Estimating the Effective Radiative Forcing of Contrail Cirrus

Evidence from previous climate model simulations has suggested a potentially low efficacy of contrails to force global mean surface temperature changes. In this paper, a climate model with a state-of-the-art contrail cirrus representation is used for fixed sea surface temperature simulations in order to determine the effective radiative forcing (ERF) from contrail cirrus. ERF is expected to be a good metric for intercomparing the quantitative importance of different contributions to surface temperature and climate impact. Substantial upscaling of aviation density is necessary to ensure statistically significant results from our simulations. The contrail cirrus ERF is found to be less than 50% of the respective instantaneous or stratosphere adjusted radiative forcings, with a best estimate of roughly 35%. The reduction of ERF is much more substantial for contrail cirrus than it is for a CO2 increase when both stratosphere adjusted forcings are of similar magnitude. Analysis of all rapid radiative adjustments contributing to the ERF indicates that the reduction is mainly induced by a compensating effect of natural clouds that provide a negative feedback. Compared to the CO2 reference case, a less positive combined water vapor and lapse rate adjustment also contributes to a more distinct reduction of contrail cirrus ERF, but not as much as the natural cloud adjustment. Based on the experience gained in this paper, respective contrail cirrus simulations with interactive ocean will be performed as the next step toward establishing contrail cirrus efficacy. ERF results of contrail cirrus from other climate models equipped with suitable parameterizations are regarded as highly desirable

Propofol decreases the axonal excitability in rat primary sensory afferents

AIMS: The aim of this present study was to investigate the changes of peripheral sensory nerve excitability produced by propofol. MAIN METHODS: In a recently described in vitro model of rodent saphenous nerve we used the technique of threshold tracking (QTRAC®) to measure changes of axonal nerve excitability of Aβ-fibres caused by propofol. Concentrations of 10μMol, 100μMol and 1000μMol were tested. Latency, peak response, strength-duration time constant (τSD) and recovery cycle of the sensory neuronal action potential (SNAP) were recorded. KEY FINDINGS: Our results have shown that propofol decreases nerve excitability of rat primary sensory afferents in vitro. Latency increased with increasing concentrations (0μMol: 0.96±0.07ms; 1000μMol 1.10±0.06ms, P<0.01). Also, propofol prolonged the relative refractory period (0μMol: 1.79±1.13ms; 100μMol: 2.53±1.38ms, P<0.01), and reduced superexcitability (0 μMol: -14.0±4.0%; 100μMol: -9.5±5.5%) and subexcitability (0μMol: 7.5±1.2%; 1000μMol: 3.6±1.2) significantly during the recovery cycle (P<0.01). SIGNIFICANCE: Our results have shown that propofol decreases nerve excitability of primary sensory afferents. The technique of threshold tracking revealed that axonal voltage-gated ion channels are significantly affected by propofol and therefore might be at least partially responsible for earlier described analgesic effects

Planwagen vs. Hefeweizen: Ein Marketingkonzept für den Elektrotechnik-Studiengang der TU Dresden im Rahmen des OSA-Projekts

Der vorliegende Vortrag dokumentiert die Entwicklung eines Marketingkonzepts für den Elektrotechnik- (ET) Studiengang der TU Dresden. Das Konzept wurde im Rahmen des Studienerfolgprojektes Online-Self-Assessment („OSA“) erarbeitet. Das Ziel bestand darin, Faktoren zu definieren, die potentiell erfolgreiche Studierende für das Studium in Dresden anziehen können. Zu diesem Zweck wurden verschiedene Informationsquellen gesichtet und eine Literaturrecherche durchgeführt. Insgesamt ergab die Recherche elf Faktoren, die drei Clustern zugeordnet werden konnten. Die gefundenen Faktoren entsprachen inhaltlich dem Anforderungsprofil eines erfolgreichen ET-Studierenden aus dem OSA-Projekt. Limitierungen der Rechercheergebnisse werden diskutiert. Die Metapher „Planwagen vs. Hefeweizen“ wird zusammenfassend verwendet, um die Botschaft des Marketingkonzepts zu transportieren. Weitere Anwendungen des Konzepts werden abschließend dargestellt

