Climate Mitigation Scenarios Research Articles

Optimistic climate mitigation scenario halves projected range loss in a neotropical dolphin

Land aridification persists in vulnerable drylands under climate mitigation scenarios

Exploring water use pathways under deep decarbonization scenarios in Canada at subnational scales using GCAM-Canada.

Abstract To stabilize global mean temperature and stay below critical thresholds, deep emission reductions have to be complemented with carbon dioxide removal. A broad portfolio of options is necessary to enable sufficient potential and mitigate sustainability concerns. So far, integrated assessment models have almost exclusively considered options on land. In this study, we show that ocean liming can make a substantial contribution to achieving ambitious climate mitigation targets. Due to the expected time needed for scale-up, the deployment potential in the first half of the century is limited, such that ocean liming can hardly reduce peak temperature. However, in the second half of the century, substantial deployment may be economically competitive. In addition, the availability of ocean liming reduces the dependence on other carbon removal options, and specifically on bioenergy. This could reduce the pressure on land and improve the sustainability of ambitious climate mitigation scenarios. However, impacts on the ocean ecosystems are still poorly understood and need to be clarified before deployment. In light of the remaining uncertainties and global and regional limitations, we suggest to limit the maximum global deployment of ocean liming in integrated assessment models to 5 GtCO2/yr carbon uptake.

Given the need to reduce greenhouse gases emissions to meet the 2 °C or 1.5 °C target of the Paris Agreement, over 150 countries currently have net-zero targets. National inventories and projections of land-based emissions and mitigation strategies have not been well developed and remain limited compared to energy sectors. Here, we provide worldwide national land-based emission and mitigation scenario data with a detailed portfolio of mitigation options. This information contributes to filling the gap between integrated assessment model estimates and national greenhouse gas inventories for land-based emissions through estimation of carbon sequestration in managed forests. Second, these data can be used as a benchmark for countries developing national targets or strategies for agriculture, forestry, and other land use sectors as well as for reviewing national contributions in global assessments in a manner consistent with integrated assessment model estimates.

Climate change mitigation policies lower greenhouse gas emissions and generally reduce fine particulate matter (PM2.5) concentrations, hereby bringing health co-benefits. Yet, the spatial and distributional air quality co-benefits in Europe of such policies are not fully understood. Here, We quantify premature mortality from air pollution in 1366 regions of Europe for different scenarios obtained from the Coupled Model Intercomparison Project Phase 6. We model PM2.5 concentrations at high spatial resolution and then combine it with population data and regional age structure and total mortality, to calculate attributable deaths. We find that the share of the European population meeting WHO (World Health Organization) guideline value for PM2.5 could exceed 90% by 2100 under the most ambitious scenario, while less than 10% under the least ambitious one. Corresponding premature deaths in Europe would total 67,000 (95% CI: 13,000–141,000) per year by the end of the century compared to 282,000 (95% CI: 202,000–364,000).

Tracing sources and assessing intervention effectiveness are crucial for controlling atmospheric particulate matter (PM) pollution. Isotopic techniques enable precise top-down tracing, but the absence of long-term, global-scale multi-compound isotopic data limits comprehensive analysis. Here, we establish a blockchain-based isotopic database, compiling 34,815 isotopic fingerprints of global PM and its emissions from 1,890 pollution events across 66 countries. This allows retrospective analysis and predictions, revealing that PM sources are distinct, dynamically changing over time, and often asynchronous with interventions. Additionally, we estimate source contributions to PM2.5 and its compounds, highlighting the increasing impact of biomass burning. Furthermore, projections indicate that by 2100, PM levels may decline to 5.38 ± 0.16 μg/m³ in the Americas and 13.9 ± 1.82 μg/m³ in Asia under climate mitigation scenarios but will still exceed WHO guidelines without further controls on natural emissions. Guiding future interventions with isotopic big data is essential for addressing air pollution challenges.

Health is at the forefront of clean air and climate action. However, most existing studies of health impacts were based on additive single-exposure effects, which often oversimplify the relationships between atmospheric components and health outcomes. This review examines various atmospheric components' common sources and differential health effects, including greenhouse gases and major air pollutants such as fine particulate matter (PM2.5). It emphasizes the need for a comparative assessment of health impacts across various atmospheric components. We further highlight black carbon as an illustrative example, given its higher toxicity compared with other major PM2.5 components. By integrating the best available findings on the differential effects of particulate matter components with multiple gridded estimates of air pollution concentrations and population data, we conducted a risk assessment to quantify the health benefits of particulate matter reductions associated with China's clean air actions (2013-2020) and future climate mitigation scenarios (2020-2060). Our assessments indicate that, in regions or during periods where black carbon accounts for a higher proportion of exposure reduction relative to other PM2.5 components, reducing per-unit concentrations of PM2.5 can prevent more premature deaths. We propose a conceptual framework for a health-oriented strategy to enhance the effectiveness of clean air and climate initiatives.

