Nature Geoscience最新文献

The Paris Agreement mandates that signatory countries enhance the transparency of their national greenhouse gas inventories. China’s inventories have reported substantial forest carbon gains using ground-based forest plot measurements, but independent satellite-based support for such inventories is lacking and the contributions from human management and anthropogenic environmental changes (atmospheric CO₂ growth, climate change and nitrogen deposition) are unknown. Here we use remote sensing and vegetation modelling to investigate the changes in woody biomass carbon and their drivers across China from 2001 to 2020. Our results show a forest cover increase of 6.2% (59.2 Mha) over this period and a woody biomass carbon sink of 208.6 ± 51.8 TgC yr⁻¹, consistent with the national inventories. The conservation of forest and woodland areas made an unexpectedly large contribution (59.2%) to the observed sink, with an additional 29.4% from anthropogenic expansion. Of these management-driven sinks, 53.7% (99.2 TgC yr⁻¹) is attributed to a direct management effect and the remaining 46.3% to the effects of environmental changes. China’s ecological restoration projects contributed 73.5% of the direct management effect. Our study provides satellite-based evidence to support China’s inventories and underscores the crucial role of human management in the nation’s woody carbon balance.

Large igneous provinces erupt highly reactive, predominantly basaltic lavas onto Earth’s surface, which should boost the weathering flux leading to long-term CO₂ drawdown and cooling following cessation of volcanism. However, throughout Earth’s geological history, the aftermaths of multiple Phanerozoic large igneous provinces are marked by unexpectedly protracted climatic warming and delayed biotic recovery lasting millions of years beyond the most voluminous phases of extrusive volcanism. Here we conduct geodynamic modelling of mantle melting and thermomechanical modelling of magma transport to show that rheologic feedbacks in the crust can throttle eruption rates despite continued melt generation and CO₂ supply. Our results demonstrate how the mantle-derived flux of CO₂ to the atmosphere during large igneous provinces can decouple from rates of surface volcanism, representing an important flux driving long-term climate. Climate–biogeochemical modelling spanning intervals with temporally calibrated palaeoclimate data further shows how accounting for this non-eruptive cryptic CO₂ can help reconcile the life cycle of large igneous provinces with climate disruption and recovery during the Permian–Triassic, Mid-Miocene and other critical moments in Earth’s climate history. These findings underscore the key role that outgassing from intrusive magmas plays in modulating our planet’s surface environment.

Bottom trawling represents the most widespread anthropogenic physical disturbance to seafloor sediments on continental shelves. While trawling-induced changes to benthic ecology have been widely recognized, the impacts on long-term organic carbon storage in marine sediments remains uncertain. Here we combined datasets of sediment and bottom trawling for a heavily trawled region, the North Sea, to explore their potential mutual dependency. A pattern emerges when comparing the surface sediment organic carbon-to-mud ratio with the trawling intensity represented by the multi-year averaged swept area ratio. The organic carbon-to-mud ratio exhibits a systematic response to trawling where the swept area ratio is larger than 1 yr⁻¹. Three-dimensional physical–biogeochemical simulation results suggest that the observed pattern is attributed to the correlated dynamics of mud and organic carbon during transport and redeposition in response to trawling. Both gain and loss of sedimentary organic carbon may occur in weakly trawled areas, whereas a net reduction of sedimentary organic carbon is found in intensely trawled grounds. Cessation of trawling allows restoration of sedimentary carbon stock and benthic biomass, but their recovery occurs at different timescales. Our results point out a need for management of intensely trawled grounds to enhance the CO₂ sequestration capacity in shelf seas.

Geomorphological and mineralogical evidence is consistent with aqueous activity on ancient Mars, yet explaining the presence of substantial liquid water on early Mars remains challenging. Another fluid, liquid CO₂, was probably present during Martian history, at least in the subsurface, and could even have been stable at the surface under a sufficiently dense CO₂-rich early atmosphere. Liquid CO₂ flows have been proposed as an alternative to water to explain morphological features, but it is widely accepted that water is the fluid responsible for mineral alteration. Interestingly, however, experimental research on geologic sequestration on Earth has revealed a surprising degree of chemical reactivity between CO₂ fluid and minerals if the fluid is water-saturated, as it would probably have been on Mars. The resulting alteration products — carbonates, phyllosilicates and possibly sulfates — are consistent with minerals found on Mars today. We therefore propose that the formation of some of the aqueous mineral alteration observed on the Martian surface may have been mediated by liquid CO₂. Further laboratory investigations are needed to test this hypothesis.

