Emergence of cascading dynamics in interacting tipping elements of ecology and climate

In ecology, climate and other fields, (sub)systems have been identified that can transition into a qualitatively different state when a critical threshold or tipping point in a driving process is crossed. An understanding of those tipping elements is of great interest given the increasing influence of humans on the biophysical Earth system. Complex interactions exist between tipping elements, e.g. physical mechanisms connect subsystems of the climate system. Based on earlier work on such coupled nonlinear systems, we systematically assessed the qualitative long-term behaviour of interacting tipping elements. We developed an understanding of the consequences of interactions on the tipping behaviour allowing for tipping cascades to emerge under certain conditions. The (narrative) application of these qualitative results to real-world examples of interacting tipping elements indicates that tipping cascades with profound consequences may occur: the interacting Greenland ice sheet and thermohaline ocean circulation might tip before the tipping points of the isolated subsystems are crossed. The eutrophication of the first lake in a lake chain might propagate through the following lakes without a crossing of their individual critical nutrient input levels. The possibility of emerging cascading tipping dynamics calls for the development of a unified theory of interacting tipping elements and the quantitative analysis of interacting real-world tipping elements.Comment: 22 pages, 8 figure

Global Tipping Points Report 2023: Ch1.2: Cryosphere tipping points.

Drastic changes in our planet’s frozen landscapes have occurred over recent decades, from Arctic sea ice decline and thawing of permafrost soils to polar amplification, the retreat of glaciers and ice loss from the ice sheets. In this chapter, we assess multiple lines of evidence for tipping points in the cryosphere – encompassing the ice sheets on Greenland and Antarctica, sea ice, mountain glaciers and permafrost – based on recent observations, palaeorecords, numerical modelling and theoretical understanding. With about 1.2°C of global warming compared to pre-industrial levels, we are getting dangerously close to the temperature thresholds of some major tipping points for the ice sheets of Greenland and West Antarctica. Crossing these would lock in unavoidable long-term global sea level rise of up to 10 metres. There is evidence for localised and regional tipping points for glaciers and permafrost and, while evidence for global-scale tipping dynamics in sea ice, glaciers and permafrost is limited, their decline will continue with unabated global warming. Because of the long response times of these systems, some impacts of crossing potential tipping points will unfold over centuries to millennia. However, with the current trajectory of greenhouse gas (GHG) emissions and subsequent anthropogenic climate change, such largely irreversible changes might already have been triggered. These will cause far-reaching impacts for ecosystems and humans alike, threatening the livelihoods of millions of people, and will become more severe the further global warming progresses

Global Tipping Points Report 2023: Ch1.5: Climate tipping point interactions and cascades.

This chapter reviews interactions between climate tipping systems and assesses the potential risk of cascading effects. After a definition of tipping system interactions, we map out the current state of the literature on specific interactions between climate tipping systems that may be important for the overall stability of the climate system. For this, we gather evidence from model simulations, observations and conceptual understanding, as well as archetypal examples of palaeoclimate reconstructions where propagating transitions were potentially at play. This chapter concludes by identifying crucial knowledge gaps in tipping system interactions that should be resolved in order to improve risk assessments of cascading transitions under future climate change scenarios

Climate tipping point interactions and cascades: A review

Climate tipping elements are large-scale subsystems of the Earth that may transgress critical thresholds (tipping points) under ongoing global warming, with substantial impacts on the biosphere and human societies. Frequently studied examples of such tipping elements include the Greenland Ice Sheet, the Atlantic Meridional Overturning Circulation (AMOC), permafrost, monsoon systems, and the Amazon rainforest. While recent scientific efforts have improved our knowledge about individual tipping elements, the interactions between them are less well understood. Also, the potential of individual tipping events to induce additional tipping elsewhere or stabilize other tipping elements is largely unknown. Here, we map out the current state of the literature on the interactions between climate tipping elements and review the influences between them. To do so, we gathered evidence from model simulations, observations, and conceptual understanding, as well as examples of paleoclimate reconstructions where multi-component or spatially propagating transitions were potentially at play. While uncertainties are large, we find indications that many of the interactions between tipping elements are destabilizing. Therefore, we conclude that tipping elements should not only be studied in isolation, but also more emphasis has to be put on potential interactions. This means that tipping cascades cannot be ruled out on centennial to millennial timescales at global warming levels between 1.5 and 2.0 ◦C or on shorter timescales if global warming surpassed 2.0 ◦C. At these higher levels of global warming, tipping cascades may then include fast tipping elements such as the AMOC or the Amazon rainforest. To address crucial knowledge gaps in tipping element interactions, we propose four strategies combining observation-based approaches, Earth system modeling expertise, computational advances, and expert knowledge

