllt insgesamt, dass sehr schnelle Wechsel in der atmosphärischen Zirkulation über Asien oder dem Indischen Ozean (d.h.: dem "Wetter") ursächlich verbunden sind mit den längerfristigen Schwankungen zwischen Eis- und Warmzeiten (dem "Klima").

Manfred Mudelsee von Climate Risk Analysis verwendete eine von ihm entwickelte mathematische Methode ("Rampe"), um die von den Kollegen gemessenen Eisbohrkerndaten zu analysieren. Die Besonderheiten sind (1) eine aufwändige brute-force-Suche nach den am besten mit den Daten übereinstimmenden Übergangszeitpunkten und (2) die wiederholte Analyse (mehrere tausend Mal) an im Computer erzeugten Versionen der Daten, bei denen der Messfehler und andere Unsicherheiten simuliert werden.

Die Wiederholungen der Rechnungen dienen dazu, die Übergangszeitpunkte in ihren Fehlern einzugrenzen, die Genauigkeit unseres Wissens zu quantifizieren. Derartige Rechnungen können heutzutage ohne großen Aufwand an herkömmlichen PCs durchgeführt werden, vor Jahren jedoch wären sie maximal Großrechnern vorbehalten gewesen.

Über Climate Risk Analysis:

Climate Risk Analysis ist ein Forschungsunternehmen zur Risikoquantifizierung extremer Wetter- und Klimaereignisse und zur Analyse von Klimazeitreihen.

Originalartikel:

Masson-Delmotte V, Stenni B, Blunier T, Cattani O, Chappellaz J, Cheng H, Dreyfus G, Edwards RL, Falourd S, Govin A, Kawamura K, Johnsen SJ, Jouzel J, Landais A, Lemieux-Dudon B, Lourantou A, Marshall G, Minster B, Mudelsee M, Pol K, Röthlisberger R, Selmo E, Waelbroeck C (2010) An abrupt change of Antarctic moisture origin at the end of Termination II. Proceedings of the National Academy of Sciences of the USA. (doi: 10.1073/pnas.0914536107)

Kontakt:

Laboratoire des Sciences du Climat et de l’Environnement
Dr. Valérie Masson-Delmotte
+33 (0)169087715
valerie.masson@cea.fr

Climate Risk Analysis
Kristín B. Ólafsdottír, Pressebeauftragte/CCO
+49 (0)51170032891
info@climate-risk-analysis.com
http://www.climate-risk-analysis.com

Copyright:

Sie können diese Pressemitteilung frei verwenden; bitte verweisen Sie auf Climate Risk Analysis und verlinken zu http://www.climate-risk-analysis.com.

5 January 2010 (PR-01/10)
Mudelsee M (in preparation): Climate Time Series Analysis: Classical Statistical and Bootstrap Methods. Springer

The book is nearly completed. From the Preface:

Climate is a paradigm of a complex system. Analysing climate data is an exciting challenge. Analysis connects the two other fields where climate scientists work, measurements and models. Climate time series analysis uses statistical methods to learn about the time evolution of climate. The most important word in this book is "estimation." We wish to know the truth about the climate evolution but have only a limited amount of data (a time series) influenced by various sources of error (noise). We cannot expect our estimate (guess, based on data) to equal the truth. However, we can determine the typical size of that deviation (error bar). Related concepts are confidence intervals or bias. Error bars help to critically assess estimation results, they prevent us from making overstatements, they guide our way to enhance the knowledge about the climate. Estimates without error bars are useless.

The complexity of the climate system and the nature of the measurement or modelling act may introduce (1) non-normal distributional shape, (2) serial dependence, (3) uneven spacing and (4) timescale uncertainties. These difficulties prohibit in many cases the classical statistical approach to derive error bars by means of calculating the theoretical distribution of the estimates. Therefore we turn to the bootstrap approach, which generates artificial resamples of the time series in the computer, repeats for each resample the estimation (yielding the replication) and calculates the error bars from the distribution of the replications. The typical number of replications is 2000. This computing-intensive approach yields likely more realistic error bars.

