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South America’s Rapid Warming During Last Deglaciation

20 June 2026 at 03:13

In a groundbreaking new study published in Nature Communications, researchers Ampuero, Stríkis, Meckler, and colleagues have unveiled compelling evidence of rapid warming in South America during the last deglaciation, a period roughly spanning from 20,000 to 10,000 years ago. This revelation not only reshapes our understanding of ancient climate dynamics in the Southern Hemisphere but also provides critical insights relevant to modern climate change scenarios. The study harnesses a suite of advanced geochemical proxies and high-resolution sediment analyses to reconstruct past temperature variations with unprecedented precision, shedding light on the complex interplay of atmospheric and oceanic processes that drove rapid temperature shifts during this critical juncture in Earth’s climate history.

The last deglaciation marks the transition from the Last Glacial Maximum (LGM), characterized by extensive ice sheets and colder global temperatures, to the relatively warmer Holocene epoch. While the general timeline of global warming during this period has been well documented, the rate and regional variability of temperature changes in South America remained less clear. This research addresses that gap by focusing on paleoclimatic archives from the Andes and adjacent lowlands, areas particularly sensitive to past climate fluctuations due to their unique topography and atmospheric circulation patterns. The team’s integration of isotopic measurements, sediment core analyses, and climate modeling has allowed them to track rapid temperature increases occurring in discrete pulses rather than gradual trends.

One of the study’s central findings is that the warming episodes in South America during the deglaciation were not synchronous with the Northern Hemisphere, suggesting a nuanced asynchronous behavior in global climate systems. This asynchrony challenges prevailing assumptions derived from mid-latitude and polar records predominantly from the Northern Hemisphere. The evidence points to a scenario where atmospheric teleconnections, influenced by shifts in the Intertropical Convergence Zone (ITCZ), played a vital role in redistributing heat between hemispheres. Changes in the ITCZ’s position and intensity appear to have triggered alterations in monsoonal patterns and precipitation regimes across tropical and subtropical South America, thereby accelerating warming trends.

Delving deeper into the proxies used, the research team employed oxygen isotope ratios (δ18O) from speleothems and lacustrine carbonate deposits, alongside organic biomarkers preserved in lake sediments. These proxies are invaluable for reconstructing past temperature and hydrological conditions. Their fine temporal resolution enabled the team to detect rapid warming events occurring over mere decades to centuries, contrasting starkly with previously assumed millennial-scale trends. This high-resolution data challenges the paradigm that post-glacial warming was a slow and steady process, underscoring the climate system’s capacity for abrupt state shifts driven by complex feedback mechanisms.

The study posits that these rapid warming events are linked to deglacial reductions in ice volume combined with rising greenhouse gas concentrations, which collectively enhanced atmospheric temperatures. However, the mechanisms responsible for regional heterogeneity in warming intensity remain a frontier of research. The authors hypothesize that the interplay between the South Atlantic Ocean’s temperature gradients and the Andes’ orographic effects created microclimates that either amplified or moderated warming signals locally. These insights highlight the intricacies of Earth’s cryosphere-atmosphere interactions, emphasizing that regional response to global forcings can diverge dramatically.

Crucially, the study carries significant implications for understanding future climate trajectories. The past rapid warming episodes provide analogs for the rate and spatial distribution of modern anthropogenic warming, especially in mountainous and tropical regions. Given that South America supports critical biodiversity hotspots and large human populations dependent on glacial-fed water resources, these findings raise concerns about the vulnerability of such systems to contemporary climate disruptions. They also stress the importance of refining climate models to incorporate regional heterogeneities and abrupt transitions observed in past climates to improve future predictions.

The methodologies applied in this study exemplify advancements in paleoclimatology. High-precision radiometric dating techniques, including uranium-thorium series and radiocarbon calibrations, ensured robust chronological frameworks. Simultaneously, the use of compound-specific isotope analyses allowed disentanglement of temperature signals from confounding hydrological changes. By merging empirical data with state-of-the-art climate model simulations, the research provides a comprehensive narrative that integrates proxy evidence with theoretical climate dynamics, fostering an interdisciplinary understanding crucial for reconstructing past climates.

