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Seit über einem halben Jahrhundert wissen wir um die erschreckenden Auswirkungen von Umweltzerstörung und Klimawandel. Zwar häufen sich internationale Umwelt- und Klimakonferenzen, doch warum handeln wir nicht konsequent gegen die verheerenden Bedrohungen? Mojib Latif wendet sich in diesem Buch der Frage zu, warum unsere Welt trotz besseren Wissens weiterhin auf gefährliche Weise den Ast absägt, auf dem sie sitzt. Latif stellt die unbequemen Fragen nach dem Versagen der Politik und den Interessen weniger mächtiger Konzerne, die von dieser fatalen Entwicklung profitieren. Die zentrale These dieses Buches ist ebenso klar wie dringlich: Der Klimawandel ist zum verhängnisvollen Verhandlungsobjekt geworden. Nur wenige dabei gewinnen – zahllose verlieren. Doch es gibt Hoffnung, und Latif zeigt den Weg: Die Zukunft nachfolgender Generationen kann gerettet werden, wenn wir uns auf globale Zusammenarbeit besinnen sowie Wohlstand und Nachhaltigkeit in Einklang bringen.

We examine the impact of horizontal resolution and model time step on the climate of the OpenIFS version 43r3 atmospheric general circulation model. A series of simulations for the period 1979–2019 are conducted with various horizontal resolutions (i.e. ∼100, ∼50, and ∼25 km) while maintaining the same time step (i.e. 15 min) and using different time steps (i.e. 60, 30, and 15 min) at 100 km horizontal resolution. We find that the surface zonal wind bias is significantly reduced over certain regions such as the Southern Ocean and the Northern Hemisphere mid-latitudes and in tropical and subtropical regions at a high horizontal resolution (i.e. ∼25 km). Similar improvement is evident too when using a coarse-resolution model (∼100 km) with a smaller time step (i.e. 30 and 15 min). We also find improvements in Rossby wave amplitude and phase speed, as well as in weather regime patterns, when a smaller time step or higher horizontal resolution is used. The improvement in the wind bias when using the shorter time step is mostly due to an increase in shallow and mid-level convection that enhances vertical mixing in the lower troposphere. The enhanced mixing allows frictional effects to influence a deeper layer and reduces wind and wind speed throughout the troposphere. However, precipitation biases generally increase with higher horizontal resolutions or smaller time steps, whereas the surface air temperature bias exhibits a small improvement over North America and the eastern Eurasian continent. We argue that the bias improvement in the highest-horizontal-resolution (i.e. ∼25 km) configuration benefits from a combination of both the enhanced horizontal resolution and the shorter time step. In summary, we demonstrate that, by reducing the time step in the coarse-resolution (∼100 km) OpenIFS model, one can alleviate some climate biases at a lower cost than by increasing the horizontal resolution.

Air-sea interaction in late boreal winter is studied over the extratropical North Atlantic (NA) during 1960–2020 by examining the relationship between sea-surface temperature (SST) and total turbulent heat flux (THF). The two quantities are positively correlated on interannual timescales over the central-midlatitude and subpolar NA, suggesting the atmosphere on average drives SST and THF variability is independent of SST. On decadal timescales and over the central-midlatitude NA the correlation is negative, suggesting ocean processes on average drive SST and THF variability is sensitive to SST. The correlation is positive over the subpolar NA. There, interannual and decadal THF variability is governed by the North Atlantic Oscillation (NAO). During the major late 20th and early 21st century SST increase in the subpolar NA diminishing oceanic heat loss associated with a weakening NAO was observed. This study suggests that the atmosphere is more sensitive to SST over the central-midlatitude than subpolar NA. Key Points: - Regional variation in the nature of air-sea interaction over the extratropical North Atlantic (NA) north of 35°N - Timescale dependence in relationship between sea-surface temperature (SST) and turbulent heat flux over the central-midlatitude NA - The atmosphere is more sensitive to SST variability over the central-midlatitude than subpolar NA

Die Frage nach der Gerechtigkeit spielt aktuell eine größere Rolle denn je. Sie betrifft die unterschiedlichsten Bereiche unseres Lebens, ob es nun um globale Themen wie den Klimawandel, Krieg oder Energiesicherheit geht, ob es Fragen der Geschlechtergerechtigkeit, der Tierethik oder der künstlichen Intelligenz berührt. Was heißt Gerechtigkeit? Wie lässt sie sich verwirklichen? Und wann kann Gerechtigkeit in Ungerechtigkeit umschlagen? Mit diesen Fragen setzen sich renommierte Forschende aus Natur- und Geisteswissenschaften der Akademie der Wissenschaften in Hamburg auseinander

