The research team, led by Hangli Yang and Haoxiang Luan with colleagues including Fei Geng, Yupeng Xu, Hongke Zheng, and Jianguang Xie, built a three-dimensional discrete element model, or DEM, of macroporous recycled concrete and constrained it with an unusually rich set of laboratory measurements. Unlike continuum models that treat concrete as a smeared material, DEM represents the structure as thousands of individual particles connected by bonds that can stretch, shear, and snap. That makes it possible to watch the internal load-bearing network, known as force chains, reorganize as frost damage accumulates. Because no existing simulation platform can directly solve heat transfer, ice–water phase change, and moisture migration together, the team used an experimentally calibrated equivalent-damage approach, updating contact stiffness and bond strengths cycle by cycle rather than applying a single blanket reduction.

The experimental foundation came from the group’s earlier tests on three concrete mixes, labeled M1–20%, M2–25%, and M5–30%, where the numbers denote paste type and designed porosity. The recycled coarse aggregate, crushed from demolished concrete with particles between 9.5 and 37.5 millimeters, consisted of a natural stone core wrapped in a layer of old cement paste covering 23.1 percent of its surface. The researchers measured an impressive array of properties at different numbers of freeze–thaw cycles: compressive, splitting tensile, and shear strengths of the new paste; nanoindentation elastic moduli of the paste, the old paste, and their interfaces with natural aggregate; the rate at which old paste detached from recycled aggregate; and the mass change, strength, and elastic modulus of full specimens.

One of the most striking findings emerged immediately. The specimens did not simply decay monotonically. Instead, their mass and elastic modulus both rose during the first 40 cycles before declining. The explanation lies in a chemical race: water entering the connected pores promoted continued hydration of residual unhydrated cement, and the additional hydration products partially filled small pores, stiffening the paste and its interfaces faster than early frost microdamage could soften them. Only after about 40 cycles did accumulated microcracking, interfacial debonding, and surface spalling win out, sending stiffness into a steep decline. Freeze–thaw deterioration, the study shows, is a staged process of competing mechanisms rather than a steady slide.

To capture the geometric side of damage, the team converted measured mass loss into a count of lost surface paste particles. Because spalling occurred mainly in new-paste bridge regions rather than in aggregate cores, the net solid mass loss could be mapped onto removal of surface paste elements from the model. The algorithm allowed only particles on the current external surface, identified by a bond coordination number below six, to be deleted, so erosion progressed gradually inward without creating nonphysical internal voids. By 160 cycles, the models had shed 817 particles for the densest mix and up to 1,775 for the most porous one, each removal representing a real loss of load-bearing contact.

Validation against compression tests was convincing. Mean errors in peak stress across all groups and cycle counts ranged from 5.2 to 6.0 percent, while peak-strain errors stayed between 12.0 and 15.5 percent. The simulated elastic moduli, though noisier with errors of 10.8 to 18.1 percent, reproduced the characteristic rise-and-fall trend, and a new porosity-controlled prediction equation for post-freeze–thaw elastic modulus achieved a mean calculation error of just 7.6 percent. After 160 cycles, the peak-stress losses reached 38.3 percent for M2–25%, 35.8 percent for M5–30%, and 32.6 percent for M1–20%, matching the laboratory ordering and confirming that freeze–thaw resistance is governed jointly by porosity and the quality of the paste and its interfaces.

The deepest insight came from tracking force chains, the quasi-linear chains of highly stressed contacts that carry most of the load through granular skeletons. In undamaged and early-cycle specimens, load flowed through a few dominant strong chains concentrated in the specimen center and along inclined diagonal paths, producing the classic X-shaped shear failure. The coefficient of variation of force-chain intensity peaked at 1.847 at 40 cycles, when stress concentration was greatest. As cycling continued, however, the degradation of paste-related interfaces and the loss of surface particles progressively severed these dominant chains, forcing load to redistribute from a few high-capacity paths to many dispersed low-capacity ones. The coefficient of variation fell to 1.609 by 160 cycles.

