Earth System Dynamics Discussions最新文献

{"title":"ESD Ideas: Global climate response scenarios for IPCC AR6","authors":"R. Sutton, E. Hawkins","doi":"10.5194/esd-2019-88","DOIUrl":"https://doi.org/10.5194/esd-2019-88","url":null,"abstract":"Abstract. Policy making on climate change routinely employs socio-economic scenarios to sample the uncertainty in future forcing of the climate system, but the IPCC has not developed similar discrete scenarios to sample the uncertainty in the global climate response. Here we argue that to enable development of robust policies this gap should be addressed, and we propose a simple methodology.","PeriodicalId":11466,"journal":{"name":"Earth System Dynamics Discussions","volume":"9 1","pages":"1-4"},"PeriodicalIF":0.0,"publicationDate":"2020-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77741168","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Standardized Vertical Velocity Anomaly Index (SVVAI): Using Atmospheric Dynamical Anomalies to Simulate and Predict Meteorological Droughts","authors":"Zhenchen Liu, Hai He, Zhiyong Wu, G. Lu, Hao Yin","doi":"10.5194/esd-2019-81","DOIUrl":"https://doi.org/10.5194/esd-2019-81","url":null,"abstract":"Abstract. Vertically downward motion of air current is physically drought-inducing, which has the potential of being a simple and universal drought indicator. The core objective of the present study is to employ vertical motion to simulate and predict droughts after investigating dynamically drought-inducing mechanism. Season-scale drought processes and spatial distributions during 2009–2016 are our concerns, and all the drought study regions of China were chosen as the research areas. Three-month SPI (SPI3) updated daily was used to identify drought processes, and original vertical motion and associated horizontal divergence were also transformed to season-scale standardized anomalies (SA) with a daily running window. In situ observation, ERA-Interim reanalysis, and CFSv2 forecast products were comprehensively employed for drought simulation and prediction. To date, the main results and conclusions are as follow: (1) Atmospheric dynamical anomalies during drought processes and key phases were uncovered. Dynamically drought-inducing features are generally characterized as the typically anomalous upper-convergence–lower-divergence patterns and the intensified downward vertical motion as expected. Signal intensities and vertical configurations are time-varying and seemingly coincide with evolution of regional processes. Particularly, vertical velocity exhibited universally strengthened downward anomalies over almost all the droughts. (2) On the basis of dynamically vertical features uncovered above, the SVVAI (Standardized Vertical Velocity Anomaly Index) is newly proposed. The SVVAI is calculated using SA-based values of vertical motion at multiple pressure levels in the troposphere. The SVVAI_ave and SVVAI_max, corresponding to the vertically average- and maximum-based computation schemes, can be adopted. (3) Drought processes and spatial distributions were simulated with the SVVAI_ave and SVVAI_max. They commonly show highly positive correlations with realistic ones over most regions, and the SVVAI_ave outperformed the SVVAI_max. (4) To further understand difference of simulation capacity, temporal correlation coefficients (TCC) of the SVVAI_ave against observed SPI3 at the grid scale were used for analysis. Positive TCCs above +0.3 occupies most areas to the east of 110° E, while large-area low TCCs (−0.1 ~ +0.3) appear to the west of 110° E over China. It is notably seen that East China and Northeast China are the two regions with highly positive TCCs (+0.6 ~ +0.8). (5) Drought prediction using the SVVAI_ave was preliminarily explored. Regarding the prospective 60-day process prediction, the predicted SVVAI_ave was equally matched with or a little better than the forecasted SPI3 in most cases. Predicted spatial distribution is preliminarily assessed via the example of the 2011 summer–autumn drought over Southwest China, and prediction performance at the occurrence, peak and termination times are inconsistent. (6) Overall, the novel SVVAI herei","PeriodicalId":11466,"journal":{"name":"Earth System Dynamics Discussions","volume":"28 1","pages":"1-28"},"PeriodicalIF":0.0,"publicationDate":"2020-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83714174","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ESD Ideas: Why are glaciations slower than deglaciations?","authors":"C. Ramadhin, C. Yi","doi":"10.5194/esd-11-13-2020","DOIUrl":"https://doi.org/10.5194/esd-11-13-2020","url":null,"abstract":"Abstract. The Earth's climate during the Quaternary is dominated by short\u0000warm interglacials and longer cold glaciations paced by external forcings\u0000such as changes in insolation. Although not observed in the solar radiation\u0000changes, the time series of the cycles display asymmetry since transitions\u0000to full glacial conditions are slower than the termination of glaciations. Here\u0000an idea is proposed for the slower transition by identifying and describing\u0000two negative sea ice feedbacks dominant during the glaciation