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1. Proposing a 1.0°C climate target for a safer future

   https://doi.org/10.1371/journal.pclm.0000234  

   Breyer, Christian; Keiner, Dominik; Abbott, Benjamin W.; Bamber, Jonathan L.; Creutzig, Felix; Gerhards, Christoph; Mühlbauer, Andreas; Nemet, Gregory F.; Terli, Özden (June 2023, PLOS Climate)

   Males, Jamie (Ed.)

   The Intergovernmental Panel on Climate Change concludes that climate change has already caused substantial damages at the current 1.2°C of global warming and that warming of 1.5°C would elevate risks of a wide-range of climate tipping points. For example, wet-bulb temperatures are already exceeding safe levels, and the melting of the Greenland and West Antartic ice sheets would lead to over ten metres of sea level rise, representing an existential threat to coastal cities, low-lying nation states, and human wellbeing worldwide. We call for a broad scientific discussion about a stricter and more ambitious climate target of 1.0°C by the end of this century. Comprehensive electrification and highly renewable energy systems offer a pathway to sub-1.5°C futures through rapid defossilisation and large-scale, electricity-based carbon dioxide removal. Independent scenarios show that restoring a stable and safe climate is attainable with coordinated policy and economic support. 

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2. Mitigation and adaptation emissions embedded in the broader climate transition

   https://doi.org/10.1073/pnas.2123486119  

   Lesk, Corey; Csala, Denes; Hasse, Robin; Sgouridis, Sgouris; Levesque, Antoine; Mach, Katharine J.; Horen Greenford, Daniel; Matthews, H. Damon; Horton, Radley M. (November 2022, Proceedings of the National Academy of Sciences)

   Climate change necessitates a global effort to reduce greenhouse gas emissions while adapting to increased climate risks. This broader climate transition will involve large-scale global interventions including renewable energy deployment, coastal protection and retreat, and enhanced space cooling, all of which will result in CO 2 emissions from energy and materials use. Yet, the magnitude of the emissions embedded in these interventions remains unconstrained, opening the potential for underaccounting of emissions and conflicts or synergies between mitigation and adaptation goals. Here, we use a suite of models to estimate the CO 2 emissions embedded in the broader climate transition. For a gradual decarbonization pathway limiting warming to 2 °C, selected adaptation-related interventions will emit ∼1.3 GtCO 2 through 2100, while emissions from energy used to deploy renewable capacity are much larger at ∼95 GtCO 2 . Together, these emissions are equivalent to over 2 y of current global emissions and 8.3% of the remaining carbon budget for 2 °C. Total embedded transition emissions are reduced by ∼80% to 21.2 GtCO 2 under a rapid pathway limiting warming to 1.5 °C. However, they roughly double to 185 GtCO 2 under a delayed pathway consistent with current policies (2.7 °C warming by 2100), mainly because a slower transition relies more on fossil fuel energy. Our results provide a holistic assessment of carbon emissions from the transition itself and suggest that these emissions can be minimized through more ambitious energy decarbonization. We argue that the emissions from mitigation, but likely much less so from adaptation, are of sufficient magnitude to merit greater consideration in climate science and policy. 

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3. Underestimation of Future Agricultural Soil N ₂ O Emissions and Abatement Needs

   https://doi.org/10.1111/gcb.70919  

   Lu, Chaoqun; Li, Linchao; Winiwarter, Wilfried; Canadell, Josep G; Liu, Weihang; Tian, Hanqin (May 2026, Global Change Biology)