That decline might superficially look like homogenization, as if the material were becoming more uniform and therefore tougher. The researchers show it is anything but. They call the phenomenon damage-induced pseudo-homogenization: the apparent evening-out of the force-chain distribution arises purely because the strongest load paths have failed, at the very moment peak stress and elastic modulus continue to fall. Simultaneously, the proportion of tensile bond failures grew, rising by 4.3 to 6.3 percent across the groups after 160 cycles, and the macroscopic failure mode shifted from X-shaped shear to longitudinal splitting as cracks found weakened interfaces and coalesced parallel to the loading direction. The toughness index dropped by up to 33.1 percent in the most porous mix, meaning the extra deformation capacity reflected damage, not ductility.

The bond-failure statistics also pinpointed the material’s Achilles’ heel. Across all freeze–thaw states, the failure rate ordering never changed: the interfaces between new and old paste, and between new paste and natural aggregate, failed most often, followed by paste-to-paste bonds, with old-paste-related bonds failing least. After 160 cycles, the fastest-growing failure rates belonged precisely to those new-paste interfaces, identifying them as the weak zones through which frost damage first develops and then transfers into the load-bearing skeleton. Notably, the tensile-failure proportion began climbing after 120 cycles for the densest mix but after only 40 cycles for the most porous one, showing how higher porosity concentrates stress and accelerates the onset of terminal damage.

Beyond its scientific contribution, the work carries practical weight for cold-region infrastructure. Permeable pavements, municipal and airport drainage bases, and sponge-city surfaces built with recycled aggregate can now be evaluated with a model that distinguishes which phases and interfaces are degrading, rather than relying on bulk indicators like mass loss or dynamic modulus that blur the picture. The authors suggest their framework can guide material selection, pore-structure design, durability assessment, and maintenance planning. The study’s validation remains an internal consistency check within a single material system, so independent confirmation on other mixes and laboratories will be the next step. But the central message stands: when ice attacks porous recycled concrete, the most dangerous change is not the damage you can weigh, but the silent rewiring of the force chains that hold the pavement together.

Subject of Research: Mesoscopic discrete element modeling of freeze–thaw deterioration mechanisms in macroporous recycled concrete

Article Title: Mesoscopic DEM study of freeze–thaw deterioration in macroporous recycled concrete: Interfacial damage, particle spalling, and force-chain reconstruction

Article References: Mesoscopic DEM study of freeze–thaw deterioration in macroporous recycled concrete: Interfacial damage, particle spalling, and force-chain reconstruction. (n.d.). https://doi.org/10.1016/j.cscm.2026.e06561

Image Credits: AI Generated

DOI: 10.1016/j.cscm.2026.e06561

Keywords: macroporous recycled concrete, freeze–thaw cycles, discrete element method, force chains, interfacial transition zone, recycled aggregate, surface spalling, pseudo-homogenization, permeable pavement, sponge city, elastic modulus, bond failure

The study, published in Environmental and Sustainability Indicators by Qing Lu, Baifei Ren, Liyan Xu, and Hang Yin, introduces what the authors call the National Ecological Security Pattern for Groundwater Preservation, or NESP-GP. The framework builds on the ecological security pattern theory first articulated in 1996, which has long guided landscape planning in China by identifying the spatially critical areas that must be protected for ecosystems to survive. But while that approach has been applied to lakes, typhoons, and broad ecological infrastructure, groundwater—the invisible backbone of water security—has largely been left out. The new work aims to close that gap by treating groundwater not as a marginal afterthought in regional planning, but as a central organizing principle.

