Communications Earth & Environment

Arctic sea-ice extent has reduced by over 40% during late summer since 1979, and the day-to-day changes in sea ice extent have shifted to more negative values. Drivers of Arctic weather that cause large short-term changes are rarely predicted more than a week in advance. Here we investigate variability in changes in sea ice extent for periods of less than 18 days and their association to Arctic cyclones and tropopause polar vortices. We find that these very rapid sea ice loss events are substantial year-round and have increased over the last 30 years in June-August due to thinning sea ice that is more susceptible to forcings from ocean waves and low-level atmospheric wind. These events occur in regions of enhanced near-surface level pressure gradients between synoptic-scale high and low pressure systems over regions of relatively thin sea ice, and are preceded by tropopause polar vortices.

Globally, the oxidative flux of petrogenic organic carbon rivals the drawdown by silicate weathering and burial of biospheric carbon. Where and how petrogenic organic carbon is susceptible to degradation along the short-path river-marine continuum in active orogens remains elusive. Here, we demonstrate the transformation of petrogenic organic carbon from a mountainous catchment in eastern Taiwan and its connecting submarine canyon. Our Raman analyses indicate that while highly graphitized carbon in slate/schist transformed into disordered form during soil development, the preferential elimination of disordered form was found along submarine transit. Additionally, quartz/rutile outperformed mica in protecting petrogenic organic carbon from transport abrasion and microbial degradation. Such an oxidative flux was estimated to be 20–35 metric tons of carbon per square kilometer per year, ranking among the greatest levels around the world and highlighting tectonically active islands and the surrounding marine systems as a hotspot of carbon emission.

Northern forests (forests north of 30°N) are major terrestrial carbon dioxide (CO2) sinks, while rapid warming can disturb their CO2 sink function. Here we use multi-year net CO2 exchange observations from 65 northern forest sites to show that the increased net CO2 uptake during warmer springs was more pronounced in old forests (>90 years old) compared to young (<40 years old) and mid-aged (40–90 years old) forests. In addition, the decreased net CO2 uptake during warmer summers and autumns was more pronounced in young forests compared to mid- and old-aged forests. Annually, this resulted in an increase in net CO2 uptake due to seasonal warming for old forests (4.8 g C m⁻² yr⁻¹) and a decrease in young- and mid-aged forests (3.2 and 0.8 g C m⁻² yr⁻¹, respectively). In future projections, increasingly uneven seasonal warming may amplify the impacts of stand age on CO2 sinks of northern forests.

Marine gas seeps are common along tectonically active margins, but they have not been previously observed along the Arabian continental margin. Here we present evidence of gas escape structures, pockmarks, and active gas seeps in the Gulf of Oman. Multibeam bathymetry, water column backscatter and physical parameters, and two-dimensional seismic reflection data were used to map active seafloor seeps and pockmarks. Circular and crescent-shaped pockmarks and complex pockmark strings were identified. These features are confined to regions shoreward of the shelf break. Thirty-five active gas bubble trains were observed, mostly not coincident with the mapped pockmarks. With progressive gas release, the gas seeps are anticipated to lead to development of pockmarks over time. Bright spots on the seismic data indicate shallow subsurface gas accumulation alongside normal fault and fracture conduits, strongly correlated to the presence of pockmarks. These findings suggest an important carbon flux into the Arabian Sea and atmosphere.

The Arctic Ocean’s Beaufort Gyre, the largest Arctic freshwater reservoir, plays a crucial role for climate and marine ecosystems. Understanding how it changes in a warming climate is therefore essential. Here, using high-resolution simulations and Coupled Model Intercomparison Project phase 6 data, we find that the Beaufort Gyre will increasingly accumulate freshwater, elevate sea level, and spin up its circulation as the climate warms. These changes, collectively referred to as inflation, are more pronounced in the Beaufort Gyre region than in other Arctic areas, amplifying the spatial asymmetry of the Arctic Ocean. The inflation is driven by increased surface freshwater fluxes and intensified surface stress from wind strengthening and sea ice decline. Current climate models tend to underestimate this inflation, which could be alleviated by high-resolution ocean models and improved atmospheric circulation simulations. The inflation of the Beaufort Gyre underscores its growing importance in a warming climate.

