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- ItemGlobal cotton production under climate change – Implications for yield and water consumption(Munich : EGU, 2021) Jans, Yvonne; von Bloh, Werner; Schaphoff, Sibyll; Müller, ChristophBeing an extensively produced natural fiber on earth, cotton is of importance for economies. Although the plant is broadly adapted to varying environments, the growth of and irrigation water demand on cotton may be challenged by future climate change. To study the impacts of climate change on cotton productivity in different regions across the world and the irrigation water requirements related to it, we use the process-based, spatially detailed biosphere and hydrology model LPJmL (Lund Potsdam Jena managed land). We find our modeled cotton yield levels in good agreement with reported values and simulated water consumption of cotton production similar to published estimates. Following the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) protocol, we employ an ensemble of five general circulation models under four representative concentration pathways (RCPs) for the 2011 2099 period to simulate future cotton yields. We find that irrigated cotton production does not suffer from climate change if CO2 effects are considered, whereas rainfed production is more sensitive to varying climate conditions. Considering the overall effect of a changing climate and CO2 fertilization, cotton production on current cropland steadily increases for most of the RCPs. Starting from _ 65 million tonnes in 2010, cotton production for RCP4.5 and RCP6.0 equates to 83 and 92 million tonnes at the end of the century, respectively. Under RCP8.5, simulated global cotton production rises by more than 50% by 2099. Taking only climate change into account, projected cotton production considerably shrinks in most scenarios, by up to one-Third or 43 million tonnes under RCP8.5. The simulation of future virtual water content (VWC) of cotton grown under elevated CO2 results for all scenarios in less VWC compared to ambient CO2 conditions. Under RCP6.0 and RCP8.5, VWC is notably decreased by more than 2000m3 t1 in areas where cotton is produced under purely rainfed conditions. By 2040, the average global VWC for cotton declines in all scenarios from currently 3300 to 3000m3 t1, and reduction continues by up to 30% in 2100 under RCP8.5. While the VWC decreases by the CO2 effect, elevated temperature acts in the opposite direction. Ignoring beneficial CO2 effects, global VWC of cotton would increase for all RCPs except RCP2.6, reaching more than 5000m3 t1 by the end of the simulation period under RCP8.5. Given the economic relevance of cotton production, climate change poses an additional stress and deserves special attention. Changes in VWC and water demands for cotton production are of special importance, as cotton production is known for its intense water consumption. The implications of climate impacts on cotton production on the one hand and the impact of cotton production on water resources on the other hand illustrate the need to assess how future climate change may affect cotton production and its resource requirements. Our results should be regarded as optimistic, because of high uncertainty with respect to CO2 fertilization and the lack of implementing processes of boll abscission under heat stress. Still, the inclusion of cotton in LPJmL allows for various large-scale studies to assess impacts of climate change on hydrological factors and the implications for agricultural production and carbon sequestration. © 2021 BMJ Publishing Group. All rights reserved.
- ItemPlanned relocation in Peru: advancing from well-meant legislation to good practice(New York : Springer, 2021) Bergmann, JonasAlong Peru’s rainforest rivers, rising flood extremes are increasingly exceeding coping capacities of vulnerable households. Peru has detailed legislation that embraces planned relocation as a strategic solution to such situations and various relocation projects are underway across the country. This research brief analyzes well-being consequences for two communities requesting relocation, using qualitative data collected from experts and 30 affected people. Initial results emphasize that weak governance, poverty, third-party involvement, and community action have influenced relocation outcomes. Delays and fragmented implementation have threatened people’s well-being. One community, waiting for land to relocate since 2015, has suffered from continued hazard exposure, deteriorated material conditions, and reduced subjective well-being. The second community achieved relocation only after a decade in detrimental limbo. Although livelihood challenges persist, its inhabitants now benefit from better market access and decreased exposure, leading to higher subjective well-being. With rising needs for relocation worldwide, the cases highlight that detailed legislation is not sufficient to safeguard people’s well-being. Advancing from well-meant legislation to good practice requires adequate institutional capacity, effective mechanisms for oversight and accountability, better engagement of third parties, and dedicated efforts to strengthen community agency.
