Low-frequency variability and CO2 transient climate change

Results from a global coupled ocean-atmosphere general circulation model (GCM) are used to perform the first in a series of studies of the various time and space scales of climate anomalies in an environment of gradually increasing carbon dioxide (CO₂) (a linear transient increase of 1% per year in the coupled model). Since observed climate anomaly patterns often are computed as time-averaged differences between two periods, climate-change signals in the coupled model are defined using differences of various averaging intervals between the transient and control integrations. Annual mean surface air temperature differences for several regions show that the Northern Hemisphere warms faster than the Southern Hemisphere and that land areas warm faster than ocean. The high northern latitudes outside the North Atlantic contribute most to global warming but also exhibit great variability, while the high southern latitudes contribute the least. The equatorial tropics warm more slowly than the subtropics due to strong upwelling and mixing in the ocean. The globally averaged surface air temperature trend computed from annual mean differences for years 23–60 is 0.03 C per year. Projecting this trend to the time of CO₂ doubling in year 100 produces a warming of 2.3° C. By chance, one particular northern winter five-year average geographical difference pattern in the Northern Hemisphere from the coupled model resembles the recent observed pattern of surface temperature and sea-level pressure anomalies. This pattern is not consistent from one five-year period to the next in any season in the model. However, multidecadal averages in the coupled model show that the North Atlantic warms less than the rest of the high northern latitudes, and recent observations may be a manifestation of this phenomenon. Consistent geographic patterns of climate anomalies forced by increased CO₂ in the model are more evident with a longer averaging interval. There is also the possibility that the CO₂ climate-change signal may itself be a function of time and space. The general pattern of zonal mean temperature anomalies for all periods in the model shows warming in the troposphere and cooling in the stratosphere. This pattern (or one similar to it taking into account the rest of the trace gases) could be looked for in observations to verify the enhanced greenhouse effect. A zonal mean pattern, however, could prove scientifically satisfactory but of little value to policymakers seeking regional climate-change forecasts. These results from the coupled model underscore the difficulty in identifying a time- and space-dependent fingerprint of greenhouse warming that has some practical use from short climatic records and point to the need to understand the mechanisms of decadal-scale variability.The National Center for Atmospheric Research is sponsored by the National Science Foundation.     

Paleoecological investigation of recent lake acidification in the Adirondack Mountains,N.Y.

Paleoecological analysis of the sediment record of 12 Adirondack lakes reveals that the 8 clearwater lakes with current pH < 5.5 and alkalinity < 10 eq l^-1 have acidified recently. The onset of this acidification occurred between 1920 and 1970. Loss of alkalinity, based on quanitative analysis of diatom assemblages, ranged from 2 to 35 eq l^-1. The acidification trends are substantiated by several lines of evidence including stratigraphies of diatom, chrysophyte, chironomid, and cladoceran remains, Ca:Ti and Mn:Ti ratios, sequentially extracted forms of Al, and historical fish data. Acidification trends appear to be continuing in some lakes, despite reductions in atmospheric sulfur loading that began in the early 1970s. The primary cause of the acidification trend is clearly increased atmospheric deposition of strong acids derived from the combustion of fossil fuels. Natural processes and watershed disturbances cannot account for the changes in water chemistry that have occurred, but they may play a role. Sediment core profiles of Pb, Cu, V, Zn, S, polycyclic aromatic hydrocarbons, magnetic particles, and coal and oil soot provide a clear record of increased atmospheric input of materials associated with the combustion of fossil fuels beginning in the late 1800s and early 1900s. The primary evidence for acidification occurs after that period, and the pattern of water chemistry response to increased acid inputs is consistent with current understanding of lake-watershed acidification processes.This is the second of a series of papers to be published by this journal which is a contribution of the Paleoecological Investigation of Recent Lake Acidification (PIRLA) project. Drs. D.F. Charles and D.R. Whitehead are guest editors for this series.     

Seismicity and codaQ values in the eastern Pyrenees: First results from the La Cerdanya seismic network

Seismicity in the La Cerdanya region of the eastern Pyrenees has been accurately mapped for the first time using data from a local seismic network. The majority of earthquakes lies on or near the La Cerdanya fault or secondary faults to the south. Coda magnitudes determined for these earthquakes, using magnitude relations from other regions, range between –0.5 and 2.2. These are, however, presumed to be underdetermined values sinceQ values appear to be very low in the La Cerdanya region. CodaQ values at a frequency of 1.5 Hz range between 17 and 120, the lowest values being obtained for the most seismically active regions. CodaQ values also increase with increasing distance, a result which indicates decreasing seismic attenuation with increasing depth in the crust.     

