Response to the eruption of Mount Pinatubo in relation to climate sensitivity in the CMIP3 models

The radiative flux perturbations and subsequent temperature responses in relation to the eruption of Mount Pinatubo in 1991 are studied in the ten general circulation models incorporated in the Coupled Model Intercomparison Project, phase 3 (CMIP3), that include a parameterization of volcanic aerosol. Models and observations show decreases in global mean temperature of up to 0.5 K, in response to radiative perturbations of up to 10 W m⁻², averaged over the tropics. The time scale representing the delay between radiative perturbation and temperature response is determined by the slow ocean response, and is estimated to be centered around 4 months in the models. Although the magniude of the temperature response to a volcanic eruption has previously been used as an indicator of equilibrium climate sensitivity in models, we find these two quantities to be only weakly correlated. This may partly be due to the fact that the size of the volcano-induced radiative perturbation varies among the models. It is found that the magnitude of the modelled radiative perturbation increases with decreasing climate sensitivity, with the exception of one outlying model. Therefore, we scale the temperature perturbation by the radiative perturbation in each model, and use the ratio between the integrated temperature perturbation and the integrated radiative perturbation as a measure of sensitivity to volcanic forcing. This ratio is found to be well correlated with the model climate sensitivity, more sensitive models having a larger ratio. Further, if this correspondence between “volcanic sensitivity” and sensitivity to CO₂ forcing is a feature not only among the models, but also of the real climate system, the alleged linear relation can be used to estimate the real climate sensitivity. The observational value of the ratio signifying volcanic sensitivity is hereby estimated to correspond to an equilibrium climate sensitivity, i.e. equilibrium temperature increase due to a doubling of the CO₂ concentration, between 1.7 and 4.1 K. Several sources of uncertainty reside in the method applied, and it is pointed out that additional model output, related to ocean heat storage and radiative forcing, could refine the analysis, as could reduced uncertainty in the observational record, of temperature as well as forcing.     

The use of benthic indicators in Europe: from the Water Framework Directive to the Marine Strategy Framework Directive

The Water Framework Directive (WFD) and the Marine Strategy Framework Directive (MSFD) are the European umbrella regulations for water systems. It is a challenge for the scientific community to translate the principles of these directives into realistic and accurate approaches. The aim of this paper, conducted by the Benthos Ecology Working Group of ICES, is to describe how the principles have been translated, which were the challenges and best way forward. We have tackled the following principles: the ecosystem-based approach, the development of benthic indicators, the definition of ‘pristine’ or sustainable conditions, the detection of pressures and the development of monitoring programs. We concluded that testing and integrating the different approaches was facilitated during the WFD process, which led to further insights and improvements, which the MSFD can rely upon. Expert involvement in the entire implementation process proved to be of vital importance.     

Seasonal variability of benthic indices: an approach to test the applicability of different indices for ecosystem quality assessment

In recent studies, several benthic biological indices were developed or used to assess the ecological quality status of marine environments. In the present study the seasonal variability of several univariate and multimetric indices was studied on a monthly scale (September 2000 until May 2002) in different areas of the North Sea such as the German Bight, the Oyster Ground and the Dogger Bank. The stations were chosen to reflect a gradient in the hydrographic regime, temperature and organic matter supply. The seasonal variability was highest for the univariate indices such as the Shannon–Wiener Index and the Hurlbert Index. Thus, due to sensitivity to recruitment the corresponding ecological status ranged from ‘good’ to ‘poor’ depending on the season. For the multimetric indices such as the AMBI or the BQI the seasonal variability and the corresponding ecological status were low. The results are discussed concerning possible consequences for ecological quality assessment especially related to the Water Framework Directive (WFD).     

Properties of circumstellar silicate dust (Review)

Es wird eine Übersicht über den gegenwärtigen Stand des Wissens über die Eigenschaften des zirkumstellaren Silikatstaubes gegeben. Nach der Darstellung der Entdeckungsgeschichte werden die Objekte zusammengestellt, in deren Spektren Silikatbanden beobachtet werden. Der Zusam-menhang zwischen den optischen Eigenschaften der Silikatteilchen und der Struktur der zirkumstellaren Hüllen bei der Bestimmung der ausgesandten Infrarotstrahlung wird analysiert, und alle wichtigeren Untersuchungen von Staubhüllen mit Silikatteilchen werden zusammengetragen. Wir diskutieren die optischen Eigenschaften des zirkumstellaren Silikatstaubes, wobei die amorphe Struktur besonders betont wird. Abschließend wird auf die Bedeutung von Feinstrukturen innerhalb der 10-μm-Bande, die bei verschiedenen Objekten beobachtet wurden, eingegangen.     

Pyroxene glasses — candidates for the interstellar silicate dust component

Experimentelle Arbeiten, die von der Universitäts-Sternwarte Jena in Zusammenarbeit mit chemischen Institutionen durchgeführt wurden, haben gezeigt, daß Pyroxengläser vielversprechende Kandidaten zur Identifizierung von Silikatstaubteilchen in der Umgebung sehr junger Objekte in Molekülwolken, z. B. BN-Objekten und T-Tauri-Sternen, sind. Die Wichtigkeit dieser Experimente besteht darin, daß sie die zur Modellierung der Quellen benötigren optischen Daten liefern und daß sie es ermöglichen, die mineralogische Beschaffenheit des Teilchenmaterials zu verstehen. In dieser Arbeit werden die Schritle, die in der jüngsten Zeit von der Jenaer Staubarbeitsgruppe in beide Richtungen unternommen wurden, beschrieben.