@article{AuerKrieglerCarlsenetal.2021, author = {Auer, Cornelia and Kriegler, Elmar and Carlsen, Henrik and Kok, Kasper and Pedde, Simona and Krey, Volker and M{\"u}ller, Boris}, title = {Climate change scenario services}, series = {One earth}, volume = {4}, journal = {One earth}, number = {8}, publisher = {Elsevier}, address = {Amsterdam}, issn = {2590-3322}, doi = {10.1016/j.oneear.2021.07.015}, pages = {1074 -- 1082}, year = {2021}, abstract = {The goal of limiting global warming to well below 2°C as set out in the Paris Agreement calls for a strategic assessment of societal pathways and policy strategies. Besides policy makers, new powerful actors from the private sector, including finance, have stepped up to engage in forward-looking assessments of a Paris-compliant and climate-resilient future. Climate change scenarios have addressed this demand by providing scientific insights on the possible pathways ahead to limit warming in line with the Paris climate goal. Despite the increased interest, the potential of climate change scenarios has not been fully unleashed, mostly due to a lack of an intermediary service that provides guidance and access to climate change scenarios. This perspective presents the concept of a climate change scenario service, its components, and a prototypical implementation to overcome this shortcoming aiming to make scenarios accessible to a broader audience of societal actors and decision makers.}, language = {en} } @article{BertramRiahiHilaireetal.2021, author = {Bertram, Christoph and Riahi, Keywan and Hilaire, J{\´e}r{\^o}me and Bosetti, Valentina and Drouet, Laurent and Fricko, Oliver and Malik, Aman and Nogueira, Larissa Pupo and van der Zwaan, Bob and van Ruijven, Bas and van Vuuren, Detlef P. and Weitzel, Matthias and Longa, Francesco Dalla and de Boer, Harmen-Sytze and Emmerling, Johannes and Fosse, Florian and Fragkiadakis, Kostas and Harmsen, Mathijs and Keramidas, Kimon and Kishimoto, Paul Natsuo and Kriegler, Elmar and Krey, Volker and Paroussos, Leonidas and Saygin, Deger and Vrontisi, Zoi and Luderer, Gunnar}, title = {Energy system developments and investments in the decisive decade for the Paris Agreement goals}, series = {Environmental research letters}, volume = {16}, journal = {Environmental research letters}, number = {7}, publisher = {IOP Publishing}, address = {Bristol}, issn = {1748-9326}, doi = {10.1088/1748-9326/ac09ae}, pages = {12}, year = {2021}, abstract = {The 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.}, language = {en} } @article{DuanZhouJiangetal.2021, author = {Duan, Hongbo and Zhou, Sheng and Jiang, Kejun and Bertram, Christoph and Harmsen, Mathijs and Kriegler, Elmar and van Vuuren, Detlef P. and Wang, Shouyang and Fujimori, Shinichiro and Tavoni, Massimo and Ming, Xi and Keramidas, Kimon and Iyer, Gokul and Edmonds, James}, title = {Assessing China's efforts to pursue the 1.5°C warming limit}, series = {Science}, volume = {372}, journal = {Science}, number = {6540}, publisher = {American Association for the Advancement of Science}, address = {Washington, DC}, issn = {1095-9203}, doi = {10.1126/science.aba8767}, pages = {378 -- 385}, year = {2021}, abstract = {Given the increasing interest in keeping global warming below 1.5°C, a key question is what this would mean for China's emission pathway, energy restructuring, and decarbonization. By conducting a multimodel study, we find that the 1.5°C-consistent goal would require China to reduce its carbon emissions and energy consumption by more than 90 and 39\%, respectively, compared with the "no policy" case. Negative emission technologies play an important role in achieving near-zero emissions, with captured carbon accounting on average for 20\% of the total reductions in 2050. Our multimodel comparisons reveal large differences in necessary emission reductions across sectors, whereas what is consistent is that the power sector is required to achieve full decarbonization by 2050. The cross-model averages indicate that China's accumulated policy costs may amount to 2.8 to 5.7\% of its gross domestic product by 2050, given the 1.5°C warming limit.}, language = {en} } @article{HarmsenKrieglervanVuurenetal.2021, author = {Harmsen, Mathijs and Kriegler, Elmar and van Vuuren, Detlef P. and van der Wijst, Kaj-Ivar and Luderer, Gunnar and Cui, Ryna and Dessens, Olivier and Drouet, Laurent and Emmerling, Johannes and Morris, Jennifer Faye and Fosse, Florian and Fragkiadakis, Dimitris and Fragkiadakis, Kostas and Fragkos, Panagiotis and Fricko, Oliver and Fujimori, Shinichiro and Gernaat, David and Guivarch, C{\´e}line and Iyer, Gokul and Karkatsoulis, Panagiotis and Keppo, Ilkka and Keramidas, Kimon and K{\"o}berle, Alexandre and Kolp, Peter and Krey, Volker and Kr{\"u}ger, Christoph and Leblanc, Florian and Mittal, Shivika and Paltsev, Sergey and Rochedo, Pedro and van Ruijven, Bas J. and Sands, Ronald D. and Sano, Fuminori and Strefler, Jessica and Arroyo, Eveline Vasquez and Wada, Kenichi and Zakeri, Behnam}, title = {Integrated assessment model diagnostics}, series = {Environmental research letters}, volume = {16}, journal = {Environmental research letters}, number = {5}, publisher = {IOP Publishing}, address = {Bristol}, issn = {1748-9326}, doi = {10.1088/1748-9326/abf964}, pages = {13}, year = {2021}, abstract = {Integrated assessment models (IAMs) form a prime tool in informing about climate mitigation strategies. Diagnostic indicators that allow comparison across these models can help describe and explain differences in model projections. This increases transparency and comparability. Earlier, the IAM community has developed an approach to diagnose models (Kriegler (2015 Technol. Forecast. Soc. Change 90 45-61)). Here we build on this, by proposing a selected set of well-defined indicators as a community standard, to systematically and routinely assess IAM behaviour, similar to metrics used for other modeling communities such as climate models. These indicators are the relative abatement index, emission reduction type index, inertia timescale, fossil fuel reduction, transformation index and cost per abatement value. We apply the approach to 17 IAMs, assessing both older as well as their latest versions, as applied in the IPCC 6th Assessment Report. The study shows that the approach can be easily applied and used to indentify key differences between models and model versions. Moreover, we demonstrate that this comparison helps to link model behavior to model characteristics and assumptions. We show that together, the set of six indicators can provide useful indication of the main traits of the model and can roughly indicate the general model behavior. The results also show that there is often a considerable spread across the models. Interestingly, the diagnostic values often change for different model versions, but there does not seem to be a distinct trend.}, language = {en} } @article{KikstraNichollsSmithetal.2022, author = {Kikstra, Jarmo S. and Nicholls, Zebedee R. J. and Smith, Christopher J. and Lewis, Jared and Lamboll, Robin D. and Byers, Edward and Sandstad, Marit and Meinshausen, Malte and Gidden, Matthew J. and Rogelj, Joeri and Kriegler, Elmar and Peters, Glen P. and Fuglestvedt, Jan S. and Skeie, Ragnhild B. and Samset, Bj{\o}rn H. and Wienpahl, Laura and van Vuuren, Detlef P. and van der Wijst, Kaj-Ivar and Al Khourdajie, Alaa and Forster, Piers M. and Reisinger, Andy and Schaeffer, Roberto and Riahi, Keywan}, title = {The IPCC Sixth Assessment Report WGIII climate assessment of mitigation pathways}, series = {Geoscientific model development}, volume = {15}, journal = {Geoscientific model development}, number = {24}, publisher = {Copernicus}, address = {Katlenburg-Lindau}, issn = {1991-959X}, doi = {10.5194/gmd-15-9075-2022}, pages = {9075 -- 9109}, year = {2022}, abstract = {While the Intergovernmental Panel on Climate Change (IPCC) physical science reports usually assess a handful of future scenarios, the Working Group III contribution on climate mitigation to the IPCC's Sixth Assessment Report (AR6 WGIII) assesses hundreds to thousands of future emissions scenarios. A key task in WGIII is to assess the global mean temperature outcomes of these scenarios in a consistent manner, given the challenge that the emissions scenarios from different integrated assessment models (IAMs) come with different sectoral and gas-to-gas coverage and cannot all be assessed consistently by complex Earth system models. In this work, we describe the "climate-assessment" workflow and its methods, including infilling of missing emissions and emissions harmonisation as applied to 1202 mitigation scenarios in AR6 WGIII. We evaluate the global mean temperature projections and effective radiative forcing (ERF) characteristics of climate emulators FaIRv1.6.2 and MAGICCv7.5.3 and use the CICERO simple climate model (CICERO-SCM) for sensitivity analysis. We discuss the implied overshoot severity of the mitigation pathways using overshoot degree years and look at emissions and temperature characteristics of scenarios compatible with one possible interpretation of the Paris Agreement. We find that the lowest class of emissions scenarios that limit global warming to "1.5 ∘C (with a probability of greater than 50 \%) with no or limited overshoot" includes 97 scenarios for MAGICCv7.5.3 and 203 for FaIRv1.6.2. For the MAGICCv7.5.3 results, "limited overshoot" typically implies exceedance of median temperature projections of up to about 0.1 ∘C for up to a few decades before returning to below 1.5 ∘C by or before the year 2100. For more than half of the scenarios in this category that comply with three criteria for being "Paris-compatible", including net-zero or net-negative greenhouse gas (GHG) emissions, median temperatures decline by about 0.3-0.4 ∘C after peaking at 1.5-1.6 ∘C in 2035-2055. We compare the methods applied in AR6 with the methods used for SR1.5 and discuss their implications. This article also introduces a "climate-assessment" Python package which allows for fully reproducing the IPCC AR6 WGIII temperature assessment. This work provides a community tool for assessing the temperature outcomes of emissions pathways and provides a basis for further work such as extending the workflow to include downscaling of climate characteristics to a regional level and calculating impacts.