2020, Smith, Steven J., Chateau, Jean, Dorheim, Kalyn, Drouet, Laurent, Durand-Lasserve, Olivier, Fricko, Oliver, Fujimori, Shinichiro, Hanaoka, Tatsuya, Harmsen, Mathijs, Hilaire, Jérôme, Keramidas, Kimon, Klimont, Zbigniew, Luderer, Gunnar, Moura, Maria Cecilia P., Riahi, Keywan, Rogelj, Joeri, Sano, Fuminori, van Vuuren, Detlef P., Wada, Kenichi

The relatively short atmospheric lifetimes of methane (CH4) and black carbon (BC) have focused attention on the potential for reducing anthropogenic climate change by reducing Short-Lived Climate Forcer (SLCF) emissions. This paper examines radiative forcing and global mean temperature results from the Energy Modeling Forum (EMF)-30 multi-model suite of scenarios addressing CH4 and BC mitigation, the two major short-lived climate forcers. Central estimates of temperature reductions in 2040 from an idealized scenario focused on reductions in methane and black carbon emissions ranged from 0.18–0.26 °C across the nine participating models. Reductions in methane emissions drive 60% or more of these temperature reductions by 2040, although the methane impact also depends on auxiliary reductions that depend on the economic structure of the model. Climate model parameter uncertainty has a large impact on results, with SLCF reductions resulting in as much as 0.3–0.7 °C by 2040. We find that the substantial overlap between a SLCF-focused policy and a stringent and comprehensive climate policy that reduces greenhouse gas emissions means that additional SLCF emission reductions result in, at most, a small additional benefit of ~ 0.1 °C in the 2030–2040 time frame. © 2020, Battelle Memorial Institute.

2020, Hurtt, George C., Chini, Louise, Sahajpal, Ritvik, Frolking, Steve, Bodirsky, Benjamin L., Calvin, Katherine, Doelman, Jonathan C., Fisk, Justin, Fujimori, Shinichiro, Klein Goldewijk, Kees, Hasegawa, Tomoko, Havlik, Peter, Heinimann, Andreas, Humpenöder, Florian, Jungclaus, Johan, Kaplan, Jed O., Kennedy, Jennifer, Krisztin, Tamás, Lawrence, David, Lawrence, Peter, Ma, Lei, Mertz, Ole, Pongratz, Julia, Popp, Alexander, Poulter, Benjamin, Riahi, Keywan, Shevliakova, Elena, Stehfest, Elke, Thornton, Peter, Tubiello, Francesco N., van Vuuren, Detlef P., Zhang, Xin

Human land use activities have resulted in large changes to the biogeochemical and biophysical properties of the Earth's surface, with consequences for climate and other ecosystem services. In the future, land use activities are likely to expand and/or intensify further to meet growing demands for food, fiber, and energy. As part of the World Climate Research Program Coupled Model Intercomparison Project (CMIP6), the international community has developed the next generation of advanced Earth system models (ESMs) to estimate the combined effects of human activities (e.g., land use and fossil fuel emissions) on the carbon–climate system. A new set of historical data based on the History of the Global Environment database (HYDE), and multiple alternative scenarios of the future (2015–2100) from Integrated Assessment Model (IAM) teams, is required as input for these models. With most ESM simulations for CMIP6 now completed, it is important to document the land use patterns used by those simulations. Here we present results from the Land-Use Harmonization 2 (LUH2) project, which smoothly connects updated historical reconstructions of land use with eight new future projections in the format required for ESMs. The harmonization strategy estimates the fractional land use patterns, underlying land use transitions, key agricultural management information, and resulting secondary lands annually, while minimizing the differences between the end of the historical reconstruction and IAM initial conditions and preserving changes depicted by the IAMs in the future. The new approach builds on a similar effort from CMIP5 and is now provided at higher resolution (0.25∘×0.25∘) over a longer time domain (850–2100, with extensions to 2300) with more detail (including multiple crop and pasture types and associated management practices) using more input datasets (including Landsat remote sensing data) and updated algorithms (wood harvest and shifting cultivation); it is assessed via a new diagnostic package. The new LUH2 products contain > 50 times the information content of the datasets used in CMIP5 and are designed to enable new and improved estimates of the combined effects of land use on the global carbon–climate system.

2020, Fofrich, Robert, Tong, Dan, Calvin, Katherine, De Boer, Harmen Sytze, Emmerling, Johannes, Fricko, Oliver, Fujimori, Shinichiro, Luderer, Gunnar, Rogelj, Joeri, Davis, Steven J.