Still, there is theoretical work to be done: how to best preserve the shape and serial dependence in the bootstrap resamples, how to estimate with smallest error bars. Uneven spacing in time series analysis has not been the preferred study object of statisticians. Timescale uncertainties and their effect on error bars (widening, but how much?) is almost completely unexplored. This book adapts existing and introduces new bootstrap algorithms for handling such problems.

About Climate Risk Analysis:

Climate Risk Analysis is a research company working on risk quantification of extreme weather or climate events.

Contact:

Dr. Manfred Mudelsee, CEO
Climate Risk Analysis
+49-511-70032892
mudelsee@climate-risk-analysis.com
http://www.climate-risk-analysis.com

Copyright:

You are free to use this press release; please refer to Climate Risk Analysis and link to http://www.climate-risk-analysis.com.

20 August 2009 (PR-02/09g)
Hitzewellen-Rangliste aufgestellt

Der Sommer 2003 in Potsdam und Prag landet hinter den 1990er Jahren, das Jahr 1834 brach Sommer- wie Winterrekorde. Das konnten Klimatologen aus Deutschland und Tschechien mit Hife eines neuen statistischen Wirkungsmaßes belegen. Sie bestätigten außerdem den Trend hin zu mehr warmen Wintern.

Die Befürchtung, dass der gegenwärtige Klimawandel vermehrt Hitzewellen mit sich bringt, ließ sich bisher quantitativ nur schwer greifen. Zum einen liegt das an "statistischen Spärlichkeiten" (extreme Ereignisse sind selten), zum anderen an unzulänglichen Methoden der Datenauswertung. Bisher lag der Fokus entweder auf der Stärke eines Ereignisses (Grad Celsius) oder auf seiner Dauer (Anzahl Tage), aber nicht auf der kombinierten Wirkung. Wissenschaftler um Manfred Mudelsee, Inhaber des Unternehmens Climate Risk Analysis in Hannover, stellen nun in der aktuellen Ausgabe der Fachzeitschrift Theoretical and Applied Climatology (Band 98, September 2009) ein neues Wirkungsmaß vor, welches dieses Methodendefizit behebt.

Die Anwendung auf die längsten und genauesten Temperaturaufzeichnungen, nämlich die von Potsdam (seit 1893) und Prag (seit 1775), ergab zum Teil Erwartetes, aber auch Unvorhergesehenes. Während das mit der Zeit vermehrte Auftreten von extrem warmen Winterperioden sich in das Bild des Klimawandels einfügt, war das im Fall der sommerlichen Hitzewellen anders. Das allgemein als katastrophal angenommene Jahr 2003 war zwar auch in Potsdam wärmer (das Mittel Juni bis August um 2,7 Grad) als der langfristige Durchschnitt, erzielte jedoch keine Rekorde. Anders dagegen die 1990er Jahre, die in mehreren Disziplinen (Sommer/Winter, Potsdam/Prag) neue "Bestmarken" aufstellten. Jedoch gab es auch in der Vergangenheit extrem heiße Sommer, und ein Trend zu mehr sommerlichen Hitzewellen ist statistisch nicht belegbar — für Potsdam und Prag.

Klima variiert nicht nur mit der Zeit, sondern auch mit dem Raum. 2003 war wohl in Südwestdeutschland, Frankreich und der Schweiz besonders, aber nicht in Potsdam oder Prag. Entsprechend hoch sind die Anforderungen an differenzierte Analysen, um das komplexe Klimageschehen quantitativ zu erfassen. Dazu helfen auch neuartige, rechenintensive statistische Verfahren wie das vorgestellte der "Rekordwirkungen". Dabei werden im Computer eine hohe Anzahl (200 000) von simulierten Wirkungskurven erzeugt, um zuverlässig beurteilen zu können, ob die gemessene Wirkungskurve innerhalb der natürlichen Bandbreite schwankt, oder ob ein Trend hin zu mehr (oder weniger) Extremen vorliegt.