}, language = {en} } @phdthesis{Kriegler2005, author = {Kriegler, Elmar}, title = {Imprecise probability analysis for integrated assessment of climate change}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus-5611}, school = {Universit{\"a}t Potsdam}, year = {2005}, abstract = {We present an application of imprecise probability theory to the quantification of uncertainty in the integrated assessment of climate change. Our work is motivated by the fact that uncertainty about climate change is pervasive, and therefore requires a thorough treatment in the integrated assessment process. Classical probability theory faces some severe difficulties in this respect, since it cannot capture very poor states of information in a satisfactory manner. A more general framework is provided by imprecise probability theory, which offers a similarly firm evidential and behavioural foundation, while at the same time allowing to capture more diverse states of information. An imprecise probability describes the information in terms of lower and upper bounds on probability. For the purpose of our imprecise probability analysis, we construct a diffusion ocean energy balance climate model that parameterises the global mean temperature response to secular trends in the radiative forcing in terms of climate sensitivity and effective vertical ocean heat diffusivity. We compare the model behaviour to the 20th century temperature record in order to derive a likelihood function for these two parameters and the forcing strength of anthropogenic sulphate aerosols. Results show a strong positive correlation between climate sensitivity and ocean heat diffusivity, and between climate sensitivity and absolute strength of the sulphate forcing. We identify two suitable imprecise probability classes for an efficient representation of the uncertainty about the climate model parameters and provide an algorithm to construct a belief function for the prior parameter uncertainty from a set of probability constraints that can be deduced from the literature or observational data. For the purpose of updating the prior with the likelihood function, we establish a methodological framework that allows us to perform the updating procedure efficiently for two different updating rules: Dempster's rule of conditioning and the Generalised Bayes' rule. Dempster's rule yields a posterior belief function in good qualitative agreement with previous studies that tried to constrain climate sensitivity and sulphate aerosol cooling. In contrast, we are not able to produce meaningful imprecise posterior probability bounds from the application of the Generalised Bayes' Rule. We can attribute this result mainly to our choice of representing the prior uncertainty by a belief function. We project the Dempster-updated belief function for the climate model parameters onto estimates of future global mean temperature change under several emissions scenarios for the 21st century, and several long-term stabilisation policies. Within the limitations of our analysis we find that it requires a stringent stabilisation level of around 450 ppm carbon dioxide equivalent concentration to obtain a non-negligible lower probability of limiting the warming to 2 degrees Celsius. We discuss several frameworks of decision-making under ambiguity and show that they can lead to a variety of, possibly imprecise, climate policy recommendations. We find, however, that poor states of information do not necessarily impede a useful policy advice. We conclude that imprecise probabilities constitute indeed a promising candidate for the adequate treatment of uncertainty in the integrated assessment of climate change. We have constructed prior belief functions that allow much weaker assumptions on the prior state of information than a prior probability would require and, nevertheless, can be propagated through the entire assessment process. As a caveat, the updating issue needs further investigation. Belief functions constitute only a sensible choice for the prior uncertainty representation if more restrictive updating rules than the Generalised Bayes'Rule are available.}, subject = {Anthropogene Klima{\"a}nderung}, language = {en} } @article{LudererMadedduMerfortetal.2021, author = {Luderer, Gunnar and Madeddu, Silvia and Merfort, Leon and Ueckerdt, Falko and Pehl, Michaja and Pietzcker, Robert C. and Rottoli, Marianna and Schreyer, Felix and Bauer, Nico and Baumstark, Lavinia and Bertram, Christoph and Dirnaichner, Alois and Humpen{\"o}der, Florian and Levesque, Antoine and Popp, Alexander and Rodrigues, Renato and Strefler, Jessica and Kriegler, Elmar}, title = {Impact of declining renewable energy costs on electrification in low-emission scenarios}, series = {Nature energy}, volume = {7}, journal = {Nature energy}, number = {1}, publisher = {Nature Publishing Group}, address = {London}, issn = {2058-7546}, doi = {10.1038/s41560-021-00937-z}, pages = {32 -- 42}, year = {2021}, abstract = {Cost degression in photovoltaics, wind-power and battery storage has been faster than previously anticipated. In the future, climate policy to limit global warming to 1.5-2 °C will make carbon-based fuels