process that\u0000could serve as a control on the intermediate stage and decrease the pace of\u0000the process.","PeriodicalId":11466,"journal":{"name":"Earth System Dynamics Discussions","volume":"51 1","pages":"13-16"},"PeriodicalIF":0.0,"publicationDate":"2020-01-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80283336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Constraints on long term warming in a climate mitigation scenario","authors":"B. Sanderson","doi":"10.5194/esd-2019-82","DOIUrl":"https://doi.org/10.5194/esd-2019-82","url":null,"abstract":"Abstract. Cumulative emissions budgets and net-zero emission target dates are often used to frame climate negotiations (Frameet al., 2014; Millar et al., 2016; Van Vuuren et al., 2016; Rogelj et al., 2015b; Matthews et al., 2012). However, their utilityfor near-term policy decisions is confounded by an uncertainties in future negative emissions capacity (Fuss et al., 2014; Smith et al., 2016; Larkin et al., 2018; Anderson and Peters, 2016) and in long term Earth System response to climate forcers(Rugenstein et al., 2019; Knutti et al., 2017; Armour, 2017) which may impact the utility of an indefinite carbon budget if peak temperatures occur significantly after net zero emissions are achieved, the likelihood of which in a simple model is conditionalon prior assumptions about the long term dynamics of the Earth System. Here we illustrate that the risks associated with nearterm positive emissions can be framed using a definite cumulative emissions budget with a 2040 time horizon, allowing thenecessity and scope for negative emissions deployment later in the century to be better informed by observed warming overcoming decades.","PeriodicalId":11466,"journal":{"name":"Earth System Dynamics Discussions","volume":"81 1","pages":"1-19"},"PeriodicalIF":0.0,"publicationDate":"2020-01-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85351822","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Precipitation Ansatz dependent Future Sea Level Contribution by Antarctica based on CMIP5 Model Forcing","authors":"C. Rodehacke, M. Pfeiffer, T. Semmler, Özgür Gurses, T. Kleiner","doi":"10.5194/esd-2019-78","DOIUrl":"https://doi.org/10.5194/esd-2019-78","url":null,"abstract":"Abstract. Various observational estimates indicate growing mass loss at Antarctica's margins but also heavier precipitation across the continent. In the future, heavier precipitation fallen on Antarctica will counteract any stronger iceberg discharge and increased basal melting of floating ice shelves driven by a warming ocean. Here, we use from nine CMIP5 models future projections, ranging from strong mitigation efforts to business-as-usual, to run an ensemble of ice-sheet simulations. We test, how the precipitation boundary condition determines Antarctica's sea-level contribution. The spatial and temporal varying climate forcings drive ice-sheet simulations. Hence, our ensemble inherits all spatial and temporal climate patterns, which is in contrast to a spatial mean forcing. Regardless of the applied boundary condition and forcing, some areas will lose ice in the future, such as the glaciers from the West Antarctic Ice Sheet draining into the Amundsen Sea. In general the simulated ice-sheet thickness grows in a broad marginal strip, where incoming storms deliver topographically controlled precipitation. This strip shows the largest ice thickness differences between the applied precipitation boundary conditions too. On average Antarctica's ice mass shrinks for all future scenarios if the precipitation is scaled by the spatial temperature anomalies coming from the CMIP5 models. In this approach, we use the relative precipitation increment per degree warming as invariant scaling constant. In contrast, Antarctica gains mass in our simulations if we apply the simulated precipitation anomalies of the CMIP5 models directly. Here, the scaling factors show a distinct spatial pattern across Antarctica. Furthermore, the diagnosed mean scaling across all considered climate forcings is larger than the values deduced from ice cores. In general, the scaling is higher across the East Antarctic Ice Sheet, lower across the West Antarctic Ice Sheet, and lowest around the Siple Coast. The latter is located on the east side of the Ross Ice Shelf.","PeriodicalId":11466,"journal":{"name":"Earth System Dynamics Discussions","volume":"2016 1","pages":"1-63"},"PeriodicalIF":0.0,"publicationDate":"2020-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86522001","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An emergent constraint on Transient Climate Response from simulated historical warming in CMIP6 models","authors":"F. Nijsse, P. Cox, M. Williamson","doi":"10.5194/esd-2019-86","DOIUrl":"https://doi.org/10.5194/esd-2019-86","url":null,"abstract":"Abstract. The transient climate response (TCR) is the metric of temperature sensitivity that is most relevant to warming in the next few decades, and contributes the biggest uncertainty to estimates of the carbon budgets consistent with the Paris targets (Arora et al., 2019). In the IPCC 5th Assessment Report (AR5), the stated likely range of TCR was given as 1.0 to 