The biological case for pediatric vulnerability rests on basic physiology. Children breathe more air per kilogram of body weight than adults, in part because their higher ventilation rates and greater oronasal partitioning toward mouth breathing increase the dose of any airborne pollutant delivered to the lower airways. Their airways are also narrower and still developing, so a given degree of inflammation or mucus production produces proportionally greater obstruction. The review emphasizes that children’s immune responses are immunologically immature and skewed toward the type 2 inflammatory pathways that define allergic asthma, meaning that environmental insults arriving during early life can both provoke acute attacks and shape the trajectory of the disease itself. When these anatomical and immunological factors combine with socioeconomic and structural disparities—substandard housing, proximity to traffic corridors, limited access to care—the burden of climate-amplified exacerbations concentrates among the children least equipped to escape it.

Air pollution remains the most extensively quantified trigger, and the review details the cellular choreography by which it initiates an attack. Particulate matter, ozone, nitrogen dioxide and diesel exhaust particles generate reactive oxygen species in the airway epithelium, damaging the barrier that normally keeps the lung’s immune system calm. Injured epithelial cells release alarmins and inflammatory mediators, and experimental work shows that diesel exhaust particles can upregulate interleukin-17A expression through ROS-dependent NF-κB signaling in airway epithelial cells, feeding neutrophilic and mixed inflammatory responses. Ozone, a powerful oxidant formed photochemically from precursor pollutants, is particularly adept at provoking epithelial injury and airway hyperresponsiveness. Global burden-of-disease analyses cited in the review attribute substantial numbers of new asthma cases and emergency room visits to ambient PM2.5, ozone and nitrogen dioxide, and meta-analyses of outdoor pollution consistently link short-term exposure spikes to exacerbations in both children and adults.

What elevates this familiar story into a climate story is the feedback between warming and pollution chemistry. Ground-level ozone formation accelerates with temperature, so heat waves and ozone episodes increasingly arrive together, compounding respiratory stress. Climate-attribution modeling has begun to disentangle how much of future pollution-related mortality and asthma morbidity will be driven by climate change itself rather than by emissions alone, with projections suggesting that a warming world will partially offset gains from cleaner air in some regions while worsening them in others. The review also highlights wildfire smoke as a rapidly growing climate-linked pollution source: attribution studies indicate that anthropogenic climate change has played a large role in driving smoke concentrations across the western United States, and epidemiological work has directly tied climate-change-induced wildfire smoke to asthma exacerbations in that region. Fine particles in smoke penetrate deep into the lung, and children in smoke-affected communities have shown measurable increases in asthma-related emergency visits during major fire events.

Temperature emerges as a second major axis, operating through mechanisms distinct from pollution. Extreme heat triggers oxidative stress, activates bronchial C-fiber sensory nerves and promotes systemic inflammation; in susceptible patients, simply breathing hot humid air can provoke bronchoconstriction through a cholinergic reflex, a finding demonstrated experimentally in asthmatic subjects. Time-series studies from Atlanta, Maryland, Montreal and elsewhere show that warm-season temperature extremes and heat events are associated with increased asthma-related emergency department visits and hospitalizations in children, and case-crossover analyses in Ontario have extended the pediatric heat signal to extreme heat days more broadly. Cold is not protective: longitudinal data from eighteen Chinese cities identified cold temperatures and sudden temperature drops as novel risk factors for exacerbation, and mouse models show that both high and low temperature extremes aggravate airway inflammation. Gene-expression studies suggest extreme temperatures can even reprogram the airway epithelium in mice and asthma patients, hinting at mechanisms that outlast the weather event itself.

The review’s treatment of relative humidity is among its most technically interesting sections. As the atmosphere warms, tropospheric relative humidity stays near constant globally while relative humidity over land declines, a divergence explained by the fact that land warms faster than the ocean surface that supplies its moisture. For the human airway, both directions matter. At low humidity, inspired air dehydrates the respiratory mucosa, and recent work in Communications Earth & Environment argues that global warming risks dehydrating and inflaming human airways directly, compromising the epithelial defenses that depend on a well-hydrated mucus layer. At high humidity, mucus clearance becomes impaired, and humid-heat combinations captured by indices such as the humidex have been linked to childhood asthma hospitalizations in time-series analyses from Hefei, China. Humidity also modifies pollution toxicity: studies in Romania found that the respiratory effects of ambient air pollution varied with air humidity, meaning that climate-driven shifts in moisture regimes can change the dose-response relationship children experience on any given day.

Beyond the three headline exposures, the review maps a web of indirect climate pathways. Lengthening pollen seasons—documented across North America through attribution analyses linking anthropogenic warming to extended and more intense allergen release—prolong the period during which sensitized children hover near the threshold of an attack. Transitional weather in spring and autumn favors the circulation of respiratory viruses, the single most common precipitant of pediatric exacerbations, and shifting season lengths alter when these viral windows overlap with pollution and pollen peaks. Extreme weather events add acute shocks: thunderstorm asthma outbreaks occur when storm outflows rupture pollen grains into respirable fragments; hurricanes and floods damage housing and mold-infest interiors; and dust storms in arid regions have been tied to asthma hospitalizations and respiratory emergency visits in Chinese cities. Each pathway operates on a different timescale, from minutes during a thunderstorm to decades of shifting seasonal norms, but all converge on the same vulnerable airway.

The authors are candid about the limits of current knowledge. Climate attribution—the quantitative assignment of a fraction of observed health outcomes to human-caused warming—has been achieved for only selected exposures, chiefly heat, wildfire smoke and ozone, while the pediatric-specific contribution of humidity shifts, dust storms and viral seasonality remains poorly quantified. Most epidemiological studies measure single pollutants or single meteorological variables, yet children are exposed to mixtures, and emerging work on joint pollutant-mixture associations suggests interactions that single-exposure models miss. Disentangling the independent effect of climate change from concurrent changes in emissions, land use and healthcare access is methodologically demanding, and the review calls for closing these attribution gaps as a research priority, particularly for the low- and middle-income settings where pediatric asthma prevalence is rising fastest.

The practical response the authors propose is adaptation now, not merely mitigation later. Heat-health and air-quality warning systems can give families and clinicians hours of lead time before dangerous conditions arrive; environmental adaptation measures, from improved housing ventilation and filtration to urban greening that cools heat islands, reduce the dose of triggers children actually receive; and equity-focused targeting directs these interventions to the high-risk populations where environmental injustice has already been shown to worsen asthma outcomes among school-age children. Deep-learning models trained on environmental variables are even being tested to forecast asthma patient volumes, offering health systems a way to anticipate surges. The review’s impact statement distills the argument: climate change amplifies the environmental triggers of pediatric asthma exacerbations, children’s physiology heightens their sensitivity to those triggers, and integrating climate-adaptation strategies into routine asthma care could measurably reduce the burden. In a century defined by warming, the authors suggest, the pediatric asthma action plan may need a new first line: check the forecast.

Subject of Research: Climate change effects on pediatric asthma exacerbations through air pollution, temperature and relative humidity

Article Title: Climate change, environmental exposures, and pediatric asthma exacerbations: air pollution, temperature, and relative humidity

Article References: Tran, X. N., Lee, Y.-L., Chang, L.-T., Chang, T.-Y., Chuang, K.-J., Ho, K.-F., Chung, K. F., Chang, J.-H., & Chuang, H.-C. (2026). Climate change, environmental exposures, and pediatric asthma exacerbations: air pollution, temperature, and relative humidity. Pediatric Research. https://doi.org/10.1038/s41390-026-05418-1

Image Credits: AI Generated

DOI: 10.1038/s41390-026-05418-1

Keywords: pediatric asthma, climate change, air pollution, extreme heat, relative humidity, wildfire smoke, ozone, pollen, thunderstorm asthma, respiratory viruses, environmental justice, asthma exacerbations

The scale of the UVic contribution reflects the university’s unusual concentration of climate expertise. Xuebin Zhang, director of the Pacific Climate Impacts Consortium, or PCIC, served on the report’s steering committee and its science advisory committee, helping shape the scope and scientific standards of the entire assessment. Roberta Hamme, director of UVic’s School of Earth and Ocean Sciences, and Francis Zwiers, scientist emeritus and former director of PCIC, served as co-ordinating lead authors on two of the report’s most consequential chapters, covering changes in the oceans and changes in Canada’s climate over time, respectively. Co-ordinating lead authors carry particular responsibility in national assessments: they oversee the drafting of chapter text, ensure that every statement traces back to peer-reviewed evidence, and reconcile the perspectives of dozens of contributing scientists into a single coherent narrative.