Here we use multi-waveband single scattering albedo observations from ground-based instruments and satellite to constrain black carbon aerosol's physical properties and loading over Xuzhou, China, and Dhaka, Bangladesh. Our daily high-resolution findings reveal smaller black carbon cores and spatially variable morphology dominate both regions. Column loadings reveal higher black carbon mass in Dhaka, while higher total aerosol mass and number are observed in Xuzhou. These findings reflect differences in emission sources, atmospheric conditions, and regulatory policies. Spatial analysis reveals notable enhanced black carbon along Dhaka’s urban riverbanks (8–9 mg m⁻²), and over rapidly changing, small industrial sites in China, indicating overlooked sources. Complex daily interactions between wind, accumulation, and dispersion challenge traditional seasonal dynamics. These findings demonstrate high-resolution data can be tailored from available remote sensing platforms, providing nuanced insights into regional air quality, enhancing assessment capabilities and informing targeted mitigation strategies.

Temporary ice roads built by the process of snow compaction, watering, and icing during cold winters are lifelines for land access in remote Arctic. In the context of the Arctic amplified warming, the vulnerability of potential ice roads under the influence of complex climate system remains unclear. Here, we construct a potential ice road assessment model that allows quantization of the climatic suitability of potential ice roads in the Arctic. Using satellite remote sensing and meteorological data, we find changes in surface air temperature and snow cover reduced the climatic suitability of potential ice roads during 1979–2017. Spatially, potential ice roads in North America face more immediate threats due to decreased snow depth compared to Eurasia. Before the end of the 21st century, we project a further decline in the climatic suitability of potential ice roads, primarily due to increasing surface air temperatures and decreasing permafrost stability. Taking precious metal/diamond exploration as an example, we conclude that mining activities associated with ice roads will face access difficulties by 2050–2100 due to the decreased potential ice roads. These results give new insights into the challenges and opportunities of Arctic overland travel.

Surface soil moisture is projected to decrease under global warming. Such projections are mostly based on climate models, which show large uncertainty (i.e., inter-model spread) partly due to inadequate observational constraint. Here we identify strong physically-based emergent relationships between soil moisture change (2070–2099 minus 1980–2014) and recent air temperature and precipitation trends across an ensemble of climate models. We extend the commonly used univariate Emergent Constraints to a bivariate method and use observed temperature and precipitation trends to constrain global soil moisture changes. Our results show that the bivariate emergent constraints can reduce soil moisture change uncertainty by 7.87%, which is four times more effective than traditional temperature-based univariate constraints. The bivariate emergent constraints change the sign of soil moisture change from negative to positive for semi-arid, dry sub-humid and humid regions and global land as a whole, but exacerbates the drying trend in arid and hyper-arid regions.

Tropical forests may be nearing critical temperatures, yet tree species may respond differently. Using high-resolution thermal, hyperspectral, and LiDAR imagery, we mapped 652 crowns of four Hawaiian tree species to study the effects of crown traits and abiotic conditions on species’ temperatures at two scales (whole crown vs. sunlit leaves). We show scale-dependent, species-specific relationships with environmental fluctuations. Net radiation was consistently the dominant determinant of crown temperature deviations from air temperature (Tdiff), while vapor pressure deficit, wind speed, and crown traits (e.g., roughness) varied in importance by species and scale. Species explained 17% and 44% of Tdiff variation at the crown and leaf scales, respectively, after controlling for climatic factors. Findings suggest that leaf temperatures overestimate larger-scale temperature differences, while canopy-scale observations underestimate leaf heat stress. Because leaf and crown traits can have opposing effects on Tdiff, disentangling these can advance our understanding of species’ thermoregulation under climate change.

Variations in water availability seasonality significantly impact society and ecosystems. While many studies have focused on mean or extreme precipitation, the response of water availability seasonality, influencing yearly water distribution beyond individual extremes, to human-induced climate change remains underexplored. Here we examine global and regional water availability seasonality changes from 1915 to 2014, quantifying how anthropogenic greenhouse gases and aerosols have influenced these variations using reanalysis and simulations from Coupled Model Intercomparison Project Phase 6. Despite large spatiotemporal uncertainties due to regional variability and model assumptions, we find that greenhouse gases significantly amplify the seasonality, while aerosols reduce it. Given that the positive effects of greenhouse gases surpass the aerosols’ negative effects, the counterbalancing influences have led to an overall enhancement in seasonality of water availability over the past century. This trend is expected to continue in the future as greenhouse gases-induced warming continues to rise and aerosol levels decline.