2.5 K, with a central estimate which was broadly consistent with the ensemble mean of the CMIP5 Earth System Models (ESMs) available at the time (1.8 ± 0.4 K). Many of the latest CMIP6 ESMs have larger climate sensitivities, with 6 of 23 models having TCR values above 2.5 K, and an ensemble mean TCR of 2.1 ± 0.4 K. On the face of it, these latest ESM results suggest that the IPCC likely range of TCR may need revising upwards, which would cast further doubt on the feasibility of the Paris targets. Here we show that rather than increasing the uncertainty in climate sensitivity, the CMIP6 models help to further constrain the likely range of TCR to 1.5–2.2 K, with a central estimate of 1.82 K. We reach this conclusion through an emergent constraint approach which relates the value of TCR to the global warming from 1970 onwards. We confirm a consistent emergent constraint on TCR when we apply the same method to CMIP5 models (Jimenez-de-la Cuesta and Mauritsen, 2019). Our emergent constraint on TCR benefits from both the large range of TCR values across the CMIP6 models, and also from the extension of the historical simulations into a period when the uncertain changes in aerosol forcing have had a far less significant impact on the trend in global warming.","PeriodicalId":11466,"journal":{"name":"Earth System Dynamics Discussions","volume":"85 1","pages":"1-14"},"PeriodicalIF":0.0,"publicationDate":"2020-01-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86908039","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Analysis of the position and strength of westerlies and trades with implications for Agulhas leakage and South Benguela upwelling","authors":"N. Tim, E. Zorita, K. Emeis, F. Schwarzkopf, A. Biastoch, B. Hünicke","doi":"10.5194/esd-10-847-2019","DOIUrl":"https://doi.org/10.5194/esd-10-847-2019","url":null,"abstract":"Abstract. The westerlies and trade winds over the South Atlantic and Indian Ocean are important drivers of the regional oceanography around southern Africa, including features such as the Agulhas Current, the Agulhas leakage, and the Benguela upwelling. Agulhas leakage constitutes a fraction of warm and saline water transport from the Indian Ocean into the South Atlantic. The leakage is stronger during intensified westerlies. Here, we analyze the wind stress of different observational and modeled atmospheric data sets (covering the last 2 millennia, the recent decades, and the 21st century) with regard to the intensity and position of the southeasterly trades and the westerlies. The analysis reveals that variations of both wind systems go hand in hand and that a poleward shift of the westerlies and trades and an intensification of westerlies took place during the recent decades. Furthermore, upwelling in South Benguela is slightly intensified when trades are shifted poleward.\u0000Projections for strength and position of the westerlies in the 21st century depend on assumed CO2 emissions and on their effect relative to the ozone forcing. In the strongest emission scenario (RCP8.5) the simulations show a further southward displacement, whereas in the weakest emission scenario (RCP2.6) a northward shift is modeled, possibly due to the effect of ozone recovery dominating the effect of anthropogenic greenhouse forcing.\u0000We conclude that the Agulhas leakage has intensified during the last decades and is projected to increase if greenhouse gas emissions are not reduced. This will have a small impact on Benguela upwelling strength and may also have consequences for water mass characteristics in the upwelling region. An increased contribution of Agulhas water to the upwelling water masses will import more preformed nutrients and oxygen into the upwelling region.","PeriodicalId":11466,"journal":{"name":"Earth System Dynamics Discussions","volume":"27 1","pages":"847-858"},"PeriodicalIF":0.0,"publicationDate":"2019-12-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85501362","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Societal breakdown as an emergent property of large-scale behavioural models of land use change","authors":"Calum Brown, B. Seo, M. Rounsevell","doi":"10.5194/ESD-10-809-2019","DOIUrl":"https://doi.org/10.5194/ESD-10-809-2019","url":null,"abstract":"Abstract. Human land use has placed enormous pressure on natural resources and ecosystems worldwide and may even prompt socio-ecological collapses under some circumstances. Efforts to avoid such collapses are hampered by a lack of knowledge about when they may occur and how they may be prevented. Computational models that illuminate potential future developments in the land system are invaluable tools in this context. While such models are widely used to project biophysical changes, they are currently less able to explore the social dynamics that will be key aspects of future global change. As a result, strategies for navigating a hazardous future may suffer from “blind spots” at which individual, social and political behaviours divert the land system away from predicted pathways. We apply CRAFTY-EU, an agent-based model of the European land system, in order to investigate the effects of human behavioural aspects of land