- ItemThe social cost of carbon and inequality: When local redistribution shapes global carbon prices(Amsterdam [u.a.] : Elsevier, 2021) Kornek, Ulrike; Klenert, David; Edenhofer, Ottmar; Fleurbaey, MarcThe social cost of carbon is a central metric for optimal carbon prices. Previous literature shows that inequality significantly influences the social cost of carbon, but mostly omits heterogeneity below the national level. We present an optimal taxation model of the social cost of carbon that accounts for inequality between and within countries. We find that climate and distributional policy can generally not be separated. If only one country does not compensate low-income households for disproportionate damages, the social cost of carbon tends to increase globally. Optimal carbon prices remain roughly unchanged if national redistribution leaves inequality between households unaffected by climate change and if the utility of households is approximately logarithmic in consumption.
- ItemAll options, not silver bullets, needed to limit global warming to 1.5 °C: a scenario appraisal(Bristol : IOP Publ., 2021-5-25) Warszawski, Lila; Kriegler, Elmar; Lenton, Timothy M.; Gaffney, Owen; Jacob, Daniela; Klingenfeld, Daniel; Koide, Ryu; Máñez Costa, María; Messner, Dirk; Nakicenovic, Nebojsa; Schellnhuber, Hans Joachim; Schlosser, Peter; Takeuchi, Kazuhiko; Van Der Leeuw, Sander; Whiteman, Gail; Rockström, JohanClimate science provides strong evidence of the necessity of limiting global warming to 1.5 °C, in line with the Paris Climate Agreement. The IPCC 1.5 °C special report (SR1.5) presents 414 emissions scenarios modelled for the report, of which around 50 are classified as '1.5 °C scenarios', with no or low temperature overshoot. These emission scenarios differ in their reliance on individual mitigation levers, including reduction of global energy demand, decarbonisation of energy production, development of land-management systems, and the pace and scale of deploying carbon dioxide removal (CDR) technologies. The reliance of 1.5 °C scenarios on these levers needs to be critically assessed in light of the potentials of the relevant technologies and roll-out plans. We use a set of five parameters to bundle and characterise the mitigation levers employed in the SR1.5 1.5 °C scenarios. For each of these levers, we draw on the literature to define 'medium' and 'high' upper bounds that delineate between their 'reasonable', 'challenging' and 'speculative' use by mid century. We do not find any 1.5 °C scenarios that stay within all medium upper bounds on the five mitigation levers. Scenarios most frequently 'over use' CDR with geological storage as a mitigation lever, whilst reductions of energy demand and carbon intensity of energy production are 'over used' less frequently. If we allow mitigation levers to be employed up to our high upper bounds, we are left with 22 of the SR1.5 1.5 °C scenarios with no or low overshoot. The scenarios that fulfil these criteria are characterised by greater coverage of the available mitigation levers than those scenarios that exceed at least one of the high upper bounds. When excluding the two scenarios that exceed the SR1.5 carbon budget for limiting global warming to 1.5 °C, this subset of 1.5 °C scenarios shows a range of 15–22 Gt CO2 (16–22 Gt CO2 interquartile range) for emissions in 2030. For the year of reaching net zero CO2 emissions the range is 2039–2061 (2049–2057 interquartile range).
- ItemClimate change reduces winter overland travel across the Pan-Arctic even under low-end global warming scenarios(Bristol : IOP Publ., 2021-2-10) Gädeke, Anne; Langer, Moritz; Boike, Julia; Burke, Eleanor J.; Chang, Jinfeng; Head, Melissa; Reyer, Christopher P.O.; Schaphoff, Sibyll; Thiery, Wim; Thonicke, KirstenAmplified climate warming has led to permafrost degradation and a shortening of the winter season, both impacting cost-effective overland travel across the Arctic. Here we use, for the first time, four state-of-the-art Land Surface Models that explicitly consider ground freezing states, forced by a subset of bias-adjusted CMIP5 General Circulation Models to estimate the impact of different global warming scenarios (RCP2.6, 6.0, 8.5) on two modes of winter travel: overland travel days (OTDs) and ice road construction days (IRCDs). We show that OTDs decrease by on average −13% in the near future (2021–2050) and between −15% (RCP2.6) and −40% (RCP8.5) in the far future (2070–2099) compared to the reference period (1971–2000) when 173 d yr−1 are simulated across the Pan-Arctic. Regionally, we identified Eastern Siberia (Sakha (Yakutia), Khabarovsk Krai, Magadan Oblast) to be most resilient to climate change, while Alaska (USA), the Northwestern Russian regions (Yamalo, Arkhangelsk Oblast, Nenets, Komi, Khanty-Mansiy), Northern Europe and Chukotka are highly vulnerable. The change in OTDs is most pronounced during the shoulder season, particularly in autumn. The IRCDs reduce on average twice as much as the OTDs under all climate scenarios resulting in shorter operational duration. The results of the low-end global warming scenario (RCP2.6) emphasize that stringent climate mitigation policies have the potential to reduce the impact of climate change on winter mobility in the second half of the 21st century. Nevertheless, even under RCP2.6, our results suggest substantially reduced winter overland travel implying a severe threat to livelihoods of remote communities and increasing costs for resource exploration and transport across the Arctic.