PCIC, based at UVic, provided much of the analytical backbone for the temperature, precipitation and extremes chapters. According to Zhang, the consortium’s scientific capacity and its world-calibre services added both data and analysis to the report, with rigorous physical science underpinning detailed assessments of past and future changes in Canadian climate, including temperature, flood, drought and fire. That kind of work involves downscaling global climate model output to regional and local scales, correcting for biases in observational records, and quantifying uncertainty so that projections are useful rather than merely alarming. Zhang emphasizes that the report is the most up-to-date assessment of how Canada’s climate is changing and why, and how it is expected to change in the future. The regional data and analysis provided by the consortium’s researchers, he notes, offer information that is directly relevant to regional and local decision makers, helping them understand the risks they face and prepare for future changes.

One of the report’s most striking findings concerns the pace of warming in Canada’s North. Like other Arctic regions of the world, Canada’s northern territories are warming much more quickly than the rest of the country, a phenomenon consistent with theoretical expectations of how a warming world behaves. Arctic amplification, driven in part by the loss of reflective snow and sea ice that once bounced sunlight back to space, means that the most dramatic temperature increases are occurring in regions where permafrost, ice roads and traditional Indigenous livelihoods are acutely sensitive to thaw. The same northern regions are also receiving more precipitation, another signal that matches what physical climate theory predicts as a warmer atmosphere holds more water vapour. British Columbia, PCIC’s primary regional focus, has experienced changes similar to those seen across most of Canada, tying the province’s experience to the national pattern.

A major technical advance in the 2026 report is its extension of Canada’s warming record back before the era of reliable nationwide measurements. Systematic national coverage of weather observations in Canada only became available in 1948, which has long limited assessments to roughly the postwar period. In the new report, however, scientists were able to estimate how much the country has warmed not just since 1948 but since the 1850 to 1900 preindustrial baseline, the reference period used in international climate targets. This was achieved despite Canada having only a smattering of meteorological observing stations prior to 1900. The breakthrough came thanks to Tong Li, a PCIC postdoctoral fellow, who developed sophisticated methods of combining the sparse available observations with results from climate models, filling the gaps in the historical record with statistically defensible estimates.

That methodological achievement matters because the preindustrial baseline is the yardstick against which global warming limits are measured. Without a credible estimate of nineteenth-century conditions, Canadian warming cannot be placed in the same frame as international targets or compared cleanly with other countries’ assessments. By blending observations with model-based reconstructions, the new analysis gives Canadian policymakers a longer and more complete trajectory of national warming, strengthening both attribution statements about the human role in observed change and projections of what further emissions will bring. The report’s synthesis chapter, led by Zwiers, provides an overall assessment of observed changes in Canada’s climate, detailed evaluations of temperature and precipitation trends, and an explicit accounting of how much human influence on the climate system has contributed to those changes.

The ocean chapter, co-ordinated by Hamme, documents equally profound changes in the waters surrounding the country. Canada’s oceans have warmed and become more acidic because of excess carbon dioxide released by human activities, and marine heatwaves are becoming both more frequent and more intense, with consequences for marine ecosystems and the coastal communities that depend on them. The physical chemistry is well understood: the oceans absorb enormous quantities of the energy trapped by greenhouse gases and a substantial share of the carbon dioxide itself, altering seawater temperature and carbonate chemistry in ways that ripple through food webs from plankton to salmon to whales. For coastal British Columbia, where fisheries, aquaculture and coastal infrastructure are tightly linked to ocean conditions, these shifts translate directly into economic and cultural risk.

Hamme frames the ocean’s role in the climate system as both a service and a warning. The oceans perform a great service to humanity, she explains, by absorbing about 90 percent of the excess heat and roughly 25 percent of the excess carbon dioxide generated by human activity, which slows the rate of climate change on land and in the atmosphere. But that buffering comes at a cost. Higher temperatures and more acidic waters affect which plants and animals can thrive in Canadian waters, rising sea levels threaten coastal communities, and more frequent and intense extreme events are harder to recover from. The report, she says, lays out in plain language how Canada is changing and what can be expected in the future depending on the choices society makes, a deliberate attempt to translate dense physical science into terms that planners, elected officials and the public can act upon.

The practical reach of the assessment extends well beyond the scientific community. The 2019 edition of the report served as the authoritative resource on Canada’s changing climate, informing engineering standards, risk assessments and policy debates across the country. The 2026 update is designed to support decision making and adaptive planning at every level, from municipal infrastructure planning and emergency management to Indigenous-led climate adaptation initiatives, water management, coastal resilience programs and updates to building codes. Engineers designing drainage systems need flood projections; health authorities need heat warnings calibrated to a warming baseline; coastal municipalities need sea-level scenarios that account for both global ocean change and local land motion. The report supplies the common evidence base for all of them.

Behind the national assessment stands a broader research enterprise. UVic researchers contribute internationally recognized expertise in climate modelling, ocean science, renewable energy systems, water security, conservation, public policy and climate adaptation, and through 12 research centres and other programs they help communities, governments and industries plan for and respond to climate and environmental change. The 2026 report demonstrates how that expertise scales up: individual scientists contributing chapters, datasets and novel methods combine into a single national picture of a country being reshaped by a changing climate. For Canada, the message of the assessment is unambiguous. The changes are already measured, the human cause is quantified, and the trajectory of the coming decades will depend on emissions choices made now, at home and around the world.

Subject of Research: The role of University of Victoria climate and ocean scientists in Canada's national climate change assessment

Article Title: How UVic researchers are helping Canada understand a changing climate

Article References: How UVic researchers are helping Canada understand a changing climate. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: climate change, Canada's Changing Climate Report 2026, University of Victoria, Pacific Climate Impacts Consortium, ocean warming, ocean acidification, marine heatwaves, Arctic amplification, climate attribution, sea level rise, climate adaptation, extreme heat

The research was led by teams at the Center for Climate, Health, and the Global Environment at Harvard T.H. Chan School of Public Health and the Department of Epidemiology at Boston University School of Public Health, in collaboration with the health data company Truveta. Their approach represents a proof of concept for what the authors describe as near-real time surveillance of climate-related health harms. Rather than waiting for administrative claims to be processed and released, the team drew directly on clinical records generated at the moment patients walked into emergency departments, transforming routine medical documentation into actionable intelligence for an ongoing climate event.

The scale of the analysis was substantial. The researchers examined 8.1 million emergency department visits recorded during the summers of 2023 through 2025, drawing on de-identified electronic health records contributed by Truveta member health systems spanning 19 Eastern U.S. states. They linked daily maximum temperatures to state-level counts of emergency department visits for all causes, heat-related illnesses, kidney diseases, and psychiatric conditions. From these connections, they estimated how much visit rates rose on hotter days and calculated how many visits during the June and August 2025 heat waves could be attributed to extreme temperatures.

The findings quantify, with unusual immediacy, just how heavily heat weighs on emergency care. During the June 2025 heat wave, approximately 9.2 percent of all-cause emergency department visits were attributable to heat, corresponding to roughly 6,986 additional visits across the 19 states studied. The August 2025 heat wave produced a similar burden, with about 8.3 percent of all-cause visits attributable to heat, or approximately 6,351 additional visits. Taken together, the two events were responsible for more than 13,000 excess emergency department visits, a surge that the authors argue demands real-time visibility and rapid response rather than retrospective accounting.

