Earths Future最新文献

This study explores the drivers of urban water use and their spatial-temporal patterns in 142 small and mid-sized cities across the Contiguous United States (CONUS) by analyzing the data directly collected from these cities and using advanced machine learning techniques. We identify five distinguished clusters across CONUS, each showing unique trends of the impact of drivers on water use. We find that socioeconomic factors significantly influence water use in eastern and southwestern cities, while climatic variables such as precipitation and temperature range dominate in central and northwestern regions. Temporal analysis reveals the impacts of major socioeconomic and climatic disruptions on urban water use in the period 2011–2021, including the COVID lockdown, the rapid growth of data centers, and the drought of 2012. In addition, our analysis suggests that economic growth in small and mid-sized US cities continues to be accompanied by rising water use, contrasting with the opposite trend observed in large cities in prior studies. This implies that as smaller cities develop, their water use may increase above current levels until incomes reach a higher threshold, highlighting the need to improve water use efficiency. This study also presents useful insights for developing effective water demand management strategies in response to climatic variability and socioeconomic growth in small and mid-sized cities.

This study uses different downscaling techniques and reference observations to investigate the characteristics of extreme storm events over the conterminous United States in historical and a projected future scenario. While previous studies agree on the projected changes in intensity and frequency of precipitation extremes, there is a lack of consensus regarding how their size will change in response to an increase in radiative forcing. Moreover, the influence of different downscaling techniques on their characteristics has not been thoroughly examined. This study employs an ensemble of high-resolution projections derived from six CMIP6 GCMs, using dynamical, statistical and artificial intelligence based downscaling techniques and two reference observations. Overall, we find noticeable differences in the size, average depth, and total precipitation volume of these storms among the climate ensembles in the historical period. Despite these differences in the historical period, we find consistent future changes across various ensembles. We find a robust projected increase in storm size during Winter and Spring but a decrease in size during Summer in the East. Nevertheless, irrespective of changes in their size, extreme storms are projected to intensify across all the ensembles and seasons.

Multiple hazard risks (MHRs) in coastal zones will continue to increase due to climate change and rising sea levels. These disproportionate impacts create shared challenges that require cross-border mitigation efforts. However, understanding how coastal areas exhibit common risk patterns and how such patterns can inform risk-based cooperation remains fairly limited. Here, we investigated international cooperation potential among 126 coastal countries from an integrated perspective of their risk similarity, geopolitical stance, and knowledge exchange. We conducted a high-resolution assessment of multiple hazard risks (including earthquakes, landslides, flooding, and cyclones) and developed a bottom-up similarity measure to identify common risk profiles across regions from both size and space. Our analysis revealed a notably high degree of risk similarity across country pairs, suggesting greater potential for cooperation than that previously recognized; 89% of country pairs with high risk similarity lacked strong partnerships in consensus-building or knowledge-sharing. This cooperation gap was even more pronounced in the Global South and small island developing states. Instead of relying solely on geographic proximity or existing alliances, we argue for a shift in focus toward partnerships grounded in shared risk challenges. This approach can help to build collective resilience to achieve Sustainable Development Goals for climate action (SDG 13) and partnerships for the goals (SDG 17).

The large-scale atmospheric circulation is a key driver for regional climate extremes, yet its response to anthropogenic forcing remains uncertain. The Pacific trough (PT) regime is a persistent circulation pattern modulating temperature, precipitation, and fires over North America. We show that the observed boreal winter-spring (December to May) PT frequency and duration have increased significantly over the past 76 years, contributing to amplified extreme anomalous heat over western and central Canada. These observed changes are not well represented in the climate simulations analyzed herein. However, our results indicate that rising greenhouse gas concentrations likely contribute to increased winter-spring PT frequency, which is further modulated by sea surface temperatures (SSTs). While the recent La Niña-like and negative Pacific Decadal Oscillation-like SST trends have dampened this increase, our results suggest that if an eventual emergence of the modeled El Niño-like response to elevated $���{\text{CO}}_2��$ were to occur in reality, it would reinstate the increase in PT frequency, duration, and downstream amplification of regional extreme heat. However, the occurrence, timing, and magnitude of this shift remain uncertain, given the complex, interlaced role of external forcings and internal variability in modulating historical trends, as well as models' inability to reproduce them. Additionally, modeling decisions regarding future trajectories for anthropogenic emissions, including aerosols and greenhouse gases, play a critical role in projecting future changes in PT frequency. Our findings underscore the need for a better understanding and modeled representation of long-term changes in the atmospheric circulation to inform climate adaptation and risk assessment.