Biosphere reserves serve as critical areas for balancing conservation with sustainable development. This study investigates land-use and land-cover changes in the North Vidzeme Biosphere Reserve (Latvia) from 1990 to 2018, employing scenario-based modeling to project future trends. Historical analyses reveal overall stability but highlight cyclical agricultural intensification and extensification, forest decline, and expansions in transitional woodland-shrub. Four scenarios—business-as-usual, sustainable development, climate adaptation and mitigation, and conservation-oriented—were evaluated for their ecological and socio-economic implications. Business-as-usual scenario continues historical trends of moderate urban growth and agricultural intensification, risking limited restoration gains. In contrast, sustainable development and climate adaptation and mitigation scenarios emphasize reforestation, biodiversity improvement, and climate resilience, aligning with the European Union 2030 Biodiversity Strategy. Conservation-oriented scenario prioritizes stabilization and minimizing anthropogenic pressures yet lacks proactive restoration measures. Statistical tests confirm that socio-economic factors, zoning, and landscape richness significantly drive land-use and land-cover changes, with most changes adhering to the North Vidzeme Biosphere Reserve regulations. However, certain non-compliant changes, such as forest-to-agriculture conversions, highlight the need for stronger enforcement. While ecological impacts such as land-use transitions, biodiversity shifts, and conservation compliance were considered, socio-economic implications were primarily discussed in relation to zoning and land-use trends rather than through a standalone analysis. These scenario-based insights offer valuable guidance for adaptive land management in protected areas.

Abstract Technical carbon dioxide removal through bioenergy with carbon capture or direct air capture (DAC) plays a role in virtually all climate mitigation scenarios. Both of these technologies rely on the use of chemical solvents or sorbents in order to capture CO2. Lately, concerns have surfaced about the cost and energy implications of producing solvents and sorbents at scale. Here, we show that the production of chemical sorbents could have significant implications on system cost, energy use and material use depending on how much they are consumed. Among the three chemical sorbents investigated, namely monoethanolamine (MEA) for post-combustion carbon capture, potassium hydroxide (KOH) for liquid DAC and polyethylenimine-silica (PEI) for solid sorbent DAC, we found that solid sorbent production for DAC represents the highest uncertainties for the system. At the high range of solid sorbent consumption, total energy system cost increased by up to 6.5%, while effects for other options were small to negligible. Scale-up of material production capacities was also substantial for MEA and PEI. While PEI has the advantage of requiring a lower sorbent regeneration temperature than KOH, the potential production cost may outweigh these benefits. There is thus a trade-off between the advantages and the additional cost uncertainty regarding sorbents. Implications of sorbent consumption for carbon capture technologies should be considered more thoroughly in scenarios relying on solid sorbent DAC.

Most climate projections represent volcanic eruptions as a prescribed constant forcing based on a historical average, which prevents a full quantification of uncertainties in climate projections. Here we show that the contribution of volcanic forcing uncertainty to the overall uncertainty in global mean surface air temperature projections reaches up to 49% in 2029, and is comparable or greater than that from internal variability throughout the 21st century. Furthermore, compared to a constant volcanic forcing, employing a stochastic volcanic forcing reduces the probability of exceeding 1.5 °C warming above pre-industrial level by at least 5% for high climate mitigation scenario, and enhances the probability of negative decadal temperature trends by up to 8%. Intermediate to high climate mitigation scenarios are particularly sensitive to the choice of future volcanic forcing implementation. We recommend the use of either a stochastic approach or prescribed constant forcing levels that sample volcanic uncertainty in future climate simulations.

Mediterranean coastal wetlands account for important biodiversity and ecosystem services. But climate-change induced sea-level rise poses a critical risk to their survival. Here, we assess these risks for Mediterranean coastal marshes, one key type of Mediterranean coastal wetlands, and identify main drivers for future coastal marsh change for the Mediterranean and comparable coastlines. We apply an integrated modelling approach that accounts for future sea-level rise, sediment accretion, coastal management and marsh inland migration processes. Depending on climate mitigation scenarios, widespread coastal marsh loss is projected, ranging from 8% to 92% of current extents. For Egypt, France, and Algeria, we predict (near) total loss of coastal marshes by 2100 for current coastal management and sediment supply scenarios. Overall, losses could at least be halved if additional inland migration space were created, e.g. through passive or active habitat restoration. Bold climate mitigation and local adaptation are needed to preserve existing coastal marshes.

