Australische James Cook Universität tritt akademische Freiheit mit Füßen

Pressemitteilung der Deutsche Wildtierstiftung vom 20. Juni 2018:

Wälder schützen – Rodung für die Windkraft stoppen
Deutsche Wildtier Stiftung begrüßt den Antrag der FDP-Bundestagsfraktion
“Im Interesse der Windkraftlobby setzt sich die Politik über das Tötungs- und Verletzungsverbot von Wildtieren tagtäglich hinweg”, kritisiert Professor Dr. Fritz Vahrenholt, Alleinvorstand der Deutschen Wildtier Stiftung. Pro Jahr sterben rund 12.000 Greifvögel – unter ihnen auch bedrohte Arten – und rund 250.000 Fledermäuse durch Windenergieanlagen. “Massive Bürgerproteste bleiben weitgehend ungehört!” Jetzt will die FDP-Bundestagsfraktion mit dem Antrag “Wälder schützen – Rodungen für die Windkraft stoppen” im Bundestag Gehör finden.

Hier weiterlesen

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Eine australische Uni feuerte einen Professor, dessen Meinung zum Klimawandel aus der Reihe tanzt. Querdenken verboten. Wer sich eigene Gedanken macht, fliegt raus. Was zunächst wie eine gute Idee aussah, wird für die Univerwaltung nun zum ernsthaften Problem. Die internationale Presse hat den Fall entdeckt und erkennt darin, was wohl jeder mit einem gesunden Menschenverstand ausgestattete Zeitgenosse darin sieht: Zensur! Lesen Sie dazu einen Artikel im Guardian vom 5. Juni 2018:

Peter Ridd’s sacking pushes the limit of academic freedom
James Cook University may have damaged its reputation with a heavy-handed approach to the academic with minority views on climate change and the reef

Weiterlesen im Guardian

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Wochenblick vom 15. Juni 2018:

Dürre-Attacken in Österreich: „Am Klimawandel liegt es nicht“
[...] Klaus Haslinger, Klimaforscher an der Zentralanstalt für Meteorologie und Geodynamik (ZAMG), von der Abteilung für Klimaforschung mit Schwerpunkt Regionale Klimaanalyse und Modellierung, Hydrologie und Trockenheit, erklärt im Gespräch mit dem „Wochenblick“, dass die derzeit sehr trockene Witterung im Grunde genommen nicht mehr als ein Wetterphänomen sei und mit dem „menschengemachten Klimawandel“ per se nichts zu tun hätte.

Weiterlesen im Wochenblick

 

Wer hat den Baobab kaputt gemacht?

Kuriose Geschichte im Stern am 14. Juni 2018:

Berühmte Baobab-Bäume: Klimawandel? Jahrtausendealte Wahrzeichen Afrikas sterben plötzlich
Wissenschaftler schlagen Alarm: Einige von Afrikas größten und ältesten Affenbrotbäumen sind im Laufe der letzten Jahre plötzlich abgestorben. Die Bäume sind entweder komplett oder in Teilen zugrunde gegangen, berichtet ein Forscherteam um Adrian Patrut im Fachblatt “Nature Plants“. Der Grund für den plötzlichen Tod der Bäume sei zwar “unklar”, heißt es in dem Bericht. Möglicherweise spielen dabei jedoch Veränderungen im Zusammenhang mit dem Klimawandel eine Rolle, vermuten die Wissenschaftler.

Alte Bäume sterben plötzlich. Nicht ungewöhnlich, möchte man meinen. Die Hintergründe sind trotzdem unklar. Da kommt der Universalschuldige gerade recht: Der Klimawandel hat Schuld. Das hat gleich drei Vorteile: 1) Das Rätsel scheint gelöst, 2) Das gibt ein tolles Paper in einer Nature-Zeitschrift, 3) mediales Interesse ist gesichert. Der folgende Absatz im Sternbericht macht stutzig:

Die betroffenen Bäume waren demnach zwischen 1100 und 2500 Jahre alt und besaßen eine stattliche Größe. Einige von ihnen waren so breit wie ein Bus.  Das Forscherteam hatte insgesamt mehr als 60 Baobab-Bäume zwischen den Jahren 2005 und 2017 untersucht. Ursprüngliches Ziel der Studie war es, den Grund für das enorme Wachstum der Bäume herauszufinden. Doch zum Erstaunen der Forscher starben neun Bäume im Laufe der Beobachtungszeit ab.

Könnte es vielleicht mit den Forschern selber zu tun haben? Mit welchen Methoden gingen sie vor? Rammten sie vielleicht eine Mess-Sonde in das Holz? Und dann ein paar Jahre später wunderte man sich, dass die Bäume alle eingingen. Nein, nein, wir waren’s nicht, das war sicher der Klimawandel…

Spaß beiseite. Im Paper selber findet sich auch kein Hinweis auf einen Zusammenhang mit dem Klimawandel, lediglich der dürre spekulative Hinweis. Mit den Hauptklimaparametern Temperatur und Niederschlag kann dies wenig zu tun  haben. Im Laufe der letzten Jahrhunderte und Jahrtausende haben die Baobabs eine wahre klimatische Achterbahnfahrt durchgemacht. Das heutige Klima liegt dabei noch voll und ganz im Bereich der natürlichen Schwankungsbreite. Siehe Luening et al. 2017 und Luening et al. 2018. Der Spiegel hat auch ein schönes Bild der Bäume.

 

Rätsel um starken Meeresspiegelanstieg an US-Ostküste aufgeklärt: Schuld hatten die Ozeanzyklen

Thema heute: Der Meeresspiegel in Nordamerika. Die University of California – Berkeley wies im März 2018 darauf hin, dass neben dem Meeresspiegelanstieg auch die Landabsenkung eine große Rolle spielt:

Sinking land will exacerbate flooding from sea level rise in Bay Area
Rising sea levels are predicted to submerge many coastal areas around San Francisco Bay by 2100, but a new study warns that sinking land — primarily the compaction of landfill in places such as Treasure Island and Foster City — will make flooding even worse.