This investigation also revisits the role of Southern Hemisphere westerly winds during glacial terminations. These winds, known to influence oceanic upwelling and atmospheric moisture transport, appear to have shifted latitudinally and intensified during warming intervals, enhancing the carbon cycle feedback through increased ocean-atmosphere exchange. Such shifts would have profound implications for regional precipitation and temperature patterns, echoing the complex feedback loops that amplify climate variability. The interplay between atmospheric circulation changes and deglacial warming elucidated in this work refines our grasp of the mechanisms driving rapid climate shifts in South America.

The detailed record of warming patterns obtained from Andean ice cores and sediment cores also reveals that local climate responses were amplified by feedback mechanisms related to vegetation changes and soil moisture dynamics. As temperatures rose, altered precipitation regimes induced shifts in ecosystem composition and land surface properties, which in turn influenced regional albedo and evapotranspiration rates. These biophysical feedbacks likely intensified warming pulses, creating nonlinear climate responses that challenge the linear projections often found in simplified models. The study’s recognition of these processes underscores the need to consider feedback loops when analyzing both past and future climate events.

Furthermore, the research highlights the influence of meltwater pulses originating from retreating glaciers on ocean circulation patterns in the South Atlantic, which may have contributed to abrupt changes in the Atlantic Meridional Overturning Circulation (AMOC). These oceanic perturbations would have cascaded into atmospheric circulation anomalies, further modulating temperature regimes. The integration of paleohydrological and oceanographic data thus provides a multidimensional perspective on how coupled ocean-atmosphere-cryosphere systems orchestrated climate variability during the last deglaciation.

The findings provoke new questions about thresholds and tipping points in paleoclimatic systems. The demonstrated rapid warming episodes suggest that even small incremental increases in external forcings can trigger disproportionately large climate responses once feedbacks are engaged. Such insights are vital for modern climate science, particularly in understanding the potential for abrupt, nonlinear climate transitions under ongoing anthropogenic pressures. By decoding the clues encoded in South America’s geological record, the study enhances our ability to forecast and mitigate the risks associated with rapid climatic changes.

Notably, this work emphasizes the importance of cross-continental and hemispheric comparisons in paleoclimatic studies. By juxtaposing South American data with Northern Hemisphere and Antarctic records, the researchers have contextualized regional warming events within the broader global climate narrative. This comparative approach reveals asynchronous yet interconnected patterns of deglacial warming, challenging simplistic notions of uniform climate shifts and advocating for more intricate, region-specific assessments of past climate dynamics.

In conclusion, the study by Ampuero et al. represents a significant stride in reconstructing past climate change with regional fidelity and temporal precision. Their identification of rapid warming intervals during the last deglaciation in South America not only enriches the scientific understanding of glacial-interglacial transitions but also provides vital lessons for the present and future. The intricate linkages among atmospheric circulation, oceanic processes, and terrestrial feedbacks revealed by this study underscore the intricacy of Earth’s climate system and the urgency of addressing rapid environmental changes from a holistic perspective. Future research inspired by this work will undoubtedly deepen insights into the mechanisms of abrupt climate change and help refine predictive climate models essential for safeguarding vulnerable ecosystems and societies.

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Subject of Research: Paleoclimatic reconstruction of rapid warming events in South America during the last deglaciation.

Article Title: Rapid warming in South America during the last deglaciation.

Article References:
Ampuero, A., Stríkis, N.M., Meckler, A.N. et al. Rapid warming in South America during the last deglaciation. Nat Commun (2026). https://doi.org/10.1038/s41467-026-74093-x

Image Credits: AI Generated

Forests’ Cooling Power Limited by Rising Dryness

17 June 2026 at 13:11

As Earth’s climate system evolves with unprecedented rapidity, forests — vital guardians of global ecological balance — are undergoing complex transformations that extend far beyond the mere sequestration of carbon. Emerging research has begun to unravel the subtle yet profound ways in which climate change reshapes the biophysical interactions between forested landscapes and their surrounding environments, particularly regarding land surface temperature dynamics. A recent groundbreaking study delves deep into these dynamics, revealing starkly contrasting trends that underscore the dualistic nature of forests as climate regulators amidst rising atmospheric dryness. This nuanced revelation challenges long-held assumptions about the uniform benefits of forest cooling and opens new frontiers for understanding ecosystem-climate feedbacks in the Anthropocene.