Perhaps the most striking pattern emerged in kidney disease. Nearly 30 percent of kidney disease-related emergency department visits during heat wave periods were attributable to heat, a proportion that underscores how profoundly high temperatures stress the body’s fluid and thermoregulatory systems. Across the entire warm season from April through August in 2023 to 2025, warmer temperatures were associated with a 6.3 percent increase in all-cause emergency department utilization, a 19.5 percent increase in visits for kidney diseases, and an 8.8 percent increase in visits for psychiatric conditions. These associations held across three consecutive summers, suggesting a consistent and predictable relationship between rising temperatures and acute health care demand.

One finding in particular carries weight for how health agencies evaluate their own programs. Intuition might suggest that heat-related emergency visits would ease as summer progresses, as residents acclimatize and heat advisories become routine. The data showed only a modest decline between the June and August heat waves. According to Amruta Nori-Sarma, the study’s lead author and deputy director of Harvard Chan C-CHANGE, this has important implications for real-time evaluation of locally implemented adaptation programs. If adaptation measures such as cooling centers or outreach campaigns are working, their effect should be visible in emergency department patterns within the same season, and if they are not working, agencies can adjust before the next event rather than the next year.

The practical applications the researchers envision extend across the preparedness landscape. Near-real-time emergency department data can validate whether heat action plans and early warning systems are actually reducing health burdens, for example by confirming whether opening cooling centers coincides with fewer heat-related visits. Rapid analyses can help target urban greening and cool infrastructure investments toward the neighborhoods and populations showing the strongest spikes during heat. Electronic health record surveillance can also highlight which groups, such as outdoor workers, older adults, or people with chronic kidney disease, need tailored public health messaging and worker protections as upcoming heat events approach. By comparing emergency department patterns before and after new measures are introduced, health agencies can see within a single summer whether programs are protecting patients.

Underlying the study is a technological shift in how clinical data can be mobilized for public health. The records used came from Truveta, a platform that aggregates de-identified electronic health records from member health systems, and were available within one week of each emergency department encounter. That turnaround, compared with the months-long lag of insurance claims, changes the fundamental character of heat surveillance: it moves from forensic reconstruction to situational awareness. As Brianna Cartwright, director and lead of Truveta Research and a co-author on the paper, noted, timely real-world data allow researchers to rapidly assess the health impacts of extreme heat across diverse populations and geographies, providing a clearer picture of risk and the potential to transform how climate-related health emergencies are monitored, understood, and answered.

The policy implications outlined by the authors are direct. They call for investment in data systems that permit timely, secure use of electronic health records for public health situational awareness, and for the integration of near-real-time emergency department surveillance into heat action plans, emergency preparedness frameworks, and broader climate resilience efforts. They also urge focused attention on the populations the data identify as most at risk, especially older adults and people with kidney disease. As Mary Willis, senior author and assistant professor of epidemiology and environmental health at Boston University School of Public Health, emphasized, the surge of more than 13,000 excess visits from just two heat waves underscores the importance of investing in timely population health surveillance and corresponding intervention strategies in an era of increasing extreme heat.

As climate change lengthens and intensifies heat seasons across the United States and beyond, the gap between harm and response has become one of the most consequential variables in public health. This study suggests that the gap can be closed not by new medical treatments but by faster information: a shift in how existing clinical data are collected, linked, and interpreted. If the approach demonstrated across 19 states can be scaled and sustained, the summers ahead may be the first in which health systems can watch a heat wave’s impact unfold in real time, redirect resources toward the patients and communities being hit hardest, and learn within weeks rather than years which protective measures actually save lives.

Subject of Research: Near-real-time surveillance of heat wave health impacts using electronic health records

Article Title: Rapid response to heat waves: Using electronic health records to protect patients in near-real time

Article References: Rapid response to heat waves: Using electronic health records to protect patients in near-real time. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: heat waves, electronic health records, emergency department visits, public health surveillance, extreme heat, kidney disease, climate change, Nature Health, Harvard Chan C-CHANGE, Boston University School of Public Health, Truveta, heat action plans

The core of the problem lies in how temperature is actually measured at the locations where people live and work. Physical weather stations are typically spaced miles apart, which means that for most cities, neighborhoods, and farm fields, no station directly records the local temperature. Researchers therefore rely on statistical estimates, often called proxies, that interpolate or model temperatures between stations or draw from gridded climate products. These proxies are the best available guesses, but the new study demonstrates that they carry measurement errors far larger than the assumptions embedded in standard econometric methods. Traditional statistical frameworks generally treat such error as negligible or as classical measurement error that merely attenuates estimated effects. The reality, Yu and Carson show, is more troubling: the errors persist over time, correlate with terrain and monitoring density, and distort the temperature signal in ways that conventional corrections cannot fix.

The magnitude of these errors is striking, and it varies enormously with geography. In mountainous regions such as Boulder, Colorado, where temperature can change dramatically over short distances due to elevation, slope, and aspect, standard weather proxies differed from actual temperatures by an average of nearly 15 degrees Fahrenheit. In flatter, more densely monitored areas such as Chicago, the corresponding errors were as low as 1 degree Fahrenheit. This spatial heterogeneity matters because climate-impact studies frequently pool data across many locations. If the proxy error is systematically larger in some places than others, and if those places differ in the outcomes being studied, the resulting estimates inherit a geographic bias that no amount of additional statistical sophistication within the regression can remove. The error is baked into the input data itself.

To put the scale of the problem in perspective, the study reports that for one commonly used weather proxy, temperature measurement errors averaged 3.3 degrees Fahrenheit, or 1.85 degrees Celsius. That figure is larger than the entire warming limit enshrined in the Paris Climate Agreement, which commits signatories to holding global temperature rise well below 2 degrees Celsius and pursuing efforts to limit it to 1.5 degrees Celsius. In other words, the uncertainty introduced by mismeasured temperature inputs in a single class of research data exceeds the full amount of warming that international policy seeks to prevent. For a field in which effect sizes are often estimated from differences of a degree or two between hot days and moderate days, an error of this magnitude is not a rounding issue. It is a first-order problem that can reshape the conclusions of an entire literature.

The empirical demonstration at the heart of the paper uses one of the most policy-relevant relationships in climate economics: the link between extreme heat and violent crime. The researchers assembled more than 20 million crime records and first estimated the heat-crime relationship using city-level crime and temperature data, treating this as a benchmark against which coarser approaches could be judged. They then aggregated both the crime data and the temperature data to the county level and re-estimated the same relationship. The result was consistent with the theoretical prediction: when both outcomes and temperatures were measured at a coarser geographic scale, the estimated effect of extreme heat on violent crime became smaller. The attenuation was not a property of the underlying physics or human behavior but an artifact of how temperature was matched to the units of observation.

This finding has implications that extend well beyond criminology. The same mismatch between temperature proxies and the true exposure of people, crops, and infrastructure affects studies of heat-related mortality, labor productivity, energy consumption, and agricultural output. Whenever the proxy error varies systematically with geography, the estimated dose-response relationship between temperature and the outcome of interest is biased. In some settings the bias runs downward, making heat appear less damaging than it truly is; in others it can run upward. The authors emphasize that the direction and size of the bias depend on how the error correlates with both the local climate and the outcome being modeled, which is precisely why simple fixes, such as adding more control variables or switching to a different functional form, cannot be relied upon to restore accuracy.

The policy stakes are considerable. Economic estimates of climate damages feed directly into cost-benefit analyses, infrastructure investments, emergency preparedness budgets, and adaptation planning. If those estimates systematically understate how severely extreme heat drives crime rates, crop losses, or health emergencies, then the scale of the policy response will be miscalibrated as well. “If climate-impact studies misestimate how severely extreme heat drives crime rates, crop loss, or health emergencies, policymakers may also misestimate the scale of the responses needed to address those impacts,” Yu said. A 15 percent understatement, compounded across dozens of sectors and repeated in every new study that inherits the same proxy problem, could translate into billions of dollars of underinvestment in cooling centers, grid hardening, heat-health early warning systems, and agricultural adaptation.