Using precise measurements of subsidence around the Bay Area between 2007 and 2011 from state-of-the-art satellite-based synthetic aperture radar (InSAR), scientists from the University of California, Berkeley, and Arizona State University mapped out the waterfront areas that will be impacted by various estimates of sea level rise by the end of the century. They found that, depending on how fast seas rise, the areas at risk of inundation could be twice what had been estimated from sea level rise only. Previous studies, which did not take subsidence into account, estimated that between 20 and 160 square miles (51 to 413 square kilometers) of San Francisco Bay shoreline face a risk of flooding by the year 2100, depending on how quickly sea levels rise.

Adding the effects of sinking ground along the shoreline, the scientists found that the area threatened by rising seawater rose to between 48 and 166 square miles (125 to 429 square kilometers). “We are only looking at a scenario where we raise the bathtub water a little bit higher and look where the water level would stand,” said senior author Roland Bürgmann, a UC Berkeley professor of earth and planetary science. “But what if we have a 100-year storm, or king tides or other scenarios of peak water-level change? We are providing an average; the actual area that would be flooded by peak rainfall and runoff and storm surges is much larger.”

The data will help state and local agencies plan for the future and provide improved hazard maps for cities and emergency response agencies. “Accurately measuring vertical land motion is an essential component for developing robust projections of flooding exposure for coastal communities worldwide,” said Patrick Barnard, a research geologist with the U.S. Geological Survey in Menlo Park. “This work is an important step forward in providing coastal managers with increasingly more detailed information on the impacts of climate change, and therefore directly supports informed decision-making that can mitigate future impacts.” The low-end estimates of flooding reflect conservative predictions of sea level rise by 2100: about one and a half feet. Those are now being questioned, however, since ice sheets in Greenland and West Antarctica are melting faster than many scientists expected. Today, some extreme estimates are as high as five and a half feet.

That said, the subsidence – which the geologists found to be as high as 10 millimeters per year in some areas – makes less of a difference in extreme cases, Bürgmann noted. Most of the Bay Area is subsiding at less than 2 millimeters per year. “The ground goes down, sea level comes up and flood waters go much farther inland than either change would produce by itself,” said first author Manoochehr Shirzaei, a former UC Berkeley postdoctoral fellow who is now an assistant professor in ASU’s School of Earth and Space Exploration and a member of NASA’s Sea Level Change planning team. Shirzaei and Bürgmann will publish their findings March 7 in the online journal Science Advances.

Combining InSAR and GPS

InSAR, which stands for interferometric synthetic aperture radar, has literally changed our view of Earth’s landscape with its ability to measure elevations to within one millimeter, or four-hundredths of an inch, from Earth orbit. While it has been used to map landscapes worldwide – Bürgmann has used InSAR data to map landslides in Berkeley and land subsidence in Santa Clara County – this may be the first time someone has combined such data with future sea level estimates, he said. The team used continuous GPS monitoring of the Bay Area to link the InSAR data to sea level estimates.

“Flooding from sea level rise is clearly an issue in many coastal urban areas,” Bürgmann said. “This kind of analysis is probably going to be relevant around the world, and could be expanded to a much, much larger scale.” In the Bay Area, one threatened area is Treasure Island, which is located in the Bay midway between San Francisco and Oakland and was created by landfill for the 1939 Golden Gate International Exposition. It is sinking at a rate of one-half to three-quarters of an inch (12 to 20 millimeters) per year. Projections for San Francisco International Airport show that when land subsidence is combined with projected rising sea levels, water will cover approximately half the airport’s runways and taxiways by the year 2100. Parts of Foster City were built in the 1960s on engineered landfill that is now subsiding, presenting a risk of flooding by 2100.

Not all endangered areas are landfill, however. Areas where streams and rivers have deposited mud as they flow into the Bay are also subsiding, partly because of compaction and partly because they are drying out. Other areas are subsiding because of groundwater pumping, which depletes the aquifer and allows the land to sink. In the early 20th century, the Santa Clara Valley at the south end of San Francisco Bay subsided as much as nine feet (three meters) due to groundwater depletion, though that has stabilized with restrictions on pumping. Shirzaei noted that flooding is not the only problem with rising seas and sinking land. When formerly dry land becomes flooded, it causes saltwater contamination of surface and underground water and accelerates coastal erosion and wetland losses. The work was supported by the National Science Foundation, National Aeronautics and Space Administration and Point Reyes Bird Observatory Conservation Science.

Paper: Global climate change and local land subsidence exacerbate inundation risk to the San Francisco Bay Area (Science Advances)

Talke et al. 2018 präsentierten Meeresspiegelpegelmessungen aus dem Hafen von Boston für die letzten 200 Jahre. In der ganzen Zeit stieg der Meeresspiegel um 28 cm an. Dies entspricht einem Anstieg von 1,45 mm pro Jahr. Hier gehts zum Paper, und hier zur Pressemitteilung.

Auf Climate Audit diskutierte Steve McIntyre im November 2017 die verschiedenen Versuche, Meeresspiegel-Hockeysticks für die US Ostküste zu produzieren. Was hatten Anhänger des Aarmismus übersehen? Trompetenstoß: Die Ozeanzyklen, speziell ENSO und NAO, wie die University of Florida am 9. August 2017 bekanntgab:

East Coast’s rapidly rising seas explained

University of Florida scientists discover cause of Atlantic coastline’s sea level rise hot spots

When the Indian River Lagoon on Florida’s Atlantic coast became much saltier after 2011, Arnoldo Valle-Levinson began to investigate. The UF professor of civil and coastal engineering sciences in the College of Engineering checked local tidal gauges, revealing that seas in the region were rising nearly 10 times faster than the long-term rate recorded in that region. When he reviewed tidal data for the entire eastern seaboard, he found similar numbers for all the tide gauge stations south of Cape Hatteras, revealing the regional extent of the “hot spot.”  Sea level rise hot spots — bursts of accelerated sea rise that last three to five years — happen along the U.S. East Coast thanks to a one-two punch from naturally occurring climate variations, according to a new study lead by Valle-Levinson.

