Vassilis Daioglou

Meeting climate pledges will require gigaton-scale carbon dioxide removal (CDR). Enhanced rock weathering and biochar provide substantial opportunities beyond conventional land-based CDR, particularly in emerging economies.

Emission reductions required to meet the goals of the Paris Agreement have been extensively analyzed using integrated assessment modeling scenarios. However, the contribution of urban areas in aggregate, globally, by region and by city type, remains underexplored. Here, we develop a spatially explicit framework to downscale global emissions pathways to urban areas, differentiated by region and city type. Ambitious climate change mitigation could deliver 21 GtCO ₂ e of greenhouse gas emission reductions in urban areas by 2050 relative to a continuation of current policies and trends, primarily by transitioning away from fossil fuels in electricity and heat supply, deep decarbonization of industry, and mitigation in the transport and buildings sectors. Mitigation potential is concentrated in established and rapidly growing cities, reflecting their high current per-capita emission levels. Asian regions with high urbanization levels dominate global urban emissions and reduction potentials. The findings underscore the central role of cities in achieving global climate targets and highlight the importance of differentiated mitigation strategies across regions and city types.

The circular economy (CE) has been gaining traction as an effective means to decarbonize the European industrial sector by reducing material demand, especially in the material- and waste-intensive building construction segment. We compare the results of the integrated assessment model IMAGE and the industry sector simulation model FORECAST to analyse the potential contribution of a CE in building construction to industry decarbonization in the European Union until 2050. Both models consistently show that the CE can lead to a reduction of final energy demand between 19% and 47% depending on the model and the sub-sector considered. While both models emphasize the role of electrification and hydrogen for a low-carbon industry, they differ regarding the use of bio-based processes: IMAGE favours bio-based processes with carbon capture, where FORECAST prioritizes electrification and hydrogen. Such different routes have profound implications for the development of the energy supply sector. The high uncertainty surrounding industrial decarbonization scenarios highlights the importance of comparing vastly different models in context of alternative future possibilities and policymaking to improve the understanding of complex systems and prevent overreliance on partial views.

COP28 marked the first time that climate negotiations at the highest level, i.e. an official Conference of the Parties’ (COP) decision, indicated clear energy-related milestones for urgent climate action by adopting specific renewable energy and energy efficiency targets for 2030, and phasing down fossil fuels by 2050. These milestones are meant to serve as yardsticks to guide the path towards mitigating climate change and meeting the Paris Agreement (PA) goals. We assess the alignment of COP28 energy outcomes with the PA goals using several leading Integrated Assessment Models (IAMs) featuring high technological, sectoral, and regional detail. This detailed assessment could inform country- and technology-specific target design, which is becoming increasingly important in a fragmented world and under growing uncertainty regarding the prioritization of climate protection in governmental agendas. We additionally use and quantify novel transformation narratives such as “electrification” versus “combustion”, which could help develop a new generation of demand-side COP mitigation targets.

While material resources form a critical foundation for human society, their extraction, processing, and use are also a major driver of environmental pressures. Understanding future material consumption is therefore vital. This study presents a comprehensive assessment of future global bulk material consumption, covering metals (steel, aluminium, copper) and non-metallic minerals (cement, sand, limestone, clay). We use the Integrated Assessment Model IMAGE, combined with a stock-driven dynamic material flow analysis model, to provide full coverage of global and regional material flows. We project material consumption for a current-policy baseline, a climate policy scenario (1.5 °C) and two scenarios that add resource efficiency measures on top of the climate policies. Following current policies, by 2050 consumption of steel, aluminium, copper are expected to increase by 25%, 97%, and 84% respectively. Cement, sand, limestone and clay increase by 5%–23%. The climate policy scenario shows increases compared to baseline across all metals and cement, especially in the 2030/2040 period driven by required electricity and vehicle system transformations. The largest relative increase is projected for copper and aluminium, i.e. 22% and 9%, compared to current policies in 2050. Combining climate policies and resource efficiency, however, can reduce the use of non-metallic minerals below current levels and stabilize steel consumption, thus enabling growth in housing, transport, and decarbonized electricity systems. The most effective measures are related to efficiency and sufficiency measures (such as building with less material and reducing floor space). Although copper and aluminium consumption continue to rise across all scenarios, this can be significantly limited by resource efficiency measures. Overall, our findings highlight that resource efficiency policies are critical to managing the additional material consumption induced by climate policy.