- ItemFrom Paris to Makkah: heat stress risks for Muslim pilgrims at 1.5 °C and 2 °C(Bristol : IOP Publ., 2021-2-9) Saeed, Fahad; Schleussner, Carl-Friedrich; Almazroui, MansourThe pilgrimages of Muslims to Makkah (Hajj and Umrah) is one of the largest religious gatherings in the world which draws millions of people from around 180 countries each year. Heat stress during summer has led to health impacts including morbidity and mortality in the past, which is likely to worsen due to global warming. Here we investigate the impacts of increasing heat stress during the peak summer months over Makkah at present levels of warming as well as under Paris Agreement's targets of 1.5 °C and 2 °C global mean temperature increase above pre-industrial levels. This is achieved by using multi member ensemble projections from the half a degree additional warming, prognosis and projected impacts project. We find a substantial increase in the exceedance probabilities of dangerous thresholds (wet-bulb temperature >24.6 °C) in 1.5 °C and 2 °C warmer worlds over the summer months. For the 3 hottest months, August, September and October, even thresholds of extremely dangerous (wet-bulb temperature >29.1 °C) health risks may be surpassed. An increase in exceedance probability of dangerous threshold is projected by two and three times in 1.5 °C and 2 °C warmer worlds respectively for May as compared to the reference climate. September shows the highest increase in the exceedance probability of extremely dangerous threshold which is increased to 4 and 13 times in 1.5 °C and 2 °C warmer worlds respectively. Based on the indicators of hazard, exposure and vulnerability, we carried out probabilistic risk analysis of life-threatening heat stroke over Makkah. A ten time increase in the heat stroke risk at higher wet-bulb temperatures for each month is projected in 2 °C warmer world. If warming was limited to 1.5 °C world, the risk would only increase by about five times, or half the risk of 2 °C. Our results indicate that substantial heat related risks during Hajj and Umrah happening over peak summer months, as it is the case for Hajj during this decade, will require substantial adaptation measures and would negatively affect the performance of the rite. Stringent mitigation actions to keep the global temperature to 1.5 °C can reduce the risks of heat related illnesses and thereby reduce the non-economic loss and damage related to one of the central pillars of a world religion.
- ItemAvenues of archetype analysis: roots, achievements, and next steps in sustainability research(Wolfville, Nova Scotia : Resilience Alliance, 2021) Eisenack, Klaus; Oberlack, Christoph; Sietz, DianaRecent years have seen a proliferation of studies that use archetype analysis to better understand and to foster transitions toward sustainability. This growing literature reveals a common methodological ground, as well as a variety of perspectives and practices. In this paper, we provide an historical overview of the roots of archetype analysis from ancient philosophy to recent sustainability science. We thereby derive core features of the archetype approach, which we frame by eight propositions. We then introduce the Special Feature, “Archetype Analysis in Sustainability Research,” which offers a consolidated understanding of the approach, a portfolio of methods, and quality criteria, as well as cutting-edge applications. By reflecting on the Special Feature’s empirical and methodological contributions, we hope that the showcased advances, exemplary applications, and conceptual clarifications will help to design future research that contributes to collaborative learning on archetypical patterns leading toward sustainability. The paper concludes with an outlook highlighting central directions for the next wave of archetype analyses.
