Communications Earth & Environment最新文献

Ship emissions are a major source of aerosols over oceans, affecting both air quality and energy balance of the climate. However, estimates of their climate forcing diverge between studies relying on visible ship-tracks and those based on models. Here we show that forcing due to visible ship-tracks accounts for just 5% of the total forcing over the southeast Atlantic shipping-lane. Most forcing from ship emissions comes from aerosols that do not form detectable ship-tracks. They are only tips of the iceberg. We make three forcing calculations, one bottom-up based on visible ship-tracks, one top-down based on spatial relationships, and a hybrid approach that combines top-down or model estimated cloud droplet number concentration changes and cloud adjustments. Although the forcing based on machine learning detected ship tracks is an order of magnitude greater than prior results using manually detected ship-tracks, it remains only 5% of that inferred by top-down or cloud adjustment based methods for pre-2020 shipping. The top-down and the combined cloud adjustments methods show similar forcing for the post-2020 reduction in ships' sulfur emission, although the methods have important regional differences in cloud adjustments that need further investigation. Our results reconcile a long-standing discrepancy in the literature and have important implications for aerosol indirect forcing and marine cloud brightening.

Basaltic melts may variably disaggregate macrocrysts (large crystals) from crystal mushes during the assembly of magma bodies beneath ocean-island volcanoes. The entrained macrocrysts modulate the crystallinity, density, and rheology of magmas, parameters that control magma system architecture and eruptive dynamics. However, the timescales, drivers, and consequences of inconstant crystal mush incorporation into carrier melts require quantification. Here, we use a suite of plagioclase-rich basalts to show that the entrainment efficiency (the ability for melts to disaggregate and entrain macrocrysts from crystal mushes) is temporally variable on inter-eruption timescales at ocean-island volcanoes. Macrocryst cargoes are predominantly out of equilibrium with their carrier melts in both chemistries and mass proportions (ratios of different macrocryst phases). Geochemical and petrological evidence reveals that macrocryst mass proportions are established in a density-stratified melt-rich reservoir shortly before eruption, whereas the absolute crystallinity is a function of crustal physics, likely driven by fluctuations of annual-to-millennial melt supply. Variations in entrainment efficiency explain several universal, but enigmatic, features in oceanic volcanic systems, such as decoupled crystallinity-temperature-time relationships and the dearth of plagioclase-rich basalts at fast-spreading mid-ocean ridges. Systematically studying temporally constrained eruptive products offers a unique window into the evolution of crystal-rich magma storage zones.

Marine net primary production supports critical ecosystem services and the carbon cycle. However, the lack of consensus in the direction and magnitude of projected change in net primary production from models undermines efforts to assess climate impacts on marine ecosystems with confidence. Here we use contemporary remote sensing net primary production trends (1998-2023) from six remote sensing algorithms to discriminate amongst fifteen divergent model projections. A model ranking scheme, based on the similarity of linear responses of net primary production to changes in sea surface temperature, chlorophyll-a and the mixed layer, finds that future declines in net primary production are more likely than presently predicted. Even the best ranking models still underestimate the sensitivity of declines in net primary production to ocean warming, suggesting shortcomings remain. Reproducing this greater temperature sensitivity may lead to even larger declines in future net primary production than presently considered for impact assessment.

Sustainability certifications have rapidly gained prominence and become standards across many industries, yet knowledge about the potential unintended consequences of their criteria remains limited. Here, we use European Space Agency multispectral imagery satellite data in combination with economic and location data to investigate whether the certification process for palm oil production results in unintended consequences. Our results indicate decreases in plantation efficiency both prior to and following the certification obtainment. Our findings highlight the importance of considering possible unintended consequences of sustainability certifications beyond their immediate goals and criteria.

The export of organic carbon from terrestrial ecosystems by erosion may play a central role in balancing the geological carbon cycle and Earth's climate over millennial timescales. However, constraints on organic carbon yields have come from sampling modern rivers that don't capture variation over decades to millennia driven by changing hydroclimate and erosion during extreme events. Here we use volumetric reconstructions of lake sedimentary fills to generate timeseries of sediment and organic carbon yields from two catchments draining the Southern Alps, New Zealand over the last millennium. The reconstructed yields indicate that earthquake-induced landslides significantly increase sediment and organic carbon yields, contributing to pulsed export that accounts for ~40% of the total. Between extreme events, organic carbon export increased twofold during centuries with a wetter reconstructed climate. Our findings suggest that the link between hydroclimate and organic carbon export may act as a negative feedback in the longer-term carbon cycle.