Karsten Kürbis, der in seiner Diplomarbeit am Institut für Meteorologie der Universität Leipzig auf den Einfall mit den Rekordwirkungen kam, ist mittlerweile beim Wetterdienstleister Meteogroup; Manfred Mudelsee, Experte für statistische Klimaanalysen und -simulationen, leitet ein Unternehmen, das Trends im Auftreten von Klima- und Wetterextremen bestimmt.

Noch einmal zurück zu den Hitzewellen in den vergangenen Jahrhunderten. Die mit den Computersimulationen gefundene Außerordentlichkeit des Jahres 1834, während dessen in Prag sowohl Winter- als auch Sommerrekorde gebrochen wurden, wird auch durch historische Dokumente belegt: Es gab es in Böhmen tagsüber keinen Frost, und im Januar 1834 schneite es kein einziges Mal.

Weitere Informationen:

Dr. Manfred Mudelsee
Climate Risk Analysis
Schneiderberg 26
30167 Hannover
Deutschland

Telefon: +49 (0)511 7003 2891
Fax: +49-511-70032892
E-Mail: mudelsee@climate-risk-analysis.com
URL: http://www.climate-risk-analysis.com

Kürbis K, Mudelsee M, Tetzlaff G, Brázdil R (2009) Trends in extremes of temperature, dew point and precipitation from long instrumental records from central Europe. Theoretical and Applied Climatology 98(1):187.

Copyright:

Sie können diese Pressemitteilung gerne verwenden; bitte verweisen Sie dabei auf Climate Risk Analysis und verlinken zu http://www.climate-risk-analysis.com.

23 June 2009 (PR-01/09)
Vacancy: Early-Stage Climate Researcher

CRA is a partner in a new, EU-funded research project. The Marie Curie Initial Training Network GATEWAYS studies the climatic role of the Agulhas current, which connects the Indian with the Atlantic Ocean and may influence European weather. CRA's task is to develop or adapt methods of statistical time series analysis, and to apply them to the palaeoclimatic records produced by the GATEWAYS partners. You are an enthusiastic researcher early in your career? Go on reading and visit the given links!

GATEWAYS short description

GATEWAYS external link

About Climate Risk Analysis:

Climate Risk Analysis is a research company working on risk quantification of extreme weather or climate events.

Contact:

Dr. Manfred Mudelsee, CEO
Climate Risk Analysis
+49-511-70032892
mudelsee@climate-risk-analysis.com
http://www.climate-risk-analysis.com

Copyright:

You are free to use this press release; please refer to Climate Risk Analysis and link to http://www.climate-risk-analysis.com.

2 December 2008 (PR-03/08)
Climate Change Perturbs Asian Monsoon Pattern

Researchers detected a trend toward more intense east-west contrasts in the surface temperature of the Indian Ocean region over past 150 years. As the contrast influences the monsoon rainfall pattern, the trend may impose a long-term socioeconomic threat.

Hanover, Germany (mudelsee.com). Analyses of past Indian Ocean temperatures reveal systematic increases of intense east-west contrasts related to climate change. This can influence monsoon rainfall patterns in coming decades.

Climate Risk Analysis, a company in Hanover, Germany quantified the trend on data measured by colleagues in the United Kingdom, Australia, Indonesia, and the United States. The study, to appear in the journal Nature Geoscience (December issue), is led by Nerilie Abram from the British Antarctic Survey in Cambridge and Michael Gagan from the Australian National University in Canberra.

Climate changes over decades to centuries are important to quantify. Their systematic nature is a signal standing out against daily weather noise. This information is useful for prediction.

For deciphering changes of Indian Ocean temperature, Abram and colleagues consulted corals. The coral carbonate skeleton reports via its oxygen isotopes the water temperatures when the coral grew. The scientists found an old coral colony on Mentawai Island, about 200 km offshore of Sumatra. In the mass-spectrometer, the coral disclosed its secret and provided a temperature record that goes back to 1858. No direct measurements from that crucial, eastern part of the Indian Ocean go back that far. Combining the Mentawai data with existing data from the western part yielded a series of east-west temperature contrast. Climatologists denote that contrast as Indian Ocean Dipole (IOD).