While residential space cooling is essential to protect populations from heat-related health impacts, cooling access is expected to remain a considerable adaptation challenge throughout the 21st century, in part due to climate change. This study explores the evolution of the residential space cooling gap and energy demand for cooling until 2100, disaggregated by region, income group, and urban/rural populations, under different mitigation and adaptation assumptions. We find that 3.6 billion people worldwide are currently exposed to heat but lacking cooling access. While expected economic development allows many to gain access to cooling appliances in the future, this progress is offset by a growing population and exacerbated by climate change. 3.4 billion people are projected to remain in the cooling gap by 2100 in our Baseline scenario, mostly within Central and South America, Africa, and South Asia, due to high rates of heat exposure and expected income inequality preventing a large share of the population from fulfilling their cooling needs. Providing cooling access to all heat-exposed populations is projected to raise cooling energy demand by 152% in 2050 and 76% in 2100. However, this increase can be avoided when combined with both policies to limit global mean temperature change to well-below 2°C and an integrated approach incorporating energy-efficient cooling technologies, passive cooling, behavioural change, and improved urban planning. This study suggests that providing global access to residential space cooling can be achieved while meeting climate change policy goals, provided targeted policy action.

Biodiversity loss is expected to escalate with every increment of global warming. Simultaneously, land-intensive climate change mitigation strategies, such as afforestation and bioenergy, may further compound biodiversity loss. So far, the magnitude of these two drivers has not been compared in the context of temperature overshoot, meaning the temporary exceedance of a targeted global warming limit. By combining spatial data on climate refugia (areas sheltering biodiversity from climate change), bioenergy cropland, and forestation for multiple cost-effective scenarios with varying levels of climate action and overshoot, we illustrate how both warming and mitigation affect today’s climate refugia across five integrated assessment models. Decisive climate action, compatible with limiting warming to 1.5 °C, reduces the combined loss of today’s climate refugia due to warming and mitigation-related land-use change by more than 50% compared to current climate policies, outweighing potentially negative implications of mitigation at the global level by limiting the magnitude and duration of warming above 1.5 °C. We observe notable differences across regions and the considered model frameworks. Overshoot implications strongly depend on the underlying biodiversity recovery assumptions.

Reaching the goals of the Paris Agreement requires a rapid transformation of global energy systems. Yet energy supply and use exert multiple pressures on ecosystems, human health, and natural resources, raising questions about the broader environmental consequences of alternative decarbonization pathways and the resources they require. Here, we analyse 24 climate mitigation pathways from three Integrated Assessment Models using a life-cycle perspective. This enables a system-wide comparison of environmental impacts and resource requirements of global final energy provision from 2020 to 2100. We find that deep decarbonization delivers substantial co-benefits for human health and ecosystem quality, but does not systematically reduce pressures on land, water, or mineral resource extraction. For metals central to electrification, climate change mitigation ambition primarily reshapes the timing of extraction rather than cumulative volumes. Pathways achieving similar climate targets can impose markedly different environmental and resource pressures, shaping the feasibility and desirability of alternative transitions.

Currently, climate impacts are mostly absent in the analysis of process-based integrated assessment models (IAMs). This is becoming increasingly problematic given the fact that climate impacts are expected to influence both baseline developments as well as the capacity to mitigate and adapt in the future. This paper presents a set of scenarios made using the IAM IMAGE with climate change impacts on labour productivity and GDP, renewable energy supply, heating and cooling demand, food production, water availability, and biodiversity. The results show that these impacts can have significant impacts on existing projections of the economic, energy and land system that usually not included in IAM projections. In the current implementation, the aggregated economic impacts often are larger in size than sectoral feedbacks such as those on energy supply and demand, GHG emissions, and food consumption. Importantly, we find that there are several hotspot areas, including Western Africa, Indonesia and the Middle East, where multiple risks accumulate more than in other regions.