Global Environmental Change Advances最新文献

Earth systems may fall into an undesirable system state if 1.5 °C of warming is exceeded. Carbon release from substantial permafrost stocks vulnerable to near-term warming represents a positive climate feedback that may increase the risk of 1.5 °C warming or greater. Methane (CH₄) is a short-lived but powerful greenhouse gas with a global warming potential 28.5 times that of carbon dioxide (CO₂) over a 100 year time span. Because permafrost thaw in the coming centuries is partly determined by the warming in the 21st century, rapid reductions in methane emissions early in the 21st century could have far reaching effects. We use a reduced complexity carbon cycle model and a permafrost feedback module to explore the possibility that accelerating reductions in methane emissions could help avoid long-term warming by limiting permafrost melt. We simulate three extended Representative Concentration Pathway (RCP) emission scenarios (RCP 2.6, 4.5, and 6) through the year 2300 and impose methane mitigation strategies where we reduce CH₄ emissions by 1%, 5% or 10% annually until the long-term scenario emission level is reached. We find that accelerated rates of methane mitigation do not sufficiently alter the global temperature anomaly to prevent or delay a permafrost feedback, nor do they result in meaningful long term reductions in temperatures. We find that the long-term magnitude of methane mitigation (i.e., long-term emission level) and not the rate of reduction, corresponds to long-term temperature change. Further study of methane-climate dynamics is necessary to fully resolve this question.

To shed light on the politics of remote sensing, a technique often regarded as objective and neutral, the subfield of critical remote sensing has emerged in the social sciences. This perspective translates its key ideas into an actionable framework that offers suggestions for how to transform remote sensing to better engage and empower people and places typically studied at a distance. First, we encourage remote sensing scientists and practitioners to weigh the consequences of exposing inaccessible or off-limits places, incorporate local knowledge and values into research design, methods, and applications, and share skills and data with stakeholders who wish to learn and use remote sensing for their own objectives. Second, we offer suggestions for teaching critical remote sensing and making research accessible and replicable. Third, we stress the importance of acknowledging that despite being conducted from afar, remote sensing can still affect the people and places it observes.

The Asian summer monsoon is one of the active synoptic scale weather phenomena, and has significant socioeconomic implications. A vast population relies on the associated precipitation, mostly dominating the agricultural practices of the region. Therefore, it is essential to assess past behavior to understand the present, including future projections. We used palaeomonsoon precipitation synthesis and Coupled Model Intercomparison Project Phase 6 (CMIP6) data to interactively show the dynamics and changes in the summer monsoon for the Asian region throughout the past millennium behavior to understand the present and future projections. In this study, we precisely analyzed and quantified the dynamics of summer precipitation variation throughout the last millennium (LM; 850–1849 CE) at an annual resolution, in which the major climatic events were the Medieval Warm Period (MWP; 900–1300 CE) and Little Ice Age (LIA; 1500–1850 CE). We also analyzed the historical or base climate (HC; 1850–2014 CE) and future monsoons (FM; 2015–2100 CE) using CMIP6 SSP2–4.5 and SSP5–8.5, to project the summer monsoon for Asia and the Indian subcontinent. The findings are encouraging, showing slightly increased precipitation during the MCA and low precipitation during the LIA in Asia. Moreover, the average summer monsoon daily rainfall remained 6.398 ± 0.634 and 6.310 ± 0.649 mm/d for the MCA and LIA, respectively, indicating a relatively slight variation in the summer monsoon precipitation during these climatic phases. In addition, for the twenty-first century, the CIMP6 projection shows increased summer monsoon precipitation over Asia, particularly in the northeast region. Further, the CMIP6 projections for SSP2–4.5 shows 6.457 ± 0.658 mm/d, and for SSP5–8.5 is 6.686 ± 0.837 mm/d for the twenty-first century. Furthermore, the results of Empirical Orthogonal Functions (EOFs) analysis suggest that the monsoon system may become more intense in some regions, whereas other regions may experience reduced precipitation in the Asia-Pacific region, with a regionally heterogeneous rise in heavy rainfall and high moisture throughout most of Asia. Orography, evaporation, moisture content, and circulation all affect the severity of precipitation in addition to fine-scale surface moisture feedback. The findings show that it is essential to consider both the past and the future to accurately estimate local and regional-scale susceptibility to climate change. Moreover, the synthesis of past data and analysis of future projections of the monsoon will provide a basis for reducing the unpredictability of future climate models.

Carbon removals associated with incremental gains in soil organic carbon (SOC) at scale have enormous potential to mitigate global warming, yet confusion over contexts that elicit SOC accrual abound. Here, we examine how bespoke interventions (through irrigation, fertiliser, crop type and rotations), antecedent SOC levels and soil type impact on long-term SOC accrual and greenhouse gas (GHG) emissions. Using a whole farm systems modelling approach informed using participatory research, we discovered an inverse relationship between antecedent SOC stocks and SOC gains realised following intervention, with greater initial SOC levels resulting in lower ex poste change in SOC. We found that SOC accrual was greatest for clays and least for sands, although changes in SOC in sandy loam soils were also low. Diversified whole farm adaptations – implemented through inclusion of grain legumes within wheat/canola crop rotations – were more conducive to improvement in SOC stocks, followed by Intensified systems (implemented through greater rates of irrigation, farm areas under irrigation, nitrogen fertiliser and inclusion of rice and maize in crop rotations). Adaptations that Simplified farm systems by reducing irrigation and fertiliser use resulted in the lowest SOC accrual. In most cases, long-term SOC stocks fell when SOC at the outset was greater than 4–5%, regardless of intervention made, soil or crop type, crop rotation, production system or climate. We contend that (1) management interventions primarily impacted SOC in the soil surface (0–30 cm) and had de minimus impact on deep SOC stocks (30–100 cm), (2) crop rotations including wheat, canola and faba beans were more conducive to improvement in SOC stocks, (3) scenarios with high status quo SOC had little impact on crop productivity, and not necessarily the lowest GHG emissions intensity, (4) productivity and GHG emissions intensity were largely a function of the quantum of nitrogenous fertiliser added, rather than SOC stocks, and (5) aspirations for improving SOC are likely to be futile if antecedent SOC stocks are already high (4–5 %). We conclude that potential for improving SOC stocks exists in contexts where antecedent stocks are low (<1%), which may include regions with land degradation, chronic erosion and/or other constraints to vegetative ground cover that could be sustainably and consistently alleviated.

Sea-level rise is unstoppable. Communities worldwide are facing difficult choices in responding to changing coastlines and estuaries. Understandably, there is little attention on the potential for repurposing inundated areas because retreat and adaptation take precedence. Repurposing may be infeasible for newly-claimed seascapes in exposed and high energy coasts. Nevertheless, for sheltered coastal areas, shallow estuaries and harbours, there may be potential for repurposing some areas for aquaculture, fisheries, wetlands, and/or blue carbon. For example, abandoned and decontaminated structures may provide fish nursery habitat as artificial reefs. Here, we present the results of a systematic literature review of potential options, along with identified benefits and implementation barriers. Our purpose is not to examine the feasibility of such options because these will be place- and context-specific; rather, we explore whether the solution space can be extended beyond the point of impact. We suggest that repurposing could be added to the PARA management framework.