Six of nine planetary boundaries are currently transgressed, many related to human land use. Conversion of sizeable land areas to biomass plantations for Bioenergy with Carbon Capture and Storage (BECCS) – often assumed in climate mitigation scenarios to meet the Paris Agreement – may exert additional pressure on terrestrial planetary boundaries. Using spatially-explicit, process-based global biogeochemical modelling, we systematically compute feedstock production potentials for BECCS under individual and joint constraints of the planetary boundaries for nitrogen flows, freshwater change, land system change and biosphere integrity (including protection of remaining forests), while reserving current agricultural areas for meeting the growing global demand for food, fodder and fibre. We find that the constrained BECCS potential from dedicated Miscanthus plantations is close to zero (0.1 gigatons of carbon dioxide equivalents per year under mid-century climate for Representative Concentration Pathway (RCP) 4.5). The planetary boundary for biosphere integrity has the largest individual effect, highlighting a particularly severe trade-off between climate change mitigation with BECCS and ecosystem preservation. Ultimately however, the overall limitation results from the joint effect of all four planetary boundaries, emphasizing the importance of a holistic consideration of Earth system stability in the context of climate change mitigation.

Carbon Capture and Storage (CCS), along with Bioenergy with Carbon Capture and Storage (BECCS), feature heavily in climate mitigation scenarios. Nevertheless, the technologies remain controversial within the broader mitigation discourse, in part for their potential to excuse delay in more ambitious emissions reductions in the short term. Sweden has included BECCS and CCS as proposed “supplementary measures” to enable the country to meet its ambitious target of achieving net negative emissions by 2045. Hajer’s Argumentative Approach to Discourse Analysis is applied to Swedish parliamentary speeches, motions, and written questions and answers, to uncover the storylines and attendant assumptions constituting Swedish policy deliberation regarding CCS and BECCS. This study finds that by problematizing climate change as an issue of emissions, actors position CCS and BECCS within a dominant neoliberal discourse and characterize them as tools to facilitate a green transition centering on industrial and economic competitiveness. This discourse lacks detail, and risks delay by oversimplifying the needs and requirements for CCS and BECCS deployment. Meanwhile, a CCS-critical discourse acknowledges the need for negative emissions but challenges storylines portraying the technology as inexpensive or easy to deploy rapidly. If pursued, this discourse could serve to sharpen the debate about the technologies and bring planning in line with aspirations, helping to avert risks of delay.

Abstract Carbon dioxide removal (CDR) is crucial to achieve the Paris Agreement’s 1.5 °C–2 °C goals. However, climate mitigation scenarios have primarily focused on bioenergy with carbon capture and storage (BECCS), afforestation/reforestation, and recently direct air carbon capture and storage (DACCS). This narrow focus exposes future climate change mitigation strategies to technological, institutional, and ecological pressures by overlooking the variety of existing CDR options, each with distinct characteristics—including, but not limited to, mitigation potential, cost, co-benefits, and adverse side-effects. This study expands the scope by evaluating CDR portfolios, consisting of any single CDR approach—BECCS, afforestation/reforestation, DACCS, biochar, and enhanced weathering—or a combination of them. We analyse the value of deploying these CDR portfolios to meet 1.5 °C goals, as well as their global and regional implications for land, energy, and policy costs. We find that diversifying CDR approaches is the most cost-effective net-zero strategy. Without the overreliance on any single approach, land and energy impacts are reduced and redistributed. A diversified CDR portfolio thus exhibits lower negative side-effects, but still poses challenges related to environmental impacts, logistics or accountability. We also investigate a CDR portfolio designed to support more scalable and sustainable climate mitigation strategies, and identify trade-offs between reduced economic benefits and lower environmental impacts. Rather than a one-size-fits-all scaling down, the CDR portfolio undergoes strategic realignment, with regional customization based on techno-economic factors and bio-geophysical characteristics. Moreover, we highlight the importance of nature-based removals, especially in Brazil, Latin America, and Africa, where potentials for avoided deforestation are the greatest, emphasizing their substantial benefits, not only for carbon sequestration, but also for preserving planetary well-being and human health. Finally, this study reveals that incentivizing timely and large-scale CDR deployment by policy and financial incentives could reduce the risk of deterring climate change mitigation, notably by minimizing carbon prices.

