CICERO Research Archive (CICERO Senter for klimaforskning)
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Are Northern Hemisphere boreal forest fires more sensitive to future aerosol mitigation than to greenhouse gas–driven warming?
Full text linkConsiderable interest exists in understanding how climate change affects wildfire activity. Here, we use the Community Earth System Model version 2 to show that future anthropogenic aerosol mitigation yields larger increases in fire activity in the Northern Hemisphere boreal forests, relative to a base simulation that lacks climate policy and has large increases in greenhouse gases. The enhanced fire response is related to a deeper layer of summertime soil drying, consistent with increased downwelling surface shortwave radiation and enhanced surface evapotranspiration. In contrast, soil column drying is muted under increasing greenhouse gases due to plant physiological responses to increased carbon dioxide and by enhanced melting of soil ice at a depth that increases soil liquid water. Although considerable uncertainty remains in the representation of fire processes in models, our results suggest that boreal forest fires may be more sensitive to future aerosol mitigation than to greenhouse gas–driven warming.publishedVersio
Climate, nature, land-use change and human rights
Full text linkA transition to a low-carbon society is deeply needed, as a combined response to both the nature crisis and the climate crisis. To achieve a sustainable transition - built on inclusion, equity, and protection of nature and human rights - these challenges need to be handled in integration. This report is based on a review of existing research and knowledge. It focuses both on how climate change impacts societies, individuals, and current land use, and on a set of climate change mitigation solutions that potentially conflict with other land-use interests. The report highlights different ways in which the low-carbon transition leaves a clear footprint on, and under the ground. For example, through renewable energy production, privatised areas for forest carbon storage, and mineral extraction. A main goal of the report is to provide knowledge for public authorities and development-cooperation agencies on how to reduce negative effects of climate change, facilitate rapid transitions to low-carbon societies, while simultaneously avoiding policies and measures that may challenge human rights or have a negative impact on the attainment of other sustainability goals.publishedVersio
Unngå, flytte, forbedre: Kartlegging av bruk av UFF-rammeverket
Full text linkKlimautvalget 2050 pekte på at tiltaksrammeverket unngå, flytte og forbedre (UFF) er sentralt for utviklingen av politikk i omstillingen til et lavutslippssamfunn. CICERO har på oppdrag fra Klima- og miljødepartementet kartlagt bruken av rammeverket. Som bakgrunn beskrives utfordringene ved en klimapolitikk som hovedsakelig er basert på teknologiforbedringer, og hvordan aktivitetsreduksjon og aktivitetsendring kan bidra til å løse problemene. UFF-begrepet og hvordan dette brukes til kategorisering av utslippsreduserende tiltak forklares. Videre omtales hvordan UFF kan brukes i utforming av politikk og virkemidler for utslippsreduksjon. Det gis eksempler på tilnærminger som er basert på UFF eller elementer som er relevante for UFF. Til slutt uvrderes funnene og relevans for videre arbeid med UFF i norsk klimapolitikk
Calibrating Tropical Forest Coexistence in Ecosystem Demography Models Using Multi-Objective Optimization Through Population-Based Parallel Surrogate Search
Full text linkTropical forest diversity governs forest structures, compositions, and influences the ecosystem response to environmental changes. Better representation of forest diversity in ecosystem demography (ED) models within Earth system models is thus necessary to accurately capture and predict how tropical forests affect Earth system dynamics subject to climate changes. However, achieving forest coexistence in ED models is challenging due to their computational expense and limited understanding of the mechanisms governing forest functional diversity. This study applies the advanced Multi-Objective Population-based Parallel Local Surrogate-assisted search (MOPLS) optimization algorithm to simultaneously calibrate ecosystem fluxes and coexistence of two physiologically distinct tropical forest species in a size- and age-structured ED model with realistic representation of wood harvest. MOPLS exhibits satisfactory model performance, capturing hydrological and biogeochemical dynamics observed in Barro Colorado Island, Panama, and robustly achieving coexistence for the two representative forest species. This demonstrates its effectiveness in calibrating tropical forest coexistence. The optimal solution is applied to investigate the recovery trajectories of forest biomass after various intensities of clear-cut deforestation. We find that a 20% selective logging can take approximately 40 years for aboveground biomass to return to the initial level. This is due to the slow recovery rate of late successional trees, which only increases by 4% over the 40-year period. This study lays the foundation to calibrate coexistence in ED models. MOPLS can be an effective tool to help better represent tropical forest diversity in Earth system models and inform forest management practices.publishedVersio
