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- ItemRobust changes in tropical rainy season length at 1.5 °C and 2 °C(Bristol : IOP Publ., 2018) Saeed, Fahad; Bethke, Ingo; Fischer, Erich; Legutke, Stephanie; Shiogama, Hideo; Stone, Dáithí A.; Schleussner, Carl-FriedrichChanges in the hydrological cycle are among the aspects of climate change most relevant for human systems and ecosystems. Besides trends in overall wetting or drying, changes in temporal characteristics of wetting and drying are of crucial importance in determining the climate hazard posed by such changes. This is particularly the case for tropical regions, where most precipitation occurs during the rainy season and changes in rainy season onset and length have substantial consequences. Here we present projections for changes in tropical rainy season lengths for mean temperature increase of 1.5 °C and 2 °C above pre-industrial levels. Based on multi-ensemble quasi-stationary simulations at these warming levels, our analysis indicates robust changes in rainy season characteristics in large parts of the tropics despite substantial natural variability. Specifically, we report a robust shortening of the rainy season for all of tropical Africa as well as north-east Brazil. About 27% of West Africa is projected to experience robust changes in the rainy season length with a mean shortening of about 7 days under 1.5 °C. We find that changes in the temporal characteristics are largely unrelated to changes in overall precipitation, highlighting the importance of investigating both separately.
- ItemEnergy system developments and investments in the decisive decade for the Paris Agreement goals(Bristol : IOP Publ., 2021-6-29) Bertram, Christoph; Riahi, Keywan; Hilaire, Jérôme; Bosetti, Valentina; Drouet, Laurent; Fricko, Oliver; Malik, Aman; Pupo Nogueira, Larissa; van der Zwaan, Bob; van Ruijven, Bas; van Vuuren, Detlef; Weitzel, Matthias; Dalla Longa, Francesco; de Boer, Harmen-Sytze; Emmerling, Johannes; Fosse, Florian; Fragkiadakis, Kostas; Harmsen, Mathijs; Keramidas, Kimon; Kishimoto, Paul Natsuo; Kriegler, Elmar; Krey, Volker; Paroussos, Leonidas; Saygin, Deger; Vrontisi, Zoi; Luderer, GunnarThe Paris Agreement does not only stipulate to limit the global average temperature increase to well below 2 °C, it also calls for 'making finance flows consistent with a pathway towards low greenhouse gas emissions'. Consequently, there is an urgent need to understand the implications of climate targets for energy systems and quantify the associated investment requirements in the coming decade. A meaningful analysis must however consider the near-term mitigation requirements to avoid the overshoot of a temperature goal. It must also include the recently observed fast technological progress in key mitigation options. Here, we use a new and unique scenario ensemble that limit peak warming by construction and that stems from seven up-to-date integrated assessment models. This allows us to study the near-term implications of different limits to peak temperature increase under a consistent and up-to-date set of assumptions. We find that ambitious immediate action allows for limiting median warming outcomes to well below 2 °C in all models. By contrast, current nationally determined contributions for 2030 would add around 0.2 °C of peak warming, leading to an unavoidable transgression of 1.5 °C in all models, and 2 °C in some. In contrast to the incremental changes as foreseen by current plans, ambitious peak warming targets require decisive emission cuts until 2030, with the most substantial contribution to decarbonization coming from the power sector. Therefore, investments into low-carbon power generation need to increase beyond current levels to meet the Paris goals, especially for solar and wind technologies and related system enhancements for electricity transmission, distribution and storage. Estimates on absolute investment levels, up-scaling of other low-carbon power generation technologies and investment shares in less ambitious scenarios vary considerably across models. In scenarios limiting peak warming to below 2 °C, while coal is phased out quickly, oil and gas are still being used significantly until 2030, albeit at lower than current levels. This requires continued investments into existing oil and gas infrastructure, but investments into new fields in such scenarios might not be needed. The results show that credible and effective policy action is essential for ensuring efficient allocation of investments aligned with medium-term climate targets.
- ItemHydro-Economic Modelling for Water-Policy Assessment Under Climate Change at a River Basin Scale: A Review(Basel : MDPI, 2020) Expósito, Alfonso; Beier, Felicitas; Berbel, JulioHydro-economic models (HEMs) constitute useful instruments to assess water-resource management and inform water policy. In the last decade, HEMs have achieved significant advances regarding the assessment of the impacts of water-policy instruments at a river basin or catchment level in the context of climate change (CC). This paper offers an overview of the alternative approaches used in river-basin hydro-economic modelling to address water-resource management issues and CC during the past decade. Additionally, it analyses how uncertainty and risk factors of global CC have been treated in recent HEMs, offering a discussion on these last advances. As the main conclusion, current challenges in the realm of hydro-economic modelling include the representation of the food-energy-water nexus, the successful representation of micro-macro linkages and feedback loops between the socio-economic model components and the physical side, and the treatment of CC uncertainties and risks in the analysis.
