The study, led by Theresa Mathes of the Technische Universität Berlin and the Leibniz Institute for Tropospheric Research, together with colleagues from the University of Leeds, Stockholm University, Uppsala University and TROPOS in Leipzig, was carried out as part of the ARTofMELT expedition, which sailed from Svalbard between 8 May and 15 June 2023. The campaign’s broader goal was to understand how atmospheric rivers, narrow corridors of warm, moist air, trigger the onset of sea ice melt. But the flux measurements collected along the way, published in the journal Atmospheric Chemistry and Physics, provide one of the longest continuous eddy covariance records of particle exchange ever obtained over the Arctic Ocean, and they carry implications that reach well beyond the expedition’s original purpose.

Aerosol particles matter enormously in the Arctic. They scatter and absorb sunlight directly, and they act as cloud condensation nuclei and ice nucleating particles, shaping the formation, brightness and lifetime of clouds. Because particle concentrations in the polar boundary layer are often very low, particularly in autumn, even small changes in the particle budget can ripple through cloud microphysics and the regional radiation balance. The Arctic is warming two to seven times faster than the global average since 1979, a phenomenon known as Arctic amplification, and shifts in the sources and sinks of aerosols are one of the feedbacks that models struggle to capture. Yet direct observations of turbulent particle fluxes over sea ice have been strikingly scarce, with most previous ship-based campaigns lasting only days to a couple of weeks.

The technical challenge of making these measurements from a moving ship is considerable. Eddy covariance, the gold-standard technique, requires capturing rapid fluctuations in vertical wind speed and particle concentration simultaneously, at sampling rates of around 10 hertz. The team mounted a sonic anemometer 20.3 meters above the surface on Oden’s foremast, alongside a heated inlet feeding a mixing-type condensation particle counter capable of detecting particles down to 7 nanometers. Because the instrument sampled air through a long tube, the researchers had to correct carefully for the time lag between wind and concentration fluctuations, for particle losses to the tubing walls, and for the motion and flow distortion of the ship itself, using motion sensors and computational fluid dynamics corrections developed for Oden. Ship exhaust contamination, an ever-present hazard on a vessel, was rigorously screened out, removing 17 percent of the data.

To interpret the fluxes, the team classified the surface upwind of the ship into three categories: closed ice, leads, and open water. This was done automatically using a machine-learning image segmentation algorithm, a random forest classifier, applied to hourly photographs taken by cameras on the ship’s decks, with the relevant camera chosen according to the prevailing wind direction. The approach allowed the researchers to attribute each 20-minute flux measurement to the type of surface it had sampled, something few previous studies have done systematically.

The headline result is a study in contrasts. Under low to moderate turbulence, closed ice behaved as expected: it was a net sink for particles, with a median deposition flux of −0.02 × 10⁶ particles per square meter per second, and deposition dominated roughly 70 percent of the intervals measured over ice. But when the wind picked up, the picture reversed. During eight high wind speed events identified during the campaign, five showed net particle emission, and during the longest of these, a storm on 24 to 26 May with winds reaching 19 meters per second, the team recorded net emission fluxes of up to 0.98 × 10⁶ particles per square meter per second, a statistically robust figure with a 95 percent confidence interval excluding zero. The inferred emission strength, calculated by subtracting a modeled deposition flux from the measured net flux, peaked at 1.57 × 10⁶ particles per square meter per second during a second storm at the end of May.

The most likely culprit is blowing snow. Strong winds lift snow grains from the surface, and because Arctic snow contains sea salt, sulfate, nitrate, organic matter and even black carbon, the sublimation of these wind-blown particles releases aerosols into the boundary layer. The particle size distributions measured during the storm events support this interpretation: elevated concentrations appeared across a broad range of diameters, roughly 30 to 300 nanometers, rather than showing the narrow nucleation-and-growth signature expected from new particle formation driven by precursor gases. The researchers also found that the strength of the particle flux correlated strongly with friction velocity, a measure of near-surface turbulence, with a correlation coefficient of 0.88, reinforcing the link between turbulent wind stress and particle exchange. The threshold wind speed for blowing snow is not fixed; it depends on temperature and snow properties, and at low temperatures mobilization could begin at winds as gentle as 6 meters per second.