Constructing the map was a formidable data challenge. Groundwater information in China is famously fragmented, scattered across ministries, provinces, and agencies, with open-source datasets extremely scarce. The researchers pulled together an extraordinary array of sources: groundwater level yearbooks from monitoring wells concentrated in key regions such as the North China Plain, the Sanjiang Plain, the Weihe Plain, and the Hexi Corridor; the Atlas of Groundwater Resources and Environment of China; provincial water resources bulletins; and layers from the Resource and Environment Data Cloud Platform. Everything was harmonized to a uniform one-kilometer grid, a resolution chosen as a pragmatic compromise between national coverage and computational feasibility. The authors are careful to stress that the result is a strategic spatial assessment, not a high-resolution portrait of local aquifer conditions.

The heart of the framework lies in its three-tiered indicator system. Nineteen indicators were organized into three categories: recharge, utilization, and socio-environmental impacts. The recharge tier captures the natural capacity of the land to replenish aquifers, incorporating average annual precipitation, topographic slope, lineament density, soil texture, depth to groundwater, aridity index, drainage density, geomorphology, and total groundwater resources. The utilization tier measures human demand, from population and GDP density to the proportion of groundwater in the total water supply and per capita water resources. The final tier captures environmental and policy pressures, including land use change, groundwater salinity, the rate of groundwater table decline, and the cone of groundwater depression—the telltale funnel formed beneath areas where pumping has dramatically outpaced replenishment.

To weight these indicators, the team assembled a panel of thirty experts from Peking University and the Chinese Research Academy of Environmental Sciences, spanning hydrogeology, ecology, landscape architecture, urban planning, geography, and environmental management. Each expert independently scored pairwise comparisons using the Analytic Hierarchy Process, a structured decision-making method developed by Thomas Saaty, with consistency ratios below 0.10 deemed acceptable. The resulting weights assigned just under half of the total influence to recharge conditions, about 31 percent to utilization pressures, and roughly 20 percent to socio-environmental impacts. A sensitivity analysis that perturbed the three top-level weights by plus or minus 20 percent showed the national pattern held firm, with Spearman correlations against the baseline ranging from 0.956 to 0.992 and priority-area overlap reaching as high as 96 percent. The map, in other words, is not an artifact of expert idiosyncrasy.

When the index was classified into five security levels using the Natural Breaks method, the geography of China’s groundwater vulnerability emerged with striking clarity. Low security areas covered the largest share of the country, 31.2 percent, followed by very low security areas at 25.3 percent and medium security areas at 21.7 percent. High security zones accounted for 15 percent, while the most alarming category—extremely low security—encompassed 6.8 percent of the study area. Taken together, nearly a third of the nation falls into the two worst tiers, where groundwater protection should command the highest management priority. The spatial logic differs sharply by region. In Northwest China, the problem is a brutal combination of meager natural recharge, driven by low precipitation and high aridity, and heavy dependence on groundwater for livelihoods. In the North China Plain, by contrast, recharge conditions are comparatively favorable, but intensive agriculture, dense populations, and a legacy of relentless extraction have imposed crushing utilization pressures.

The researchers validated their map in two independent ways. First, they compared GRACE satellite observations—which track changes in Earth’s gravity field to estimate shifts in terrestrial water storage—with groundwater monitoring well records over the period 2006 to 2016. The two datasets showed statistically significant but strongly scale-dependent agreement: Spearman’s correlation rose from a modest 0.127 at the native GRACE grid scale to 0.396 when observations were aggregated across 16-by-16 blocks, with directional agreement climbing to 68.1 percent. The lesson is that agreement between satellite and well data improves as their spatial footprints align, offering evidence of broad regional consistency rather than aquifer-level validation. Second, the team compared their security index against China’s official 2024 groundwater overexploitation delineation across eighteen provinces. Provinces with larger officially designated overexploitation areas showed significantly lower NESP-GP values, with a Spearman correlation of minus 0.505, lending independent external credibility to the national pattern.