While Saharan dust’s influence on sea surface temperature variability in the tropical North Atlantic is well-documented, its effects on the equatorial region remain underexplored. This relationship is particularly important due to the strong influence of equatorial Atlantic variability on both local and remote climates. Here, we use observational and reanalysis data to investigate Saharan dust’s role in boreal winter, a period when dust transport is typically near the equator. A unique footprint of Saharan dust forcing is revealed, as well as a complex, non-monotonic response. Specifically, in contrast to the expected cooling due to shortwave blocking by Saharan dust, lower tropospheric warming, and stabilization lead to a strong sea surface warming off the coast of northwestern Africa and to the development of an off-equatorial warm front. The front drives cross-equatorial winds that induce a northward shift of the Atlantic rain belt, equatorial cooling, and equatorial wave activity leading to delayed equatorial warming. Winter Saharan dust is therefore an important contributor to equatorial Atlantic variability, with cross-regional implications.

Permafrost is a considerable carbon reservoir harboring up to 1700 petagrams of carbon accumulated over millennia, which can be mobilized as permafrost thaws under global warming. Recent studies have highlighted that a fraction of this carbon can be transformed to atmospheric volatile organic compounds, which can affect the atmospheric oxidizing capacity and contribute to the formation of secondary organic aerosols. In this study, active layer soils from the seasonally unfrozen layer above the permafrost were collected from two distinct locations of the Greenlandic permafrost and incubated to explore their roles in the soil-atmosphere exchange of volatile organic compounds. Results show that these soils can actively function as sinks of these compounds, despite their different physiochemical properties. Upper active layer possessed relatively higher uptake capacities; factors including soil moisture, organic matter, and microbial biomass carbon were identified as the main factors correlating with the uptake rates. Additionally, uptake coefficients for several compounds were calculated for their potential use in future model development. Correlation analysis and the varying coefficients indicate that the sink was likely biotic. The development of a deeper active layer under climate change may enhance the sink capacity and reduce the net emissions of volatile organic compounds from permafrost thaw.

Aquatic foods are crucial for global food and nutrition security, but overfishing has led to depleted fish stocks, threatening both food security and the environment. Here, we combine a fish stock model with a global agriculture and food market model in order to analyze scenarios involving a continuation of current fishing trends versus optimal management through maximum sustainable yield targets. Maximum sustainable yield management of overfished stocks could increase yields by 10.6 Megatons, equivalent to 12% of total catches and 6% of aquatic animal production in 2022. This would alleviate the need for aquaculture expansion by an equivalent of 3 years of growth in the aquaculture sector at its current level, and reduce meat and feed demand. Lower food prices and additional supply could enhance global food security. Conversely, continued overfishing will likely lead to lower catches over time, adding pressure to the agricultural and aquaculture sectors. Although maximum sustainable yield management is not a panacea, it represents a positive step towards achieving sustainable food production.

Flash droughts, characterized by their rapid onset, substantially affect terrestrial ecosystems. However, the sensitivity of ecosystem productivity to the rapid development of flash droughts under varying vegetation conditions remains poorly understood. Here we investigate the ecosystem response to the speed of flash drought onset for different plant functional types, considering the decline rate of root-zone soil moisture and standardized gross primary productivity anomaly. Our findings reveal a significant increase of approximately 10% in the proportion of 1- and 2-pentad (5 and 10 days) onset flash droughts leading to negative standardized gross primary productivity anomalies during 2001–2018. Furthermore, while standardized gross primary productivity anomalies decline at higher rates, they do not promptly respond on a shorter timescale to faster-onset flash droughts compared to slower-onset flash droughts. Vegetation types with shallower root systems exhibit higher sensitivities to faster-onset flash droughts, suggesting an escalating threat to terrestrial ecosystems in a changing climate.