International efforts to avoid dangerous climate change aim for large and rapid reductions of fossil fuel CO2 emissions worldwide, including nearly complete decarbonization of the electric power sector. However, achieving such rapid reductions may depend on early retirement of coal- and natural gas-fired power plants. Here, we analyze future fossil fuel electricity demand in 171 energy-emissions scenarios from Integrated Assessment Models (IAMs), evaluating the implicit retirements and/or reduced operation of generating infrastructure. Although IAMs calculate retirements endogenously, the structure and methods of each model differ; we use a standard approach to infer retirements in outputs from all six major IAMs and—unlike the IAMs themselves—we begin with the age distribution and region-specific operating capacities of the existing power fleet. We find that coal-fired power plants in scenarios consistent with international climate targets (i.e. keeping global warming well-below 2 °C or 1.5 °C) retire one to three decades earlier than historically has been the case. If plants are built to meet projected fossil electricity demand and instead allowed to operate at the level and over the lifetimes they have historically, the roughly 200 Gt CO2 of additional emissions this century would be incompatible with keeping global warming well-below 2 °C. Thus, ambitious climate mitigation scenarios entail drastic, and perhaps un-appreciated, changes in the operating and/or retirement schedules of power infrastructure.

2020, Malik, Aman, Bertram, Christoph, Despres, Jacques, Emmerling, Johannes, Fujimori, Shinichiro, Garg, Amit, Kriegler, Elmar, Luderer, Gunnar, Mathur, Ritu, Roelfsema, Mark, Shekhar, Swapnil, Vishwanathan, Saritha, Vrontisi, Zoi

Cost-effective achievement of the Paris Agreement's long-term goals requires the unanimous phase-out of coal power generation by mid-century. However, continued investments in coal power plants will make this transition difficult. India is one of the major countries with significant under construction and planned increase in coal power capacity. To ascertain the likelihood and consequences of the continued expansion of coal power for India's future mitigation options, we use harmonised scenario results from national and global models along with projections from various government reports. Both these approaches estimate that coal capacity is expected to increase until 2030, along with rapid developments in wind and solar power. However, coal capacity stranding of the order of 133–237 GW needs to occur after 2030 if India were to pursue an ambitious climate policy in line with a well-below 2 °C target. Earlier policy strengthening starting after 2020 can reduce stranded assets (14–159 GW) but brings with it political economy and renewable expansion challenges. We conclude that a policy limiting coal plants to those under construction combined with higher solar targets could be politically feasible, prevent significant stranded capacity, and allow higher mitigation ambition in the future.

2020, Hasegawa, Tomoko, Sands, Ronald D., Brunelle, Thierry, Cui, Yiyun, Frank, Stefan, Fujimori, Shinichiro, Popp, Alexander

Bioenergy is expected to play an important role in the achievement of stringent climate-change mitigation targets requiring the application of negative emissions technology. Using a multi-model framework, we assess the effects of high bioenergy demand on global food production, food security, and competition for agricultural land. Various scenarios simulate global bioenergy demands of 100, 200, 300, and 400 exajoules (EJ) by 2100, with and without a carbon price. Six global energy-economy-agriculture models contribute to this study, with different methodologies and technologies used for bioenergy supply and greenhouse-gas mitigation options for agriculture. We find that the large-scale use of bioenergy, if not implemented properly, would raise food prices and increase the number of people at risk of hunger in many areas of the world. For example, an increase in global bioenergy demand from 200 to 300 EJ causes a − 11% to + 40% change in food crop prices and decreases food consumption from − 45 to − 2 kcal person−1 day−1, leading to an additional 0 to 25 million people at risk of hunger compared with the case of no bioenergy demand (90th percentile range across models). This risk does not rule out the intensive use of bioenergy but shows the importance of its careful implementation, potentially including regulations that protect cropland for food production or for the use of bioenergy feedstock on land that is not competitive with food production. © 2020, The Author(s).

2020, Ai, Zhipin, Hanasaki, Naota, Heck, Vera, Hasegawa, Tomoko, Fujimori, Shinichiro

Large-scale deployment of bioenergy plantations would have adverse effects on water resources. There is an increasing need to ensure the appropriate inclusion of the bioenergy crops in global hydrological models. Here, through parameter calibration and algorithm improvement, we enhanced the global hydrological model H08 to simulate the bioenergy yield from two dedicated herbaceous bioenergy crops: Miscanthus and switchgrass. Site-specific evaluations showed that the enhanced model had the ability to simulate yield for both Miscanthus and switchgrass, with the calibrated yields being well within the ranges of the observed yield. Independent country-specific evaluations further confirmed the performance of the H08 (v.bio1). Using this improved model, we found that unconstrained irrigation more than doubled the yield under rainfed condition, but reduced the water use efficiency (WUE) by 32 % globally. With irrigation, the yield in dry climate zones can exceed the rainfed yields in tropical climate zones. Nevertheless, due to the low water consumption in tropical areas, the highest WUE was found in tropical climate zones, regardless of whether the crop was irrigated. Our enhanced model provides a new tool for the future assessment of bioenergy–water tradeoffs.

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, Detlef

We 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'.

2020, Daioglou, Vassilis, Muratori, Matteo, Lamers, Patrick, Fujimori, Shinichiro, Kitous, Alban, Köberle, Alexandre C., Bauer, Nico, Junginger, Martin, Kato, Etsushi, Leblanc, Florian, Mima, Silvana, Wise, Marshal, van Vuuren, Detlef P.