After UF scientists identified the hot spot reaching from Cape Hatteras to Miami, they probed the causes by analyzing tidal and climate data for the U.S. eastern seaboard. The study, published online today in Geophysical Research Letters, shows that seas rose in the southeastern U.S. between 2011 and 2015 by more than six times the global average sea level rise that is already happening due to human-induced global warming. The study’s findings suggest that future sea level rise resulting from global warming will also have these hot spot periods superimposed on top of steadily rising seas, said study co-author Andrea Dutton, assistant professor in UF’s department of geological sciences in the College of Liberal Arts and Sciences. “The important point here is that smooth projections of sea level rise do not capture this variability, so adverse effects of sea level rise may occur before they are predicted to happen,” Dutton said. “The entire U.S. Atlantic coastline is vulnerable to these hot spots that may amplify the severity of coastal flooding.”

The combined effects of El Niño (ENSO) and the North Atlantic Oscillation (NAO), both of which are naturally occurring climate processes, drove the recent hot spot, according to the study. Study authors also discovered similar hot spots at various positions along the U.S. eastern seaboard over the past century. They found that these past hot spots are also explained by the combined influence of ENSO and NAO. The finding challenges previous arguments that a hot spot north of Cape Hatteras over the past few decades was due to a slowdown of circulation in the North Atlantic, which is itself due to global warming. Instead, study authors discovered the combination of these two naturally occurring ocean-atmosphere processes explained both the timing and the location of hot spots observed along the entire U.S. Atlantic coast, Dutton said.

While a slowdown of circulation in the North Atlantic can further exacerbate sea level rise in the northeast, it does not explain the accelerations observed in the southeast, and was not required to explain the hot spots observed in the northeast, according to the study. The authors found that hot spots observed over the past century were created by the influence of ENSO that affects the amount of water that accumulates in the western portion of the North Atlantic and causes seas to rise along the entire U.S. Atlantic coast. This sea level rise is then concentrated to the north or south by the NAO, which is a measure of the atmospheric pressure difference between Iceland and the Azores.

Valle-Levinson said hot spots are difficult to predict and it’s not clear if the hot spots will worsen with time. By decreasing emissions, he said we may be able to stabilize rising seas long-term, but the trend will likely be difficult to reverse. “It’s amazing to see construction along the East Coast. That’s the worst place to build anything,” said Valle-Levinson, who described the future for some southeastern U.S. cities as “Venice-like.” “We need to understand that the ocean is coming.” The study was also co-authored by Jonathan Martin, a UF professor of geological sciences in the College of Liberal Arts and Sciences.

Das Virginia Institute of Marine Science gibt offenbar eine Art von “Karteikarte” für US-Küstenpegel und ihren Wasserstandsverlauf heraus. Hier nachlesen. Wer noch viel mehr über die US-Meeresspiegelmessungen wissen möchte, wird bei Judith Cury fündig.

 

Vor 5300 Jahren lag der Meeresspiegel in Surinam und Guyana etwa 1m höher als heute

In einer Arbeit von Khan et al. 2017 wird die Meeresspiegelgeschichte der Karibik während der letzten 10.000 Jahre berichtet. Nach Ende der letzten Eiszeit vor 11.000 Jahren stieg der Meeresspiegel in Surinam und Guyana mit einer Rate von 11 mm pro Jahr an. Das ist etwa 5 mal schneller als heute. Im mittleren und späten Holozän (also seit 5000 Jahren vor heute), betrug der Meeresspiegelanstieg dann weniger als 2,4 mm pro Jahr. Übrigens: Vor 5300 Jahren lag der Meeresspiegel in den beiden Ländern etwa 1 m über dem heutigen Stand. Überrascht? Abstract:

Drivers of Holocene sea-level change in the Caribbean
We present a Holocene relative sea-level (RSL) database for the Caribbean region (5°N to 25°N and 55°W to 90°W) that consists of 499 sea-level index points and 238 limiting dates. The database was compiled from multiple sea-level indicators (mangrove peat, microbial mats, beach rock and acroporid and massive corals). We subdivided the database into 20 regions to investigate the influence of tectonics and glacial isostatic adjustment on RSL. We account for the local-scale processes of sediment compaction and tidal range change using the stratigraphic position (overburden thickness) of index points and paleotidal modeling, respectively. We use a spatio-temporal empirical hierarchical model to estimate RSL position and its rates of change in the Caribbean over 1-ka time slices. Because of meltwater input, the rates of RSL change were highest during the early Holocene, with a maximum of 10.9 ± 0.6 m/ka in Suriname and Guyana and minimum of 7.4 ± 0.7 m/ka in south Florida from 12 to 8 ka. Following complete deglaciation of the Laurentide Ice Sheet (LIS) by ∼7 ka, mid-to late-Holocene rates slowed to < 2.4 ± 0.4 m/ka. The hierarchical model constrains the spatial extent of the mid-Holocene highstand. RSL did not exceed the present height during the Holocene, except on the northern coast of South America, where in Suriname and Guyana, RSL attained a height higher than present by 6.6 ka (82% probability). The highstand reached a maximum elevation of +1.0 ± 1.1 m between 5.3 and 5.2 ka. Regions with a highstand were located furthest away from the former LIS, where the effects from ocean syphoning and hydro-isostasy outweigh the influence of subsidence from forebulge collapse.