Current remote sensing approaches to monitoring forest degradation in support of countries measurement,reporting and verification (MRV) systems for REDD+

Forest degradation is a global phenomenon and while being an important indicator and precursor to further forest loss, carbon emissions due to degradation should also be accounted for in national reporting within the frame of UN REDD+. At regional to country scales, methods have been progressively developed to detect and map forest degradation, with these based on multi-resolution optical, synthetic aperture radar (SAR) and/or LiDAR data. However, there is no one single method that can be applied to monitor forest degradation, largely due to the specific nature of the degradation type or process and the timeframe over which it is observed. The review assesses two main approaches to monitoring forest degradation: first, where detection is indicated by a change in canopy cover or proxies, and second, the quantification of loss (or gain) in above ground biomass (AGB). The discussion only considers degradation that has a visible impact on the forest canopy and is thus detectable by remote sensing. The first approach encompasses methods that characterise the type of degradation and track disturbance, detect gaps in, and fragmentation of, the forest canopy, and proxies that provide evidence of forestry activity. Progress in these topics has seen the extension of methods to higher resolution (both spatial and temporal) data to better capture the disturbance signal, distinguish degraded and intact forest, and monitor regrowth. Improvements in the reliability of mapping methods are anticipated by SAR-optical data fusion and use of very high resolution data. The second approach exploits EO sensors with known sensitivity to forest structure and biomass and discusses monitoring efforts using repeat LiDAR and SAR data. There has been progress in the capacity to discriminate forest age and growth stage using data fusion methods and LiDAR height metrics. Interferometric SAR and LiDAR have found new application in linking forest structure change to degradation in tropical forests. Estimates of AGB change have been demonstrated at national level using SAR and LiDAR-assisted approaches. Future improvements are anticipated with the availability of next generation LiDAR sensors. Improved access to relevant satellite data and best available methods are key to operational forest degradation monitoring. Countries will need to prioritise their monitoring efforts depending on the significance of the degradation, balanced against available resources. A better understanding of the drivers and impacts of degradation will help guide monitoring and restoration efforts. Ultimately we want to restore ecosystem service and function in degraded forests before the change is irreversible.     

Zur Bildung und Zusammensetzung der brennbaren Gesteine

Zusammenfassung Vorbedingung für die Bildung von Brennsteinlagerstätten ist die Bildung von Hohlformen der Erdoberfläche. Als solche kommen in erster Linie orogene Vortiefen und Zwischensenken, sowie epirogene Senken in Frage. Je nach Schnelligkeit und Vollständigkeit der Abdichtung bleiben u. U. auch leichter zersetzliche Stoffe erhalten; dementsprechend entstehen aus meerischen Gyttjen unter zunächst oxydativen Bedingungen Brennsteine von der Art des Kuckersits, aus meerischen Sapropelen polybituminöse Gesteine und Erdöl. Festländisch bilden sich die Kohlen, zu denen auch Unterwasserablagerungen (Bogheads=Algengyttjen; Cannels = Dy, Sapropel, Gyttja; beide stets mit Dy-Grundmasse) gehören. Porphyrine und Metallgehalte gestatten eine Unterscheidung der Haupttypen der Brenngesteine und eine Zuweisung des Erdöls zu den Sapropelgesteinen.Bei der Kohlenbildung spielt das Lignin die Hauptrolle, die Zellulose wird im Torf und während früher Braunkohlenstadien abgebaut. Bei der Bildung der Kerogengesteine werden die Eiweißstoffe zersetzt, Fette und Kohlehydrate spielen wohl die Hauptrolle. Nur bei der Bildung der Sapropelite einschl. des Erdöls spielen außer Kohlehydraten (und den geringen Mengen von Fetten und Ölen) die Eiweißstoffe eine wesentliche Rolle. Die erstentstehenden Öle sind Alkane. Oberflächeneinflüsse (z. B. Tiefenstandwasser mit Sauerstoffsalzen) bewirken die Naphtenisierung; infolge der damit verbundenen Temperaturerhöhung entstehen die Aromaten, die sich später wieder in Naphtene zurückbilden.Die qualitative Geochemie verbindet die Anreicherung von Elementen und Molekülen in Gesteinen mit den Vorgängen, die im Ablagerungs- und Umbildungsraum herrschen (Fazies, Diagenese usw.). Sie führt zur Kennzeichnung der Ablagerungs- und Umbildungsräume durch typische Elemente oder Moleküle, bzw. durch deren Vergesellschaftung oder Mengenverhältnis.     