Towards Determining the Contrail Cirrus Efficacy

Contrail cirrus has been emphasized as the largest individual component of aircraft climate impact, yet respective assessments have been based mainly on conventional radiative forcing calculations. As demonstrated in previous research work, individual impact components can have different efficacies, i.e., their effectiveness to induce surface temperature changes may vary. Effective radiative forcing (ERF) has been proposed as a superior metric to compare individual impact contributions, as it may, to a considerable extent, include the effect of efficacy differences. Recent climate model simulations have provided a first estimate of contrail cirrus ERF, which turns out to be much smaller, by about 65%, than the conventional radiative forcing of contrail cirrus. The main reason for the reduction is that natural clouds exhibit a substantially lower radiative impact in the presence of contrail cirrus. Hence, the new result suggests a smaller role of contrail cirrus in the context of aviation climate impact (including proposed mitigation measures) than assumed so far. However, any conclusion in this respect should be drawn carefully as long as no direct simulations of the surface temperature response to contrail cirrus are available. Such simulations are needed in order to confirm the power of ERF for assessing contrail cirrus efficacy

Radiative forcing and rapid atmospheric adjustments induced by contrail cirrus

The sustainability of worldwide air traffic forms an important issue due to its expected large growth rates in the coming decades. Contrail cirrus is regarded to be the largest contributor to aviation climate impact and thus plays an important role in considerations towards limiting aviation induced climate change. Here, we present results from global climate model simulations, designed to determine the adjusted radiative forcing (RFadj) and the effective radiative forcing (ERF) of contrail cirrus. For a 2050 air traffic scenario a RFadj of 160 mWm-2 was determined, which corresponds to an increase by a factor of more than 3 compared to 2006 values (49 mWm-2) and thus highlights the largely growing impact of air traffic in a future climate. However, as has been indicated by earlier studies, the efficacy of RFadj of linear contrails in forcing surface temperature is significantly reduced and it stands to reason that this might hold for contrail cirrus as well. For this reason we also performed ERF simulations which account for further rapid radiative adjustments in the atmosphere, not included in RFadj, and thus may form a better metric for estimating surface temperature changes. ERF of contrail cirrus is found to be severely reduced by between 50 and 75% (best estimate about 65%), compared to RFadj. In a subsequent feedback analysis the rapid adjustments, which are physically responsible for the reduced ERF, have been determined. A large negative cloud adjustment, due to a decline of natural cirrus cover, is found to be the main driver of the substantial reduction. For a CO2 doubling simulation, the reduction of ERF in comparison to the RFadj is found to be much smaller

An Unrecognized Source of PCB Contamination in Schools and Other Buildings

An investigation of 24 buildings in the Greater Boston Area revealed that one-third (8 of 24) contained caulking materials with polychlorinated biphenyl (PCB) content exceeding 50 ppm by weight, which is the U.S. Environmental Protection Agency (U.S. EPA) specified limit above which this material is considered to be PCB bulk product waste. These buildings included schools and other public buildings. In a university building where similar levels of PCB were found in caulking material, PCB levels in indoor air ranged from 111 to 393 ng/m(3); and in dust taken from the building ventilation system, < 1 ppm to 81 ppm. In this building, the U.S. EPA mandated requirements for the removal and disposal of the PCB bulk product waste as well as for confirmatory sampling to ensure that the interior and exterior of the building were decontaminated. Although U.S. EPA regulations under the Toxic Substances Control Act stipulate procedures by which PCB-contaminated materials must be handled and disposed, the regulations apparently do not require that materials such as caulking be tested to determine its PCB content. This limited investigation strongly suggests that were this testing done, many buildings would be found to contain high levels of PCBs in the building materials and potentially in the building environment. The presence of PCBs in schools is of particular concern given evidence suggesting that PCBs are developmental toxins