Peinlich: Klimamodelle bekommen den Regen nicht in den Griff

Bartlein et al. 2017 machten eine eklatante Schwäche der Klimamodelle bekannt: Für die Zeit vor 5000 Jahren errechnen die Modelle im Vergleich zu den geologisch ermittelten Werten viel zu hohe Temperaturen und zu geringe Niederschläge. Abstract:

Underlying causes of Eurasian midcontinental aridity in simulations of mid‐Holocene climate
Climate model simulations uniformly show drier and warmer summers in the Eurasian midcontinent during the mid‐Holocene, which is not consistent with paleoenvironmental observations. The simulated climate results from a reduction in the zonal temperature gradient, which weakens westerly flow and reduces moisture flux and precipitation in the midcontinent. As a result, sensible heating is favored over evaporation and latent heating, resulting in substantial surface‐driven atmospheric warming. Thus, the discrepancy with the paleoenvironmental evidence arises initially from a problem in the simulated circulation and is exacerbated by feedback from the land surface. This region is also drier and warmer than indicated by observations in the preindustrial control simulations, and this bias arises in the same way: zonal flow and hence moisture flux into the midcontinent are too weak, and feedback from the land surface results in surface‐driven warming. These analyses suggest the need to improve those aspects of climate models that affect the strength of westerly circulation.

Yuan & Zhu 2018 weisen darauf hin, dass Effekte der Ozeanzyklen PDO und AMO unbedingt in Niederschlags-Simulationen mit einbezogen werden sollten, um die Prognoseleistung zu verbessern:

A First Look at Decadal Hydrological Predictability by Land Surface Ensemble Simulations
Abstract: The prediction of terrestrial hydrology at the decadal scale is critical for managing water resources in the face of climate change. Here we conducted an assessment by global land model simulations following the design of the fifth Coupled Model Intercomparison Project (CMIP5) decadal hindcast experiments, specifically testing for the sensitivity to perfect initial or boundary conditions. The memory for terrestrial water storage (TWS) is longer than 6 years over 11% of global land areas where the deep soil moisture and aquifer water have a long memory and a nonnegligible variability. Ensemble decadal predictions based on realistic initial conditions are skillful over 31%, 43%, and 59% of global land areas for TWS, deep soil moisture, and aquifer water, respectively. The fraction of skillful predictions for TWS increases by 10%–16% when conditioned on Pacific Decadal Oscillation and Atlantic Multidecadal Oscillation indices. This study provides a first look at decadal hydrological predictability, with an improved skill when incorporating low‐frequency climate information.

Plain Language Summary: Decadal prediction, which was initially proposed to more accurately project near‐term (e.g., 10–30 years) climate change by using the experiences in weather and seasonal climate forecasting, has raised a wide concern since the IPCC CMIP5 project. The climate community is now trying to transition the decadal prediction from a pure research to a quasi‐real‐time operational effort. However, very limited information is known about the decadal hydrological predictability over land, which is more relevant to the livelihood and stakeholders. Here we combine an ensemble simulation method that is widely used to assess seasonal hydrological predictability, with the experimental design of the CMIP5 decadal climate hindcasts, to provide a first look at decadal hydrological predictability and skill by carrying out over 2,000 years global land model simulations. We found skillful decadal prediction for terrestrial water storage over one third land areas where deep soil moisture and aquifer have a nonnegligible variability. And the skill can be further enhanced by incorporating low‐frequency teleconnection information from Atlantic and Pacific Oceans. This study suggests that it is possible to provide water resources managers useful hydrological forecast information over arid and semiarid regions a few years or even a decade in advance.

Eine hochinteressante neue Arbeit stammt von Bothe et al. 2018. Darin stellen sie zunächst fest, dass die Niederschläge in Großbritannien während der vergangenen 350 Jahre stark von den Ozeanzyklen abhängen und externe Faktoren nahezu keine Rolle spielen. Zudem bemängeln sie eine starke Diskrepanz zwischen Modellsimulationen und echten Messdaten. Kurz gesagt: Die Modelle bekommen die Realität einfach nicht in den Griff. Abstract:

Inconsistencies between observed, reconstructed, and simulated precipitation over the British Isles during the last 350 years
The scarcity of long instrumental records, uncertainty in reconstructions, and insufficient skill in model simulations hamper assessing how regional precipitation changed over past centuries. Here, we use standardised precipitation data to compare global and regional climate simulations and reconstructions and long observational records of seasonal mean precipitation in England and Wales over the past 350 years. The effect of the external forcing on the precipitation records appears very weak. Internal variability dominates all records. Even the relatively strong exogenous forcing history of the late 18th and early 19th century shows only little effect in synchronizing the different records. Multi-model simulations do not agree on the changes over this period. Precipitation estimates are also not consistent among reconstructions, simulations, and instrumental observations regarding the probability distributions’ changes in the quantiles for severe and extreme dry or wet conditions and in the standard deviations. We have also investigated the possible link between precipitation and temperature variations in the various data sets. This relationship is also not consistent across the data sets. Thus, one cannot reach any clear conclusions about precipitation changes in warmer or colder background climates during the past centuries. Our results emphasize the complexity of changes in the hydroclimate during the most recent historical period and stress the necessity of a thorough understanding of the processes affecting forced and unforced precipitation variability.

 

TU Delft: Überschwemmungen in Europa zeigen während der vergangenen 150 Jahre keinen Anstieg von finanziellen Schäden oder Opferzahlen

Die TU Delft gab am 31. Mai 2018 per Pressemitteilung eine gute Nachricht bekannt: Während der letzten 150 Jahre haben sich weder die Opferzahlen, noch die finanziellen Schäden im Zusammenhang mit Überschwemmungen in Europa erhöht, wenn man entsprechende Korrekturen für demographische und ökonomische Veränderungen berücksichtigt:

No increase in losses in Europe from floods in the past 150 years

Extreme hydrological events are generally predicted to become more frequent and damaging in Europe due to warming climate. Researchers from TU Delft and Rice University (Houston) have now shown that, correcting for economic and demographic changes, there has been no increase in financial losses and fatalities from floods in the last 150 years. They have reported on their findings in Nature Communications.