Manfred Mudelsee from Climate Risk Analysis found that hundred years ago only every eighteen years an intense IOD occurred while at present it is every three to four years. Temperature differences generate winds, and the IOD influences the Asian monsoon system. Ongoing climate changes in the region may therefore also change rainfall patterns, with socioeconomic consequences.

"Risk estimations have inherent uncertainties, coming ultimately from our incomplete knowledge about the climate," says Mudelsee. "But uncertainty does not warrant inaction. Implementing a long-term monsoon risk management may be less costly."

About Climate Risk Analysis:

Climate Risk Analysis is a research company working on risk quantification of extreme weather or climate events. Other recent publications deal with Canadian wildfires or hurricanes in the Boston area.

Publications:

Abram, Gagan, Cole, Hantoro, Mudelsee (2008) Recent intensification of tropical climate variability in the Indian Ocean. Nature Geoscience. (doi:10.1038/ngeo357)

Besonen, Bradley, Mudelsee, Abbott, Francus (2008) A 1000-year, annually-resolved record of hurricane activity from Boston, Massachusetts. Geophysical Research Letters 35:L14705. (doi:10.1029/2008GL033950)

Girardin, Mudelsee (2008) Past and future changes in Canadian boreal wildfire activity. Ecological Applications 18:391. (doi:10.1890/07-0747.1)

Contact:

Dr. Manfred Mudelsee, CEO
Climate Risk Analysis
+49-511-91701390
mudelsee@climate-risk-analysis.com
http://www.climate-risk-analysis.com

Copyright:

You are free to use this press release; please refer to Climate Risk Analysis and link to http://www.climate-risk-analysis.com.

2. Dezember 2008 (PR-03/08g)
Klimawandel stört Monsun-Muster in Asien

Wissenschaftler stellten einen Trend hin zu häufigeren starken Ost-West-Kontrasten in der Oberflächentemperatur des Indischen Ozeans über die vergangenen 150 Jahre fest. Da der Kontrast das Muster des Monsun-Regenfalls bestimmt, könnte der Trend eine langfristige sozioökonomische Bedrohung darstellen.

Hannover, Deutschland (mudelsee.com). Analysen vergangener Temperaturen des Indischen Ozeans enthüllen systematische Zunahmen in der Häufigkeit intensiver Ost-West-Kontraste, die mit dem Klimawandel zusammenhängen. Dies kann die Regenfallmuster des Monsuns in den kommenden Dekaden beeinflussen.

Climate Risk Analysis, ein Unternehmen in Hannover, quantifizierte den Trend an Daten, welche von Kollegen in Großbritannien, Australien, Indonesien und den Vereinigten Staaten gemessen wurden. Die Studie, die in der Dezember-Ausgabe des Fachmagazins Nature Geoscience erscheint, wurde geleitet von Nerilie Abram vom British Antarctic Survey in Cambridge und Michael Gagan von der Australian National University in Canberra.

Klimaänderungen über Dekaden und Jahrhunderte sind wichtig zu quantifizieren. Ihre systematischen Eigenschaften stellen ein Signal dar, welches gegenüber dem täglichen Wetterrauschen heraussticht. Derartige Information ist wichtig für Vorhersagen.