- ItemSensitivity of ecosystem-protected permafrost under changing boreal forest structures(Bristol : IOP Publ., 2021-8-2) Stuenzi, Simone M.; Boike, Julia; Gädeke, Anne; Herzschuh, Ulrike; Kruse, Stefan; Pestryakova, Luidmila A.; Westermann, Sebastian; Langer, MoritzBoreal forests efficiently insulate underlying permafrost. The magnitude of this insulation effect is dependent on forest density and composition. A change therein modifies the energy and water fluxes within and below the canopy. The direct influence of climatic change on forests and the indirect effect through a change in permafrost dynamics lead to extensive ecosystem shifts such as a change in composition or density, which will, in turn, affect permafrost persistence. We derive future scenarios of forest density and plant functional type composition by analyzing future projections provided by the dynamic global vegetation model (LPJ-GUESS) under global warming scenarios. We apply a detailed permafrost-multilayer canopy model to study the spatial impact-variability of simulated future scenarios of forest densities and compositions for study sites throughout eastern Siberia. Our results show that a change in forest density has a clear effect on the ground surface temperatures (GST) and the maximum active layer thickness (ALT) at all sites, but the direction depends on local climate conditions. At two sites, higher forest density leads to a significant decrease in GSTs in the snow-free period, while leading to an increase at the warmest site. Complete forest loss leads to a deepening of the ALT up to 0.33 m and higher GSTs of over 8 ∘C independently of local climatic conditions. Forest loss can induce both, active layer wetting up to four times or drying by 50%, depending on precipitation and soil type. Deciduous-dominated canopies reveal lower GSTs compared to evergreen stands, which will play an important factor in the spreading of evergreen taxa and permafrost persistence under warming conditions. Our study highlights that changing density and composition will significantly modify the thermal and hydrological state of the underlying permafrost. The induced soil changes will likely affect key forest functions such as the carbon pools and related feedback mechanisms such as swamping, droughts, fires, or forest loss.
- ItemThe meso scale as a frontier in interdisciplinary modeling of sustainability from local to global scales(Bristol : IOP Publ., 2023) Johnson, Justin Andrew; Brown, Molly E.; Corong, Erwin; Dietrich, Jan Philipp; C. Henry, Roslyn; Jeetze, Patrick José von; Leclère, David; Popp, Alexander; Thakrar, Sumil K.; Williams, David R.Achieving sustainable development requires understanding how human behavior and the environment interact across spatial scales. In particular, knowing how to manage tradeoffs between the environment and the economy, or between one spatial scale and another, necessitates a modeling approach that allows these different components to interact. Existing integrated local and global analyses provide key insights, but often fail to capture ‘meso-scale’ phenomena that operate at scales between the local and the global, leading to erroneous predictions and a constrained scope of analysis. Meso-scale phenomena are difficult to model because of their complexity and computational challenges, where adding additional scales can increase model run-time exponentially. These additions, however, are necessary to make models that include sufficient detail for policy-makers to assess tradeoffs. Here, we synthesize research that explicitly includes meso-scale phenomena and assess where further efforts might be fruitful in improving our predictions and expanding the scope of questions that sustainability science can answer. We emphasize five categories of models relevant to sustainability science, including biophysical models, integrated assessment models, land-use change models, earth-economy models and spatial downscaling models. We outline the technical and methodological challenges present in these areas of research and discuss seven directions for future research that will improve coverage of meso-scale effects. Additionally, we provide a specific worked example that shows the challenges present, and possible solutions, for modeling meso-scale phenomena in integrated earth-economy models.
- ItemCommon but differentiated leadership: strategies and challenges for carbon neutrality by 2050 across industrialized economies(Bristol : IOP Publ., 2020) Schreyer, Felix; Luderer, Gunnar; Rodrigues, Renato; Pietzcker, Robert C.; Baumstark, Lavinia; Sugiyama, Masahiro; Brecha, Robert J.; Ueckerdt, FalkoGiven their historic emissions and economic capability, we analyze a leadership role for representative industrialized regions (EU, US, Japan, and Australia) in the global climate mitigation effort. Using the global integrated assessment model REMIND, we systematically compare region-specific mitigation strategies and challenges of reaching domestic net-zero carbon emissions in 2050. Embarking from different emission profiles and trends, we find that all of the regions have technological options and mitigation strategies to reach carbon neutrality by 2050. Regional characteristics are mostly related to different land availability, population density and population trends: While Japan is resource limited with respect to onshore wind and solar power and has constrained options for carbon dioxide removal (CDR), their declining population significantly decreases future energy demand. In contrast, Australia and the US benefit from abundant renewable resources, but face challenges to curb industry and transport emissions given increasing populations and high per-capita energy use. In the EU, lack of social acceptance or EU-wide cooperation might endanger the ongoing transition to a renewable-based power system. CDR technologies are necessary for all regions, as residual emissions cannot be fully avoided by 2050. For Australia and the US, in particular, CDR could reduce the required transition pace, depth and costs. At the same time, this creates the risk of a carbon lock-in, if decarbonization ambition is scaled down in anticipation of CDR technologies that fail to deliver. Our results suggest that industrialized economies can benefit from cooperation based on common themes and complementary strengths. This may include trade of electricity-based fuels and materials as well as the exchange of regional experience on technology scale-up and policy implementation.