No constraint on long-term tropical land carbon-climate feedback uncertainties from interannual variability
Full text linkUnraveling drivers of the interannual variability of tropical land carbon cycle is critical for understanding land carbon-climate feedbacks. Here we utilize two generations of factorial model experiments to show that interannual variability of tropical land carbon uptake under both present and future climate is consistently dominated by terrestrial water availability variations in Earth system models. The magnitude of this interannual sensitivity of tropical land carbon uptake to water availability variations under future climate shows a large spread across the latest 16 models (2.3 ± 1.5 PgC/yr/Tt H2O), which is constrained to 1.3 ± 0.8 PgC/yr/Tt H2O using observations and the emergent constraint methodology. However, the long-term tropical land carbon-climate feedback uncertainties in the latest models can no longer be directly constrained by interannual variability compared with previous models, given that additional important processes are not well reflected in interannual variability but could determine long-term land carbon storage. Our results highlight the limited implication of interannual variability for long-term tropical land carbon-climate feedbacks and help isolate remaining uncertainties with respect to water limitations on tropical land carbon sink in Earth system models.publishedVersio
Interactions between atmospheric composition and climate change - progress in understanding and future opportunities from AerChemMIP, PDRMIP, and RFMIP
Full text linkThe climate science community aims to improve our understanding of climate change due to anthropogenic influences on atmospheric composition and the Earth's surface. Yet not all climate interactions are fully understood, and uncertainty in climate model results persists, as assessed in the latest Intergovernmental Panel on Climate Change (IPCC) assessment report. We synthesize current challenges and emphasize opportunities for advancing our understanding of the interactions between atmospheric composition, air quality, and climate change, as well as for quantifying model diversity. Our perspective is based on expert views from three multi-model intercomparison projects (MIPs) – the Precipitation Driver Response MIP (PDRMIP), the Aerosol Chemistry MIP (AerChemMIP), and the Radiative Forcing MIP (RFMIP). While there are many shared interests and specializations across the MIPs, they have their own scientific foci and specific approaches. The partial overlap between the MIPs proved useful for advancing the understanding of the perturbation–response paradigm through multi-model ensembles of Earth system models of varying complexity. We discuss the challenges of gaining insights from Earth system models that face computational and process representation limits and provide guidance from our lessons learned. Promising ideas to overcome some long-standing challenges in the near future are kilometer-scale experiments to better simulate circulation-dependent processes where it is possible and machine learning approaches where they are needed, e.g., for faster and better subgrid-scale parameterizations and pattern recognition in big data. New model constraints can arise from augmented observational products that leverage multiple datasets with machine learning approaches. Future MIPs can develop smart experiment protocols that strive towards an optimal trade-off between the resolution, complexity, and number of simulations and their length and, thereby, help to advance the understanding of climate change and its impacts.publishedVersio
Observationally constrained analysis of sulfur cycle in the marine atmosphere with NASA ATom measurements and AeroCom model simulations
Full text linkThe atmospheric sulfur cycle plays a key role in air quality, climate, and ecosystems, such as pollution, radiative forcing, new particle formation, and acid rain. In this study, we compare the spatially and temporally resolved measurements from the NASA Atmospheric Tomography (ATom) mission with simulations from five AeroCom III models for four sulfur species (dimethyl sulfide (DMS), sulfur dioxide (SO2), particulate methanesulfonate (MSA), and particulate sulfate (SO4)). We focus on remote regions over the Pacific, Atlantic, and Southern oceans from near the surface to ∼ 12 km altitude range covering all four seasons. In general, the differences among model results can be greater than 1 order of magnitude. Comparing with observations, model-simulated SO2 is generally low, whereas SO4 is generally high. Simulated DMS concentrations near the sea surface exceed observed levels by a factor of 5 in most cases, suggesting potential overestimation of DMS emissions in all models. With GEOS model simulations of tagging emission from anthropogenic, biomass burning, volcanic, and oceanic sources, we find that anthropogenic emissions are the dominant source of sulfate aerosol (40 %–60 % of the total amount) in the ATom measurements at almost all altitudes, followed by volcanic emissions (18 %–32 %) and oceanic sources (16 %–32 %). Similar source contributions can also be derived at broad ocean basins and on monthly scales, indicating the representativeness of ATom measurements for global ocean. Our work presents the first assessment of AeroCom sulfur study using ATom measurements, providing directions for improving sulfate simulations, which remain the largest uncertainty in radiative forcing estimates in aerosol climate models.publishedVersio