Um die Änderungen der Temperatur des Indischen Ozeans zu entziffern, wandten sich Abram und Kollegen an Korallen. Das Karbonatgerüst der Koralle teilt über seine Sauerstoffisotope die Wassertemperatur mit, bei der die Koralle wuchs. Die Wissenschaftler fanden eine alte Korallenkolonie auf der Mentawai-Insel, ungefähr 200 km vor der Küste Sumatras. Im Massenspektrometer enthüllte die Koralle ihr Geheimnis und stellte eine Temperatur-Zeitreihe zur Verfügung, die bis ins Jahr 1858 zurückreicht. Keine direkte Beobachtung von diesem kritisch wichtigen, östlichen Teil des Indiks geht derart weit zurück. Indem die Mentawai-Daten zusammen mit existierenden Daten vom westlichen Teil kombiniert wurden, konnte eine Zeitreihe des Ost-West-Kontrastes bestimmt werden. Klimaforscher nennen diesen Kontrast den Indian Ocean Dipole (IOD).

Manfred Mudelsee von Climate Risk Analysis fand heraus, dass vor hundert Jahren nur jedes achtzehnte Jahr ein starker IOD-Kontrast herrschte, während er gegenwärtig bereits alle drei bis vier Jahre auftritt. Temperaturunterschiede erzeugen Winde, und der IOD beeinflusst das Asiatische Monsun-System. Die aktuellen Klimaänderungen in der Region könnten deshalb ebenfalls das Regenfall-Muster verändern – mit sozioönomischen Konsequenzen.

"Risiko-Abschätzungen weisen inhärente Unsicherheiten auf," sagt Mudelsee. "Aber Unsicherheit befugt uns nicht zu Untätigkeit. Die Einrichtung eines langfristigen Monsun-Risikomanagements kann kostengünstiger sein."

Über Climate Risk Analysis:

Climate Risk Analysis ist ein Forschungsunternehmen zur Risikoquantifizierung extremer Wetter- und Klimaereignisse. Weitere kürzliche Veröffentlichungen behandeln Waldbrände in Kanada oder Hurrikane in der Gegend um Boston.

Veröffentlichungen:

Abram, Gagan, Cole, Hantoro, Mudelsee (2008) Recent intensification of tropical climate variability in the Indian Ocean. Nature Geoscience. (doi:10.1038/ngeo357)

Besonen, Bradley, Mudelsee, Abbott, Francus (2008) A 1000-year, annually-resolved record of hurricane activity from Boston, Massachusetts. Geophysical Research Letters 35:L14705. (doi:10.1029/2008GL033950)

Girardin, Mudelsee (2008) Past and future changes in Canadian boreal wildfire activity. Ecological Applications 18:391. (doi:10.1890/07-0747.1)

Kontakt:

Dr. Manfred Mudelsee, CEO
Climate Risk Analysis
+49-511-91701390
mudelsee@climate-risk-analysis.com
http://www.climate-risk-analysis.com

Copyright:

Sie können diese Pressemitteilung frei verwenden; bitte verweisen Sie auf Climate Risk Analysis und verlinken zu http://www.climate-risk-analysis.com.

26 September 2008 (PR-02/08)
Boston hurricane frequency over last millennium linked to ocean surface temperatures

Amherst, MA, USA. The frequency of hurricanes striking the Boston area has varied widely over the last millennium, with periods of lowest activity corresponding to cooler surface temperatures in the tropical North Atlantic Ocean, according to newly published research from the University of Massachusetts Amherst.

Sediments deposited in Lower Mystic Lake, which straddles Medford and Arlington, show that during some centuries Boston was struck by only two to three intense hurricanes. At other times, such as the 13th century, the area experienced the impact of up to eight extreme events.

"There is obviously concern about how hurricane activity might change in the future," says post-doctoral researcher Mark Besonen of the UMass Amherst Climate System Research Center. "By studying how it has varied naturally in the past we can better understand the underlying factors that affect hurricane development."

Results were published online July 24 in Geophysical Research Letters. Additional researchers include Raymond Bradley, a UMass Amherst professor of geosciences, Manfred Mudelsee of Climate Risk Analysis in Hannover, Germany, Mark Abbott, a professor of geology at the University of Pittsburgh, and Pierre Francus, a research scientist at the Institut National de la Recherche Scientifique in Québec, Canada.