   ABSTRACT Agricultural soils are the largest human‐induced source of nitrous oxide (N₂O) due to the extensive fertilizer use in crop production. Despite progress made in global N₂O budget accounting, using the IPCC‐derived static emission factors (EF) limits our capability to project future changes in agricultural N₂O emissions and identify cost‐effective mitigation strategies. Here, we use a physics‐informed AI‐driven dynamic EF modeling framework to project direct agricultural soil N₂O emissions induced by mineral fertilizer additions under various climate and nitrogen (N) regulation policy scenarios. Compared to projections based on static EF, our study yields higher future N₂O emissions by 0.3–1.1 Tg N year⁻¹across scenarios by 2050, implying greater abatement needs to combat climate change. The gap between static and dynamic EF approaches is projected to widen to 29%–34% by mid‐century. Under moderate‐ to high‐ambition N regulation policies, we project that a 25% emission reduction can be reached before 2050, while a 45% reduction is only attainable under high‐ambition N policies and strong climate action. The potential for N₂O mitigation due to a policy shift varies substantially among regions, with seven top source regions contributing 76%–87% of global N₂O reduction. Adopting N₂O reduction technologies in hotspot areas would significantly accelerate the timeline for achieving the 25% reduction goal. Improving fertilizer management on croplands can provide climate benefits comparable to, or even exceeding, those of enhancing soil carbon sequestration, particularly in regions with low nitrogen use efficiency. Our findings highlight the higher mitigation potential of targeting N₂O emission hotpots and the urgency of implementing policy shifts. 

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4. Energy systems in scenarios at net-zero CO2 emissions

   https://doi.org/10.1038/s41467-021-26356-y  

   DeAngelo, Julianne; Azevedo, Inês; Bistline, John; Clarke, Leon; Luderer, Gunnar; Byers, Edward; Davis, Steven J. (December 2021, Nature Communications)

   null (Ed.)

   Abstract Achieving net-zero CO 2 emissions has become the explicitgoal of many climate-energy policies around the world. Although many studies have assessed net-zero emissions pathways, the common features and tradeoffs of energy systems across global scenarios at the point of net-zero CO 2 emissions have not yet been evaluated. Here, we examine the energy systems of 177 net-zero scenarios and discuss their long-term technological and regional characteristics in the context of current energy policies. We find that, on average, renewable energy sources account for 60% of primary energy at net-zero (compared to ∼14% today), with slightly less than half of that renewable energy derived from biomass. Meanwhile, electricity makes up approximately half of final energy consumed (compared to ∼20% today), highlighting the extent to which solid, liquid, and gaseous fuels remain prevalent in the scenarios even when emissions reach net-zero. Finally, residual emissions and offsetting negative emissions are not evenly distributed across world regions, which may have important implications for negotiations on burden-sharing, human development, and equity. 

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5. We Must Stop Fossil Fuel Emissions to Protect Permafrost Ecosystems

   https://doi.org/10.3389/fenvs.2022.889428  

   Abbott, Benjamin W.; Brown, Michael; Carey, Joanna C.; Ernakovich, Jessica; Frederick, Jennifer M.; Guo, Laodong; Hugelius, Gustaf; Lee, Raymond M.; Loranty, Michael M.; Macdonald, Robie; et al (June 2022, Frontiers in Environmental Science)

   Climate change is an existential threat to the vast global permafrost domain. The diverse human cultures, ecological communities, and biogeochemical cycles of this tenth of the planet depend on the persistence of frozen conditions. The complexity, immensity, and remoteness of permafrost ecosystems make it difficult to grasp how quickly things are changing and what can be done about it. Here, we summarize terrestrial and marine changes in the permafrost domain with an eye toward global policy. While many questions remain, we know that continued fossil fuel burning is incompatible with the continued existence of the permafrost domain as we know it. If we fail to protect permafrost ecosystems, the consequences for human rights, biosphere integrity, and global climate will be severe. The policy implications are clear: the faster we reduce human emissions and draw down atmospheric CO 2 , the more of the permafrost domain we can save. Emissions reduction targets must be strengthened and accompanied by support for local peoples to protect intact ecological communities and natural carbon sinks within the permafrost domain. Some proposed geoengineering interventions such as solar shading, surface albedo modification, and vegetation manipulations are unproven and may exacerbate environmental injustice without providing lasting protection. Conversely, astounding advances in renewable energy have reopened viable pathways to halve human greenhouse gas emissions by 2030 and effectively stop them well before 2050. We call on leaders, corporations, researchers, and citizens everywhere to acknowledge the global importance of the permafrost domain and work towards climate restoration and empowerment of Indigenous and immigrant communities in these regions. 

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