Correcting

An analysis of long-term trends in flood losses should account for changes in size and distribution of population and assets. Without correcting reported losses for changes in exposure, studies (logically) report a significant upward trend in losses. ‘Such ‘normalization’ processes have also proven to be important for explaining trends in other natural hazards’, says Dominik Paprotny, researcher at TU Delft and lead author of the paper in Nature Communications.

So adverse consequences of floods change are influenced by both natural and socio-economic trends and interactions. In Europe, previous studies of historical flood losses that were corrected for demographic and economic growth (‘normalized’) have been limited, leading to an incomplete representation of trends in losses over time. ‘After adjusting nominal losses for demographic and economic growth, no significant trends in flood losses, both on European scale and for individual countries were observed.’

Less fatalities

Paprotny and his colleagues utilized a gridded reconstruction of flood exposure in 37 European countries and a new database of damaging floods since 1870. ‘Our results indicate that, after correcting for changes in flood exposure, there has been an increase in annually inundated area and number of persons affected since 1870, but we have also found a substantial decrease in flood fatalities. For more recent decades we found a considerable decline in financial losses per year. We estimate, however, that there is large underreporting of smaller floods beyond most recent years, and show that underreporting has a substantial impact on observed trends.’

Changes

Extreme hydrological events are generally predicted to become more frequent and damaging in Europe due to warming climate and there seems to be large consensus regarding the trajectory of future climatic developments. ‘There is however less confidence in the changes in flood losses as a result of climate change so far’, says Paprotny. ‘Qualitative and quantitative hydrological studies for Europe have indicated no general continental-wide trend in river flood occurrences, extreme precipitation, or annual maxima of runoff. However, substantial variations between different catchments have been observed, ranging from an increase in north-western Europe to no trend or a decrease in other parts of the continent. Similar findings were reported for storminess along the European coasts.’

Bereits im September 2017 hatte eine Forschergruppe um Glenn Hodgkins in einer Studie Trends großer Fluten in Europa und Nordamerika berechnet. Nur wenige Flüsse zeigten einen signifikanten Langzeittrend, der jedoch aufgrund der hohen Anzahl an Datensätzen auch bei einem Zufallsexperiment aufgetreten wäre. Stattdessen scheint das Flutgeschehen in Europa und Nordamerika eng an den Ozeanzyklus der Atlantischen Multidekadenoszillation gebunden zu sein. Hier der Abstract:

 Climate-driven variability in the occurrence of major floods across North America and Europe
Concern over the potential impact of anthropogenic climate change on flooding has led to a proliferation of studies examining past flood trends. Many studies have analysed annual-maximum flow trends but few have quantified changes in major (25–100 year return period) floods, i.e. those that have the greatest societal impacts. Existing major-flood studies used a limited number of very large catchments affected to varying degrees by alterations such as reservoirs and urbanisation. In the current study, trends in major-flood occurrence from 1961 to 2010 and from 1931 to 2010 were assessed using a very large dataset (>1200 gauges) of diverse catchments from North America and Europe; only minimally altered catchments were used, to focus on climate-driven changes rather than changes due to catchment alterations. Trend testing of major floods was based on counting the number of exceedances of a given flood threshold within a group of gauges. Evidence for significant trends varied between groups of gauges that were defined by catchment size, location, climate, flood threshold and period of record, indicating that generalizations about flood trends across large domains or a diversity of catchment types are ungrounded. Overall, the number of significant trends in major-flood occurrence across North America and Europe was approximately the number expected due to chance alone. Changes over time in the occurrence of major floods were dominated by multidecadal variability rather than by long-term trends. There were more than three times as many significant relationships between major-flood occurrence and the Atlantic Multidecadal Oscillation than significant long-term trends.

 

Einen guten Journalisten erkennt man daran, dass er sich nicht gemein macht mit einer Sache, auch nicht mit einer guten Sache

Bei der Deutschen Welle gibt es eine Sendung namens Wirtschaft_plus. Der Journalist Thomas Spahn berichtete dort, dass Elektromobile nicht so umweltschonend sind wie landläufig angenommen wird. Das Video hat Robert Scherleitner zur Verfügung gestellt. Anzuschauen hier bei Notrickszone. Thomas Spahns Motto ist vorbildlich. Auf seiner Profilseite der Deutschen Welle schreibt er:

“Einen guten Journalisten erkennt man daran, dass er sich nicht gemein macht mit einer Sache, auch nicht mit einer guten Sache.”

Notrickszone weist in diesem Zusammenhang auch auf einen Artikel auf shz.de hin:

Schwedische Untersuchung: Akkus in Elektroautos belasten das Klima
Der Anschein, mit dem Elektroauto eine klimafreundliche Alternative zu herkömmlichen Fahrzeugen gefunden zu haben, bröckelt. Denn schon die Produktion der für die Autos lebenswichtigen Lithium-Ionen-Batterien geht mit enormen Emissionen einher. Das besagt eine neue schwedische Studie, die die bisherigen Untersuchungen in einer Metastudie analysiert und zusammengefasst hat, so die Fach-Zeitschrift „Ingeniøren“.

Weiterlesen auf shz.de

Ganz  frisch im Juni 2018 zum Thema herausgekommen ist eine Arbeit von Ajanovic und Haas im Fachblatt Environment, Development and Sustainability:

Electric vehicles: solution or new problem?
Since electric vehicles (EVs) have been recognized as a technology that reduces local air pollution while improving transport energy security, they have been promoted in many countries. Yet, mainly due to their high costs, especially in the case of pure battery electric vehicles, and a lack of proper infrastructure, the use of EVs is still very limited. In this paper, some of the major barriers and the future challenges are discussed. The current problems are mainly attributed to two categories: (1) the battery performances and costs, as well as battery production including issue of material availability and (2) environmental benefits of EVs depending on the sources used for the electricity generation and their carbon intensity. The major conclusions are that (1) research and development with respect to batteries has by far the highest priority and (2) it has to be ensured that the electricity used in EVs is generated largely from renewable energy sources.