Importantly, the study does not merely diagnose the problem; it offers practical guidance for researchers choosing among the growing menu of temperature data products. No single proxy performs best everywhere. In regions with dense weather-station networks, measurements from nearby stations can outperform more complex gridded products, because direct observations at close range capture local conditions that interpolated grids smooth away. In areas where monitoring is sparse, gridded data may perform better, since they incorporate additional information such as satellite retrievals and reanalysis models that partially compensate for the absence of ground stations. The practical lesson is that proxy choice should be an explicit, location-specific decision grounded in validation against known temperatures, rather than a default driven by convenience or habit. Researchers can and should quantify the likely proxy error for their study region before drawing substantive conclusions from it.

The broader prescription, according to the authors, is to reduce measurement error at its source by improving the spatial resolution of temperature monitoring itself. Expanding and maintaining dense weather-station networks would shrink the interpolation distances that generate proxy error in the first place. Equally important is more carefully matching temperature measurements to the locations where exposure actually occurs: where people live, where farms grow crops, where businesses operate, and where ecosystems are under stress. A temperature recorded at an airport runway may poorly represent the heat experienced in a nearby low-income neighborhood with little tree cover, and a county average may poorly represent the conditions on any given field within it. Closing that gap between what is measured and what is experienced is, the study suggests, one of the most cost-effective ways to improve the reliability of climate-impact science.

For a research community increasingly asked to inform high-stakes decisions about adaptation and mitigation, the message is sobering but constructive. The tools exist to do better: denser station networks, careful proxy validation, and matching data to the true units of exposure. What the Yu and Carson study adds is a quantified warning that the status quo carries a measurable cost, one large enough to rival the very climate signal that decades of research have worked to detect. As extreme heat intensifies and its consequences for health, safety, agriculture, and energy systems grow, ensuring that the temperatures feeding into those analyses are accurate is not a technical footnote. It is a prerequisite for knowing, with confidence, how much is truly at stake.

Subject of Research: Measurement error in temperature proxies used in economic climate-impact studies

Article Title: Temperature measurement error may cause climate-impact studies to understate impacts by 15% or more

Article References: Temperature measurement error may cause climate-impact studies to understate impacts by 15% or more. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: climate impacts, temperature measurement error, extreme heat, violent crime, weather stations, gridded climate data, econometrics, Paris Agreement, public health, crop yields, adaptation policy, Wake Forest University

The research team analyzed global climate data spanning 45 years, from 1979 to 2023, focusing on four distinct dimensions of heatwave behavior: the seasonal onset date of the first heatwave, the end date of the last heatwave, the total length of the heatwave season, and the onset speed of the season’s opening event. This approach departs from conventional heatwave studies, which have traditionally concentrated on frequency, intensity, and duration. By shifting attention to timing and development rate, the researchers uncovered patterns of change that standard metrics have largely overlooked.

The numbers reveal a systematic restructuring of the heatwave season across the planet. On average, the first heatwave of the year has been starting 3.29 days earlier per decade, while the last heatwave has been ending 5.41 days later per decade. Taken together, these shifts have extended the global heatwave season by 8.71 days per decade. Over the full 45-year study period, that means the first heatwave has advanced by roughly two weeks, the last heatwave now arrives about 24 days later in the year, and the overall season during which land areas are vulnerable to extreme heat has lengthened by approximately 39 days.

These trends are not confined to a few unlucky regions. Across global land areas, 72 percent showed a trend toward earlier heatwave onset, 79.6 percent exhibited later heatwave end dates, and a remarkable 92.1 percent experienced lengthening heatwave seasons. The changes were generally more pronounced in drylands, the arid and semi-arid regions where ecosystems and human populations are often already operating close to their thermal and water limits. The breadth of these percentages suggests that the expansion of the heatwave season is a near-global phenomenon rather than a patchwork of regional anomalies.

Perhaps the most consequential finding concerns how quickly the first heatwave of each season develops. The researchers classified each season’s opening heatwave as rapid-onset, moderate-onset, or slow-onset, based on the relative timing of the temperature peak within each event. A rapid-onset heatwave is one that reaches its peak temperature early in its course, leaving little time for gradual acclimatization. From 2001 to 2023, the proportion of rapid-onset first heatwaves within heatwave-affected land areas increased significantly, signaling a recent and accelerating shift toward faster heatwave development worldwide.

The implications of that shift are sobering. As Xu Wenfang of the South China Botanical Garden, the study’s first author and one of its corresponding authors, explained, research attention has historically centered on whether heatwaves are becoming more frequent, stronger, and longer. The new results show that their timing and onset speed are changing as well. If heatwaves arrive earlier and develop more rapidly, the window available for societies and ecosystems to prepare and adapt could shrink even further, compounding the risks posed by the intensification of extreme heat itself.

Agriculture emerges as a particularly exposed sector. The study found that longer heatwave seasons are expanding the exposure of crops to extreme heat during critical stages of reproduction, such as flowering and silking, when a single episode of intense heat can sharply reduce yields. From 2001 to 2023, the proportion of crop areas experiencing heatwave exposure during these vulnerable reproductive stages increased by between 1.6 percent and 13.3 percent for several major crops, compared with the baseline period of 1979 to 2000. Heatwave exposure also extended into earlier and later stages of crop development, meaning that the entire growing cycle faces a broadening threat.

This agricultural dimension illustrates why heatwave timing matters as much as heatwave magnitude. Crops have evolved phenological calendars in which flowering and grain filling occur within relatively narrow windows; heat stress during those windows can sterilize pollen, abort kernels, and cascade into harvest losses. When the heatwave season stretches at both ends, the probability that these sensitive stages coincide with extreme heat rises even if individual events do not break temperature records. Earlier onset also means that crops, wildlife, and human populations may encounter their first extreme heat of the year before they have physiologically or behaviorally adjusted to summer conditions.

The researchers argue that their findings provide new insight into global heatwave change by elevating timing and development speed to the status of core climate risk indicators. In practical terms, this means that heat monitoring and early-warning systems should consider not only how hot an event will be and how long it will last, but also when in the season it arrives and how quickly the first heatwave climbs to its temperature peak. Incorporating onset timing and onset speed into risk frameworks could sharpen the usefulness of forecasts, giving public health agencies, farmers, and grid operators a more complete picture of the hazards ahead.

The potential applications span multiple domains. In public health, earlier and faster-developing heatwaves could inform the timing of heat action plans, hospital preparedness, and community outreach, particularly for vulnerable groups such as the elderly and outdoor workers. In agriculture, season-length information could guide planting decisions, irrigation scheduling, and the selection of crop varieties with different reproductive timing. In ecosystem management and energy supply, where heatwaves simultaneously stress natural systems and drive peak electricity demand for cooling, an expanded and faster-onset heat season adds pressure on infrastructure and conservation planning alike. By documenting that the heatwave calendar itself is shifting under a warming climate, the study adds a new layer of scientific evidence for adaptation strategies, and it underscores a broader message: the pace of climate change is being felt not only in the intensity of extremes but in the shrinking time left to respond to them.

Subject of Research: Global changes in heatwave seasonal timing, onset speed, and crop exposure under a warming climate

Article Title: Heatwaves on land start earlier and develop faster worldwide

Article References: Heatwaves on land start earlier and develop faster worldwide. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: heatwaves, climate change, Nature Climate Change, onset timing, heatwave season, drylands, crop exposure, early-warning systems, extreme heat, global warming, risk assessment, Chinese Academy of Sciences

The problem the team identifies sits in the middle of the evaluation spectrum. At one end are well-bounded, closed-form tasks, such as multiple-choice medical exams or legal benchmark suites like MEDQA and LEXGLUE, where correctness is specified in advance and scored at scale. At the other end are highly professionalized expert domains, where validation rests on formal standards and regulatory norms. Between these poles lies a growing class of intermediate, situational, and interdisciplinary queries that are neither reducible to fixed answers nor stabilized by consensus authority. Recent polling shows that activities such as targeted information searches and idea generation rank among the top uses of generative AI, and categories like medical advice and legal document drafting have expanded sharply between 2024 and 2025, meaning models are increasingly treated as entry points into specialized knowledge once mediated by professionals.