Local food systems and community development: a symbiotic relation? A case study of three rural municipalities in Norway
Full text linkPolicy makers and researchers are increasingly emphasising the need for more diversified and localised food systems. This study investigates relations between local food systems and community development, revealing how local food is linked with identity, social relations, and community pride. We also address barriers and enablers for developing such links. We conducted an in-depth case study of local food systems in three Norwegian rural municipalities. Our results show how local food systems are linked to geographical location, and how they strengthen social relations by bringing actors in the food system closer together, fostering mutual responsibilities, pride, and a sense of belonging in local communities. We argue that local food is not only for somewhere, but from here, thus adding meaning and accountability to local food regimes. Local food exchange is motivated by mutual moral obligations and value-driven preferences, enabling reconnection between different actors in the food system. This is a central factor in local food’s contribution to community development and sustainability in food systems. Our findings furthermore demonstrate the importance of non-conventional exchange channels for local food distribution and exchange. Some findings nevertheless also show a need for efforts to make local food more affordable and available for most citizens. Together, the cases studied show that a holistic and context-dependent development of local food systems is necessary to provide pathways for communities to expand the role of local food as part of their community development and in order to enhance sustainability.publishedVersio
Healthier and sustainable food at work and beyond: A study of user and organisational practices in a Norwegian municipal canteen
Full text linkThis paper applies a practice-theoretical perspective to the study of user and organisational practices in a municipal canteen engaged in the promotion of healthy and sustainable food in Oslo. The city council defines sustainable and healthy food in terms of less meat, increased consumption of fruit, vegetables, pulses and seasonal food, and reduced food waste. It is estimated that this type of diet, together with cutting food waste, could result in a 20–25 % reduction in emissions from food consumption in Norwegian public institutions (van Oort et al., 2021). Additionally, dietary changes could, if spilled over, have a significant impact on total national emissions, since food is the third-largest emission category in Norwegian households (Steen-Olsen et al., 2016). The single action considered to have the greatest impact is reducing the consumption of meat and dairy. These products make up 80 % of total household food emissions in Norway, and red meat alone accounts for 35 % (van Oort et al., 2021). Reducing the consumption of red and processed meat is also a matter of public health, considering the positive relationship between processed red meat and some forms of cancerpublishedVersio
Asian Anthropogenic Aerosol Forcing Played a Key Role in the Multidecadal Increase in Australian Summer Monsoon Rainfall
No full textObservations show a significant increase in Australian summer monsoon (AUSM) rainfall since the mid-twentieth century. Yet the drivers of this trend, including the role of anthropogenic aerosols, remain uncertain. We addressed this knowledge gap using historical simulations from a suite of Coupled Model Intercomparison Project phase 6 (CMIP6) models, the CESM2 Large Ensemble, and idealized single-forcing simulations from the Precipitation Driver Response Model Intercomparison Project (PDRMIP). Our results suggest that Asian anthropogenic aerosol emissions played a key role in the observed increase in AUSM rainfall from 1930 to 2014, alongside the influence of internal variability. Sulfate aerosol emissions over Asia led to regional surface cooling and strengthening of the climatological Siberian high over eastern China, which altered the meridional temperature and sea level pressure gradients across the Indian Ocean. This caused an intensification and southward shift of the Australian monsoonal westerlies (and the local Hadley cell) and resulted in a precipitation increase over northern Australia. Conversely, the influence of increased greenhouse gas concentrations on AUSM rainfall was minimal due to the compensation between thermodynamically induced wettening and transient eddy-induced drying trends. At a larger scale, aerosol and greenhouse gas forcing played a key role in the climate response over the Indo-Pacific sector and eastern equatorial Pacific, respectively (coined the “tropical Pacific east–west divide”). These findings contribute to an improved understanding of the drivers of the multidecadal trend in AUSM rainfall and highlight the need to reduce uncertainties in future projections under different aerosol emission trajectories, which is particularly important for northern Australia’s agriculture.publishedVersio