Permafrost thaw poses diverse risks to Arctic environments and livelihoods. Understanding the effects of permafrost thaw is vital for informed policymaking and adaptation efforts. Here, we present the consolidated findings of a risk analysis spanning four study regions: Longyearbyen (Svalbard, Norway), the Avannaata municipality (Greenland), the Beaufort Sea region and the Mackenzie River Delta (Canada) and the Bulunskiy District of the Sakha Republic (Russia). Local stakeholders’ and scientists’ perceptions shaped our understanding of the risks as dynamic, socionatural phenomena involving physical processes, key hazards, and societal consequences. Through an inter- and transdisciplinary risk analysis based on multidirectional knowledge exchanges and thematic network analysis, we identified five key hazards of permafrost thaw. These include infrastructure failure, disruption of mobility and supplies, decreased water quality, challenges for food security, and exposure to diseases and contaminants. The study’s novelty resides in the comparative approach spanning different disciplines, environmental and societal contexts, and the transdisciplinary synthesis considering various risk perceptions.

Questions about when early members of the genus Homo adapted to extreme environments like deserts and rainforests have traditionally focused on Homo sapiens. Here, we present multidisciplinary evidence from Engaji Nanyori in Tanzania’s Oldupai Gorge, revealing that Homo erectus thrived in hyperarid landscapes one million years ago. Using biogeochemical analyses, precise chronometric dating, palaeoclimate simulations, biome modeling, fire history reconstructions, palaeobotanical studies, faunal assemblages, and archeological evidence, we reconstruct an environment dominated by semidesert shrubland. Despite these challenges, Homo erectus repeatedly occupied fluvial landscapes, leveraging water sources and ecological focal points to mitigate risk. These findings suggest archaic humans possessed an ecological flexibility previously attributed only to later hominins. This adaptability likely facilitated the expansion of Homo erectus into the arid regions of Africa and Eurasia, redefining their role as ecological generalists thriving in some of the most challenging landscapes of the Middle Pleistocene.

Nitrate (NO3⁻) leaching from nitrogen (N) fertilized soils is a significant global concern, affecting both the environment and public health. However, substantial uncertainties and variabilities in NO3⁻ leaching factors (LFs) among regions or crops impede accurate assessments of NO3⁻ leaching. Here we synthesize 2500 field observations worldwide and show that LFs vary by an order of magnitude across regions and crops, primarily driven by hydroclimatic and edaphic conditions rather than N fertilizer management. Global cropland NO3⁻ leaching from synthetic N fertilization, calculated through spatially explicit (15.4, 14.8–16.1 Tg N yr–1) and crop-specific (12.9, 11.0–14.8 Tg N yr–1) LFs, is 41% lower than the Intergovernmental Panel on Climate Change Tier 1 global inventory. Over 47% of this leaching is concentrated in China, India, and the United States, with maize, wheat, rice and vegetables accounting for nearly half of it. Improved regional and crop-specific LFs will provide a benchmark for NO3⁻ leaching abatement by pinpointing potential global hotspots.

The greening of previously barren landscapes in the Arctic is one of the most relevant responses of terrestrial ecosystem to climate change. Analyses of satellite data (available since ~1980) have revealed a widespread tundra advance consistent with recent global warming, but the length is insufficient to resolve the long-term variability and the precise timing of the greening onset. Here, we measured plant-derived biomarkers from an Arctic fjord sediment core as proxies for reconstructing past changes in tundra vegetation during the transition from the Little Ice Age to modern warming. Our findings revealed a rapid expansion of the tundra since the beginning of the twentieth century, largely coinciding with the decline of summer sea ice extent and glacier retreat. The greening trend inferred from biomarker analysis peaked significantly in the late 1990s, along with a shift in the tundra community towards a more mature successional stage. Most of these signals were consistent with the biomolecular fingerprints of vascular plant species that are more adapted to warmer conditions and have widely expanded in proglacial areas during recent decades. Our results suggest that the greening of Arctic fjords may have occurred earlier than previously thought, improving our mechanistic understanding of vegetation-climate-cryosphere interactions that will shape tundra vegetation under future warming projections.