To illustrate the gap, the authors contrast two kinds of questions. A prompt asking a model to diagnose a 45-year-old man with chest pain and ST-segment elevation can be scored against an established clinical benchmark. But asking how traditional Ayurvedic practices should inform post-heart-attack rehabilitation in rural India demands cultural nuance, historical knowledge, and interdisciplinary synthesis that no fixed test set can capture. Similarly, predicting wheat yields under a two-degree temperature rise can be checked against a crop model, while designing a community heat-action plan for an oasis town facing desertification, with local cultural practices and resource constraints in mind, requires open-ended, scenario-based judgment. Climate adaptation, the study argues, is precisely such a domain: inherently interdisciplinary, regionally contingent, and short on the codified corpora that make medical and legal benchmarking feasible.

The team’s answer draws on the traditions of qualitative data analysis. SQEs are streamlined, rubric-based assessments of limited sets of open-ended responses, conducted by trained human coders. The word qualitative here does not mean unstructured or subjective; evaluative categories are developed through engagement with research literature and theoretical frameworks, and responses are scored against transparent, analytically grounded criteria. The word small refers to a design principle borrowed from the qualitative methodologist Johnny Saldaña’s notion of code parsimony: rubric dimensions should be added only when they designate a salient area of performance that matters to the stated use case. Sparse code sets prioritize interpretability, inter-rater reliability, and transparency, allowing small teams without dedicated evaluation infrastructure to produce defensible assessments.

As a demonstration, the researchers built the Desert Language Model Evaluation Framework, or DLEF, a rubric for evaluating open-ended guidance on extreme heat adaptation, developed from materials produced by Arizona State University’s Knowledge Exchange for Resilience. The framework consists of 35 prompts derived from seven core heat-related questions, each with four location-specific variations across Scottsdale, Phoenix, Guadalupe, and Flagstaff, Arizona, covering topics such as heat stroke diagnosis, home weatherization, air conditioning failures, outdoor worker safety, and public transportation. Each prompt was submitted to GPT-4o ten times, yielding 350 location-based responses and 100 medical responses per condition, collected with automated Selenium scripts in November 2024. Textual consistency was measured using TF-IDF vectorization and cosine similarity, and response quality was scored across five dimensions: Place-Based Fit, General Fit and Feasibility, Executive Path, Uncertainty and Intellectual Humility, and Affect and Emotional Intelligence.

The human validation results were revealing. Two trained coders independently scored a sample of 70 items, and inter-rater reliability, measured with quadratic-weighted Cohen’s kappa, was strongest for the adaptation-relevant dimensions: Place-Based Fit reached 0.91, Executive Path 0.66, and General Fit and Feasibility 0.56, while Uncertainty and Humility (0.24) and Affect and Emotional Intelligence (0.28) fell well short of acceptable thresholds. Mixed-effects models reinforced the pattern, with Place-Based Fit showing the strongest systematic variation tied to prompt characteristics. Substantively, GPT-4o showed surface-level sensitivity to place, often naming a city when given, but limited ability to translate location into genuinely tailored advice. Prompts anchored in low-desert localities such as Scottsdale, Phoenix, and Guadalupe scored higher than those for high-desert Flagstaff, and prompts with no location specified performed worst, a pattern consistent with the distribution of the model’s training data. Apartment prompts received lower feasibility ratings than single-family or mobile homes, reflecting limited attention to the user’s actual control over infrastructure.

The study then asked whether a human-validated SQE could be replicated by automated LLM-as-judge scoring. Four open-weight models, Llama 3.1 8B, Qwen 8B, GPT-OSS 20B, and Mistral 26B, were deployed locally at temperature zero and asked to score the same 70 items under eight prompt variants that systematically varied expert versus nonexpert framing and the type of anchor examples provided. No single configuration achieved acceptable agreement, defined as kappa of at least 0.60, across all five dimensions. Place-Based Fit was the sole dimension approaching reliable replication, with GPT-OSS 20B under the nonexpert condition with human-grounded anchors reaching a mean human-agent kappa of 0.772, equivalent to 85 percent of the human-human baseline. Executive Path never exceeded 30 percent of human agreement under any model or variant. Crucially, the correlation between human inter-rater reliability and best automated agreement across dimensions was significant (Pearson r = 0.686, p = 0.005), suggesting that how consistently humans can apply a rubric predicts whether machines can replicate it.

To understand why, the team turned to mechanistic interpretability. Using the National Deep Inference Fabric and the NNsight library, they extracted last-layer hidden states from Llama 3.1 8B and 70B at the token immediately preceding score generation and trained linear probes to predict human consensus scores. For Place-Based Fit, where human agreement was high, probe accuracy was also high, and principal component analysis revealed a visible score-level gradient along the first principal component in the 70B model, indicating that the construct was geometrically organized in the model’s representations in a way consistent with human judgment. Strikingly, at the 8B scale the probe kappa of 0.713 exceeded the model’s own output agreement with human raters, suggesting the model internally represented place-sensitivity better than its scores reflected, a distinction that matters because it points to prompt design or calibration fixes rather than a need for a bigger model.

The Uncertainty and Humility dimension told a cautionary counter-story. Probe kappa exceeded the human-human baseline under all conditions, reaching 0.588 for the 70B model against a human kappa of just 0.244. Yet per-rater analysis showed that this apparent alignment was partly an artifact of averaging divergent rater scores toward the middle of the scale, a phenomenon the authors link to what recent work calls the consistency-bias paradox: high internal consistency in an AI judge does not guarantee valid measurement. When a model produces more consistent scores than humans on a dimension where humans disagree, it has more likely converged on its own interpretation of the construct than faithfully operationalized the codebook’s intent. High automated agreement on a poorly operationalized dimension, the authors argue, is a validity concern rather than evidence of scalability.

The broader implication is that human inter-rater reliability should function not merely as a quality check on a rubric but as a prior estimate of whether automated replication is feasible at all. Dimensions defined by observable, surface-detectable features of text are candidates for automation at sufficient model scale, while dimensions requiring inferential judgment about tone, structure, or epistemic stance remain dependent on human coding. The authors propose a five-stage workflow of rubric development, human calibration, automation screening, scaled deployment, and periodic revalidation, and they caution that prompt configurations validated for one model family may not transfer to another even at the same parameter count. SQEs are not a replacement for large-scale benchmarks or professional panel adjudication, but they offer a principled, repeatable strategy for the dynamic, contested, and interdisciplinary settings where AI systems are increasingly deployed, and where, as the foundation paradox makes clear, the consequences of untested guidance may be greatest.

Subject of Research: Evaluation of large language model performance in open-ended, interdisciplinary domains using small qualitative, human-in-the-loop assessment frameworks

Article Title: Performance within the foundation paradox: the case for small qualitative evaluations

Article References: Simeone, M., Hyatt, J., Bienenstock, E. J., Babu, R., & Solis, P. (2026). Performance within the foundation paradox: the case for small qualitative evaluations. Neural Computing and Applications, 38(19), Article 777. https://doi.org/10.1007/s00521-026-12328-0

Image Credits: AI Generated

DOI: 10.1007/s00521-026-12328-0

Keywords: large language models, model evaluation, small qualitative evaluations, inter-rater reliability, LLM-as-judge, mechanistic interpretability, climate adaptation, extreme heat, qualitative data analysis, foundation models, benchmarking, GPT-4o

The special issue assembles twelve studies examining disasters and their effects on older adults across the United States, Puerto Rico, and China, spanning home- and community-based care, assisted living communities, and nursing homes. Together, the research paints a picture of hazard exposure that is rarely limited to one event. Researchers trace how childhood adversity, extreme heat, air pollution, and multiple losses following hurricanes can shape cognitive function, mental health, and daily functioning decades later in life. Other studies document how disasters can cause sustained disruptions to home health and therapy services well beyond the central disaster zone, rippling outward through the networks of care that frail and homebound older adults depend upon daily. Still others reveal that pre-existing differences in staffing levels, organizational structure, and resident involvement leave assisted living communities and nursing homes unevenly prepared, meaning that two facilities in the same storm path may face radically different outcomes.

