| 1. |
- Abrams, Jesse F., et al.
(författare)
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Committed Global Warming Risks Triggering Multiple Climate Tipping Points
- 2023
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Ingår i: Earth's Future. - 2328-4277. ; 11:11
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Tidskriftsartikel (refereegranskat)abstract
- Many scenarios for limiting global warming to 1.5(degrees)C assume planetary-scale carbon dioxide removal sufficient to exceed anthropogenic emissions, resulting in radiative forcing falling and temperatures stabilizing. However, such removal technology may prove unfeasible for technical, environmental, political, or economic reasons, resulting in continuing greenhouse gas emissions from hard-to-mitigate sectors. This may lead to constant concentration scenarios, where net anthropogenic emissions remain non-zero but small, and are roughly balanced by natural carbon sinks. Such a situation would keep atmospheric radiative forcing roughly constant. Fixed radiative forcing creates an equilibrium committed warming, captured in the concept of equilibrium climate sensitivity. This scenario is rarely analyzed as a potential extension to transient climate scenarios. Here, we aim to understand the planetary response to such fixed concentration commitments, with an emphasis on assessing the resulting likelihood of exceeding temperature thresholds that trigger climate tipping points. We explore transients followed by respective equilibrium committed warming initiated under low to high emission scenarios. We find that the likelihood of crossing the 1.5(degrees)C threshold and the 2.0(degrees)C threshold is 83% and 55%, respectively, if today's radiative forcing is maintained until achieving equilibrium global warming. Under the scenario that best matches current national commitments (RCP4.5), we estimate that in the transient stage, two tipping points will be crossed. If radiative forcing is then held fixed after the year 2100, a further six tipping point thresholds are crossed. Achieving a trajectory similar to RCP2.6 requires reaching net-zero emissions rapidly, which would greatly reduce the likelihood of tipping events.
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| 2. |
- Ahlström, Anders, et al.
(författare)
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Widespread Unquantified Conversion of Old Boreal Forests to Plantations
- 2022
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Ingår i: Earth's Future. - : John Wiley & Sons. - 2328-4277. ; 10:11
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Tidskriftsartikel (refereegranskat)abstract
- Across the boreal biome, clear-cutting of old, previously non clear-cut forests with high naturalness followed by tree planting or seeding is a major land use change. However, how much previously uncut forest has been converted to plantations remains unquantified. We combine Swedish national databases on clear-cuts and forest inventories to show that at least 19% of all clear-cuts since 2003 have occurred in old forests that were most likely not previously cut and planted or seeded. Old forests have been cut and lost at a steady rate of ∼1.4% per year for the same period, and at this rate they will disappear by the 2070s. There is further evidence that this type of unreported forest conversion is occurring across much of the world's boreal forest.
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| 3. |
- Azar, Christian, 1969, et al.
(författare)
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DICE and the Carbon Budget for Ambitious Climate Targets
- 2021
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Ingår i: Earth's Future. - 2328-4277. ; 9:7
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The Dynamic Integrated Climate-Economy (DICE) model is one of the most influential Integrated Assessment Models available. Its founder Professor William Nordhaus was recently awarded Sveriges Riksbank Prize in Economic Sciences in Memory of Alfred Nobel due to his pioneering work on the economics of climate change. In a recent paper in American Economic Journal: Economic Policy, Nordhaus uses the model to conclude that a 2.5°C target is almost out of reach. In this paper, we update DICE 2016 R2 with state-of-the-art models of the carbon cycle, heat uptake into the oceans, and the role of non-CO2 forcers. We find that the allowable remaining carbon budget (over the period 2015–2100) to meet a 2.5°C target to be 2,360 GtCO2 whereas the estimate obtained using DICE 2016 R2 is about 460 GtCO2. Nordhaus's estimate of the remaining carbon budget for this target is hence five times lower than estimates made by our updated DICE. We also compare our results with estimates by the Intergovernmental Panel on Climate Change (IPCC), and find our results to be in line with the carbon budgets presented in IPCC SR 1.5. We explain the reasons behind the difference between our result and that of Nordhaus and propose that an updated climate module in DICE is warranted.
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| 4. |
- Borgomeo, E., et al.
(författare)
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Tackling the Trickle: Ensuring Sustainable Water Management in the Arab Region
- 2020
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Ingår i: Earth's Future. - 2328-4277. ; 8:5
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Forskningsöversikt (refereegranskat)abstract
- Water scarcity in the Arab region is intensifying due to population growth, economic development, and the impacts of climate change. It is manifested in groundwater depletion, freshwater ecosystem degradation, deteriorating water quality, low levels of water storage per capita, and added pressures on transboundary water resources. High-income Arab countries have sought to circumvent the ever-present challenges of water scarcity through agricultural imports (virtual water trade), desalination, and, increasingly, wastewater reuse. In this review article, we argue that the narrative of water scarcity and supply-side technological fixes masks more systemic issues that threaten sustainable water management, including underperforming water utilities, protracted armed conflict and displacement, agricultural policies aimed at self-sufficiency, evolving food consumption behaviors, the future of energy markets, and educational policy. Water management challenges, particularly on the demand side, and responses in the Arab region cannot be understood in isolation from these broader regional and international political and socioeconomic trends. Recognizing the complex and interdependent challenges of water management is the first step in reforming approaches and shifting to more sustainable development outcomes and stability in the Arab region and beyond. ©2020 The Authors.