Forests have long been recognized as crucial climate buffers, primarily through their capacity for carbon storage and evapotranspiration-driven cooling effects. The new research pivots attention to a complementary biophysical mechanism: the difference in growing-season land surface temperature (LST) between forested areas and adjacent open lands, designated as ∆LSTgs. By systematically quantifying ∆LSTgs globally across a span of more than two decades (2001–2023), the researchers uncovered contrasting temporal patterns that vary profoundly with geography and changing atmospheric conditions. Notably, these patterns defy a simplistic narrative of consistent forest cooling, instead revealing a dynamic response heavily modulated by atmospheric humidity levels.

Central to these divergent forest temperature dynamics is the rising vapor pressure deficit (VPD), a measure of atmospheric dryness that quantifies the difference between the amount of moisture in the air and its saturation point. The study identifies VPD as the predominant driver behind the observed variations in ∆LSTgs, exerting a stronger influence than other conventional climatic factors such as temperature, precipitation, or solar radiation. This finding shines light on the critical role that atmospheric moisture stress plays in forest surface energy exchanges, fundamentally altering the cooling potential traditionally attributed to forests under wetter conditions.

However, the forest response to this intensifying atmospheric dryness is far from uniform across global biomes. The research highlights a pivotal interaction between VPD fluctuations and plant hydraulic traits, particularly stomatal regulation strategies embodied by anisohydricity, a measure of plants’ ability to regulate water loss through stomata under drought stress. Forests exhibiting high anisohydricity maintain more open stomata even under dry conditions, enabling continued transpiration and evaporative cooling but at increased risk of hydraulic failure. In contrast, isohydric forests tightly conserve water by closing stomata earlier, reducing cooling at the leaf surface.

Intriguingly, this stomatal regulatory behavior correlates with latitude, delineating distinct forest cooling trajectories. Tropical forests near the equator tend to display more isohydric characteristics. Here, rising VPD often surpasses the hydraulic safety threshold of these ecosystems, leading to stomatal closure and a consequent weakening of forest cooling effects. This trend portends a diminished capacity of tropical forests to mitigate local heating as atmospheric dryness intensifies, potentially accelerating heat stress on these already vulnerable ecosystems.

Conversely, high-latitude forests manifest a more anisohydric strategy, maintaining open stomata under increasing VPD levels that nonetheless remain within their hydraulic safety margins. As a result, these boreal and temperate forests continue to sustain transpiration-driven cooling, which paradoxically intensifies with rising VPD. This phenomenon enhances the biophysical benefits of northern forests, amplifying their role as regional climate coolants and underscoring the heterogeneous nature of forest climate feedbacks across latitudes.

This nuanced physiological interplay yields profound implications regarding future forest-climate interactions under global warming. It underscores that elevated atmospheric dryness will not only influence ecosystem carbon dynamics but also significantly alter the biophysical feedback mechanisms by which forests regulate surface temperatures. As VPD continues to climb worldwide, the traditional ecological services of forests, particularly their cooling benefits, may become compromised in many parts of the globe, particularly within tropical zones critical for biodiversity and global climate regulation.

Moreover, the study’s integrative approach—which combines satellite observations of surface temperature with detailed climatological measurements and physiological trait data—provides a comprehensive framework to understand how climatic stressors mediate forest cooling effects. By leveraging large-scale data spanning two decades, the researchers offer robust evidence that forest cooling is not static but dynamically contingent on complex interactions among atmospheric moisture, plant hydraulics, and geographic distribution, emphasizing the need for ecosystem-specific climate mitigation strategies.

The findings challenge the prevailing optimism about forests’ capacity to offset warming through biophysical means alone. In vulnerable tropical regions, the erosion of cooling benefits linked to stomatal closure under heightened VPD may exacerbate heat stress, increase fire risk, and undermine forest resilience. This could trigger feedback loops accelerating tropical forest degradation and amplifying global warming, raising alarm over the future of these essential carbon sinks.