Aus den Conclusions:

One of the largest challenges for the future will be to provide clean carbon-free sources for electricity generation. While this is a minor problem in countries with large shares of renewables as Norway, Austria or Sweden, in most other countries which largely use coal for electricity generation (e.g., China, Turkey, Greece), it may cause a severe barrier. Currently, in many countries, the CO2 emissions per kWh of electricity generated are very high, leading to the effect that virtually no reduction in GHG emissions is brought about by EVs. Future policy designs should ensure high environmental benefits of EVs.

Neuer Kälterekord in der Antarktis: fast minus 100 Grad

Unerwartete Meldung am 1. Juli 2018 in der Tagesschau:

Neuer Kälterekord in der Antarktis
Bislang galten die 1983 gemessenen minus 89,2 Grad als niedrigste jemals gemessene Temperatur auf der Erde. Doch nun wurde in der Antarktis ein neuer Kälterekord dokumentiert: fast minus 100 Grad.

Weiterlesen bei der Tagesschau.

Hier die dazugehörige Pressemitteilung des National Snow and Ice Data Center (NSIDC) vom 25. Juni 2018:

New study explains Antarctica’s coldest temperatures

Tiny valleys near the top of Antarctica’s ice sheet reach temperatures of nearly -100 degrees Celsius, according to a new study published this week in Geophysical Research Letters. The finding could change scientists’ understanding of just how low temperatures can get at Earth’s surface, and how it happens, according to the researchers. After sifting through data from several Earth-observing satellites, scientists announced in 2013 that they found surface temperatures of -93 degrees Celsius (-135 degrees Fahrenheit) in several spots on the East Antarctic Plateau, a high snowy plateau in central Antarctica that encompasses the South Pole. That preliminary study has been revised with new data showing that the coldest sites actually reach -98 degrees Celsius (-144 degrees Fahrenheit). The temperatures are observed during the southern polar night, mostly during July and August.

When the researchers first announced they had found the coldest temperatures on Earth five years ago, they determined that persistent clear skies and light winds are required for temperatures to dip this low. But the new study adds a twist to the story: Not only are clear skies necessary, but the air must also be extremely dry, because water vapor blocks the loss of heat from the snow surface. The researchers observed the ultra-low temperatures in small dips or shallow hollows in the Antarctic Ice Sheet where cold, dense, descending air pools above the surface and can remain for several days. This allows the surface, and the air above it, to cool still further, until the clear, calm, and dry conditions break down and the air mixes with warmer air higher in the atmosphere.

“In this area, we see periods of incredibly dry air, and this allows the heat from the snow surface to radiate into space more easily,” said Ted Scambos, a senior research scientist at the National Snow and Ice Data Center at the University of Colorado Boulder and the study’s lead author. The record of -98 degrees Celsius is about as cold as it is possible to get at Earth’s surface, according to the researchers. For the temperature to drop that low, clear skies and dry air need to persist for several days. Temperatures could drop a little lower if the conditions lasted for several weeks, but that’s extremely unlikely to happen, Scambos said.

Finding the coldest place

The high elevation of the East Antarctic Plateau and its proximity to the South Pole give it the coldest climate of any region on Earth. The lowest air temperature ever measured by a weather station, -89 degrees Celsius (-128 degrees Fahrenheit), was recorded there at Russia’s Vostok Station in July 1983. But weather stations can’t measure temperatures everywhere. So in 2013, Scambos and his colleagues decided to analyze data from several Earth-observing satellites to see if they could find temperatures on the plateau even lower than those recorded at Vostok.

In the new study, they analyzed satellite data collected during the Southern Hemisphere’s winter between 2004 and 2016. They used data from the MODIS instrument aboard NASA’s Terra and Aqua satellites as well as data from instruments on NOAA’s Polar Operational Environmental Satellites. The researchers observed snow surface temperatures regularly dropping below -90 degrees Celsius (-130 degrees Fahrenheit) almost every winter in a broad region of the plateau, more than 3,500 meters (11,000 feet) above sea level. Within this broad region, they found dozens of sites had much colder temperatures. Nearly 100 locations reached surface temperatures of -98 degrees Celsius.

The atmosphere in this region can sometimes have less than 0.2 mm total precipitable water above the surface. But even when it is that dry and cold, the air traps some of the heat and sends it back to the surface. This means that the cooling rates are very slow as the surface temperatures approach the record values. Conditions do not persist long enough—it could take weeks—for the temperatures to dip below the observed records. However, the temperature measured from satellites is the temperature of the snow surface, not the air above it. So the study also estimated the air temperatures by using nearby automatic weather stations and the satellite data. Interestingly, even though the coldest sites were spread out over hundreds of kilometers, the lowest temperatures were all nearly the same. That got them wondering: Is there a limit to how cold it can get on the plateau?

How cold is it really?

Using the difference between the satellite measurements of the lowest surface snow temperatures at Vostok and three automated stations, and the air temperatures at the same place and time, the researchers inferred that the air temperatures at the very coldest sites (where no stations exist) are probably around -94 degrees Celsius, or about -137 degrees Fahrenheit. The research team has also developed a set of instruments designed to survive and operate at the very coldest places through the winter and measure both snow and air temperatures. They are planning to deploy the instruments in the next year or two, during the Antarctic summer when the temperatures are a comparatively mild -30 degrees Celsius (-22 degrees Fahrenheit).

See the American Geophysical Union news release here.