Chile has endured a decade-long “mega-drought,” yet it remains unclear whether this represents a temporary climate anomaly or the onset of long-term aridification. While droughts are typically temporary events, persistent or recurrent droughts can indicate a transition toward aridification, that is, a gradual shift to drier conditions. We assessed how temporal changes in water supply and demand at multiple time scales affect vegetation productivity and land cover changes in continental Chile to diagnose the region's climate trajectory from drought to aridification. Since 2000, much of the region has seen a continuous decrease in water supply alongside a rise in atmospheric water demand. Further, in water-limited ecoregions, evapotranspiration, likely reflecting reduced transpiration or vegetation cover, has declined over time, with this trend intensifying over longer time scales. A long-term decline in water availability and shifting demand have led to declining vegetation productivity, especially in the Chilean Matorral and the Patagonia Steppe ecoregions. We discovered a link between these declines and drought indices related to soil moisture and actual evapotranspiration at time scales of up to 12 months. Further, our results indicate that the trends in drought indices account for up to 78% of shrubland and 40% of forest area changes across all ecoregions. The most important variable explaining cropland changes is the burned area. Our findings suggest that Chile is undergoing a transition from episodic drought to aridification, underscoring the need for adaptation strategies aligned with this emerging baseline.

Extreme sea levels leading to coastal flooding result of the combined action of waves, storm suges and astronomical tides, often referred to as the total water level (TWL), under storm conditions. Identifying different types of storms, along with their associated durations and uncertainties, provides valuable information for constructing accurate hydrographs and generating reliable flood maps. In this study, we characterize TWL storms, considering their shape and duration, with a focus on coastal flood analysis across Europe. Our proposed approach comprises three steps. First, we classify TWL storms based on their shape. We identify four storm types around Europe that reflect the different relative contributions of TWL components. Second, we introduce a method to determine the duration of individual historical storms, which is applied to estimate the durations of return level events using storm duration functions. We emphasize the importance of accurate duration functions, especially for the longest storms observed in the Mediterranean Sea, for both historical and extrapolated return period events. Third, we implement a new method to design hydrographs for extreme events, enabling the assessment of water volumes resulting from different scenarios. Due to regional variability of scenarios, the semi-enclosed Baltic and Mediterranean Seas exhibit storm surge-dominated and mixed-type storms, respectively, with associated uncertainties exceeding 20%. Our approach considers uncertainties in both storm shape and duration, particularly when the contribution of TWL components is unknown.

Balancing hydropower development with river sediment connectivity is essential for meeting energy demands while mitigating impacts on river ecosystems and delta communities. Here, we introduce an integrated modeling framework to jointly explore water and sediment release strategies alongside dam planning, addressing the complex interplay between sediment transport, hydrology, and reservoir operations. Applied to the 3S river basin, a critical tributary of the Mekong River, the framework provides novel insights into optimizing sediment connectivity and hydropower production. By analyzing spatio-temporal sediment dynamics and employing multi-objective optimization, we assess how coordinated reservoir management can reconcile competing objectives. Our results show a fundamental shift in sediment transport dynamics, with hydropower infrastructure replacing hydro-climatic variability as the dominant control. Since 2018, sediment loads at the basin outlet have dropped from an average of 25 Mt/yr to less than 10 Mt/yr, primarily due to Lower Sesan 2 dam. Optimizing flushing and sluicing strategies, we reveal the importance of coordinated reservoir operations: 57% of the identified Pareto-optimal solutions outperform current dam management practices in all the objectives considered. This study highlights the importance of integrating sediment management with hydropower development and operations, providing a transferable framework for sustainable river basin management globally.