Over leads and open water, the story was more nuanced. Both surfaces showed a mixture of emission and deposition events, with median fluxes close to zero, suggesting that while open ocean and cracks in the ice can act as particle sources, through mechanisms such as bubble bursting and sea spray, their net contribution during the campaign was modest. The researchers note that whitecaps in pack ice regions are smaller and less frequent than in the open ocean, which may explain the weak net emission observed. They also caution that open water periods were underrepresented in the filtered dataset because the ship was typically underway when open water was present, and surface classification was restricted to periods of slow drift.

What makes these findings consequential is the trajectory of the Arctic itself. Climate models project continued sea ice loss and a corresponding expansion of open water, which is expected to change the frequency and intensity of the particle exchange processes documented here. As the ice retreats, local particle sources, whether from leads, open water or wind-blown snow, are likely to play a growing role in the regional aerosol budget, with knock-on effects for cloud formation and the surface energy balance. Whether the net climatic effect is cooling, through brighter clouds reflecting more sunlight, or warming, through changes in cloud lifetime and phase, remains poorly constrained, and competing source and sink processes make the outcome genuinely uncertain.

By providing hard observational constraints on particle fluxes over three distinct surface types, the ARTofMELT dataset gives modelers something they have long lacked: direct numbers against which to test deposition schemes and emission parameterizations in the High Arctic. The team’s data are publicly available through the PANGAEA repository. As the researchers conclude, quantifying particle deposition on closed ice and emissions from leads and storm-whipped snowfields is a step toward reducing the stubborn uncertainties that still surround Arctic aerosol-cloud-climate interactions, in a region where the stakes of getting the feedbacks right could not be higher.

Subject of Research: Turbulent aerosol particle exchange between the atmosphere and sea ice, leads and open water in the High Arctic

Article Title: Turbulent atmospheric particle fluxes in the High Arctic: surface type dependence and variability

Article References: Mathes, T., Brooks, I., Murto, S., Tjernström, M., Kojoj, J., Zieger, P., Prytherch, J., Wehner, B., & Held, A. (2026). Turbulent atmospheric particle fluxes in the High Arctic: surface type dependence and variability. Atmospheric Chemistry and Physics, 26(19), 14507-14530. https://doi.org/10.5194/acp-26-14507-2026

Image Credits: AI Generated

DOI: 10.5194/acp-26-14507-2026

Keywords: Arctic, aerosol particles, eddy covariance, sea ice, blowing snow, particle fluxes, cloud condensation nuclei, Arctic amplification, leads, sea spray aerosol, ARTofMELT, dry deposition

The technical achievement behind these numbers is considerable. EC-Earth3-HR resolves the atmosphere at roughly 40 kilometres horizontally with 91 vertical levels, and the ocean at 0.25 degrees with 75 depth layers, roughly double the atmospheric resolution and a much finer ocean grid than the standard-resolution configuration used in the sixth phase of the Coupled Model Intercomparison Project, CMIP6. Finer grids matter enormously in this part of the world, because the Arctic is stitched together by narrow straits such as the Fram Strait, the Bering Strait and the passages of the Canadian Arctic Archipelago, through which warm Atlantic water and fresh Arctic outflow must be routed correctly if the simulated climate is to behave realistically. Higher ocean resolution also sharpens the representation of the Gulf Stream and the North Atlantic Current, whose positions control sea surface temperature gradients that feed back into atmospheric circulation and storm tracks.

Crucially, the team did not simply crank up the resolution. Earlier high-resolution experiments under the High Resolution Model Intercomparison Project, HighResMIP, were constrained by short spin-ups of only 30 to 50 years and limited tuning, and in some cases performed no better than their coarser counterparts. The new model, by contrast, underwent a dedicated tuning campaign. The atmosphere was first tuned in standalone runs forced with prescribed sea surface temperatures, targeting a top-of-atmosphere radiative imbalance close to observational estimates, while monitoring surface temperature and precipitation to avoid unphysical drift. The ocean and sea ice components were then tuned through fifteen coupled experiments of 50 to 180 years each under fixed 1981 forcing, iteratively adjusting parameters governing ocean mixing, eddy diffusivity, snow thermal conductivity and sea ice albedo. The result was a model stable enough to sustain a 350-year pre-industrial control run with negligible drift in surface temperature, sea ice, upper-ocean heat content and overturning strength.