The most provocative application of the new map concerns China’s sponge cities. The sponge city program, launched through a 2014 technical guide from the Ministry of Housing and Urban-Rural Development, aims to make urban landscapes absorb, store, purify, and reuse rainwater through low-impact development. Its core planning indicator, the volume capture ratio of annual rainfall, is currently zoned almost entirely by regional precipitation patterns—subsurface conditions, groundwater dynamics, and soil characteristics receive comparatively little consideration. By overlaying the NESP-GP onto the existing zoning, the researchers identified striking mismatches in parts of southern Hubei, northern Shandong, and the Jianghan Plain, where groundwater security conditions diverge from the rain-centric planning framework. In water-scarce northern China, they argue, sponge city construction should incorporate reasonable groundwater recharge indicators informed by local precipitation and groundwater level data, much as a case study in Jinan showed that a 75 percent volume capture ratio could help preserve the city’s famous springs by boosting recharge.

The authors are careful about the limits of their claims. The overlay analysis is explicitly a screening-level planning reference, not a recalibration of engineering targets, and any adjustments to capture ratios should be grounded in site-specific hydrological and hydrogeological assessment. The datasets underlying the map largely reflect conditions up to 2016, which means the notably low scores for the North China Plain do not capture more recent groundwater recovery attributed to the South-to-North Water Diversion Project and tightened extraction controls—developments that recent research suggests have significantly reversed the long-term decline in that region’s water table. The framework is meant to complement, not replace, process-based hydrogeological modeling, and the researchers recommend that future versions incorporate water quality data, pollutant monitoring, updated observations, and comparisons between expert-derived weights and data-driven alternatives.

Even with those caveats, the study represents a conceptual shift with implications far beyond China’s borders. Groundwater supplies a substantial share of the world’s irrigation and drinking water, and aquifer depletion from the North China Plain to California’s Central Valley has repeatedly shown that recovery, when possible at all, takes decades. By embedding groundwater into the ecological security pattern framework, the researchers offer governments a template for shifting water management away from narrow, single-source supply thinking and toward integrated spatial planning that treats aquifers as living ecological infrastructure. The invisible water beneath our feet, the study suggests, can no longer afford to remain invisible in the places where cities are planned—and as climate change tightens its grip on global water cycles, the maps that reveal it may become some of the most important documents of the century.

Subject of Research: A national ecological security pattern framework for assessing groundwater sustainability in China and integrating groundwater considerations into sponge city planning

Article Title: A National Ecological Security Pattern for Groundwater sustainability in China: Implications for sponge city planning

Article References: Lu, Q., Ren, B., Xu, L., & Yin, H. (2026). A National Ecological Security Pattern for Groundwater sustainability in China: Implications for sponge city planning. Environmental and Sustainability Indicators, 32, Article 101536. https://doi.org/10.1016/j.indic.2026.101536

Image Credits: AI Generated

DOI: 10.1016/j.indic.2026.101536

Keywords: groundwater, ecological security pattern, China, sponge city, GRACE satellite, aquifer depletion, North China Plain, analytic hierarchy process, water resources management, spatial planning, groundwater recharge, low impact development

The study rests on an extraordinary evidence base: more than 4.2 million reported cases of bacillary dysentery recorded across 338 Chinese cities between 2005 and 2020. That sixteen-year window captures both the period before the sponge city initiative launched in 2015 and the years of its early rollout, allowing the researchers to observe how disease dynamics shifted as urban landscapes were transformed. The surveillance data, drawn from China’s national infectious disease reporting system, were linked with high-resolution meteorological reanalysis data from the ERA5-Land dataset produced by the European Centre for Medium-Range Weather Forecasts, enabling the team to pinpoint precisely when and where flood conditions occurred relative to each reported case.