- ItemCorrigendum: Air quality and health implications of 1.5 °C–2 °C climate pathways under considerations of ageing population: a multi-model scenario analysis (2021 Environ. Res. Lett. 16 045005)(Bristol : IOP Publ., 2021) Rafaj, Peter; Kiesewetter, Gregor; Krey, Volker; Schoepp, Wolfgang; Bertram, Christoph; Drouet, Laurent; Fricko, Oliver; Fujimori, Shinichiro; Harmsen, Mathijs; Hilaire, Jérôme; Huppmann, Daniel; Klimont, Zbigniew; Kolp, Peter; Aleluia Reis, Lara; van Vuuren, DetlefWe have identified an error in the text of section 3.3 where the health co-benefits of 1.5 °C + MFR scenario in the whole of Asia are compared to the reference. In the last paragraph of the section 3.3 (page 11), the manuscript states that 'Across the Asia domain, this reduction is approximately 2.5-3 million cases or 40%-51% depending on the IAM used'. Unfortunately, the numbers quoted here were accidentally taken from a sensitivity analysis using different integrated exposure-response curves (GBD-2010, obtained from Global Burden of Disease Collaborative Network 2013), which have not been used in the results shown in the paper-our results are based on the GBD-2013 version, reported by Forouzanfar et al (2015). The correct statement is: 'Across the Asia domain, this reduction is approximately 1.2-1.5 million cases or 33%-42% depending on the IAM used'. The same correction applies to the statement in the Conclusions section 5 (4th paragraph, page 14), which should read: 'The 1.5 °C + MFR scenario decreases premature deaths by 33%-42% across Asia, compared to NPi'.
- ItemResponsibility Under Uncertainty: Which Climate Decisions Matter Most?(Amsterdam : Baltzer Science Publ., 2023) Botta, Nicola; Brede, Nuria; Crucifix, Michel; Ionescu, Cezar; Jansson, Patrik; Li, Zheng; Martínez, Marina; Richter, TimWe propose a new method for estimating how much decisions under monadic uncertainty matter. The method is generic and suitable for measuring responsibility in finite horizon sequential decision processes. It fulfills “fairness” requirements and three natural conditions for responsibility measures: agency, avoidance and causal relevance. We apply the method to study how much decisions matter in a stylized greenhouse gas emissions process in which a decision maker repeatedly faces two options: start a “green” transition to a decarbonized society or further delay such a transition. We account for the fact that climate decisions are rarely implemented with certainty and that their consequences on the climate and on the global economy are uncertain. We discover that a “moral” approach towards decision making — doing the right thing even though the probability of success becomes increasingly small — is rational over a wide range of uncertainties.
- ItemSeasonal prediction of Indian summer monsoon onset with echo state networks(Bristol : IOP Publ., 2021-7-1) Mitsui, Takahito; Boers, NiklasAlthough the prediction of the Indian Summer Monsoon (ISM) onset is of crucial importance for water-resource management and agricultural planning on the Indian sub-continent, the long-term predictability—especially at seasonal time scales—is little explored and remains challenging. We propose a method based on artificial neural networks that provides skilful long-term forecasts (beyond 3 months) of the ISM onset, although only trained on short and noisy data. It is shown that the meridional tropospheric temperature gradient in the boreal winter season already contains the signals needed for predicting the ISM onset in the subsequent summer season. Our study demonstrates that machine-learning-based approaches can be simultaneously helpful for both data-driven prediction and enhancing the process understanding of climate phenomena.
- ItemThe mutual dependence of negative emission technologies and energy systems(Cambridge : RSC Publ., 2019) Creutzig, Felix; Breyer, Christian; Hilaire, Jérôme; Minx, Jan; Peters, Glen P.; Socolow, RobertWhile a rapid decommissioning of fossil fuel technologies deserves priority, most climate stabilization scenarios suggest that negative emission technologies (NETs) are required to keep global warming well below 2 °C. Yet, current discussions on NETs are lacking a distinct energy perspective. Prominent NETs, such as bioenergy with carbon capture and storage (BECCS) and direct air carbon capture and storage (DACCS), will integrate differently into the future energy system, requiring a concerted research effort to determine adequate means of deployment. In this perspective, we discuss the importance of energy per carbon metrics, factors of future cost development, and the dynamic response of NETs in intermittent energy systems. The energy implications of NETs deployed at scale are massive, and NETs may conceivably impact future energy systems substantially. DACCS outperform BECCS in terms of primary energy required per ton of carbon sequestered. For different assumptions, DACCS displays a sequestration efficiency of 75–100%, whereas BECCS displays a sequestration efficiency of 50–90% or less if indirect land use change is included. Carbon dioxide removal costs of DACCS are considerably higher than BECCS, but if DACCS modularity and granularity helps to foster technological learning to <100$ per tCO2, DACCS may remove CO2 at gigaton scale. DACCS also requires two magnitudes less land than BECCS. Designing NET systems that match intermittent renewable energies will be key for stringent climate change mitigation. Our results contribute to an emerging understanding of NETs that is notably different to that derived from scenario modelling.