The evaluation against observations is broadly encouraging. Global mean surface air temperature in EC-Earth3-HR tracks the ERA5 reanalysis closely, and the model reproduces the observed warming since 1950 better than the standard-resolution ensemble, which runs consistently too warm at the surface of the ocean. Global mean sea surface temperature sits near the HadISST observational dataset. The model also captures the observed amplitude of Atlantic overturning variability measured by the RAPID-MOCHA array at 26.5 degrees north, and it reproduces both the trend and the rapid loss event in Arctic sea ice during the early 2000s. Not every bias disappears: sea surface temperature errors of up to about five degrees Celsius persist along the North American east coast and in the southern subpolar gyre, land temperatures run roughly two degrees too cold, and the double Intertropical Convergence Zone bias survives. But the pattern of improvement is real, and the model’s sea ice and overturning behaviour is now close enough to reality to lend weight to its projections.

Those projections are the headline. Under SSP2-4.5, a middle-of-the-road scenario chosen because it aligns most closely with current stated policies, September Arctic sea ice area in the high-resolution model falls below one million square kilometres, the conventional threshold for practically ice-free conditions, from around 2040, reaching fully ice-free by 2050. The standard-resolution version of the same model does not cross that threshold as early. The high-resolution simulation also warms less overall, both globally and in the Arctic, yet weakens the overturning circulation more. By 2100 the model’s Arctic has warmed by about seven degrees relative to pre-industrial conditions, roughly double the global anomaly of 3.2 degrees, a vivid expression of Arctic amplification. The strongest near-term sea ice losses are projected for the Central Arctic Basin and the Canadian Arctic Archipelago, while the end-of-century winter ice edge retreats most dramatically in the Barents, Greenland and Bering Seas.

The fate of the Atlantic Meridional Overturning Circulation emerges as the study’s deepest contribution. The AMOC transports warm, salty water northward in the upper Atlantic; that water cools, becomes denser and sinks at high latitudes, driving a southward return flow at depth. Reconstructions suggest the circulation has weakened since the mid-twentieth century and may now be weaker than at any time in at least 1,600 years, though the observational record is debated. Climate models agree it will weaken further, but disagree on how fast. In EC-Earth3-HR, the AMOC index drops from about 21 sverdrups to about 13 sverdrups over the twenty-first century, a reduction of roughly 39 percent, compared with about 25 percent in the standard-resolution ensemble. The simulated overturning cell becomes shallower and less extensive, and a pronounced cooling anomaly, the so-called North Atlantic warming hole, develops in the eastern subpolar gyre, concentrated in the upper few hundred metres.

To understand why, the researchers dissected the three great convection regions of the North Atlantic: the Labrador Sea, the Irminger Sea and the Greenland Sea. In all three, surface waters become progressively lighter through the twenty-first century as warming and freshening increase stratification, suppressing the winter deep mixing that feeds dense water into the deep ocean. A volumetric diagnostic, the Deep Mixed Volume, shows deep convection collapsing toward zero by around 2020 in the Greenland Sea and by about 2050 in the Labrador and Irminger Seas. Yet the team is careful to note a subtlety that is often lost in public discussion: deep convection and the overturning circulation are related but not interchangeable. Even after deep mixing ceases entirely in their simulation, roughly two-thirds of the AMOC’s strength persists, because dense water formed elsewhere continues to sink and because the descent of waters crossing the Greenland-Scotland ridges sustains part of the overturning.

The study’s methodological innovation is a new volume-budget framework for diagnosing deep-water formation that does not rely on vertical velocity fields, which many model archives do not store. Instead, it infers sinking from the net horizontal transports of water crossing the lateral boundaries of each convection region, above and below a reference depth of 1,000 metres, with volume conservation dictating the implied downward transfer. Applied to the historical period, the framework attributes about 52 percent of the overturning at 45 degrees north to the Irminger Sea, 22 percent to the Labrador Sea, 14 percent to the Greenland-Iceland-Norwegian Seas and 12 percent to deep Arctic inflow. The budgets close to within 0.1 sverdrups, and the regional decomposition proves robust to alternative choices of reference depth.