To isolate the acute effect of flooding on disease risk, the researchers employed a case-crossover design, an epidemiological technique in which each case of dysentery effectively serves as its own control. By comparing each patient’s flood exposure in the days immediately before illness onset with their exposure during comparable control periods, the design automatically strips away confounding from individual characteristics, seasonal patterns, and stable city-level factors. The team modeled the lagged relationship using distributed lag nonlinear models, allowing the effect of a flood to accumulate and decay over time rather than assuming a single-day impact. Their findings were unambiguous: flood exposure elevated bacillary dysentery risk over a lag period extending to 28 days, with severe floods producing the strongest effects.

The vulnerability was not evenly distributed across the population. School-aged children emerged as the group most sensitive to floods overall, a pattern consistent with their greater exposure to contaminated water and surfaces and their still-developing immune defenses. For severe floods, however, the burden shifted toward the elderly, whose physiological resilience and access to care can be compromised during disaster conditions. These age-specific patterns echo a broader literature linking hydrometeorological hazards to child diarrhea and enteric infections, and they underscore that flood adaptation policies carry direct consequences for the most demographically sensitive members of society.

The second and arguably more consequential half of the analysis addressed whether the sponge city initiative actually changed the flood-disease relationship. Launched by the Chinese government in 2015, the program promotes green infrastructure—permeable pavements, rain gardens, constructed wetlands, green roofs, and restored urban waterways—designed to absorb, store, and purify stormwater at its source rather than channeling it through overburdened pipe networks. Because participation was not random, the researchers used a quasi-experimental difference-in-differences framework, comparing 27 sponge cities against 27 carefully matched non-sponge cities over the same period. This approach, adapted from modern econometric methods for staggered policy adoption, estimates what would have happened to disease risk in the absence of the intervention.

The results point to a genuine protective effect. Cities that adopted sponge city development showed lower flood-related bacillary dysentery risk than their matched counterparts, and the benefit deepened over time. The greatest reduction—12.2 percent—was observed by the third year after the initiative, a trajectory consistent with the gradual build-out of green infrastructure and the time required for absorption capacity, drainage performance, and water quality improvements to mature. Event-study estimates confirmed that the divergence between sponge and non-sponge cities emerged only after policy implementation, strengthening the causal interpretation of the findings.

Perhaps the most policy-relevant discovery concerns where the benefits were largest. The protective effect of sponge city development was strongest in cities that started with weaker baseline infrastructure—places with fewer public toilets, lower water pipeline density, and less favorable industrial profiles. In other words, nature-based adaptation delivered its greatest health dividends precisely where conventional sanitation and water systems were least able to buffer flood impacts. This finding challenges the assumption that green infrastructure is a luxury of wealthy cities and instead positions it as an equity tool, capable of narrowing health gaps between developed and less-developed urban settings.

The mechanistic logic behind these results is straightforward. Floods overwhelm combined sewer systems, causing untreated wastewater to mix with floodwater and contaminate surface water, wells, and distribution networks. Green infrastructure interrupts this chain by reducing the volume and velocity of stormwater runoff, limiting sewer overflows, and filtering pollutants before they reach water bodies. By dampening the hydrological shock of heavy rainfall, sponge city features reduce both the probability that pathogens enter the water supply and the duration of human exposure to contaminated environments. The epidemiological signal observed in this study is thus a plausible downstream consequence of well-documented hydrological and water-quality mechanisms.

The study’s scale and methodological rigor distinguish it from earlier work on green infrastructure and health. Previous systematic reviews had catalogued the social and well-being benefits of stormwater-focused green infrastructure but offered little quantitative evidence on infectious disease outcomes, and prior Chinese studies of floods and dysentery were typically confined to single provinces or short time frames. By combining a nationwide case-crossover analysis with a quasi-experimental policy evaluation across matched city pairs, the researchers triangulated the flood-disease association from two independent analytical directions, each with different vulnerability to bias. The convergence of the two approaches lends considerable weight to the conclusion that the observed risk reductions reflect a real intervention effect rather than pre-existing differences between city types.

