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

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

Effective radiative forcing of contrail cirrus

Contrail cirrus is regarded to make a main contribution to aviation climate impact and is thus playing a key role for respective mitigation considerations. The stratosphere adjusted radiative forcing of line-shaped contrails has been found to have reduced efficacy in inducing a surface temperature response. Hence, stratosphere adjusted radiative forcing may be of limited value as a metric for the climate impact from contrails or from contrail cirrus. Here, we present first results from global climate model simulations designed to determine the effective radiative forcing of contrail cirrus, as effective radiative forcing is now considered as a more reliable metric. The procedure is not as straightforward as it is for impacts from well-mixed greenhouse gases, because contrail cirrus forms a spatially and temporally varying perturbation and its impact is small compared to the internal variability simulated by the model for atmospheric radiative fluxes. Yet, by means of a sophisticated modeling strategy it is shown that the effective radiative forcing of contrail cirrus is indeed significantly smaller than its stratosphere adjusted radiative forcing. Hence, the assumption of a reduced climate impact, compared with what existing radiative forcing estimates have been suggesting, is confirmed by our simulations

Effective radiative forcing and rapid adjustments of contrail cirrus

Contrail cirrus is regarded to be the largest contributor to aviation climate impact and thus plays an important role in developing strategies towards limiting aviation induced climate change. So far the climate impact relevance of contrails and contrail cirrus was estimated in terms of stratosphere adjusted radiative forcing. It has been shown that the efficacy of stratosphere adjusted radiative forcing of linear contrails in forcing surface temperature is significantly reduced. Thus stratosphere adjusted radiative forcing may be a questionable metric for assessing the climate impact. Here, we present results from global climate model simulations, designed to determine the effective radiative forcing of contrail cirrus, as effective radiative forcing is now considered as a superior metric for inter-comparing contributions to a total climate impact (in this case, for aviation). Effective radiative forcing is found to be significantly lower than the corresponding stratospheric adjusted radiative forcing. For a CO2 increase forcing of comparable magnitude, the reduction of effective radiative forcing in comparison to the stratosphere adjusted forcing is much smaller. Thus the climate impact to be deduced from our simulations is reduced compared to existing radiative forcing estimates. In a subsequent feedback analysis the rapid radiative adjustments, which are physically responsible for the reduced effective radiative forcings, have been determined. A large negative cloud adjustment, due to a loss of natural cirrus cover, is found to be the main driver of the substantial reduction in the contrail cirrus case

Effektiver Strahlungsantrieb und schnelle Rückkopplungen von Kondensstreifen-Zirren

Kondensstreifen-Zirren liefern den größten Beitrag zur Klimawirkung des Luftverkehrs und spielen daher eine wichtige Rolle bei der Begrenzung des durch die Luftfahrt verursachten Klimawandels. Bislang wurde der Beitrag zur Klimawirkung von Kondensstreifen und Kondensstreifen-Zirren auf der Basis des stratosphären-adjustierter Strahlungsantrieb bewertet. Es wurde aber bereits gezeigt, dass die Wirksamkeit des stratosphären-adjustierten Strahlungsantriebs von linienhaften Kondensstreifen hinsichtlich einer Temperaturänderung am Boden deutlich reduziert ist. Der stratosphären-adjustierte Strahlungsantrieb stellt somit im Falle von Kondensstreifen-Zirren eine eher ungeeignete Größe zur Abschätzung der Klimawirkung dar. Hier präsentieren wir Ergebnisse von globalen Klimamodellsimulationen zur Berechnung von effektiven Strahlungsantrieben, welche nach neuestem Kenntnisstand wahrscheinlich ein wesentlich besseres Maß zum Vergleich von Beiträgen zur totalen Klimawirksamkeit darstellen. Unsere Simulationen zeigen einen deutlich verringerten effektiven Strahlungsantrieb im Vergleich zum stratosphären-adjustierten Strahlungsantrieb. Somit ist die zu erwartende Klimawirkung von Kondensstreifen-Zirren, im Vergleich zu bisherigen Abschätzungen des Strahlungsantriebs, deutlich reduziert. Für ein CO2 Erhöhungsexperiment gleicher Stärke fällt die Reduktion des effektiven Strahlungsantriebs im Vergleich zum stratosphären-adjustierten Strahlungsantrieb wesentlich kleiner aus. Zur Klärung der physikalischen Ursachen des reduzierten effektiven Strahlungsantriebs wurden die schnellen Strahlungsrückkopplungen mit Hilfe einer Rückkopplungsanalyse nach dem "partial radiative pertubation"-Verfahren bestimmt. Im Kondensstreifenfall ist die Reduktion auf eine stark negative Wolkenrückkopplung, bedingt durch die Abnahme von natürlichen Wolken, zurückzuführen. Dagegen wird die Abnahme im CO2 Fall hauptsächlich durch eine negative Rückkopplung der Landoberflächentemperatur verursacht

IRF8 is associated with a GCB-type of DLBCL and exceptionally involved in a translocation t(14;16) (q32.33;q24.1)

ABSTRACT Chromosomal translocations involving the immunoglobulin loci represent frequent oncogenic events in B-cell lymphoma development. Although IRF8 (ICSBP-1) protein expression has been demonstrated in germinal centre B-cells and related lymphomas in a single report, the IRF8 gene was not described as an IGH translocation partner. In a discovery driven approach we searched for new translocation partners of the IGH in DLBCL by long distance inverse (LDI) PCR and Sanger sequencing. A t(14;16)(q32.33;q24.1) IGH/IRF8 was detected in a CD5+ de novo DLBCL, confirmed by translocation specific PCR and FISH analysis. No further IRF8 aberration could be identified neither by LDI-PCR in additional five CD5+ DLBCL nor by FISH on 78 FFPE biopsies. Subsequent screening for IRF8 by immunohistochemistry revealed IRF8 expression in 18/78 (23%) correlating with a GCB type of DLBCL. This hitherto unknown translocation t(14;16)(q32.33;q24.1) is alike to represent the initiator of a multistep lymphomagenesis in a CD5+ de novo DLBCL