The long-term sea-level commitment from Antarctica

info:eu-repo/semantics/publishe

The long-term sea-level commitment from Antarctica

With a sea-level rise potential of 58 m sea-level equivalent, the future evolution of the Antarctic IceSheet under progressing warming is of importance for coastal communities, ecosystems and theglobal economy. Short-term projections of the sea-level contribution from Antarctica in the recentice sheet model intercomparison ISMIP6 range from a slight mass gain (-7.8 cm) to a mass loss ofup to 30.0 cm sea-level equivalent at the end of the century under Representative ConcentrationPathway 8.5 (Seroussi et al. 2020, Edwards et al. 2021). However, due to high inertia of thesystem, the ice sheet response to perturbations in its climatic boundary conditions are ratherslow. Consequences of potentially triggered unstable ice loss due to positive feedbackmechanisms may therefore play out over long timescales (on the order of millennia). Projectionsof the committed sea-level change at a given point in time, that is the sea-level change whicharises by fixing the climatic boundary conditions and letting the ice sheet evolve over severalmillennia, might differ substantially from the sea-level change expected at that point in time(Winkelmann et al. 2022).Previous assessments of the long-term contribution to sea-level rise from the Antarctic Ice Sheethave been primarily restricted to a single model and have rarely explored the full range of intraand inter-model parameter uncertainties. Here, we determine the long-term, multi-millennial sealevel contribution from mass balance changes of the Antarctic Ice Sheet by means of two ice sheetmodels, the Parallel Ice Sheet Model (PISM) and the fast Elementary Thermomechanical Ice Sheet(f.ETISh) model. More specifically, we assess the response of the Antarctic Ice Sheet to atmosphericand oceanic forcing conditions derived from state-of-the-art climate model projections availablefrom the sixth phase of the Coupled Model Intercomparison Project (CMIP6) under the SharedSocioeconomic Pathways SSP5-8.5 and SSP1-2.6 available until the year 2300. The sea-levelcommitment from the Antarctic Ice Sheet is quantified by branching off at regular intervals in timeand running the ice sheet models for several millennia under fixed climate conditions. Keyuncertainties related to ice dynamics as well as to interactions with the bed, atmosphere andocean are taken into account in an ensemble approach.info:eu-repo/semantics/nonPublishe

Long-term Antarctic ice sheet projections with a historically-calibrated ice-sheet model

Recent observations show that the Antarctic ice sheet is currently losing mass at an accelerating rate in areas subject to high sub-shelf melt rates. The resulting thinning of the floating ice shelves reduces their ability to restrain the ice flowing from the grounded ice sheet towards the ocean, hence raising the sea level by increased ice discharge. Despite a relatively good understanding of the drivers of current Antarctic mass changes, projections of the Antarctic ice sheet are associated with large uncertainties, especially under high‐emission scenarios. This uncertainty may notably be explained by unknowns in the long-term impacts of basal melting and changes in surface mass balance. Here, we use observationally-calibrated ice-sheet model projections to investigate the future trajectory of the Antarctic ice sheet until the end of the millennium related to uncertainties in the future balance between sub-shelf melting and ice discharge on the one hand, and the changing surface mass balance on the other. Our large ensemble of simulations, forced by a panel of CMIP6 climate models, suggests that the ocean will be the main driver of short-term Antarctic mass loss, triggering ice loss in the West Antarctic ice sheet (WAIS) already during this century. Under high-emission pathways, ice-ocean interactions will result in a complete WAIS collapse, likely completed before the year 2500 CE, as well as a significant grounding-line retreat in the East Antarctic ice sheet (EAIS). We show that with regional near-surface warming higher than +7.5°C, which may occur by the end of this century under unabated emission scenarios, major ice loss is expected as the increase in surface runoff outweighs the increase in snow accumulation, leading to a decrease in the mitigating role of the ice sheet surface mass balance.info:eu-repo/semantics/nonPublishe

Measles vaccination campaigns-international experience A scoping review of supplementary immunization activities (SIAs)