According to Besonen, what is known about variations in hurricane activity is based on a very short record. Satellite observations used today began in the 1960s, and systematic aircraft reconnaissance of storms only started in the mid-1940s. The instrumental record goes back a bit farther, about 130 years, but historical records before that time are patchy. "Fortunately, we can turn to the geologic record to extend our understanding of hurricane activity further—looking back 1,000 years or more," says Besonen.

The use of geologic records to create hurricane strike histories for a given area is a new field of research called paleotempestology that only started 15 years ago. Typically, scientists have focused on coastal ponds and marshes, looking for sand layers deposited by hurricane storm surges. However, Besonen focused his efforts further inland and used sediments in Lower Mystic Lake.

"Lower Mystic Lake offered a fantastic opportunity for a Boston area record because each year is represented by a discrete layer of sediment called a varve that accumulates at the bottom of the lake," says Besonen. "You can count these varves like tree rings to go back in time."

Within the Mystic Lake sediments, Besonen found occasional layers of coarse sediment that had washed into the lake during flooding events. By counting the varves, he was able to determine the year in which each of these sand layers was deposited. Using historical records as guidance, he ruled out spring freshets and Nor'easter storms as possible mechanisms for the flooding events, and recognized that the majority of these anomalies occurred in years when hurricanes were known to have struck the Boston area.

"A hurricane strike often causes vegetation disturbance and tree blow-down, which exposes lots of fresh, loose sediment," says Besonen. "The intense precipitation associated with hurricanes picked up the sediment and deposited it in the lake to form the graded beds containing coarser sediment that we see."

The Lower Mystic Lake hurricane record extends back to 1011 A.D., more than 600 years before the first European settlers arrived in the Boston area. The number of hurricanes striking the Boston area was lower in the 11th century and the 17th to 19th centuries, with higher activity noted in the 12th to 16th centuries. In general, periods of decreased activity corresponded to times when sea surface temperatures in the tropical North Atlantic were cooler, with increased activity corresponding to periods when sea surface temperatures are inferred to have been warmer.

Sea surface temperature is one of the parameters known to moderate hurricane activity today, but models of future change are uncertain. "Long-term records like those from Mystic Lake provide climate modelers with a way of testing if their understanding of changes in hurricane activity over time are correct," says Besonen. "If their models can reproduce the past record correctly, we have more confidence in their simulations of future changes."

However, Besonen cautions that a record from a single point, such as Mystic Lake, may not represent hurricane activity in the entire North Atlantic basin. "The scientific community is actively debating the importance of other factors, such as wind shear, that affect hurricane development on longer timescales," says Besonen. "We really need more records, like the one from Mystic Lake, from other areas to help answer these questions with confidence."

Original source: Press release, University of Massachusetts Amherst, Office of News and Information, Amherst, MA, USA

Contact: Dr. M. Besonen (telephone: +1 413545 0229, email: besonen@geo.umass.edu)

Copyright: You are free to use this press release; please cite the original source.

25 September 2008 (PR-01/08)
Climate Risk Analysis company goes online: better knowledge, better decisions

Hannover, Germany. "Climate Risk Analysis is a research company working for you on risk quantification of extreme climate/weather events. Better knowledge (risk estimates) is the basis for better decisions in this world of climate changes, for fewer losses of life and less economic damages."

Dear visitor! It is with great pleasure that I announce the birth of our website. Not many words need to be added to the welcome sentences on home/index.html cited above. CRA works for you and collaborates with you, whether you are from the private or the public sector. Our spirit is to supply our clients with better knowledge and better numbers.

Let me thank cordially the many who contributed to developing www.climate-risk-analysis.com. Colleagues in Earth Sciences and Statistics gave hints. CRA is proud of the broad composition and the world-class calibre of its Scientific Advisory Board. The designers did a splendid job. Friends shared their impressions and emotions, to name a few: Mersku Alkio, Rita Erven and David Weisman.

Dr. Manfred Mudelsee
CEO, Climate Risk Analysis

Copyright: You are free to use this press release; please cite Climate Risk Analysis and link to www.climate-risk-analysis.com in online pages.