Projected forward, the picture is regionally lopsided in a way that matters. By the 2070 to 2100 period, deep-water formation in the Labrador Sea collapses from 3.9 to 0.2 sverdrups, effectively shutting down, while the Greenland Sea loses 62 percent of its contribution and the Irminger Sea only 13 percent. The Labrador Sea therefore emerges as the dominant driver of long-term AMOC weakening, a conclusion reinforced by the strongest correlation between regional deep-water formation and overturning strength over the full simulation. Paradoxically, the Irminger Sea, which contributes the most to sustaining the circulation today, is the most resilient basin, partly because its diagnosed sinking includes the downstream descent of dense overflow waters spilling over the Denmark Strait. Total deep-water formation across the three basins falls by 5.8 sverdrups, slightly exceeding the 5.6 sverdrup decline in the overturning itself, with the small difference compensated by increased deep inflow from the Arctic.

For a general audience, the message is twofold. First, the Arctic’s summer sea ice may vanish within about fifteen years under a moderate emissions pathway, earlier than many standard-resolution assessments imply, with consequences for Arctic ecosystems, Northern Hemisphere weather patterns and the amplification of regional warming. Second, the weakening of the Atlantic overturning is not a single-number story: it is the sum of distinct regional processes, some collapsing quickly and others eroding slowly, and understanding which basin fails first is essential for anticipating how sea surface temperatures, European climate and extreme events will respond. The authors caution that their results rest on a single-member simulation and that ensemble studies, along with refinement of the new diagnostic against observations, will be needed to firm up the timing. But the demonstration that a properly tuned, high-resolution model can reproduce observed sea ice decline and overturning variability, and then project sharper changes than its coarser predecessor, is a significant step toward narrowing the uncertainty that has long shrouded the future of the North Atlantic.

Subject of Research: High-resolution climate modelling of Arctic sea ice decline and Atlantic Meridional Overturning Circulation weakening under climate change

Article Title: Historical Climate and Future Projection in the North Atlantic and Arctic: Insights from EC-Earth3 High-Resolution Simulations

Article References: Karami, M. P., Koenigk, T., Wang, S., Navarro Labastida, R., Kruschke, T., Carréric, A., Ortega, P., Wyser, K., Fuentes Franco, R., de Boer, A. M., Sicard, M., & Aldama Campino, A. (2026). Historical Climate and Future Projection in the North Atlantic and Arctic: Insights from EC-Earth3 High-Resolution Simulations. Earth System Dynamics, 17(4), 1151-1176. https://doi.org/10.5194/esd-17-1151-2026

Image Credits: AI Generated

DOI: 10.5194/esd-17-1151-2026

Keywords: Arctic sea ice, AMOC, North Atlantic, deep-water formation, EC-Earth3, climate modelling, Labrador Sea, Irminger Sea, Greenland Sea, SSP2-4.5, HighResMIP, Arctic amplification

The North Atlantic Oscillation, usually abbreviated as NAO, describes the see-saw of atmospheric pressure between the Azores High in the subtropics and the Icelandic Low farther north. When the pressure difference is strong, the NAO is said to be in a positive phase, steering powerful westerly winds and storms across the North Atlantic toward northern Europe. When the difference weakens, the negative phase, those storm tracks shift southward. For southern Greenland, present-day meteorological measurements show a clear signature: positive NAO phases bring cooler but wetter conditions to the region. What scientists did not know, because instrumental records extend back barely a century and a half, was whether this relationship held steady through the deeper past, across the natural climate swings of the last several millennia.

Closing that gap required a creative solution to a stubborn measurement problem. How do you measure rainfall or snowfall over thousands of years when no one was there to record it? The answer, the researchers realized, lay in the unusual geology surrounding Narsaq Sound, the fjord in southwestern Greenland where the team recovered its core. The rocks flanking the sound are unusually rich in niobium, a rare Earth element that is normally scarce in the ocean and remains chemically stable once deposited in the environment. That stability makes niobium an ideal natural tracer: whenever concentrations of the element spike in the fjord’s sediments, it signals that increased amounts of niobium-bearing material were being washed or ground into the water by local glaciers and by the river draining the surrounding catchment.