Most climate change mitigation scenarios rely on increased use of bioenergy to decarbonize the energy system. Here we use results from the 33rd Energy Modeling Forum study (EMF-33) to investigate projected international bioenergy trade for different integrated assessment models across several climate change mitigation scenarios. Results show that in scenarios with no climate policy, international bioenergy trade is likely to increase over time, and becomes even more important when climate targets are set. More stringent climate targets, however, do not necessarily imply greater bioenergy trade compared to weaker targets, as final energy demand may be reduced. However, the scaling up of bioenergy trade happens sooner and at a faster rate with increasing climate target stringency. Across models, for a scenario likely to achieve a 2 °C target, 10–45 EJ/year out of a total global bioenergy consumption of 72–214 EJ/year are expected to be traded across nine world regions by 2050. While this projection is greater than the present trade volumes of coal or natural gas, it remains below the present trade of crude oil. This growth in bioenergy trade largely replaces the trade in fossil fuels (especially oil) which is projected to decrease significantly over the twenty-first century. As climate change mitigation scenarios often show diversified energy systems, in which numerous world regions can act as bioenergy suppliers, the projections do not necessarily lead to energy security concerns. Nonetheless, rapid growth in the trade of bioenergy is projected in strict climate mitigation scenarios, raising questions about infrastructure, logistics, financing options, and global standards for bioenergy production and trade. © 2020, The Author(s).

2020, Roelfsema, Mark, van Soest, Heleen L., Harmsen, Mathijs, van Vuuren, Detlef P., Bertram, Christoph, den Elzen, Michel, Höhne, Niklas, Iacobuta, Gabriela, Krey, Volker, Kriegler, Elmar, Luderer, Gunnar, Riahi, Keywan, Ueckerdt, Falko, Després, Jacques, Drouet, Laurent, Emmerling, Johannes, Frank, Stefan, Fricko, Oliver, Gidden, Matthew, Humpenöder, Florian, Huppmann, Daniel, Fujimori, Shinichiro, Fragkiadakis, Kostas, Gi, Keii, Keramidas, Kimon, Köberle, Alexandre C., Aleluia Reis, Lara, Rochedo, Pedro, Schaeffer, Roberto, Oshiro, Ken, Vrontisi, Zoi, Chen, Wenying, Iyer, Gokul C., Edmonds, Jae, Kannavou, Maria, Jiang, Kejun, Mathur, Ritu, Safonov, George, Vishwanathan, Saritha Sudharmma

Many countries have implemented national climate policies to accomplish pledged Nationally Determined Contributions and to contribute to the temperature objectives of the Paris Agreement on climate change. In 2023, the global stocktake will assess the combined effort of countries. Here, based on a public policy database and a multi-model scenario analysis, we show that implementation of current policies leaves a median emission gap of 22.4 to 28.2 GtCO2eq by 2030 with the optimal pathways to implement the well below 2 °C and 1.5 °C Paris goals. If Nationally Determined Contributions would be fully implemented, this gap would be reduced by a third. Interestingly, the countries evaluated were found to not achieve their pledged contributions with implemented policies (implementation gap), or to have an ambition gap with optimal pathways towards well below 2 °C. This shows that all countries would need to accelerate the implementation of policies for renewable technologies, while efficiency improvements are especially important in emerging countries and fossil-fuel-dependent countries.

2020, Daioglou, Vassilis, Rose, Steven K., Bauer, Nico, Kitous, Alban, Muratori, Matteo, Sano, Fuminori, Fujimori, Shinichiro, Gidden, Matthew J., Kato, Etsushi, Keramidas, Kimon, Klein, David, Leblanc, Florian, Tsutsui, Junichi, Wise, Marshal, van Vuuren, Detlef P.

Bioenergy is expected to play an important role in long-run climate change mitigation strategies as highlighted by many integrated assessment model (IAM) scenarios. These scenarios, however, also show a very wide range of results, with uncertainty about bioenergy conversion technology deployment and biomass feedstock supply. To date, the underlying differences in model assumptions and parameters for the range of results have not been conveyed. Here we explore the models and results of the 33rd study of the Stanford Energy Modeling Forum to elucidate and explore bioenergy technology specifications and constraints that underlie projected bioenergy outcomes. We first develop and report consistent bioenergy technology characterizations and modeling details. We evaluate the bioenergy technology specifications through a series of analyses—comparison with the literature, model intercomparison, and an assessment of bioenergy technology projected deployments. We find that bioenergy technology coverage and characterization varies substantially across models, spanning different conversion routes, carbon capture and storage opportunities, and technology deployment constraints. Still, the range of technology specification assumptions is largely in line with bottom-up engineering estimates. We then find that variation in bioenergy deployment across models cannot be understood from technology costs alone. Important additional determinants include biomass feedstock costs, the availability and costs of alternative mitigation options in and across end-uses, the availability of carbon dioxide removal possibilities, the speed with which large scale changes in the makeup of energy conversion facilities and integration can take place, and the relative demand for different energy services. © 2020, The Author(s).