@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{vanSoestAleluiaReisBaptistaetal.2021, author = {van Soest, Heleen L. and Aleluia Reis, Lara and Baptista, Luiz Bernardo and Bertram, Christoph and Despr{\´e}s, Jacques and Drouet, Laurent and den Elzen, Michel and Fragkos, Panagiotis and Fricko, Oliver and Fujimori, Shinichiro and Grant, Neil and Harmsen, Mathijs and Iyer, Gokul and Keramidas, Kimon and K{\"o}berle, Alexandre C. and Kriegler, Elmar and Malik, Aman and Mittal, Shivika and Oshiro, Ken and Riahi, Keywan and Roelfsema, Mark and van Ruijven, Bas and Schaeffer, Roberto and Silva Herran, Diego and Tavoni, Massimo and {\"U}nl{\"u}, Gamze and Vandyck, Toon and van Vuuren, Detlef P.}, title = {Global roll-out of comprehensive policy measures may aid in bridging emissions gap}, series = {Nature communications}, volume = {12}, journal = {Nature communications}, number = {1}, publisher = {Nature Publishing Group UK}, address = {London}, doi = {10.1038/s41467-021-26595-z}, pages = {10}, year = {2021}, abstract = {Closing the emissions gap between Nationally Determined Contributions (NDCs) and the global emissions levels needed to achieve the Paris Agreement's climate goals will require a comprehensive package of policy measures. National and sectoral policies can help fill the gap, but success stories in one country cannot be automatically replicated in other countries. They need to be adapted to the local context. Here, we develop a new Bridge scenario based on nationally relevant, short-term measures informed by interactions with country experts. These good practice policies are rolled out globally between now and 2030 and combined with carbon pricing thereafter. We implement this scenario with an ensemble of global integrated assessment models. We show that the Bridge scenario closes two-thirds of the emissions gap between NDC and 2 °C scenarios by 2030 and enables a pathway in line with the 2 °C goal when combined with the necessary long-term changes, i.e. more comprehensive pricing measures after 2030. The Bridge scenario leads to a scale-up of renewable energy (reaching 52\%-88\% of global electricity supply by 2050), electrification of end-uses, efficiency improvements in energy demand sectors, and enhanced afforestation and reforestation. Our analysis suggests that early action via good-practice policies is less costly than a delay in global climate cooperation.}, language = {en} } @article{RiahiBertramHuppmannetal.2021, author = {Riahi, Keywan and Bertram, Christoph and Huppmann, Daniel and Rogelj, Joeri and Bosetti, Valentina and Cabardos, Anique-Marie and Deppermann, Andre and Drouet, Laurent and Frank, Stefan and Fricko, Oliver and Fujimori, Shinichiro and Harmsen, Mathijs and Hasegawa, Tomoko and Krey, Volker and Luderer, Gunnar and Paroussos, Leonidas and Schaeffer, Roberto and Weitzel, Matthias and van der Zwaan, Bob and Vrontisi, Zoi and Longa, Francesco Dalla and Despr{\´e}s, Jacques and Fosse, Florian and Fragkiadakis, Kostas and Gusti, Mykola and Humpen{\"o}der, Florian and Keramidas, Kimon and Kishimoto, Paul and Kriegler, Elmar and Meinshausen, Malte and Nogueira, Larissa Pupo and Oshiro, Ken and Popp, Alexander and Rochedo, Pedro R. R. and {\"U}nl{\"u}, Gamze and van Ruijven, Bas and Takakura, Junya and Tavoni, Massimo and van Vuuren, Detlef P. and Zakeri, Behnam}, title = {Cost and attainability of meeting stringent climate targets without overshoot}, series = {Nature climate change}, volume = {11}, journal = {Nature climate change}, number = {12}, publisher = {Nature Publishing Group}, address = {London}, issn = {1758-678X}, doi = {10.1038/s41558-021-01215-2}, pages = {1063 -- 1069}, year = {2021}, abstract = {Global emissions scenarios play a critical role in the assessment of strategies to mitigate climate change. The current scenarios, however, are criticized because they feature strategies with pronounced overshoot of the global temperature goal, requiring a long-term repair phase to draw temperatures down again through net-negative emissions. Some impacts might not be reversible. Hence, we explore a new set of net-zero CO2 emissions scenarios with limited overshoot. We show that upfront investments are needed in the near term for limiting temperature overshoot but that these would bring long-term economic gains. Our study further identifies alternative configurations of net-zero CO2 emissions systems and the roles of different sectors and regions for balancing sources and sinks. Even without net-negative emissions, CO2 removal is important for accelerating near-term reductions and for providing an anthropogenic sink that can offset the residual emissions in sectors that are hard to abate.}, 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} }