One of the most sobering findings highlighted in the editorial concerns persistent gaps in individual preparedness. Even older adults who live with chronic illness or who have lived through previous disasters may lack concrete plans for continuing medical care during a power outage or an evacuation. Devices such as oxygen concentrators, refrigerated medications, dialysis schedules, and mobility equipment all depend on infrastructure and logistics that fail precisely when disasters hit. Yet the research also identifies factors that strengthen preparedness and recovery: prior experience, resilience, hope, self-efficacy, caregiving relationships, and reliable access to information all emerge as protective resources. The editorial’s argument is that these modifiable factors can be deliberately cultivated by families, clinicians, and community organizations, rather than left to chance, and that doing so represents one of the most practical pathways to reducing harm in an era of intensifying climate-related hazards.

“Motivation alone is not enough,” said Peterson, of the University of South Florida School of Aging Studies. “Older adults need information that is timely, relevant, and meets their needs and life circumstances. And they need better support from all the organizations with a role in disaster planning and recovery, from emergency management and health care providers to home care, respite, and long-term care facilities.” The statement underscores a recurring theme across the special issue: preparedness campaigns that treat older adults as a homogeneous group, or that rely on generic checklists, fail to account for the enormous diversity of health status, living arrangement, caregiving situation, and geographic exposure found within the aging population itself. A rural older adult living alone with limited transportation faces a fundamentally different risk profile than a resident of a well-staffed urban nursing facility, and effective planning must reflect those differences.

The psychological dimension of disasters receives particular attention in the issue. “Disasters do not only threaten physical health. For older adults, they can cut people off from normal routines, relationships, and the caregivers they rely on. Those losses can have lasting psychological effects,” said special issue guest editor Lisa M. Brown, PhD, ABPP, of the Department of Clinical Psychology at Palo Alto University. “When preparedness includes mental health, caregiver support, and trauma-informed care, older adults—and the staff and families who care for them—will be better able to cope during a crisis and throughout recovery.” Brown’s framing points to a frequently overlooked mechanism of harm: the severing of social ties and daily routines that anchor cognitive and emotional stability in later life. For people living with dementia, the loss of familiar caregivers and environments during evacuation can accelerate decline, while the trauma of repeated evacuations can accumulate across successive storm seasons.

The third guest editor, David M. Dosa, MD, MPH, professor of medicine and chief of geriatrics at UMass Chan Medical School, emphasized the shared societal stakes of the research. “Disasters are apolitical events,” he said. “We must do our very best as a society to understand how best to prepare for and respond to disasters. Articles like the ones in this special issue can help us do just that and must be encouraged.” Dosa’s comment reflects a growing consensus among geriatricians and emergency management researchers that disaster science for older adults has historically been underfunded and fragmented, with lessons learned in one jurisdiction rarely translated into policy or practice elsewhere. The special issue is intended, in part, to consolidate evidence across settings and nations so that preparedness can become a systematic discipline rather than an improvised response.

Technically, the editorial points toward a set of concrete interventions. These include integrating disaster planning into routine clinical care, so that emergency medication supplies, power-dependency registries, and evacuation plans are established during ordinary medical visits rather than in the frantic hours before a storm. They also include building organizational capacity within assisted living communities and nursing homes, tailoring preparedness approaches to each facility’s geographic and structural vulnerabilities, and creating community-based programs that account for the full range of older adults’ circumstances, particularly in rural areas where emergency services are sparse and response times are long. The emphasis on organizational capacity reflects findings that facilities with stronger staffing, clearer chains of command, and greater resident involvement consistently fare better when hazards strike, suggesting that preparedness is as much an institutional property as an individual one.

Taken together, the twelve studies and the framing editorial deliver a clear analytical conclusion: disaster vulnerability in later life cannot be understood by examining a single event in isolation. Preparedness and recovery depend on the accumulation and interaction of prior experiences, health and social conditions, institutional capacity, geography, and access to trustworthy information. A hurricane that spares one older adult may devastate a neighbor with the same age but a different constellation of chronic illness, social isolation, and care arrangements. This systems-level view challenges the traditional emergency management model, which often treats affected populations as uniform and response as a short-term operation with a defined end point. For older adults, the research suggests, recovery may extend months or years, and the disruption of home health services far outside the disaster zone can be as consequential as the hazard itself.

The editorial also carries implications for policy at a moment when climate change is increasing the frequency and intensity of heat waves, wildfires, and severe storms across the aging societies of North America and East Asia. Because the population aged sixty-five and older is growing rapidly in all three regions studied, the number of people exposed to complex emergencies will rise even if hazard frequency alone did not increase. Strengthening modifiable factors such as resilience, self-efficacy, caregiving relationships, and access to information, while simultaneously addressing gaps in the health care, home care, and long-term care systems on which older adults rely, offers communities a concrete agenda for improving safety and security before, during, and after disasters. The editorial, published in the Journal of Applied Gerontology, will be freely accessible in perpetuity, a decision that its authors hope will speed the translation of its findings into emergency management practice, clinical protocols, and community programs serving one of the most vulnerable populations in any disaster.

Subject of Research: Disaster preparedness and complex emergencies affecting older adult populations

Article Title: New editorial in special issue calls for stronger disaster preparedness for older adults

Article References: New editorial in special issue calls for stronger disaster preparedness for older adults. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: disaster preparedness, older adults, gerontology, Journal of Applied Gerontology, hurricanes, extreme heat, nursing homes, assisted living, mental health, climate-related hazards, long-term care, resilience

The study focused on what climate scientists call compound climate extremes, situations in which two or more extreme events, such as drought and extreme heat, occur at the same time or in close succession. While previous research has typically examined the impacts of individual climate events in isolation, the authors argue that this approach may systematically underestimate the risks posed by climate change, because extremes rarely occur alone in the real world. Between 2001 and 2020, the period covered by the analysis, compound heat and moisture extremes were recorded at least once in every one of the 88,116 forest plots examined, underscoring how widespread these overlapping stresses have already become.

Why should simultaneous extremes be so much more damaging than single events? The study points to amplifying mechanisms that link the atmosphere, the soil and the living tissue of trees. Extreme heat can intensify drought by increasing evapotranspiration, the process by which water is transferred from the land surface to the atmosphere through evaporation and through transpiration from plant leaves. As temperatures climb, trees lose water faster through their stomata, the microscopic pores on their leaves, which deepens the water stress caused by reduced rainfall and drier soils. The combined effect is a physiological squeeze that a forest experiencing either heat or drought alone might survive, but which can push trees beyond their limits when both arrive together.

Heat can also combine with excessive moisture rather than too little of it. When heavy rainfall or waterlogging coincides with high temperatures, soils can become saturated and oxygen-starved, a condition that exacerbates hypoxia in root systems. Roots deprived of oxygen begin to suffer damage, impairing the tree’s ability to take up water and nutrients even after conditions improve. In other words, whether the moisture extreme is a deficit or a surplus, its interaction with heat tends to amplify the harm, producing negative impacts on forest productivity that exceed what either event would cause on its own.

To measure these effects across such a vast area, the researchers combined two complementary sources of information: satellite observations and forest inventory data. The satellite record provided measures of forest productivity, allowing the team to track how much carbon forests captured and how sharply that capture declined during extreme events. The inventory data added ground-based detail about the composition of each plot, including the number and variety of tree species present. This pairing of remote sensing with field surveys allowed the scientists to evaluate two distinct properties of forest ecosystems: resistance, meaning a forest’s ability to withstand a climate extreme while it is happening, and resilience, measured by how effectively the forest recovers its productivity afterwards.

Across all of the plots analysed, the pattern was consistent. When forests were exposed to compound heat and moisture extremes, they generally showed lower resistance and poorer recovery than when they were subjected to individual climate extremes. Productivity fell more steeply during the events, and the return to normal levels of growth was slower and less complete. This finding matters because forests are among the most productive ecosystems on Earth and play a central role in the global carbon cycle, absorbing a substantial share of the carbon dioxide emitted by human activity. If compound extremes erode both the capacity of forests to absorb carbon and their ability to rebound, projections of the future carbon cycle may need to account for these interacting stresses rather than treating them one at a time.