Conversely, the sustained or even enhanced cooling in high-latitude forests might partially offset regional warming trends, but the balance of such compensatory effects at the global scale remains uncertain. These complexities highlight an urgent need to integrate physiological and biophysical forest attributes into predictive climate models, allowing for more accurate assessments of forest contributions to local and global temperature regulation.

Crucially, the research points to the hydraulic safety margin as a vital threshold parameter dictating the tipping points at which forests transition from cooling to warming agents. This insight offers potential pathways for management interventions aimed at bolstering forest hydraulic resilience, such as selective species planting or conservation strategies tailored to optimize ecosystem-level responses to rising VPD.

In a broader context, the study underscores that atmospheric dryness—often overshadowed by temperature-centric perspectives on climate change—constitutes a formidable and multifaceted challenge for forest ecosystems worldwide. Rising VPD alters not only physiological processes at the leaf level but also cascades through landscape-scale energy budgets, with cascading impacts on regional climate patterns, hydrology, and ecosystem services.

As the global community contemplates reforestation and afforestation policies as climate mitigation tools, these findings call for a recalibrated understanding that accounts for the limits imposed by plant hydraulic behavior and atmospheric moisture constraints. The simplistic paradigm of “more trees equal cooler climate” must evolve into a sophisticated appreciation of when, where, and how forest ecosystems can be expected to maintain their biophysical cooling contributions in a drying and warming world.

Ultimately, this pioneering research adds a critical dimension to our grasp of climate-vegetation feedbacks, illuminating the complex, sometimes counterintuitive outcomes of drying atmospheres on forested landscapes. By highlighting the paramount role of VPD and stomatal regulation across global latitudinal gradients, it informs the scientific community, policymakers, and conservationists alike about the nuanced realities shaping the future of Earth’s green lungs and their vital climate services.

Understanding these relationships better will be indispensable to crafting adaptable and resilient conservation strategies capable of sustaining the biophysical cooling functions of forests. The study’s revelations lay groundwork for future research probing genetic, species-specific, and ecosystem-level hydraulic traits, as well as remote sensing advancements to monitor forest physiological stress and energy exchanges in real time under changing climates.

As atmospheric dryness intensifies in the coming decades, the fate of forests as biophysical climate modulators will hinge on the delicate balance between environmental stressors and intrinsic plant water regulation mechanisms. This research presents an urgent clarion call to incorporate these intricate biophysical and physiological insights into forest management and climate policy frameworks, lest the cooling benefits of the planet’s forests risk becoming relics of a less-dry past.


Subject of Research:
Forest biophysical effects on land surface temperature under changing atmospheric dryness and climate conditions.

Article Title:
Globally constrained forest biophysical cooling benefits under rising atmospheric dryness.

Article References:
Zhang, C., Su, Y., Liao, Z. et al. Globally constrained forest biophysical cooling benefits under rising atmospheric dryness. Nat. Clim. Chang. (2026). https://doi.org/10.1038/s41558-026-02677-y

Image Credits: AI Generated

DOI: https://doi.org/10.1038/s41558-026-02677-y

Human Impact Quadruples Coastal Sea-Level Extremes

16 June 2026 at 14:59

In a groundbreaking study published in Nature Climate Change, scientists have unveiled compelling evidence that human-driven sea-level rise has drastically intensified the frequency of extreme coastal flooding events since the dawn of the 20th century. This new research, led by Dangendorf and colleagues, synthesizes extensive tide-gauge data with historical climate model simulations, revealing that the incidence of once-rare 1-in-100-year coastal flooding events has surged approximately twelvefold on a global scale. The findings highlight an unsettling reality: anthropogenic radiative forcing has quadrupled the likelihood of such extremes, fundamentally reshaping the landscape of coastal hazard risk worldwide.