The ocean annually absorbs about a quarter of all anthropogenic carbon dioxide (CO₂) emissions. Global estimates of air–sea CO₂ fluxes are typically based on bulk measurements of CO₂ in air and seawater and neglect the effects of vertical temperature gradients near the ocean surface. Theoretical and laboratory observations indicate that these gradients alter air–sea CO₂ fluxes, because the air–sea CO₂ concentration difference is highly temperature sensitive. However, in situ field evidence supporting their effect is so far lacking. Here we present independent direct air–sea CO₂ fluxes alongside indirect bulk fluxes collected along repeat transects in the Atlantic Ocean (50° N to 50° S) in 2018 and 2019. We find that accounting for vertical temperature gradients reduces the difference between direct and indirect fluxes from 0.19 mmol m⁻² d⁻¹ to 0.08 mmol m⁻² d⁻¹ (N = 148). This implies an increase in the Atlantic CO₂ sink of ~0.03 PgC yr⁻¹ (~7% of the Atlantic Ocean sink). These field results validate theoretical, modelling and observational-based efforts, all of which predicted that accounting for near-surface temperature gradients would increase estimates of global ocean CO₂ uptake. Accounting for this increased ocean uptake will probably require some revision to how global carbon budgets are quantified.

In 2022, Europe faced an extensive summer drought with severe socioeconomic consequences. Quantifying the influence of human-induced climate change on such an extreme event can help prepare for future droughts. Here, by combining observations and climate model outputs with hydrological and land-surface simulations, we show that Central and Southern Europe experienced the highest observed total water storage deficit since satellite observations began in 2002, probably representing the highest and most widespread soil moisture deficit in the past six decades. While precipitation deficits primarily drove the soil moisture drought, human-induced global warming contributed to over 30% of the drought intensity and its spatial extent via enhanced evaporation. We identify that 14–41% of the climate change contribution was mediated by the warming-driven drying of the soil that occurred before the hydrological year of 2022, indicating the importance of considering lagged climate change effects to avoid underestimating associated risks. Human-induced climate change had qualitatively similar effects on the extremely low observed river discharges. These results highlight that global warming effects on droughts are already underway, widespread and long lasting, and that drought risk may escalate with further human-induced warming in the future.

The Earth’s mantle is divided by the circum-Pacific subduction girdle into the African and Pacific domains, each featuring a large low-shear-wave-velocity province (LLSVP) in the lower mantle. However, how this hemispherical-scale mantle structure links to Earth’s plate tectonic evolution remains unclear. Previous geochemical work has suggested the presence of a north–south hemispheric subdivision, with large-scale mantle heterogeneities in the Southern Hemisphere, termed the DUPAL (Dupré and Allegre) anomaly. Here we compile elemental and isotopic data of both shallow-mantle-derived oceanic igneous rocks from mid-ocean ridges and deeper-mantle plume-related samples (ocean islands and oceanic plateaus) and analyse these using supervised machine learning classification methods. Data from both shallow- and deeper-mantle-sourced samples illustrate a consistent chemical dichotomy. Our results indicate that heterogeneities in the present-day shallow and deep mantle are not exclusively controlled by the north–south hemispheric DUPAL anomaly. Instead, they are consistent with a chemical dichotomy between the African and Pacific mantle domains and their associated LLSVPs. These observations can best be explained by tectonic supercycles over the past one billion years involving two supercontinents and two superoceans.

Centennial-scale increases of atmospheric carbon dioxide, known as carbon dioxide jumps, are identified during deglacial, glacial and interglacial periods and linked to the Northern Hemisphere abrupt climate variations. However, the limited number of identified carbon dioxide jumps prevents investigating the role of orbital background conditions on the different components of the global carbon cycle that may lead to such rapid atmospheric carbon dioxide releases. Here we present a high-resolution carbon dioxide record measured on an Antarctic ice core between 260,000 and 190,000 years ago, which reveals seven additional carbon dioxide Jumps. Eighteen of the 22 jumps identified over the past 500,000 years occurred under a context of high obliquity. Simulations performed with an Earth system model of intermediate complexity point towards both the Southern Ocean and the continental biosphere as the two main carbon sources during carbon dioxide jumps connected to Heinrich ice rafting events. Notably, the continental biosphere appears as the obliquity-dependent carbon dioxide source for these abrupt events. We demonstrate that the orbital-scale external forcing directly impacts past abrupt atmospheric carbon dioxide changes.

Climate over land—where humans live and the majority of food is produced—is changing rapidly, driving severe impacts through extreme heat, wildfires, drought and flooding. Our ability to monitor and model this changing climate is being transformed through new observational systems and increasingly complex Earth system models. But fundamental understanding of the processes governing land climate has not kept pace, weakening our ability to interpret and utilize data from these advanced tools. Here we argue that for land-climate science to accelerate forwards, an alternative approach is needed. We advocate a parallel scientific effort, one emphasizing robust theories, that aims to inspire current and future land-climate scientists to better comprehend the processes governing land climate, its variability and extremes and its sensitivity to global warming. Such an effort, we believe, is essential to better understand the risks people face, where they live, in an era of climate change.