And what drives more sediment into a fjord? More precipitation. Heavier rainfall and snowfall intensify erosion and runoff, flushing greater quantities of rock flour and weathered material into the marine basin, where it settles layer upon layer, building a chronological archive of the region’s hydroclimate. The team detected these variations using X-ray fluorescence scanning, a technique that fires X-rays at the sediment core and measures the characteristic fluorescence emitted by different elements, allowing researchers to map chemical changes down the core at extremely fine resolution. It is, according to the study, the first time niobium, an element more familiar for its commercial role in the steel and electronics industries, has ever been used as a tracer for past precipitation.

The sediment core itself was collected in 2022 during research expedition MSM 111, known as BAFFDEEP, aboard the German research vessel Maria S. Merian. The voyage, funded through the MARUM Cluster of Excellence The Ocean Floor, Earth’s Uncharted Interface, carried the team to the fjords of southern Greenland, where the aurora borealis lit the deck as the ship sailed toward its sampling grounds. From the mud recovered at Narsaq Sound, the scientists extracted a continuous record of elemental concentrations that they could then compare against independent archives of the North Atlantic Oscillation, including other paleoclimate records that preserve a signal of the oscillation’s past behavior.

The comparison produced an unambiguous result. Throughout the roughly 5,000-year record, niobium concentrations rose and fell in step with reconstructed NAO variability, and the only explanation consistent with the data was the same relationship observed today: when the oscillation was in a positive phase, precipitation over southwestern Greenland was higher while temperatures were lower. The pattern held through the medieval period, through the Little Ice Age, and across the natural climate fluctuations of the late Holocene, the current warm epoch that began around 12,000 years ago. Niobium concentrations were highest following the retreat of the Greenland Ice Sheet in the early Holocene, around 11,600 years ago, and the subsequent record tracked the oscillation with striking fidelity.

What surprised the team most, lead author Dr. Johan Faust explained, was the persistence of the signal. Across thousands of years, spanning vastly different background climates, the influence of the North Atlantic Oscillation on southern Greenland’s hydroclimate remained essentially unchanged. That kind of stationarity is precious to climate scientists. It suggests that the physical mechanisms linking the oscillation to Greenland’s precipitation and temperature are robust features of the North Atlantic system, not artifacts of a particular climate regime, and it lends confidence to projections that treat the NAO as a stable lever on the region’s ice.

The stakes of that lever are considerable. Precipitation plays a critical role in the behavior of glaciers and ice sheets, because snowfall accumulates on the ice surface and, over time, compacts into new ice, adding mass, while warming removes it through melt. The study’s authors note that the NAO-driven pattern of cooler, wetter conditions during positive phases likely influenced the advance and retreat of local glaciers throughout the late Holocene, as well as the overall mass of the ice in the region. In other words, the ebb and flow of atmospheric pressure over the Atlantic has been a quiet architect of Greenland’s icy landscape, shaping where ice grew and where it shrank long before satellites and weather stations existed.

Looking forward, the implications cut against simple intuition. Some climate models predict that a warming world will favor more consistently positive NAO phases. If the relationship documented in the Narsaq Sound sediments holds in the future, that shift could increase precipitation over southwestern Greenland, potentially promoting the growth of local glaciers even as global temperatures continue to climb. The scenario does not overturn the broader picture of a warming Arctic, where Arctic Amplification causes high-latitude coastal regions to heat faster than the global average, but it introduces a crucial regional nuance: in some parts of the cryosphere, changing atmospheric circulation could partially offset, or at least complicate, the expected response to warming.

Whether that offset materializes depends on how faithfully the models capture the future behavior of the oscillation, a question that remains actively debated. What the new study provides is a benchmark: a 5,000-year demonstration that the NAO-precipitation link over southern Greenland is persistent and strong, rooted in the region’s distinctive geology and readable from the mud of a single fjord. As researchers continue to refine projections of the Greenland Ice Sheet’s contribution to sea level, records like this one, extracted from marine sediments with an X-ray scanner and an unlikely rare Earth element, offer a rare and valuable window into how the ice has responded to natural climate variability in the deep past, and a sobering guide to how it may respond to the changes still to come.