Future changes in the southeastern tropical Atlantic interannual sea surface temperature (SST) variability in response to increasing greenhouse gas concentrations are investigated utilizing the global climate model FOCI. In that model, the Coastal Angola Benguela Area (CABA) is among the regions of the tropical Atlantic that exhibits the largest surface warming. Under the worst-case scenario of the Shared Socioeconomic Pathway 5-8.5 (SSP5-8.5), the SST variability in the CABA decreases by about 19% in 2070–2099 relative to 1981–2010 during the model’s peak interannual variability season May–June–July (MJJ). The weakening of the MJJ interannual temperature variability spans the upper 40 m of the ocean along the Angolan and Namibian coasts. The reduction in variability appears to be related to a diminished surface-layer temperature response to thermocline-depth variations, i.e., a weaker thermocline feedback, which is linked to changes in the mean vertical temperature gradient. Despite improvements made by embedding a high-resolution nest in the ocean a significant SST bias remains, which might have implications for the results.

We examine the impact of horizontal resolution and model time step on climate of the OpenIFS version 43R3 atmosphere general circulation model. A series of simulations for the period 1979–2019 are conducted with various horizontal resolutions (i.e., ~100, ~50, and ~25 km) while maintaining the same time step (i.e., 15 minutes) and using different time steps (i.e., 60, 30 and 15 minutes) at 100 km horizontal resolution. We find that the surface zonal wind bias reduces significantly over certain regions such as the Southern Ocean, the Northern Hemisphere mid-latitudes, and in tropical and subtropical regions at high horizontal resolution (i.e., ~25 km). Similar improvement is evident too when using a coarse resolution model (~100 km) with a smaller time step (i.e., 30 and 15 minutes). We also find improvements in Rossby wave amplitude and phase speed as well as weather regime patterns when a smaller time step or higher horizontal resolution is used. The improvement in the wind bias when using the shorter time step is mostly due to an increase in shallow and mid-level convection that enhances vertical mixing in the lower troposphere. The enhanced mixing allows frictional effects to influence a deeper layer and reduces wind and wind speed throughout the troposphere. However, precipitation biases generally increase with higher horizontal resolution or smaller time step, whereas the surface-air temperature bias exhibits a small improvement over North America and the Eastern Eurasian continent. We argue that the bias improvement in the highest horizontal resolution (i.e., ~25 km) configuration benefits from a combination of both the enhanced horizontal resolution and the shorter time step. In summary, we demonstrate that by reducing the time step in the OpenIFS model, one can alleviate some climate biases at a lower cost than by increasing the horizontal resolution.

We investigate the origin of the equatorial Pacific cold sea surface temperature (SST) bias and its link to wind biases, local and remote, in the Kiel Climate Model (KCM). The cold bias is common in climate models participating in the 5 th and 6 th phases of the Coupled Model Intercomparison Project. In the coupled experiments with the KCM, the interannually varying NCEP/CFSR wind stress is prescribed over four spatial domains: globally, over the equatorial Pacific (EP), the northern Pacific (NP) and southern Pacific (SP). The corresponding EP SST bias is reduced by 100%, 52%, 12% and 23%, respectively. Thus, the EP SST bias is mainly attributed to the local wind bias, with small but not negligible contributions from the extratropical regions. Erroneous ocean circulation driven by overly strong winds cause the cold SST bias, while the surface-heat flux counteracts it. Extratropical Pacific SST biases contribute to the EP cold bias via the oceanic subtropical gyres, which is further enhanced by dynamical coupling in the equatorial region. The origin of the wind biases is examined by forcing the atmospheric component of the KCM in a stand-alone mode with observed SSTs and simulated SSTs from the coupled experiments. Wind biases over the EP, NP and SP regions originate in the atmosphere model. The cold EP SST bias substantially enhances the wind biases over all three regions, while the NP and SP SST biases support local amplification of the wind bias. This study suggests that improving surface-wind stress, at and off the equator, is a key to improve mean-state equatorial Pacific SST in climate models.