- ItemExploring uncertainties in global crop yield projections in a large ensemble of crop models and CMIP5 and CMIP6 climate scenarios(Bristol : IOP Publ., 2021) Mueller, Christoph; Franke, James; Jaegermeyr, Jonas; Ruane, Alex C.; Elliott, Joshua; Moyer, Elisabeth; Heinke, Jens; Falloon, Pete D.; Folberth, Christian; Francois, LouisConcerns over climate change are motivated in large part because of their impact on human society. Assessing the effect of that uncertainty on specific potential impacts is demanding, since it requires a systematic survey over both climate and impacts models. We provide a comprehensive evaluation of uncertainty in projected crop yields for maize, spring and winter wheat, rice, and soybean, using a suite of nine crop models and up to 45 CMIP5 and 34 CMIP6 climate projections for three different forcing scenarios. To make this task computationally tractable, we use a new set of statistical crop model emulators. We find that climate and crop models contribute about equally to overall uncertainty. While the ranges of yield uncertainties under CMIP5 and CMIP6 projections are similar, median impact in aggregate total caloric production is typically more negative for the CMIP6 projections (+1% to −19%) than for CMIP5 (+5% to −13%). In the first half of the 21st century and for individual crops is the spread across crop models typically wider than that across climate models, but we find distinct differences between crops: globally, wheat and maize uncertainties are dominated by the crop models, but soybean and rice are more sensitive to the climate projections. Climate models with very similar global mean warming can lead to very different aggregate impacts so that climate model uncertainties remain a significant contributor to agricultural impacts uncertainty. These results show the utility of large-ensemble methods that allow comprehensively evaluating factors affecting crop yields or other impacts under climate change. The crop model ensemble used here is unbalanced and pulls the assumption that all projections are equally plausible into question. Better methods for consistent model testing, also at the level of individual processes, will have to be developed and applied by the crop modeling community.
- ItemImproving the evidence base: A methodological review of the quantitative climate migration literature(Amsterdam [u.a.] : Elsevier, 2021) Hoffmann, Roman; Šedová, Barbora; Vinke, KiraThe question whether and how climatic factors influence human migration has gained both academic and public interest in the past years. Based on two meta-analyses, this paper systematically reviews the quantitative empirical literature on climate-related migration from a methodological perspective. In total, information from 127 original micro- and macro-level studies is analyzed to assess how different concepts, research designs, and analytical methods shape our understanding of climate migration. We provide an overview of common methodological approaches and present evidence on their potential implications for the estimation of climatic impacts. We identify five key challenges, which relate to the i) measurement of migration and ii) climatic events, iii) the integration and aggregation of data, iv) the identification of causal relationships, and v) the exploration of contextual influences and mechanisms. Advances in research and modelling are discussed together with best practice cases to provide guidance to researchers studying the climate-migration nexus. We recommend for future empirical studies to employ approaches that are of relevance for and reflect local contexts, ensuring high levels of comparability and transparency.
- ItemResolving ecological feedbacks on the ocean carbon sink in Earth system models(Göttingen : Copernicus Publ., 2021) Armstrong McKay, David I.; Cornell, Sarah E.; Richardson, Katherine; Rockström, JohanThe Earth's oceans are one of the largest sinks in the Earth system for anthropogenic CO2 emissions, acting as a negative feedback on climate change. Earth system models project that climate change will lead to a weakening ocean carbon uptake rate as warm water holds less dissolved CO2 and as biological productivity declines. However, most Earth system models do not incorporate the impact of warming on bacterial remineralisation and rely on simplified representations of plankton ecology that do not resolve the potential impact of climate change on ecosystem structure or elemental stoichiometry. Here, we use a recently developed extension of the cGEnIE (carbon-centric Grid Enabled Integrated Earth system model), ecoGEnIE, featuring a trait-based scheme for plankton ecology (ECOGEM), and also incorporate cGEnIE's temperature-dependent remineralisation (TDR) scheme. This enables evaluation of the impact of both ecological dynamics and temperature-dependent remineralisation on particulate organic carbon (POC) export in response to climate change. We find that including TDR increases cumulative POC export relative to default runs due to increased nutrient recycling (+∼1.3 %), whereas ECOGEM decreases cumulative POC export by enabling a shift to smaller plankton classes (−∼0.9 %). However, interactions with carbonate chemistry cause opposite sign responses for the carbon sink in both cases: TDR leads to a smaller sink relative to default runs (−∼1.0 %), whereas ECOGEM leads to a larger sink (+∼0.2 %). Combining TDR and ECOGEM results in a net strengthening of POC export (+∼0.1 %) and a net reduction in carbon sink (−∼0.7 %) relative to default. These results illustrate the degree to which ecological dynamics and biodiversity modulate the strength of the biological pump, and demonstrate that Earth system models need to incorporate ecological complexity in order to resolve non-linear climate–biosphere feedbacks.