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| 5. |
- Borja, Sonia, et al.
(författare)
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Global Wetting by Seasonal Surface Water Over the Last Decades
- 2020
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Ingår i: Earth's future. - : John Wiley and Sons Inc. - 2328-4277. ; 8:3
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Tidskriftsartikel (refereegranskat)abstract
- Surface water bodies and their changes in the landscape are critical for societies and ecosystems. However, the global change in surface water area over the last decades remains unclear, as recent studies using the same satellite data disagree on its direction. Here, we reanalyze reported maps of global water classification based on that data in order to estimate the changes in long-term average surface water area from the first (1985-2000) to the second (2001-2015) half of the recent 30-year period (1985-2015). We find a net gain in global surface water area by 100,454 km(2), primarily due to seasonal water gains (83,329 km(2)). Over the world, we identify net wetting in 187 and net drying in 57 regional hydrological catchments, with the greatest water gain in Sabarmati (India) and loss in Amu Darya (Uzbekistan). We provide an interactive map to further explore the highly heterogeneous local changes around the world.
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| 6. |
- Boysen, Lena R., et al.
(författare)
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The limits to global-warming mitigation by terrestrial carbon removal
- 2017
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Ingår i: Earth's Future. - 2328-4277. ; 5:5, s. 463-474
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Tidskriftsartikel (refereegranskat)abstract
- Massive near-term greenhouse gas emissions reduction is a precondition for staying well below 2 degrees C global warming as envisaged by the Paris Agreement. Furthermore, extensive terrestrial carbon dioxide removal (tCDR) through managed biomass growth and subsequent carbon capture and storage is required to avoid temperature overshoot in most pertinent scenarios. Here, we address two major issues: First, we calculate the extent of tCDR required to repair delayed or insufficient emissions reduction policies unable to prevent global mean temperature rise of 2.5 degrees C or even 4.5 degrees C above pre-industrial level. Our results show that those tCDR measures are unable to counteract business-as-usual emissions without eliminating virtually all natural ecosystems. Even if considerable (Representative Concentration Pathway 4.5 [RCP4.5]) emissions reductions are assumed, tCDR with 50% storage efficiency requires >1.1 Gha of the most productive agricultural areas or the elimination of > 50% of natural forests. In addition, > 100 MtN/yr fertilizers would be needed to remove the roughly 320 GtC foreseen in these scenarios. Such interventions would severely compromise food production and/or biosphere functioning. Second, we reanalyze the requirements for achieving the 160-190 GtC tCDR that would complement strong mitigation action (RCP2.6) in order to avoid 2 degrees C overshoot anytime. We find that a combination of high irrigation water input and/or more efficient conversion to stored carbon is necessary. In the face of severe trade-offs with society and the biosphere, we conclude that large-scale tCDR is not a viable alternative to aggressive emissions reduction. However, we argue that tCDR might serve as a valuable supporting actor for strong mitigation if sustainable schemes are established immediately. Plain Language Summary In 2015, parties agreed to limit global warming to well below 2 degrees C above pre-industrial levels. However, this requires not only massive near-term greenhouse gas emissions reductions but also the application of negative emission techniques that extract already emitted carbon dioxide from the atmosphere. Specifically, this could refer to the establishment of extensive plantations of fast-growing tree and grass species in combination with biomass conversion to carbon-saving products. Although such deployment is seen as promising, its carbon sequestration potentials and possible side-effects still remain to be studied in depth. In this study, we analyzed two feasibility aspects of such a negative emissions approach using biomass plantations and carbon utilization pathways. First, we show that biomass plantations with subsequent carbon immobilization are likely unable to repair insufficient emission reduction policies without compromising food production and biosphere functioning due to its space-consuming properties. Second, the requirements for a strong mitigation scenario staying below the 2 degrees C target would require a combination of high irrigation water input and development of highly effective carbon process chains. Although we find that this strategy of sequestering carbon is not a viable alternative to aggressive emission reductions, it could still support mitigation efforts if sustainably managed.
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| 7. |
- Brimicombe, Chloe, et al.