increasingly scarce and expensive. Here we show that further progress in solar- and wind-power technology along with carbon pricing to reach the Paris Climate targets could make electricity cheaper than carbon-based fuels. In combination with demand-side innovation, for instance in e-mobility and heat pumps, this is likely to induce a fundamental transformation of energy systems towards a dominance of electricity-based end uses. In a 1.5 °C scenario with limited availability of bioenergy and carbon dioxide removal, electricity could account for 66\% of final energy by mid-century, three times the current levels and substantially higher than in previous climate policy scenarios assessed by the Intergovernmental Panel on Climate Change. The lower production of bioenergy in our high-electrification scenarios markedly reduces energy-related land and water requirements.}, language = {en} } @article{MalikBertramKriegleretal.2021, author = {Malik, Aman and Bertram, Christoph and Kriegler, Elmar and Luderer, Gunnar}, title = {Climate policy accelerates structural changes in energy employment}, series = {Energy policy}, volume = {159}, journal = {Energy policy}, publisher = {Elsevier Science}, address = {Amsterdam}, issn = {0301-4215}, doi = {10.1016/j.enpol.2021.112642}, pages = {8}, year = {2021}, abstract = {The employment implications of decarbonizing the energy sector have received far less attention than the technology dimension of the transition, although being of critical importance to policymakers. In this work, we adapt a methodology based on employment factors to project future changes in quantity and composition of direct energy supply jobs for two scenarios - (1) relatively weak emissions reductions as pledged in the nationally determined contributions (NDC) and (2) stringent reductions compatible with the 1.5 °C target. We find that in the near-term the 1.5°C-compatible scenario results in a net increase in jobs through gains in solar and wind jobs in construction, installation, and manufacturing, despite significant losses in coal fuel supply; eventually leading to a peak in total direct energy jobs in 2025. In the long run, improvements in labour productivity lead to a decrease of total direct energy employment compared to today, however, total jobs are still higher in a 1.5 °C than in an NDC scenario. Operation and maintenance jobs dominate future jobs, replacing fuel supply jobs. The results point to the need for active policies aimed at retraining, both inside and outside the renewable energy sector, to complement climate policies within the concept of a "just transition".}, language = {en} } @article{MerfortBauerHumpenoederetal.2023, author = {Merfort, Leon and Bauer, Nico and Humpen{\"o}der, Florian and Klein, David and Strefler, Jessica and Popp, Alexander and Luderer, Gunnar and Kriegler, Elmar}, title = {Bioenergy-induced land-use-change emissions with sectorally fragmented policies}, series = {Nature climate change}, volume = {13}, journal = {Nature climate change}, number = {7}, publisher = {Nature Publ. Group}, address = {London}, issn = {1758-678X}, doi = {10.1038/s41558-023-01697-2}, pages = {685 -- 692}, year = {2023}, abstract = {Controlling bioenergy-induced land-use-change emissions is key to exploiting bioenergy for climate change mitigation. However, the effect of different land-use and energy sector policies on specific bioenergy emissions has not been studied so far. Using the global integrated assessment model REMIND-MAgPIE, we derive a biofuel emission factor (EF) for different policy frameworks. We find that a uniform price on emissions from both sectors keeps biofuel emissions at 12 kg CO2 GJ-1. However, without land-use regulation, the EF increases substantially (64 kg CO2 GJ-1 over 80 years, 92 kg CO2 GJ-1 over 30 years). We also find that comprehensive coverage (>90\%) of carbon-rich land areas worldwide is key to containing land-use emissions. Pricing emissions indirectly on the level of bioenergy consumption reduces total emissions by cutting bioenergy demand but fails to reduce the average EF. In the absence of comprehensive and timely land-use regulation, bioenergy thus may contribute less to climate change mitigation than assumed previously.}, language = {en} } @article{MerfortBauerHumpenoederetal.2023, author = {Merfort, Leon and Bauer, Nico and Humpen{\"o}der, Florian and Klein, David and Strefler, Jessica and Popp, Alexander and Luderer, Gunnar and Kriegler, Elmar}, title = {State of global land regulation inadequate to control biofuel land-use-change emissions}, series = {Nature climate change}, volume = {13}, journal = {Nature climate change}, number = {7}, publisher = {Nature Publ. Group}, address = {London}, issn = {1758-678X}, doi = {10.1038/s41558-023-01711-7}, pages = {610 -- 612}, year = {2023}, abstract = {Under current land-use regulation, carbon dioxide emissions from biofuel production exceed those from fossil diesel combustion. Therefore, international agreements need to ensure the effective and globally comprehensive protection of natural land before modern bioenergy can effectively contribute to achieving carbon neutrality.}, language = {en} }