Yet the study also identified a powerful buffer against this damage: biodiversity. Forest plots containing a wider variety of tree species experienced smaller declines in productivity during compound climate extremes and recovered more effectively afterwards. The researchers describe this protective effect as a form of biological insurance, a concept in ecology that captures how diversity spreads risk across a community. Different tree species differ in their rooting depths, water-use strategies, drought tolerances and heat responses. When conditions turn hostile, a diverse forest is more likely to contain species that can keep functioning, sustaining the ecosystem’s overall productivity even as more vulnerable species struggle. In a monoculture or a species-poor stand, by contrast, a single stress can affect nearly every tree at once, leaving the whole system exposed.

Dr Hannah White, Senior Lecturer in Ecology and Conservation at Anglia Ruskin University and a co-author of the study, emphasised the stakes. Forests, she noted, are vital to how the planet functions but are increasingly exposed to more frequent and intense extreme weather events as the climate changes. She explained that much of the research to date has concentrated on individual extremes such as droughts or heatwaves, whereas the new study, drawing on extensive forest survey data and satellite-derived productivity measures, shows that when these extremes occur together the consequences can be substantially more severe, reducing both a forest’s ability to withstand disturbance and its capacity to recover afterwards. Crucially, she added, forests with a greater diversity of tree species consistently performed better under these challenging conditions.

The implications extend well beyond ecology. Because biodiversity appears to govern forest stability under compound extremes, the findings have direct relevance for future carbon cycle projections, which inform climate models and the estimates of carbon sinks used in international climate policy. They also carry practical weight for forest management and restoration. Planting or preserving a mixture of native tree species, rather than relying on single-species stands, could help forests maintain their productivity and their carbon storage through the increasingly volatile decades ahead. In this sense, the study reframes biodiversity not simply as a conservation goal in its own right, but as a functional component of climate resilience, a living hedge against a future in which heat, drought and deluge increasingly arrive hand in hand.

The research, published in Nature Communications under the title Biodiversity buffers forest ecosystems from compound climate extremes, stands as one of the most comprehensive assessments to date of how interacting climate extremes affect forest ecosystems at continental scale. By demonstrating that the whole of a compound event can exceed the sum of its parts, and that tree diversity measurably softens the blow, it offers both a warning and a measure of hope. The warning is that climate risk assessments built on single events may be too optimistic for the world that is emerging. The hope is that one of the most effective defences against that world may already be growing in the world’s forests, in the quiet variety of the trees that stand there.

Subject of Research: The role of tree species diversity in forest resistance and resilience to compound climate extremes

Article Title: Tree diversity protects forests from climate extremes

Article References: Tree diversity protects forests from climate extremes. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: tree diversity, biodiversity, compound climate extremes, drought, extreme heat, forest resilience, forest resistance, carbon cycle, evapotranspiration, Nature Communications, forest productivity, climate change

The center, known as SCEHSC, has built its reputation on research with real regulatory consequences. Its scientists have supported studies of air pollution that proved highly influential in the development of regulatory standards, work that helped quantify the toll that traffic-related emissions take on children’s lungs and cardiovascular systems. Beyond air quality, the center’s portfolio now spans extreme heat and wildfires, per- and polyfluoroalkyl substances known as PFAS, and the environmental determinants of cardiorespiratory health, neurodevelopment and cognitive aging, kidney and liver disease, metabolic dysfunction and diabetes. The new grant allows the center to continue backing these efforts through pilot funding, service cores that supply expertise in exposure assessment, study design, biostatistics and data science, and programs devoted to community engagement, research translation and science communication.

Rob McConnell, MD, professor of population and public health sciences at the Keck School of Medicine and director of SCEHSC, framed the renewal as an investment in a proven model of scientific incubation. Over the years, he noted, the center has helped researchers turn promising ideas into research programs that address some of the most pressing environmental health challenges, and the new funding will allow it to build on that track record while expanding into emerging areas of the field. His co-leadership team includes Lida Chatzi, MD, PhD, who serves as deputy director, and Joseph Leo Wiemels, PhD, who co-directs the center’s Translational Research Support Core and directs the doctoral program in epidemiology at the Keck School.

Among the center’s most consequential contributions is its role in developing the Children’s Health Study, a long-term investigation of air pollution and respiratory and metabolic health that has followed more than 12,000 children across Southern California. Because the cohort spans communities with sharply different pollution profiles, the study has offered some of the clearest evidence anywhere in the world that exposure to traffic exhaust and other airborne contaminants measurably impairs lung growth and metabolic health in children. Findings from this research have been used extensively by decision makers to shape air quality standards and other regulations at the local, state and federal levels, making the center one of the rare academic enterprises whose work can be traced directly into public policy.

The center’s infrastructure extends well beyond grant dollars. It provides laboratory facilities, career development programs, working groups and scientific retreats that help researchers develop and advance new ideas. With more than 50 members across USC and UC Irvine, the center places particular emphasis on supporting junior investigators. Since 2020, its Career Development Program has mentored 15 junior faculty members and 22 postdoctoral researchers. Those investigators have published 104 papers with center support as lead or senior authors, four have been promoted, and seven have secured tenure-track positions. Wiemels described the center as essentially a bespoke resource that investigators can access when they have an important environmental health question but need additional expertise, infrastructure or funding to pursue it.

Central to the center’s impact is its pilot program, which provides early funding and support to help investigators transform promising ideas into established research programs. The economics of the model are striking: the program has generated a 30-to-1 return on its investments, with modest pilot awards helping researchers attract substantially larger follow-on support, primarily from the NIH. In a field where preliminary data are often the gatekeeper to major grants, that leverage function makes the center a kind of venture catalyst for environmental health science, seeding the small, risky studies that later grow into programmatic research efforts.

The ShARP Center offers the clearest case study of that pipeline in action. The Southern California Superfund Research and Training Program for PFAS Assessment, Remediation and Prevention was established last year with a $14 million NIH grant to investigate the health effects of PFAS and develop strategies for prevention and remediation. It grew from years of preliminary research and collaboration supported by SCEHSC, which provided pilot funding for population studies examining PFAS exposure in relation to liver and metabolic disease, supported research mapping PFAS contamination in drinking water, enabled the collection, archiving and analysis of preliminary samples, and convened USC investigators and national experts to identify research priorities that ultimately helped shape the ShARP program. Chatzi said the center gave her team the opportunity to take some of their earliest observations about PFAS and human health and build them into a much larger translational research program, one now moving beyond identifying associations toward understanding how these chemicals affect human biology and developing strategies to reduce exposure and prevent their health effects.

Other recently funded pilot projects illustrate the breadth of questions the center is willing to back at an early stage. Current projects include studies of the health effects of last year’s destructive urban wildfires, the effects of extreme weather on radon exposure, the capacity of cool roofs to reduce the impacts of extreme heat, environmental influences on adolescent brain development, and potential ways to mitigate PFAS-related liver damage. Because the center maintains research infrastructure in place, it can also respond quickly to pressing community concerns, including environmental disasters. After the Lineage fire, which burned for seven days at a Boyle Heights warehouse in June, the center’s Community Engagement Core supported community members in collecting air and water samples, and the center funded time-sensitive pilot projects to launch studies of the fire’s potential health effects, beginning with sample analysis to determine what chemicals may have been released and spread through the surrounding community.

That rapid-response capacity reflects a philosophy that McConnell described as central to the center’s mission: community engagement means listening to the concerns that people are experiencing firsthand and making sure those needs shape the research the center supports. The approach inverts the traditional top-down model in which academic scientists choose their questions in isolation. In Boyle Heights, a densely populated neighborhood adjacent to industrial corridors and freight routes, residents’ worries about chemical contamination after the warehouse fire became the impetus for federally supported sampling and analysis within weeks rather than years, a speed that conventional grant cycles rarely allow.