For decades, the debate around the extent to which human activities have contributed to sea-level rise and associated coastal flooding has been mired with uncertainties. Previous studies often grappled with limited observational records or lacked the comprehensive modeling necessary to isolate human influence from natural variability. The novel detection and attribution framework employed in this study marks a significant advancement by bridging long-term tide-gauge observations—some extending back over a century—with sophisticated simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5). This approach allowed the researchers to untangle complex interactions and discern the fingerprints of anthropogenic climate forcing with unprecedented clarity.

The critical driver identified by the team is relative sea-level rise, a multifaceted phenomenon encompassing both ocean surface height changes and vertical land movements relative to the coast. Since the 1960s, this relative sea-level rise has been overwhelmingly dominated by human-induced factors, principally the accumulation of greenhouse gases in the atmosphere that trap heat and accelerate melting of ice sheets and glaciers. As sea levels climb, coastal areas become increasingly susceptible to flooding from storm surges, high tides, and extreme weather events that were historically rare or even unheard of.

Statistically, this change translates into dramatic shifts in risk profiles: an event that would have been expected once every century historically now occurs on average every eight years globally. In some regions, the frequency increase is even more pronounced, reflecting the heterogeneous nature of sea-level rise and the role of localized factors, such as land subsidence or ocean currents. This amplification of coastal extremes poses grave implications for millions of people living in low-lying coastal zones, threatening infrastructure resilience, habitability, and economic stability.

Furthermore, while natural variability—cycles such as the El Niño Southern Oscillation or decadal ocean oscillations—continues to influence regional patterns of extreme sea-level frequency, the study finds this factor has become secondary along the majority of the world’s coastlines. The persistent upward trend linked to human-induced climate change overrides traditional weather and climate fluctuations that once dominated flood risk patterns. This paradigm shift underscores the urgency for integrating anthropogenic impact assessments into coastal planning, adaptation strategies, and disaster risk management frameworks.

Importantly, the researchers emphasize the robustness of their attribution method. By leveraging both historical forcing scenarios and single-forcing climate experiments, they effectively isolate the role of anthropogenic emissions in driving observed changes relative to natural external forcings alone. This dual-layered methodological approach lends high confidence to the assertion that the quadrupling of extreme coastal flooding frequency can be directly ascribed to human actions rather than fluctuations within natural climate variability.

The study’s implications extend beyond scientific understanding to the realm of public policy and coastal resilience investments. Coastal communities and governments must recognize that reliance on historical flood records for designing infrastructure or emergency response plans is increasingly inadequate under changing climatic conditions. Instead, adaptation measures must be informed by updated probabilistic assessments that reflect the new normal of elevated flood risk driven by irreversible sea-level rise trends.

Moreover, the multidisciplinary nature of the research highlights the necessity of fostering collaboration between oceanography, climatology, engineering, urban planning, and social sciences to address these daunting challenges holistically. Translating these findings into actionable strategies necessitates sharing data, predictive models, and risk communication tools across sectors to enhance community preparedness and reduce vulnerability.

While the findings are sobering, they also provide a critical lens through which future mitigation efforts can be evaluated. The clear attribution of increased coastal extremes to anthropogenic radiative forcing underscores the urgency of reducing greenhouse gas emissions to stem the rate of sea-level rise. Without substantial global mitigation and adaptation measures, the frequency and severity of coastal flooding are poised to escalate further, amplifying humanitarian and economic costs.

This research represents a decisive step in bridging observational science with climate modeling to elucidate the tangible impacts of climate change on society. By quantifying how past emissions have already altered coastal flood hazard, it lays a factual foundation for reinforcing scientific consensus, informing legal frameworks, and guiding international climate policy negotiations. The real-world consequences are evident on shorelines worldwide: what were once millennia-scale flood events now disturb communities every decade.

The multidisciplinary approach also exemplifies how integrating historical tide-gauge records with advanced climate models can serve as a blueprint for detecting and attributing other climate extremes, such as heatwaves or droughts. This opens pathways for further studies that refine our understanding of anthropogenic influence across diverse environmental domains, fostering more precise risk assessments and adaptive responses.