Schoenfeld S, Niewald A-K, Matysiak-Klose D, Razum O. Masernimpfkampagnen – internationale Erfahrungen Ein Scoping Review zu „supplementary immunization activies“ (SIAs). PRAVENTION UND GESUNDHEITSFORDERUNG. 2020;15(3):195-208.Hintergrund Angesichts der Masernausbrüche wird für Deutschland der Einsatz von Masernimpfkampagnen („supplementary immunization activities“ [SIAs]) diskutiert. Eine Evidenzbasis für einen Einsatz in den Zielgruppen Deutschlands fehlt bislang. Ziel der Arbeit 1. Welche Informationen zur Durchführung von SIAs sind verfügbar? 2. Lassen sich auf Basis der Informationen Trends erkennen, welche Merkmale von SIAs mit einer Inzidenzreduktion einhergehen? Material und Methoden Anhand eines Scoping Reviews wurden Informationen zu Masern-SIAs recherchiert. „Least developed countries“ wurden ausgeschlossen. Ergänzend wurden Inzidenzveränderungen zwischen den Jahren vor und nach der SIA in den betrachteten Ländern und Jahren berechnet. Ergebnisse Es wurden 82 SIAs aus 82 Ländern (20 Artikel) eingeschlossen. Informationen zur Umsetzung beschränken sich meist auf die veröffentlichten Daten der WHO. In 90 % der niedriginzidenten Länder blieben die Masernneuerkrankungsraten nach SIAs niedrig. Die Neuerkrankungsraten der 27 mittelinzidenten Länder entwickelten sich unterschiedlich. In 5 Ländern (19 %) stieg die Inzidenz, in 11 (41 %) blieb sie konstant und in 11 (41 %) sank sie. In 87 % der hochinzidenten Länder reduzierten sich die Inzidenzen. Diskussion Die Dokumentation ist nicht ausreichend, um gesicherte Empfehlungen für entsprechende Zielgruppen oder konkrete Umsetzungsstrategien in Deutschland zu geben. Trotz der unterschiedlichen Voraussetzungen in den Ländern war der Einsatz von SIAs meist mit einem Rückgang oder einer Stabilisierung der Inzidenzraten verbunden. In nur jedem zweiten Land sank die Inzidenz nach Durchführung einer SIA. Es werden sechs Handlungsempfehlungen für zukünftige SIA-Planungen gegeben.Background In view of continuing measles outbreaks, the use of supplementary immunization activities (SIAs) is being discussed for Germany. There is currently no evidence to support the use of SIAs for the target groups in Germany. Objectives What information is available on the implementation of SIAs? Based on the available data, which characteristics of SIAs are associated with a reduction in incidence? Materials and methods A scoping review on measles SIAs was conducted. Least developed countries were excluded. Changes in incidence trends in the relevant countries were calculated in the years before and after the SIA. Results A total of 82 SIAs from 82 countries (20 articles) were included. Information on the implementation is mostly limited to data published by World Health Organization. There was no change in measles incidence in the countries with a low level of incidence. The incidence of the 27 middle-incident countries developed differently. In 5 countries (19%) the incidence increased, in 11 (41%) it remained constant and in 11 (41%) the incidence decreased. In 87% of the high-incidence countries the incidence decreased. Conclusions The available documentation of SIAs is insufficient to provide reliable recommendations for corresponding target groups or concrete implementation strategies in Germany. Despite differing conditions in the included countries, the use of SIAs was usually associated with a decrease or stabilization of incidence rates. In only half of the countries did the incidence drop after a SIA. Six recommendations for action are given for future SIA planning

Phase synchronisation in the Kuroshio Current System

The Kuroshio Current System in the North Pacific displays path transitions on a decadal timescale. It is known that both internal variability involving barotropic and baroclinic instabilities and remote Rossby waves induced by North Pacific wind stress anomalies are involved in these path transitions. However, the precise coupling of both processes and its consequences for the dominant decadal transition timescale are still under discussion. Here, we analyse the output of a multi-centennial high-resolution global climate model simulation and study phase synchronisation between Pacific zonal wind stress anomalies and Kuroshio Current System path variability. We apply the Hilbert transform technique to determine the phase and find epochs where such phase synchronisation appears. The physics of this synchronisation are shown to occur through the effect of the vertical motion of isopycnals, as induced by the propagating Rossby waves, on the instabilities of the Kuroshio Current System

What do we mean, ‘tipping cascade’?

Based on suggested interactions of potential tipping elements in the Earth’s climate and in ecological systems, tipping cascades as possible dynamics are increasingly discussed and studied. The activation of such tipping cascades would impose a considerable risk for human societies and biosphere integrity. However, there are ambiguities in the description of tipping cascades within the literature so far. Here we illustrate how different patterns of multiple tipping dynamics emerge from a very simple coupling of two previously studied idealized tipping elements. In particular, we distinguish between a two phase cascade, a domino cascade and a joint cascade. A mitigation of an unfolding two phase cascade may be possible and common early warning indicators are sensitive to upcoming critical transitions to a certain degree. In contrast, a domino cascade may hardly be stopped once initiated and critical slowing down-based indicators fail to indicate tipping of the following element. These different potentials for intervention and anticipation across the distinct patterns of multiple tipping dynamics should be seen as a call to be more precise in future analyses of cascading dynamics arising from tipping element interactions in the Earth system