The renewed funding will also push the center into two new domains. The first is artificial intelligence: SCEHSC is bringing AI expertise from USC’s Information Sciences Institute into environmental health research, including through new collaborations with Yolanda Gil, PhD, research professor of computer science and spatial sciences at the Viterbi School of Engineering, and Deborah Khider, PhD, a lead data scientist at ISI. Machine learning methods hold particular promise for exposure assessment, where vast streams of sensor, satellite and electronic health record data can be fused to estimate what people breathe, drink and touch at unprecedented resolution. The second expansion targets cancer: the center is broadening its work on environmental exposures linked to cancer in children and adults in collaboration with the USC Norris Comprehensive Cancer Center. Together, the moves signal a center that, after more than thirty years of continuous NIH support, intends to spend its next chapter connecting environmental science to the frontiers of computation and oncology, while keeping its founding commitment to communities living on the front lines of exposure. The research is supported by NIH grant P30ES007048.

Subject of Research: NIH funding for environmental health sciences research on pollution, PFAS and related exposures

Article Title: $8 million NIH grant advances research on environmental health

Article References: $8 million NIH grant advances research on environmental health. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: NIH grant, environmental health, air pollution, PFAS, USC Keck School of Medicine, Children's Health Study, pilot funding, wildfire smoke, extreme heat, artificial intelligence, cancer research, community engagement

The numbers carry formal uncertainty estimates that underscore their robustness: 3.29 plus or minus 0.12 days per decade for onset, 5.41 plus or minus 0.12 days for ending, and 8.71 plus or minus 0.17 days for season length. These are not marginal statistical artifacts. The trend towards earlier onset covered 72.0 percent of global land area, later ending extended across 79.6 percent, and longer heatwave seasons swept 92.1 percent of the continents. Statistically significant trends, the strictest test, were detected across 13.4 percent of land for onset, 20.3 percent for ending and 34.4 percent for season length. In other words, nearly every corner of the inhabited world is experiencing a heatwave calendar that is drifting steadily away from the pattern that defined the twentieth century.

What makes the study methodologically distinctive is its treatment of heatwave timing as a set of measurable phenological metrics, analogous to the way ecologists track the first flowering of spring or the migration of birds. The team defined heatwave onset as the date of the first heatwave event in each year, ending as the date of the last, and season length as the interval between them. Detection relied on the ERA5 hourly climate reanalysis from the Copernicus Climate Change Service as the primary dataset, with the Berkeley Earth daily gridded land temperature product and the Japanese JRA-3Q reanalysis serving as independent checks. Cross-validation across these three sources, each built on different assimilation systems and input observations, guards against the possibility that the trends are artifacts of a single dataset’s quirks.

Beyond the calendar metrics, the researchers introduced a classification of onset speed, distinguishing heatwaves that build gradually from those that erupt almost without warning. Their analysis of first-heatwave onset-speed types revealed a recent global shift towards faster onset, meaning that the first heatwave of the year increasingly arrives as a sudden spike rather than a slow ramp. This finding has immediate operational consequences. Heat-health warnings, grid operators and agricultural advisory systems are typically calibrated to the assumption that dangerous heat develops over days, giving populations and infrastructure time to adjust. A heatwave that materializes within a day or two compresses that window dangerously, catching vulnerable populations before cooling centers open, before water systems are stressed-tested and before crops can be shielded.

The spatial geography of the trends adds a second layer of concern. Drylands, the arid and semi-arid regions that already cover roughly forty percent of the terrestrial surface and are home to billions of people, experienced more pronounced timing shifts than humid regions. The physical reasoning is grounded in land-atmosphere feedback. In moist environments, incoming solar energy is partly consumed by evaporation, a process that cools the surface and moderates temperature extremes. In drylands, depleted soil moisture removes this evaporative brake, allowing more of the sun’s energy to translate directly into sensible heat. As aridity intensifies under warming, this feedback loop tightens, priming dry regions for both earlier and more abrupt heatwave development. Previous work has linked flash droughts to accelerated heatwave onset over East China, and soil moisture feedbacks were implicated in the record-breaking early-season heatwave that struck North China in 2023, consistent with the global pattern the new study documents.

The asymmetry between the onset and ending trends is itself revealing. Ending dates are retreating into the year at nearly 5.4 days per decade, faster than onset dates are advancing at 3.3 days per decade, which means the heatwave season is not merely shifting earlier but expanding from both ends, with the autumn side stretching more aggressively. This expansion pattern matters for ecosystems that synchronize their life cycles with thermal cues. Crops are particularly exposed: high temperatures during flowering and grain filling can slash yields even when the rest of the growing season is benign, and studies of the 2018 European heatwave showed lasting legacy effects on ecosystem productivity that persisted well beyond the event itself. A heatwave season that encroaches on late spring and early autumn extends the window of vulnerability for wheat, maize, rice and other staples whose developmental stages are tightly timed.

Human health risks scale with timing in ways that conventional heatwave metrics miss entirely. Epidemiological research has shown that the first heatwave of the season carries an amplified effect on heat-related hospitalizations among older adults, because physiological acclimatization and behavioral adaptation have not yet kicked in. Mortality risk attributable to high ambient temperatures, established across dozens of countries in the multicountry Multi-City Multi-Country Collaborative Research analyses, is modulated by when in the season the heat arrives. An earlier first heatwave therefore strikes a population that is simultaneously less physiologically prepared and less institutionally prepared, before emergency protocols are activated and before public health messaging reaches the most vulnerable. The timing dimension compounds the well-documented increases in heatwave frequency, intensity and duration documented by earlier global assessments.

The infrastructure consequences are equally concrete. Heatwaves strain electricity systems precisely when cooling demand peaks, and documented outages in China during extreme heat illustrate how reliability erodes under thermal stress. Renewable power systems face their own vulnerabilities, since wind generation can falter during stagnant heat domes while solar output degrades at high panel temperatures. The 2025 European heatwave imposed measurable costs on power systems across the continent. Economic modeling suggests that global supply chains amplify these costs, transmitting localized heat shocks through trade networks to distant consumers. A heatwave season that starts weeks earlier and ends weeks later multiplies the cumulative exposure hours for every one of these systems, and the study’s finding that 92.1 percent of land shows lengthening seasons implies few regions are spared.

The authors argue that their findings demand a structural change in how heat risk is managed. Early-warning systems, they contend, must incorporate heatwave timing metrics alongside frequency and intensity, shifting from reactive alerts to proactive seasonal preparation. Risk assessments that treat heatwave season as a fixed window will systematically underestimate exposure as that window widens. Adaptation planning, from urban cooling infrastructure to agricultural planting calendars to energy system reserve margins, needs to internalize the fact that the dangerous season now begins more than three days earlier each decade and ends more than five days later. Because the trends are roughly linear over the 45-year record, continued warming implies continued drift, with the cumulative shift since 1979 already amounting to roughly two weeks of additional heatwave season on average.

The study also demonstrates the value of open science infrastructure. All supporting data, from the ERA5 and JRA-3Q reanalyses to TerraClimate water balance products, MODIS land cover classifications and crop phenology datasets, are openly available, and the authors’ processed datasets and analysis code are archived on Figshare, enabling independent replication of the heatwave detection and trend analysis. The statistical framework, which accounts for autocorrelation in spatial fields using methods designed to avoid the overstated significance that has plagued comparable grid-cell trend studies, sets a methodological benchmark for future timing analyses. As the planet continues to warm, the calendar of extreme heat is being rewritten, and the new results make clear that anticipating when heatwaves will strike has become as important as knowing how severe they will be. The first hot day of the year, once a predictable marker of summer’s arrival, is now an advancing front in a changing climate, and it is arriving faster than society is prepared for.

Subject of Research: Long-term global changes in heatwave timing, including onset, ending, season length and onset speed, across land areas from 1979 to 2023

Article Title: Earlier and faster heatwave onset on land under a warming climate

Article References: Xu, W., Wu, D., Ciais, P., Wang, Y.-P., Huang, M., Yuan, W., & Liu, J. (2026). Earlier and faster heatwave onset on land under a warming climate. Nature Climate Change. https://doi.org/10.1038/s41558-026-02762-2

Image Credits: AI Generated

DOI: 10.1038/s41558-026-02762-2

Keywords: heatwaves, climate change, heatwave onset, heatwave season, drylands, extreme heat, early-warning systems, ERA5 reanalysis, land-atmosphere feedback, public health, climate risk, Nature Climate Change