Biodiversity–ecosystem functioning experiments have established generally positive species richness-productivity relationships in plots of single ecosystem types, typically grassland or forest. However, it remains unclear whether these findings apply in real-world landscapes that resemble a heterogeneous mosaic of different ecosystem and plant types that interact through biotic and abiotic processes. Here, we show that landscape-level diversity, measured as number of land-cover types (different ecosystems) per 250×250 m, is positively related to landscape-wide remotely-sensed primary production across all of North America, covering 16 of 18 ecoregions of Earth. At higher landscape diversity, productivity was temporally more stable, and 20-year greening trends were accelerated. These effects occurred independent of local species diversity, suggesting emergent mechanisms at hitherto neglected levels of biological organization. Specifically, mechanisms related to interactions among land-cover types unfold at the scale of entire landscapes, similar to, but not necessarily resulting from, interactions between species within single ecosystems.

The Campi Flegrei caldera (Italy) is among the most productive volcanoes of the Mediterranean area. However, the volcanic history preceding the VEI 7 Campanian Ignimbrite eruption (~40 ka) is still poorly constrained. Here, we use a tephra dispersal model to reconstruct the eruption source parameters of the Maddaloni/X-6 eruption (~109 ka), one of the most widespread Late Pleistocene Mediterranean marker tephra from Campi Flegrei. Our results suggest that the eruption was characterized by an early Plinian phase involving ~6 cubic kilometers (within the range of 3–21 cubic kilometers) of magma, followed by a co-ignimbrite phase erupting ~148 cubic kilometers (range of 60–300 cubic kilometers). This ranks the Maddaloni/X-6 as a high-magnitude (M7.6) eruption, resulting at least as the second largest known event from Campi Flegrei. This study provides insights into the capability of the Campi Flegrei magmatic system to repeatedly generate large explosive eruptions, which has broad implications for hazard assessment in the central Mediterranean area.

El Niño/Southern Oscillation variability has conspicuous impacts on ecosystems and severe weather. Here, we probe the effects of anthropogenic aerosols and greenhouse gases on El Niño/Southern Oscillation variability during the historical period using a broad set of climate models. Increased aerosols significantly amplify El Niño/Southern Oscillation variability primarily through weakening the mean advection feedback and strengthening the zonal advection and thermocline feedbacks, as linked to a weaker annual cycle of sea surface temperature in the eastern equatorial Pacific. They prevent extreme El Niño events, reduce interannual sea surface temperature skewness in the tropical Pacific, influence the likelihood of El Niño/Southern Oscillation events in April and June and allow for more El Niño transitions to Central Pacific events. While rising greenhouse gases significantly reduce El Niño/Southern Oscillation variability via a stronger sea surface temperature annual cycle and attenuated thermocline feedback. They promote extreme El Niño events, increase SST skewness, and enlarge the likelihood of El Niño/Southern Oscillation peaking in November while inhibiting Central Pacific El Niño/Southern Oscillation events.

Knowing the transport properties of iron at the Earth’s core conditions is essential for the geophysical modeling of Earth’s magnetic field generation. Besides by extreme pressures and temperatures (which cause scattering by thermal disorder to dominate), transport may be also influenced by the presence of light elements and electron-electron scattering. We used a combination of molecular dynamics, density functional theory, and dynamical mean-field theory methods to examine the impact of oxygen impurities on the electronic correlations and transport in the Earth’s liquid outer core. We find electronic correlations to be moderately enhanced by oxygen admixture. At realistic 10 atomic% of oxygen, the thermal conductivity suppression by electronic correlations (about 20%) is of the same magnitude as that due to oxygen inclusion. Hence, both play an equally important role in reducing the conductivity and stabilizing the geodynamo. We also explain the reduction of Lorenz ratio in core matter.

Reduction in aerosol cooling unmasks greenhouse gas warming, exacerbating the rate of future warming. The strict sulfur regulation on shipping fuel implemented in 2020 (IMO2020) presents an opportunity to assess the potential impacts of such emission regulations and the detectability of deliberate aerosol perturbations for climate intervention. Here we employ machine learning to capture cloud natural variability and estimate a radiative forcing of +0.074 ±0.005 W m⁻² related to IMO2020 associated with changes in shortwave cloud radiative effect over three low-cloud regions where shipping routes prevail. We find low detectability of the cloud radiative effect of this event, attributed to strong natural variability in cloud albedo and cloud cover. Regionally, detectability is higher for the southeastern Atlantic stratocumulus deck. These results raise concerns that future reductions in aerosol emissions will accelerate warming and that proposed deliberate aerosol perturbations such as marine cloud brightening will need to be substantial in order to overcome the low detectability.