Agricultural production costs represent less than half of total food prices for higher-income countries and will likely further decrease globally. Added-value components such as transport, processing, marketing and catering show increasing importance in food value chains, especially as countries undergo a nutrition transition towards more complex and industrial food systems. Here, using a combined statistical and process-based modelling framework, we derive and project the value-added component of food prices for 136 countries and 11 different food groups, for food-at-home and food-away-from-home. We identify the declining but differentiated producer share in consumer food prices across food products, and provide scenarios of future consumer prices under a business-as-usual as well as climate mitigation scenarios. Food price increases from policies targeting agricultural producers, such as greenhouse gas taxes, are not as stark when transmitted to consumers owing to higher value added in higher-income countries, while a pronounced effect remains in lower-income countries, even in coming decades.

Corrigendum to “Large inequalities in climate mitigation scenarios are not supported by theories of distributive justice” [Energy Res. Soc. Sci. 118 (2024) 103813

Abstract Different human activities and associated emissions of CO2 and non-CO2 radiative forcing agents and feedbacks determine the final state of Earth’s climate. To understand and explain contributions to global temperature changes, many emission-based metrics have been employed, such as CO2-equivalent or -forcing equivalent. None of these metrics, however, include dynamic responses from Earth system feedbacks in terms of carbon and heat redistribution, known to play an increasingly important role in ambitious mitigation scenarios. Here we introduce a framework that allows for an assessment of such feedbacks in addition to CO2, non-CO2 anthropogenic forcing and natural external variability contributions. FROT (Framework for Radiative cOntributions to Temperature response) allows for an assessment of components of direct radiative impact to the system (climate forcing), as well as Earth system feedbacks concerning heat and carbon. The framework is versatile in terms of applications and allows for exploring individual components contributions to, for example, temperature stabilisation simulations, or comparisons in different models and scenarios, as it can reasonably explain their simulated temperature variability. Here, we apply FROT to both an intermediate complexity and a fully coupled Earth system model, as we simulate highly ambitious mitigation scenarios. Comparing temperature stabilisation scenarios, we can show that both net-zero CO2 emissions and small amounts of positive CO2 emissions could lead to a stable global temperature trajectory. Our assessment reveals that the effects of non-CO2 climate forcings, especially the development of sulphate aerosols in the atmosphere, and the dynamics of the carbon cycle, play a pivotal role in the final level of warming and in enabling a temperature stabilisation. Under highly ambitious climate mitigation scenarios it becomes crucial to include Earth system feedbacks, specifically ocean heat uptake, to understand interannual to decadal temperature development, since previously secondary processes now become increasingly dominant. Our framework offers the opportunity to do so.

Our understanding of drought evolution and land-atmosphere interactions under climate mitigation scenarios remains limited. Here, we analyzed future drought under net-zero and net-negative emission scenarios using the Community Earth System Model version 2, particularly focusing on three atmospheric CO2 states: linearly increases, decreases, and a return to the initial state. Interestingly, results revealed that net-zero emissions are more effective for drought mitigation than net-negative targets. Drying trends and drought characteristics — such as the duration, frequency, intensity, and area expansion are prominently increased under net-negative emissions due to higher potential evapotranspiration (PET). This is because the soil moisture and temperature couplings are stronger over drought regions and years, especially under net-negative forcing, with notable impacts in Central Africa and South Asia. Nevertheless, both target scenarios offer regional benefits, such as weakened dryness. This suggests that mitigating CO2 alone may not be sufficient to manage future droughts, highlighting the need for advanced water management strategies.

The 2023 Canadian forest fires have been extreme in scale and intensity with more than seven times the average annual area burned compared to the previous four decades1. Here, we quantify the carbon emissions from these fires from May to September 2023 on the basis of inverse modelling of satellite carbon monoxide observations. We find that the magnitude of the carbon emissions is 647 TgC (570–727 TgC), comparable to the annual fossil fuel emissions of large nations, with only India, China and the USA releasing more carbon per year2. We find that widespread hot–dry weather was a principal driver of fire spread, with 2023 being the warmest and driest year since at least 19803. Although temperatures were extreme relative to the historical record, climate projections indicate that these temperatures are likely to be typical during the 2050s, even under a moderate climate mitigation scenario (shared socioeconomic pathway, SSP 2–4.5)4. Such conditions are likely to drive increased fire activity and suppress carbon uptake by Canadian forests, adding to concerns about the long-term durability of these forests as a carbon sink5–8.