The implications extend well beyond China. Rapid urbanization and climate change are intensifying pluvial flooding in cities across Asia, Africa, and Latin America, where aging drainage systems and dense populations create fertile conditions for waterborne disease transmission. The Chinese experience suggests that climate adaptation and public health protection should not be treated as separate policy silos: the same permeable surfaces and urban wetlands that mitigate flood peaks also appear to suppress the infectious disease burden that follows in floods’ wake. For governments weighing the costs of green infrastructure investment, the study provides a rare quantified health co-benefit—one that accrues fastest and largest in the communities least equipped to cope with flooding. As climate volatility grows, the sponge city model offers a template for building cities that are not only drier, but measurably healthier.

Subject of Research: The effect of China's sponge city development initiative on flood-related bacillary dysentery risk

Article Title: Reduced flood-related bacillary dysentery risk with sponge city development in China

Article References: Zhang, L., Zha, Q., Zhao, H., Liu, C., Wang, Y., Ji, J. S., Huang, C., & Luo, B. (2026). Reduced flood-related bacillary dysentery risk with sponge city development in China. Nature Cities. https://doi.org/10.1038/s44284-026-00514-z

Image Credits: AI Generated

DOI: 10.1038/s44284-026-00514-z

Keywords: sponge city, bacillary dysentery, flooding, green infrastructure, waterborne disease, China, public health, climate adaptation, case-crossover design, urban resilience, quasi-experimental study, Nature Cities

What unfolded across China in the summer of 2026 was not a string of isolated bad luck. It was, according to the scientists and commentary accompanying the events, a demonstration of a new normal: extreme events once labeled “once-in-a-century” are increasingly compound, concurrent, and geographically dispersed, arriving faster than the institutions and infrastructure built to manage them. A warming trend that outpaces the global average, as officially acknowledged by Chinese meteorological authorities, is raising both the frequency and the intensity of extremes. When a single season delivers typhoon remnants to a northeastern inland province, catastrophic urban flooding to central China, and near-record heat to the northwest simultaneously, the premise that hazards arrive one at a time, separated by decades of recovery and planning, collapses entirely.

The term “once-in-a-century” is shorthand for an event with a 1 percent chance of occurring in any given year, a statistical construct known to hydrologists as the hundred-year return period. Specialists have long recognized that this language is easily misinterpreted: it describes a probability, not a promise that such an event will occur only once every hundred years. In any given century, a 1-percent-annual-chance flood may strike twice, three times, or not at all, and independent river basins can each experience their own hundred-year event in the same year. Yet the intuitive public reading — that a community has earned a century of safety after surviving one such flood — persists, and it shapes how residents, officials, and even engineers respond when the waters return far sooner than the label implies.

Climate change has rendered the historical baseline on which those return periods rest effectively obsolete. The statistics embedded in flood maps and design standards assume stationarity, the idea that the range of natural variability observed in the past will continue into the future. That assumption no longer holds. On 20 July 2021, Zhengzhou recorded 201.9 millimeters of rainfall in a single hour, a new national record, with three-day cumulative rainfall of 617.1 millimeters, approaching the city’s entire annual mean. The deluge overwhelmed a city that had, in part, been built under China’s “sponge city” programme, an ambitious urban design initiative intended to absorb and reuse stormwater rather than shunt it into overburdened drainage networks. Four years later, in August 2025, Zhengzhou’s flood-control emergency response was again raised to Level III, with work, business, classes, and public transport suspended citywide. The hundred-year flood had taken four years to make its second appearance.

These events carry direct and severe health consequences, from drowning and traumatic injury to the disruption of routine and emergency medical care. Globally, public health systems have developed genuine capacity to respond to the acute aftermath of a single flood. China’s Centers for Disease Control and Prevention, for example, issues detailed post-flood guidance on indoor mold identification and remediation, with explicit precautions for vulnerable groups including pregnant women, children under 12, adults over 65, and people with asthma. This is well-designed, evidence-based guidance. But it is guidance calibrated to a single, bounded event: dry the building, remove saturated porous materials within 48 hours, ventilate, and protect vulnerable residents during cleanup. It says nothing about a household, or a health system, absorbing a second or third such event within years rather than decades, nor about heat and flood advisories issued in the same week to the same population. Adaptation guidance built for isolated disasters, however rigorous, is necessary but insufficient for compound, recurring ones.