management at the continental scale. We explore a range of potential futures using climatic and socio-economic scenarios and present a coherent set of cross-sectoral projections without imposed equilibria or optimisation. These projections include various behavioural responses to scenarios including non-economic motivations, aversion to change and heterogeneity in decision-making. We find that social factors and behavioural responses have dramatic impacts on simulated dynamics and can contribute to a breakdown of the land system's essential functions in which shortfalls in food production of up to 56 % emerge. These impacts are largely distinct from, and at least as large as, those of projected climatic change. We conclude that the socio-economic aspects of future scenarios require far more detailed and varied treatment. In particular, deviation from simple economic rationality at individual and aggregate scales may profoundly alter the nature of land system development and the achievability of policy goals.","PeriodicalId":11466,"journal":{"name":"Earth System Dynamics Discussions","volume":"1 1","pages":"809-845"},"PeriodicalIF":0.0,"publicationDate":"2019-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84698765","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Yardangs and Dunes: Minimum- and Maximum-Dissipation Aeolian Landforms","authors":"R. Lorenz","doi":"10.5194/esd-2019-73","DOIUrl":"https://doi.org/10.5194/esd-2019-73","url":null,"abstract":"Abstract. Yardangs are ridges formed in soft rock by aeolian erosion in a unidirectional wind environment, and often have a 4 : 1 length : width ratio that is associated with a minimum-drag shape for a given width. Dunes are emergent aeolian landforms formed by accumulation and removal of sand particles. Dunes have a range of morphologies (barchans, stars, linear, transverse etc.) which can be mapped to the sand supply and the diversity of wind directions. The dune pattern that generally emerges is one that maximizes gross bedform normal transport (GBNT). For fixed imposed wind speed, a minimum drag force corresponds to a minimum dissipation, whereas maximum sand transport corresponds to maximum dissipation. These examples illuminate a more general paradox in non-equilibrium thermodynamics, wherein entropy production rates may be maximized or minimized depending, vaguely, on the degrees of freedom in the system. In these geomorphological examples, however, the difference is informatively clear: whereas yardangs emerge simply by removal of material alone and dissipation is minimized, dunes form by the much less constrained removal and accumulation to maximize dissipation.","PeriodicalId":11466,"journal":{"name":"Earth System Dynamics Discussions","volume":"94 2 1","pages":"1-13"},"PeriodicalIF":0.0,"publicationDate":"2019-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83876193","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Pacific Ocean heat engine: global climate's regulator","authors":"Roger N. Jones, J. Ricketts","doi":"10.5194/esd-2019-72","DOIUrl":"https://doi.org/10.5194/esd-2019-72","url":null,"abstract":"Abstract. Climate change is routinely represented as a smoothly changing signal surrounded by statistical noise. However, on decadal timescales, warming proceeds as a sequence of steady-state regimes punctuated by abrupt shifts. Here we present evidence that this process is regulated by a heat engine spanning the tropical Pacific Ocean. The eastern-central Pacific maintains steady-state conditions, collecting heat and delivering it to the Western Pacific warm pool. This acts as distributor, transporting heat upwards and to the poles. The heat engine is networked within the climate system, linking different oscillations and circulations as heat energy is dissipated. The process is self-regulating. Steady-state regimes will persist until they become unstable and need more or less power depending on the direction of forcing. Under greenhouse gas forcing, shifts initiated within the heat engine propagate broadly across the shallow ocean, followed by warming over land and at higher latitudes. The heat engine was in free mode during the early 20th century, dominated by decadal variability. From the 1960s, it switched into forced mode, initiating a stepladder-like pattern of warming in regional and global climate. The most recent shift commenced in the warm pool in December 2012, ending the so-called hiatus (1997–2013). During 2014–15, surface temperatures warmed abruptly by ~ 0.25 °C globally and > 0.5 °C over northern hemisphere land and high latitudes. With increasing forcing, the heat engine will shift more frequently. Rapid decreases in greenhouse gas emissions will slow the process and potentially, could stabilise it. Managing unavoidable change requires developing the capacity to predict shifts in advance. Planning for rapid changes in extreme events is an urgent priority.","PeriodicalId":11466,"journal":{"name":"Earth System Dynamics Discussions","volume":"11 14 1","pages":"1-42"},"PeriodicalIF":0.0,"publicationDate":"2019-11-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85578263","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}