(författare)
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Borderless Heat Hazards With Bordered Impacts
- 2021
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Ingår i: Earth's Future. - : American Geophysical Union (AGU). - 2328-4277. ; 9:9
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Tidskriftsartikel (refereegranskat)abstract
- Heatwaves are increasing in frequency, duration, and intensity due to climate change. They are associated with high mortality rates and cross-sectional impacts including a reduction in crop yield and power outages. Here we demonstrate that there are large deficiencies in reporting of heatwave impacts in international disasters databases, international organization reports, and climate bulletins. We characterize the distribution of heat stress across the world focusing on August in the Northern Hemisphere, when notably heatwaves have taken place (i.e., 2003, 2010, and 2020) for the last 20 years using the ERA5-HEAT reanalysis of the Universal Thermal Comfort Index and establish heat stress has grown larger in extent, more so during a heatwave. Comparison of heat stress against the emergency events impacts database and climate reports reveals underreporting of heatwave-related impacts. This work suggests an internationally agreed protocol should be put in place for impact reporting by organizations and national government, facilitating implementation of preparedness measures, and early warning systems.
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| 8. |
- Bring, Arvid, et al.
(författare)
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Contrasting Hydroclimatic Model-Data Agreements Over the Nordic-Arctic Region
- 2019
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Ingår i: Earth's Future. - : John Wiley and Sons Inc. - 2328-4277. ; 7:12, s. 1270-1282
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Tidskriftsartikel (refereegranskat)abstract
- Rapid changes in high-latitude hydroclimate have important implications for human societies and environment. Previous studies of different regions have indicated better agreement between climate model results and observation data for the thermodynamic variable of surface air temperature (T) than for the water variables of precipitation (P), evapotranspiration (ET), and runoff (R). Here we compare climate model output with observations for 64 Nordic and Arctic hydrological basins of different sizes, and for the whole region combined. We find an unexpectedly high agreement between models and observations for R, about as high as the model-observation agreement for T and distinctly higher than that for P or ET. Model-observation agreement for R and T is also consistently higher on the whole-region scale than individual basin scales. In contrast, model-observation agreement for P and ET is overall lower, and for some error measures also lower for the whole region than for individual basins of various scales. Region-specific soil freeze-thaw bias of climate models can at least partly explain the low model-observation agreement for P and ET, while leaving modeled R relatively unaffected. Thereby, model projections for this region may be similarly reliable and directly useful for large-scale average conditions of R as of T.
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| 9. |
- Bring, Arvid, et al.
(författare)
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Implications of freshwater flux data from the CMIP5 multimodel output across a set of Northern Hemisphere drainage basins
- 2015
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Ingår i: EARTHS FUTURE. - 2328-4277. ; 3:6, s. 206-217
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Tidskriftsartikel (refereegranskat)abstract
- The multimodel ensemble of the Coupled Model Intercomparison Project, Phase 5 (CMIP5) synthesizes the latest research in global climate modeling. The freshwater system on land, particularly runoff, has so far been of relatively low priority in global climate models, despite the societal and ecosystem importance of freshwater changes, and the science and policy needs for such model output on drainage basin scales. Here we investigate the implications of CMIP5 multimodel ensemble output data for the freshwater system across a set of drainage basins in the Northern Hemisphere. Results of individual models vary widely, with even ensemble mean results differing greatly from observations and implying unrealistic long-term systematic changes in water storage and level within entire basins. The CMIP5 projections of basin-scale freshwater fluxes differ considerably more from observations and among models for the warm temperate study basins than for the Arctic and cold temperate study basins. In general, the results call for concerted research efforts and model developments for improving the understanding and modeling of the freshwater system and its change drivers. Specifically, more attention to basin-scale water flux analyses should be a priority for climate model development, and an important focus for relevant model-based advice for adaptation to climate change.
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| 10. |
- Bring, Arvid, et al.
(författare)
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Pan-Arctic river discharge : Prioritizing monitoring of future climate change hot spots
- 2017
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Ingår i: Earth's Future. - 2328-4277. ; 5:1, s. 72-92
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Tidskriftsartikel (refereegranskat)abstract
- The Arctic freshwater cycle is changing rapidly, which will require adequate monitoring of river flows to detect, observe, and understand changes and provide adaptation information. There has, however, been little detail about where the greatest flow changes are projected, and where monitoring therefore may need to be strengthened. In this study, we used a set of recent climate model runs and an advanced macro-scale hydrological model to analyze how flows across the continental pan-Arctic are projected to change and where the climate models agree on significant changes. We also developed a method to identify where monitoring stations should be placed to observe these significant changes, and compared this set of suggested locations with the existing network of monitoring stations. Overall, our results reinforce earlier indications of large increases in flow over much of the Arctic, but we also identify some areas where projections agree on significant changes but disagree on the sign of change. For monitoring, central and eastern Siberia, Alaska, and central Canada are hot spots for the highest changes. To take advantage of existing networks, a number of stations across central Canada and western and central Siberia could form a prioritized set. Further development of model representation of high-latitude hydrology would improve confidence in the areas we identify here. Nevertheless, ongoing observation programs may consider these suggested locations in efforts to improve monitoring of the rapidly changing Arctic freshwater cycle.
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