Analyses of observations point to a more detectable change signal in the frequency than magnitude of flood events across the conterminous United States (CONUS); however, little is known about how the frequency of these events is projected to change under different scenarios. Here we apply a statistical attribution-and-projection approach to thousands of streamgages across CONUS and assess how the frequency of flood events is expected to change under multiple scenarios. We find that more frequent flood events are projected for the eastern United States, whereas decreases are slightly more common than increases in the U.S. Southwest and Great Plains. Additionally, the seasonality of flood events is projected to shift, with distinct regional patterns based on geography, topography, and season. These changes are expected to manifest themselves by the middle of this century, highlighting the pressing needs for flood mitigation and adaptation efforts.

Rice production represents a major global food source and a significant contributor to greenhouse gas (GHG) emissions. While nitrogen fertilization and water-saving irrigation are recognized as effective GHG mitigation strategies in rice cultivation, their synergistic effects and underlying mechanisms remain inadequately characterized. Based on 2,689 observations from 203 peer-reviewed articles across 129 sites in major Asian rice cultivation areas, this meta-analysis quantifies the comprehensive impacts of coupled water-nitrogen management on rice yield and GHG emissions. Results revealed that nitrogen fertilization alone increased yield by 38.26% but elevated global warming potential (GWP) by 56.98%, whereas Alternate Wetting and Drying (AWD) irrigation reduced CH₄ emissions (50.71%) and GWP (43.73%) without significantly affecting yield. Combined implementation of both practices increased yield by 46.67% while reducing yield-scaled GWP (GHGI) by 36.17%. Under AWD conditions, nitrogen application rates of 180–270 kg ha⁻¹ maximized GHGI reduction potential (42.31%). Random forest analysis identified soil pH, fertilizer type and precipitation as key determinants of mitigation efficacy. Our spatially-explicit water-nitrogen optimization model demonstrated that 67% of regional rice fields are suitable for AWD implementation, and that current nitrogen inputs could be reduced by 31% while maintaining yields and achieving a 49% reduction in GHGI. This study reveals critical water-nitrogen synergistic mechanisms in rice agroecosystems and provides quantitative frameworks for optimizing management practices at regional scales, offering a sustainable pathway toward achieving future food security and climate change mitigation goals in Earth's most productive rice regions.

Flood protection authorities are not prepared for compound flood risk in estuaries—now and in the face of climate change. Climate projections are rarely downscaled appropriately to assess future changes in storm surge and concurrent river discharge extremes, and their interactions to exacerbate flooding. This is the first time that hourly and fine spatial resolution (7/2.2 km sea level/precipitation), physically consistent, climate projections are used to assess changes in storm surge and river discharge-driven compound events. The analysis, applied to the Dyfi estuary, western UK, uses 12 downscaled perturbed parameter ensembles for the high-emissions “RCP8.5” scenario from a global climate model (HadGEM3-GC3.0). Residual surge and river discharge projections are assessed independently to identify changes in magnitudes and return periods—then combined to identify changing patterns of dependence and timing of compound events. Under RCP8.5 scenario to 2080, river discharge is expected to increase by 28%–29% for 1/20 and 1/50-year events. Extreme (95th percentile) discharge events are more likely to occur concurrently with extreme surges, and compound events will occur more often, and with a shorter time lag between peak surge and peak discharge—potentially compounding flooding further. The analysis provided forcing conditions representative of future 1 in 20-year and 1 in 50-year events used to simulate a potential increased flood footprint in the estuary. The research raises the question of the wider pattern of future compound events throughout the UK, and worldwide, highlighting the critical need for downscaled, coastal and fluvial projections to futureproof flood management strategies.