Gegenläufiges Verhalten des Verlaufes von Druck und Temperatur in der Unteren Troposphäre

Zusammenfassung Der vertkkale Temperaturgradient hat bei ausgewahlten Stationen einen jährlichen Gang, der nicht durch den täglichen Temperaturgang erklärbar ist. Die jährliche Temperaturschwankung in Abhängigkeit von der Höhe zeigt ein gegenläufiges Verhalten zwischen den unteren und den mittleren Schichten der Troposphäre. Beide Erscheinungen weisen darauthin, dass man die Troposphäre nicht als eine Schicht von einheitlichem Aufbau ansehen kann. Die interdiurnen Anderungen von Druck und Temperatur in den einzelnen Höhenschichten und ihr gegenläufiges Verhalten zwingen dazu eine untere Schicht in der Troposphäre auszusondern, die scho gelegentlich früher beobachtet und dann als Störungsschicht bezeichnet wurde. Diese Beobachtungen sind aber einer Verallgemeinerung fähig, indem diese untere Schicht als planetarische Erscheinung aufzufassen und als Grundschicht der Atmosphäre zu kennzeichnen ist.

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Summary The vertical temperature gradient for selectet stations shows an annual variation which cannot be explained by the diurnal variation of temperature. The annual variation of temperature at fixed levels in the lower layers of atmosphere shows a trend opposite to these variations at fixed elevations in the middle layers. This fact indicates that the troposphere cannot be regarded as a layer of uniform structure. The interdiurnal variations of pressure and temperature for the individual levels and their opposite trend compel us to postulate within the troposphere a lower layer as has been observed before in various occasions and then called the layer of disturbation. It is possible to generalize these observations and to conceive of the lower layer as a planetary phenomenon and as the ground layer of the atmosphere.

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Riassunto Il gradiente termico verticale presenta una variazione annuale che non può venir spiegata con la variazione diurna della temperatura. La variazione annuale della temperatura a livelli determinati nei bassi strati dell'atmosfera rivela un andamento opposto a quello che si riscontra negli strati centrali della troposfera. I due fatti dimostrano che la tropofera non può venir considerata come uno strato avente struttura uniforme. Le variazioni interdiurne della pressione e della temperatura nei singoli strati verticali ed il loro comportamento inverso conducono all'esistenza di uno strato inferiore in seno alla troposfera, già prima occasionalmente osservato e definito strato di perturbazione. Simili osservazioni sono atte a venir generalizzate in quanto questo strato inferiore è concepibile come fenomeno planetärio e come strato base dell'atmosfera.

     

Typen der Grundschicht

Zusammenfassung Ausserhalb des schlechten Wetters der Tiefdruckgebiete ist der Str?mungszustand der unteren Troposph?re so gestaltet, dass wir diese in zwei deutlich getrennte Stockwerke einteilen k?nnen. Das untere Stockwerk nennen wir die Grundschicht. Für diese Schicht und die sie oben begrenzende Sperrschicht werden die Bezeichnungen Peplos und Peplopause vorgeschlagen. Die Grundschicht zeigt deuthch sich abhebende Typen im Aufbau, die sich in fast allen Khmagebieten wiederfinden lassen.

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Summary Beyond the bad weather of the low pressure areas the structure of the current conditions in the lower tropopause is such that we can differentiate distinctly between two separate levels. The lower level is calles the ground layer. It is suggestes to introduce for that layer and the adjacent border layer above the designations ?peplos? and ?peplopause?. The ground layer shows certain definite structural characteristics recurring in nearly all climatic zones.

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Riassunto Al difuori delle condizioni che si riscontrano con cattivo tempo nelle depressioni isobariche, il regime delle correnti atmosferiche della bassa troposfera è dominato da due parti o strati nettamente distinti in quota. Di queste due parti quella inferiore viene indicata strato di base; proponendo la denominazione di peplos per la stessa e di peplopausa per il suo strato limite. In seno allo strato di base si riscontrano definite caratteristiche strutturali comuni a quasi tutte le zone climatiche.

     

Abtrennung und Bestimmung von kolloidalen Kornklassen mit e iner Durchlaufzentrifugea

Zusammenfasung Der Hauptbestandteil der Zentrifuge ist ein um seine Längsachse rotierender Hohl-zylinder, durch den man eine kolloidale Suspension in kontinuierlichem Fluß hindurchschickt. Es werden 2 Methoden beschrieben: Aus der gewichtsmäßigen Verteilung des; im Zylinder abgeschiedenen Niederschlags wird die Verteilungskurve des suspendierten Materials ermittelt. Es wird zweitens die Abtrennung von Kornklassen durch wiederholtes Auszentrifugieren erörtert. Beide Verfahren werden durch Auszentrifugieren einer Quarzsuspension auf ihre praktische Brauchbarkeit geprüft.