Download a copy of the paper here.

 

Vor 8000 Jahren war es in Grönland 5°C wärmer als heute: Grönlandeis robuster als gedacht

Die Webseite The best schools hat nun die 15 prominentesten Klimawissenschaftler gekürt. Dabei wird strikt zwischen Vertretern der Alarmlinie und Skeptikern unterschieden. Dabei standen 10 Plätze für die IPCC-Linie zur Verfügung, jedoch nur halb soviele für die Skeptiker. Hier die Top 5 der Skeptiker:

1. Lennart O. Bengtsson

2. John R. Christy

3. Judith A. Curry

4. Richard S. Lindzen

5. Nir J. Shaviv

Hier nachzulesen.

——————-

Forscher der Northwestern University untersuchten Seeablagerungen in Grönland und machten dabei eine unerwartete Entdeckung. In den 8000 Jahre alten Sedimenten fanden sie Überreste von Fliegen, die heute nur 1500 km weiter südlich anzutreffen sind. Damals muss es in Grönland also sehr viel wärmer gewesen sein, mit Temperaturen die etwa 5°C über den heutigen lagen. Die unerwarte große vorindustrielle Wärme bringt nun aber Probleme: Das Grönlandeis schmolz viel weniger als es die gängigen Klimamodelle für dieses Temperaturniveau errechnen. Was machte das Eis so robust gegenüber der Wärme? Die Forscher können nur spekulieren und vermuten, dass verstärkter Schneefall einen Teil des Schmelzverlustes ausgeglichen haben könnte. Hier die Pressemitteilung der Northwestern University vom 4. Juni 2018 (Gradangaben bezehen sich auf Fahrenheit):

Ancient Greenland was much warmer than previously thought

Discovery helps researchers understand how Greenland’s ice sheet responds to warming. A tiny clue found in ancient sediment has unlocked big secrets about Greenland’s past and future climate.

Just beyond the northwest edge of the vast Greenland Ice Sheet, Northwestern University researchers have discovered lake mud that beat tough odds by surviving the last ice age. The mud, and remains of common flies nestled within it, record two interglacial periods in northwest Greenland. Although researchers have long known these two periods — the early Holocene and Last Interglacial — experienced warming in the Arctic due to changes in the Earth’s orbit, the mix of fly species preserved from these times shows that Greenland was even warmer than previously thought. This information could help researchers better gauge Greenland’s sensitivity to warming, by testing and improving models of climate and ice sheet behavior. Those models could then improve predictions of how Greenland’s ice sheet, which covers 80 percent of the Arctic country and holds enough ice to equal 20 feet of global sea level, might respond to man-made global warming.

“Northwest Greenland might feel really remote, but what happens to that ice sheet is going to matter to everyone in New York City, Miami and every coastal city around the world,” said Yarrow Axford, the study’s senior author and an associate professor of Earth and planetary sciences in Northwestern’s Weinberg College of Arts and Sciences. “One of the big uncertainties in climate science remains how fast the Earth changes when it gets warmer. Geology gives us an opportunity to see what happened when the Earth was warmer than today.” Published today, June 4, in the Proceedings of the National Academy of Sciences, the study included contributions from collaborators at Dartmouth College.

People might be surprised to see how today’s frigid Greenland looked during the past two interglacial periods. Today, northwest Greenland hovers in the 30s and low 40s Fahrenheit and weathers snowstorms in summer. But average summer temperatures in the early Holocene (8,000 to 11,000 years ago) and Last Interglacial (116,000 to 130,000 years ago) climbed well into the 50s. During the Last Interglacial, global sea levels increased by 15 to 30 feet, largely due to thinning of Greenland and Antarctica’s ice sheets. But now Northwestern’s team believes northern Greenland’s ice sheet experienced stronger warming than previously thought, which could mean that Greenland is more responsible for that sea-level rise.

Layers of time

To measure these ancient temperatures, researchers look to ice cores and lake sediment cores. Because ice and lake sediment form by an incremental buildup on annual layers of snow or mud, these cores contain archives of the past. By looking through the layers, researchers can pinpoint climate clues from eons ago. Finding lake sediments older than about 10,000 years, however, has been historically very difficult in Greenland. “The classic thing that glaciers do is slide,” Axford said. “So when the ice sheet grows larger, all this wonderful geology gets scooped up and spat out into the oceans.” But Axford’s team found an area where this wasn’t the case. The climate in northwest Greenland houses the perfect conditions to preserve the sediments within a small lake that Axford’s team affectionately calls “Wax Lips Lake” because of its shape.

“During the last ice age, the ice sheet there was just thin enough, and the atmosphere was just cold enough that the ice sheet froze to the ground instead of melting at its base and sliding,” said Jamie McFarlin, a Ph.D. student in Northwestern’s department of Earth and planetary sciences, who led the study. “It grew on top of itself and preserved most of the geology below.” “The ice gently tip-toed over this spot instead of plowing over it,” Axford added.

After taking a two-meter-long tube of sediment from Wax Lips Lake’s lakebed, McFarlin combed through the layers to investigate those from the early Holocene and Last Interglacial periods. It was then that she noticed a mix of lake fly species, called chironomids, that suggested a warmer climate during both periods. Especially surprising: The Last Interglacial period swarmed with another type of insect known as the phantom midge. Although phantom midges have been reported in low abundance in northern climates, one would have to travel 1,000 miles south to Canada’s Labrador province to find phantom midges at comparable abundance to the Last Interglacial in northwest Greenland. “As far as we know, it’s never been found in Greenland. We think this is the first time anyone has reported it in ancient sediments or modern lakes there,” Axford said. “We were really surprised to see how far north it migrated.”