As sea-level rise is an inherently irreversible process on human timescales due to the inertia of ice sheet dynamics and ocean warming, the findings provide a stark warning: coastal adaptation efforts are not just a future necessity but a pressing present-day imperative. Infrastructure, ecosystems, and human livelihoods require immediate attention to enhance resilience against the increasing frequency and magnitude of extreme flooding events.

Intriguingly, the researchers note that while natural variability modulates regional sea-level extremes, the dominant influence of anthropogenic factors means that future projections must prioritize human emissions pathways in determining coastal risk profiles. This insight is critical for scenario planning, helping policymakers balance mitigation commitments with targeted adaptation investment.

The study also implicitly raises questions about climate justice and equity. Coastal flooding disproportionately affects marginalized and economically vulnerable populations who often lack resources to adapt effectively. By clarifying the human role in escalating risk, the research bolsters the rationale for equitable climate finance, resilience building, and inclusive policymaking that considers vulnerable communities on the frontlines.

Looking ahead, continued monitoring of tide-gauge networks combined with evolving climate model ensembles will be essential to track ongoing changes and refine attribution analyses. Enhanced granularity in data and simulations will improve local-scale predictions, making it possible to tailor adaptation strategies to specific coastal contexts while maintaining awareness of the global trend driven by human influence.

The transformative increase in the frequency of historic extreme sea-level events also poses profound questions for insurance industries, urban planners, and emergency services. Accurate quantification of risk escalation empowers these sectors to re-evaluate existing standards and contingency plans, potentially prompting innovation in flood defenses, land-use policies, and disaster preparedness protocols.

In conclusion, this penetrating investigation unequivocally establishes that human-induced climate change has already entrenched itself as a dominant driver of coastal flooding extremes worldwide, quadrupling the frequency of events that were once exceedingly rare. The study’s convergence of empirical data and model simulations offers undeniable proof that anthropogenic sea-level rise is reshaping coastal hydrodynamics and hazard exposure. Amid escalating climate threats, these insights compel a rethink of how societies anticipate, prepare for, and mitigate coastal flood risk in a warming world.

Subject of Research: Human-induced sea-level rise and its impact on the frequency of extreme coastal flooding events.

Article Title: Human-driven sea-level rise has quadrupled the frequency of coastal sea-level extremes since 1900.

Article References:
Dangendorf, S., Sun, Q., Maduwantha, P. et al. Human-driven sea-level rise has quadrupled the frequency of coastal sea-level extremes since 1900. Nat. Clim. Chang. (2026). https://doi.org/10.1038/s41558-026-02659-0

DOI: https://doi.org/10.1038/s41558-026-02659-0

Hundreds of sea level studies have underestimated ocean rise

16 June 2026 at 11:30

A warming climate has been helping drive a global rise in sea levels. A new analysis now finds that hundreds of major studies missed just how much sea levels have risen. Past estimates were too low, the new study shows. On average, true sea levels are 20 to 30 centimeters (8 to 12 inches) higher than what past studies reported.

This means that the toll of future sea level rise is even greater than expected.

Katharina Seeger and Philip Minderhoud did the research. They work at Wageningen University in the Netherlands. These physical geographers evaluated data from 385 global and regional studies. All had been published between 2009 and 2025.

Some 99 percent of the studies had incorrectly estimated ocean height, they found. And 45 of the studies were used a few years ago in a major report. It was issued by a global panel of climate experts convened by the United Nations.

Knowing the rate of ocean rise is crucial for coastal planners around the world. It helps them predict when sea water will start to flood — and permanently cover — large swaths of land. The errors in past studies, the researchers say, mean that coastal land may disappear faster than expected. In some places, it could vanish as much as a century sooner than thought.

The team shared its findings in the April 16 Nature.

A one-meter (39-inch) rise in sea level — which could happen within a century — could submerge an area more than 30 percent bigger than scientists thought. That would take away land from 77 to 132 million people. That’s 48 to 68 percent more people than previous estimates.

Sea level rise is slow. But it’s also dangerous if you ignore it, says Anders Levermann. “That’s basically what we’ve done, unknowingly,” he says. “These estimates now tell us that we are much further in the future than we thought we were.” A climate scientist, Levermann works at the Potsdam Institute for Climate Research in Germany.