The problem is not merely communicative but structural. Reservoirs, drainage systems, evacuation routes, and emergency stockpiles are sized against historical exceedance probabilities, and insurance and recovery budgets are paced to the expectation of long intervals between catastrophic losses. When extremes cluster, recovery is truncated. Communities still repairing one flood face the next before foundations have dried, and the cumulative physical and psychological burden of repeated displacement and rebuilding accumulates in ways that single-event frameworks never anticipated. Meanwhile, simultaneous hazards compete for the same response capacity: the personnel, shelters, and supply chains needed for flood evacuation in one province are the same resources a heat emergency in another might demand, and heat itself compounds flood risk by pre-conditioning drought, hardening soils, and altering atmospheric moisture available for subsequent downpours.

Three shifts follow from this pattern, argued in commentary published in The Lancet Regional Health – Western Pacific by John S. Ji and Qihong Deng. First, risk communication should retire probabilistic century-scale language in public-facing materials in favor of terms that convey trend and recurrence, such as “increasingly frequent severe rainfall” rather than “once-in-a-century flood,” so that recurrence within a decade is not received as a statistical anomaly requiring no institutional response. The words officials choose shape whether a second hundred-year flood in four years is read as a freak coincidence or as evidence of a trend demanding action. Second, infrastructure and early-warning design standards, including within the sponge city and reservoir safety programmes, should incorporate non-stationary risk models that use recent-period distributions rather than full-record historical baselines, which mathematically dilute the recent shift toward higher-intensity rainfall. A century of rain-gauge data in which the wettest years cluster in the last decade tells a very different story than the same record averaged across its full length.

Third, public health guidance should evolve from single-event response protocols toward compound-event and cumulative-exposure frameworks, addressing populations facing sequential or simultaneous heat and flood risks within the same season, as well as the mental and physical health burdens of repeated displacement and recovery. That means modeling the health effects of mold exposure after repeated inundation, planning clinically for populations that experience flooding and extreme heat within weeks of one another, and treating the psychological toll of chronic disaster exposure as a first-order public health concern rather than an afterthought. The tools exist — epidemiological surveillance, seasonal forecasting, and increasingly sophisticated artificial intelligence-based forecasting and digital simulation systems that Chinese cities are already deploying — but they must be aimed at the compound problem, not the singular one.

Experts and meteorological authorities have officially acknowledged the warming trend and the rising frequency of extremes, and there are encouraging signs of technical adaptation in forecasting and alerting. Public health guidance and infrastructure standards, however, continue to speak as if these events remain rare. This summer made the mismatch impossible to ignore. Flood warnings in the northeast and heat alerts in the northwest arrived in the same week, and a city rebuilt to absorb the once-unthinkable watched the once-unthinkable return within a political term. The climate has changed. The language, and the standards built upon it, need to change with it.

Subject of Research: Compound climate extremes and the obsolescence of once-in-a-century risk communication

Article Title: Compound climate extremes and “once-in-a-century” risk communication

Article References: Ji, J. S., & Deng, Q. (2026). Compound climate extremes and “once-in-a-century” risk communication. The Lancet Regional Health – Western Pacific, 74, Article 101973. https://doi.org/10.1016/j.lanwpc.2026.101973

Image Credits: AI Generated

DOI: 10.1016/j.lanwpc.2026.101973

Keywords: compound climate extremes, once-in-a-century flood, risk communication, non-stationary risk, sponge city, Zhengzhou rainfall, Typhoon Bavi, Tropical Storm Maysak, public health preparedness, extreme heat, climate change, flood resilience