The bigger picture

Discovering this mix of insects means northwest Greenland’s average July during the last two interglacial periods most likely climbed above 50 degrees and possibly into the high 50s during the Last Interglacial. This confirms controversial geological records constructed from ice cores taken nearby, which also indicated significant warming during these time periods. “Other records have shown that northern Greenland’s climate was much warmer than people expected during those periods, and those results received justified skepticism,” Axford said. “Now we have an independent record that confirms that when the Arctic warmed in the past, there was especially strong warming in northern Greenland.” This data will help the broader scientific community further hone climate and ice sheet models used to project future changes.

“This is the kind of ground-truthing that we need to get really accurate climate models and projections,” said Magdalena Osburn, an assistant professor of Earth and planetary sciences at Northwestern, who coauthored the study. “We’re finding that, in some cases, models don’t include temperatures that are warm enough for this part of the world.” There is one caveat. Well-known changes in Earth’s orbit caused warming during the early Holocene and Last Interglacial periods. Today, warming stems from man-made sources and is happening much faster than warming during those interglacial periods. That means there is a chance that Earth might not respond to current-day warming in the same way. “Past climate is our best analog for future warming, and our results hint that land at these very high latitudes in the Arctic may warm even more than predicted in the coming century,” Axford said. “But nothing in Earth’s past is a perfect analog because what’s happening today is totally unprecedented.”

 

 

Hier der Abstract von Farlin et al. 2018:

Pronounced summer warming in northwest Greenland during the Holocene and Last Interglacial
Projections of future rates of mass loss from the Greenland Ice Sheet are highly uncertain because its sensitivity to warming is unclear. Geologic reconstructions of Quaternary interglacials can illustrate how the ice sheet responded during past warm periods, providing insights into ice sheet behavior and important tests for data-model comparisons. However, paleoclimate records from Greenland are limited: Early Holocene peak warmth has been quantified at only a few sites, and terrestrial sedimentary records of prior interglacials are exceptionally rare due to glacial erosion during the last glacial period. Here, we discuss findings from a lacustrine archive that records both the Holocene and the Last Interglacial (LIG) from Greenland, allowing for direct comparison between two interglacials. Sedimentary chironomid assemblages indicate peak July temperatures 4.0 to 7.0 °C warmer than modern during the Early Holocene maximum in summer insolation. Chaoborus and chironomids in LIG sediments indicate July temperatures at least 5.5 to 8.5 °C warmer than modern. These estimates indicate pronounced warming in northwest Greenland during both interglacials. This helps explain dramatic ice sheet thinning at Camp Century in northwest Greenland during the Early Holocene and, for the LIG, aligns with controversial estimates of Eemian warming from ice core data retrieved in northern Greenland. Converging geologic evidence for strong LIG warming is challenging to reconcile with inferred Greenland Ice Sheet extent during the LIG, and the two appear incompatible in many models of ice sheet evolution. An increase in LIG snowfall could help resolve this problem, pointing to the need for hydroclimate reconstructions from the region.

 

Im Jahr 2099 könnte fast die gesamte boreale Klimazone landwirtschaftlich nutzbar werden

Derzeit sind etwa zwei Drittel der borealen, kaltgemäßigten Klimazone der Erde landwirtschaftlich nicht nutzbar. Es ist schlicht zu kalt, um dort etwas anbauen zu können. Forscher des Priestley International Centre for Climate haben jetzt berechnet, dass bei fortschreitendem Klimawandel gegen Ende des Jahrhunderts nahezu die gesamte boreale Region geeignete Bedingungen für die Landwirtschaft aufweisen wird. Die nördliche Wachstumsgrenze wird sich dabei 1200 km nach Norden verschieben. Neue Kornkammern für eine noch immmer rapide wachsende Menschheit. Hier die Pressemitteilung des Priestley International Centre for Climate vom 30. Mai 2018:

Climate change could increase arable land

Climate change could expand the agricultural feasibility of the global boreal region by 44 per cent by the end of the century, according to new research. However, the scientists warn that the same climate trends that would increase land suitable for crop growth could also significantly change the global climatic water balance – negatively impacting agriculture in the rest of the world.

An international team of scientists have assessed the impact of climate change on land that could support agriculture in the boreal region, which includes large sections of Canada, Sweden, Norway, Finland, Russia and the United States. They found that the upper edge of land suitable for crop growth could shift as far north as 1,200km from the current position with the most dramatic changes occurring in the inner-continental regions of North America and Eurasia. Currently only 32 per cent of the boreal region falls into ‘growing degree days’ – the climate parameter linked to crop growth – and rainfall requirements for small cereal crops, such as oats and barley.

Using global climate models the team was able to predict the future extent of growing degree days and changes in rainfall. The study, published in Scientific Reports, estimates that by 2099 roughly 76 per cent of the boreal region could reach the right conditions for agriculture. However, the study also warns that while total rainfall will generally increase on an annual basis, a warmer climate will also lead to more evaporation with potentially dramatic impact on the climatic water balance, both geographically and across seasons. For example while the inner continental regions would suffer drought conditions during the summer, the regions around the ocean’s rims could see an increase in water available to crops. Additionally, regions that would suffer temporary summer droughts might see wetter autumns which would have a negative impact on the harvest season.

Study co-author Professor Joseph Holden, water@leeds director at the University of Leeds, said: “Climate change will have a profound impact on our agricultural regions. A projected consequence is the loss of farmland and crops from areas that are currently productive – cause for concern regarding long term global food security. Therefore we need to know whether in northern high latitudes new areas will become suitable for crops. “Understanding future environmental conditions will be vital for agricultural production. But any plans for northward agricultural expansion must be done carefully and with long term environmental sustainability in mind.”

Study lead author Dr Adrian Unc, from Grenfell Campus, Memorial University Canada, said: “We must not forget that any changes in land use has extensive impacts on the entire natural ecosystem, impacts that must be understood and included in any planning effort. After all we must insure that a short–term gain does not come at the cost of a long– term loss in ecosystem sustainability.”