Central Asia hosts some of the world's last relatively healthy mountain glaciers and is heavily dependent on snow and ice melt for downstream water supply, though the causes of this stable glacier state are not known. We combine recent in-situ observations, climate reanalysis and remote sensing data to force a land-surface model to reconstruct glacier changes over the last two decades (1999-2023) and disentangle their causes over a benchmark glacierized catchment in Tajikistan. We show that snowfall and snow depth have been substantially lower since 2018, leading to a decline in glacier health and reduced runoff generation. Remote-sensing observations confirm wider snow depletion across the Northwestern Pamirs, suggesting that a lack of snowfall might be a cause of mass losses regionally. Our results provide an explanation for the recent decline in glacier health in the region, and reinforce the need to better understand the variability of precipitation.

Forecasting catastrophic failures that threaten life and property remains a formidable challenge. A major hurdle lies in the intermittent rupture dynamics of heterogeneous materials. This erratic pattern challenges conventional time-to-failure predictive models, which typically assume a smooth, monotonic power law acceleration. Here, we propose a unified failure model based on a log-periodic power law that encapsulates the intermittent acceleration-deceleration sequences within a single framework. We validate this unified model using a global dataset of 109 historical geohazard events including landslides, rockbursts, glacier breakoffs, and volcanic eruptions, spanning a century and across seven continents. We show that our model significantly outperforms the conventional approach, offering a robust and versatile framework for describing the complex rupture behavior of diverse geomaterials such as rock, soil, and ice at the site scale. This unified perspective not only broadens the model's applicability across diverse geohazards but also highlights its potential to enhance early warning systems.

Mass loss from ice sheets in Greenland and Antarctica has quadrupled since the 1990s and now represents the dominant source of global mean sea-level rise from the cryosphere. This has raised concerns about their future stability and focussed attention on the global mean temperature thresholds that might trigger more rapid retreat or even collapse, with renewed calls to meet the more ambitious target of the Paris Climate Agreement and limit warming to +1.5 °C above pre-industrial. Here we synthesise multiple lines of evidence to show that +1.5 °C is too high and that even current climate forcing (+1.2 °C), if sustained, is likely to generate several metres of sea-level rise over the coming centuries, causing extensive loss and damage to coastal populations and challenging the implementation of adaptation measures. To avoid this requires a global mean temperature that is cooler than present and which we hypothesise to be closer to +1 °C above pre-industrial, possibly even lower, but further work is urgently required to more precisely determine a 'safe limit' for ice sheets.

Market-based instruments, including competitive tenders, are central to funding global environmental restoration and management projects. Recently, tenders have been utilised to fund Nature-based Solutions schemes for Natural Flood Management, with the explicit purpose of achieving co-benefits; flood management and reducing inequities. While multiple studies consider the efficacy of Nature-based Solutions for tackling inequities, no prior research has quantified whether the resource allocation for these projects has been conducted equitably. We analyse two national natural flood management programmes funded through competitive tenders in England to explore who benefits by considering the characteristics of projects, including socio-economic, geographical (e.g. rurality) and flood risk dynamics. Our results suggest that inequity occurs at both the application and funding stages of Nature-based Solutions projects for flood risk management. This reflects wider international challenges of using market-based instruments for environmental resource allocation. Competitive tenders have the potential to undermine the equitable benefits of Nature-based Solutions.

Accurate basal melt prediction is crucial for assessing ice sheet stability and sea level rise. Recent observations at eastern Thwaites Glacier reported low melt rates despite warm ocean waters. Weak vertical mixing due to low current speeds and strong density stratification suppresses melting. However, the basal melt parameterization approach in ocean models overestimates the melt rates there. Hence, we revisit the parameterization by applying an ice-ocean boundary current model to a simple horizontal ice base. This setting creates a boundary layer (BL) over a dynamically stable pycnocline. We show that the pycnocline's low diffusivity restricts heat transfer, causing models to overpredict melting, especially for weaker far-field currents. While reducing the prescribed BL depth can minimize this overprediction in ocean models, a better fix might be prescribing an upper melt rate limit for slower currents. We also propose a physics-based parameterization framework that more accurately emulates physics in models and observations.