One problem: geoids

Some of the analyzed studies had focused on sea level rise. Others had focused on storm surges, tsunamis or other coastal hazards. And a common mistake emerged in nine out of every 10 of the studies, the researchers say.

It had to do with the type of data used.

Researchers usually gauge coastal flood hazards by comparing a site’s land elevation to sea levels. Ideally, those sea levels come from actual measurements. Those can come from satellites. Or they could be from tidal gauges, ocean buoys or other tools.

But few of the studies Seeger and Minderhoud reviewed had included such direct sea-level measurements. Instead, the studies had relied on wonky, digital shapes called geoids (GEE-oids).

Geoids are imaginary shapes. They’re meant to approximate Earth’s sea level. They don’t show big ice sheets or giant mountain peaks. Instead, they show Earth as a sort of irregular ball of water with an undulating surface.

Diagram showing a side view of land with a hill and the ocean on the left. Three lines are labeled: Earth's surface (black line) shows the bumpy ground; a geoid estimate of sea level (green dashed line) extends lower than the ocean and land in some places; and an ellipsoid estimate (red dashed line) is a smooth, slightly tilted line that pretends Earth is a perfect oval shape.
This image shows how two average global surface models can vary from Earth’s actual land elevations and sea level. The geoid model (green hashed line) appears lower than the ocean height and far lower than an alternative ellipsoid model (red hashed line).USGS; adapted by L. Steenblik Hwang

But there are two key problems to using geoids to gauge sea level, Seeger and Minderhoud say. First, geoids can be off by several meters. Gravity data are key for making geoids. So geoids are less accurate where gravity data are poor. Those areas include the Global South.

Second, geoids do not account for many other things that can affect sea level. These include ocean circulation and currents. Winds, tides and water temperatures also play roles.

It’s possible to correct for these geoid problems, Minderhoud said at a March 3 news briefing. But the new research shows that few scientists studying coastal hazards make those fixes.

Geoid assumptions led to errors in 90 percent of the reviewed studies. Another 9 percent did not align measurements of sea level and land elevation properly. Fewer than one percent of the studies properly aligned such data, Seeger said.

An aerial view of houses on a beach. Two of the house are partly or completely in the water.
A drone view of these homes in Summer Haven, Fla., show they are already so close to sea level — and at times partially below it — that they can easily be washed away as sea levels continue to climb. Aerial_Views/E+/Getty Images Plus

Average errors varied by region

To see how far off sea-level numbers had been in most studies, Seeger and Minderhoud turned to satellite data. These data measured sea-surface heights globally. Compared to these, geoid-based studies had underestimated coastal sea level by an average of 24 to 27 centimeters (about 10 inches).

Errors were more than three times that size for some places. Among these were parts of Southeast Asia and the Indo-Pacific.

For a few places, estimates of sea levels had actually been too high. These regions included the northern Mediterranean and Antarctica.  That was also true for some islands in the Atlantic and Pacific.

Study estimates were closest for eastern North America and northern and western Europe. Overall, though, most measured sea levels were higher than what past studies had published.

This means the advance of the oceans “is even worse than what’s been reported,” says Patrick Barnard. A coastal geologist, he works at the University of California, Santa Cruz. The new work, he says, is important for planners. It suggests they should be cautious when using findings from big-picture studies to guide local efforts to adapt to sea level rise.

To help future studies, Seeger and Minderhoud have publicly shared coastal sea-level data. These include the most recent actual measurements.

Microsoft taps Alt Carbon in sign of India’s growing role in carbon removal

11 June 2026 at 16:00
Alt Carbon said the agreement followed more than a year of scientific review and due diligence, with Microsoft requiring additional verification and data-sharing measures.

My Book “The Physics of Creation” Now on Sale on Creation Today

11 June 2026 at 00:55
My book, "The Physics of Creation: The Creator’s Ultimate Design for Earth," is now available for download at CreationToday.org for under $5. The book offers a unique perspective on the universe, linking physical laws to an intelligent Creator, and explores how scientific principles align with the biblical creation narrative.

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