Subject of Research: Reconstruction of Holocene precipitation in southwestern Greenland using niobium tracers in marine sediments to assess the influence of the North Atlantic Oscillation on ice-sheet behavior

Article Title: The atmospheric pattern that has shaped Greenland’s climate for thousands of years

Article References: The atmospheric pattern that has shaped Greenland’s climate for thousands of years. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: Greenland, North Atlantic Oscillation, precipitation, niobium, sediment core, X-ray fluorescence, Holocene, Greenland Ice Sheet, glaciers, paleoclimate, Arctic Amplification, MARUM

That gap is what motivated a team led by Sarah Safieddine of LATMOS/IPSL in Paris to attempt something no one had done before: a global, day-and-night intercomparison of six skin temperature datasets spanning 2008 to 2022. The study, published in the journal Earth Observation, brings together the Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA’s Terra satellite, the European Space Agency’s Land Surface Temperature Climate Change Initiative product (LST CCI v3.00), the ESA CCI and Copernicus Climate Change Service sea surface and sea ice temperature analysis, the ERA5 reanalysis produced by the European Centre for Medium-Range Weather Forecasts, and two distinct products derived from the Infrared Atmospheric Sounding Interferometer (IASI) flying on the Metop satellites: the EUMETSAT all-sky Climate Data Record and a newly developed clear-sky neural-network retrieval. The verdict after fifteen years of data is strikingly coherent: the fingerprint of climate change is unmistakable across nearly all of them, with a handful of fascinating regional exceptions.

The technical challenge of comparing these products is considerable, because each measures something subtly different. Thermal infrared instruments such as MODIS and IASI retrieve skin temperature from radiances in the atmospheric window between 8 and 13 micrometers, where most natural surfaces emit close to a perfect blackbody. By inverting Planck’s law, accounting for surface emissivity, the instruments convert measured radiance into temperature. But infrared retrievals only work under cloud-free skies, and atmospheric water vapour always leaves its mark. Microwave radiometry can peer through clouds, but its surface emissivity is far more variable and its spatial resolution much coarser. Reanalysis products like ERA5 offer complete, all-sky fields, yet their skin temperature is a model variable constrained by data assimilation rather than a direct observation, making it sensitive to how the model parameterises soil, vegetation, and snow. No single dataset can claim to be the universal truth, which is precisely why systematic intercomparison matters.

The team harmonised everything onto a common one-degree grid, restricted the analysis to comparable local solar times between roughly 09:30 and 10:30 in the morning and 21:30 and 22:30 in the evening, and applied dataset-appropriate cloud filtering. Over land, the results were largely reassuring. Daytime global means agreed within about 2 kelvin across the datasets, and the deseasonalised anomalies, which strip away the annual cycle to reveal underlying variability, tracked each other closely. The major modes of interannual variability, including the strong 2015 to 2016 El Niño warming and the subsequent 2020 to 2022 La Niña cooling, appeared consistently in every record, a sign that the fundamental climate signal is robust regardless of which instrument is doing the measuring.

Two systematic quirks did emerge, however, and both carry lessons for anyone using these products. The ESA LST CCI dataset ran consistently warmer than the others, but the team traced this to viewing geometry rather than calibration error: LST CCI restricts retrievals to view zenith angles within 22 degrees of nadir, while MODIS averages across its full 60-degree swath, where longer atmospheric paths and angular emissivity effects systematically depress retrieved temperatures. More concerning were step-like discontinuities in the LST CCI anomalies at sensor transitions, when the record switched from AATSR to MODIS Terra in 2012 and to Sentinel-3B’s SLSTR-B in 2018, indicating residual inhomogeneities that users of this version must treat with caution. At night, MODIS revealed a second surprise: a pervasive cold bias relative to every other product, larger than can be explained by its slightly later overpass time alone. Previous validation studies have found average nighttime biases of around minus 1.6 kelvin against ground stations, with cloud-screening issues and surface heterogeneity in snowy, icy, and arid regions likely contributing.

Over the ocean, the picture was cleaner still. Because the sea surface is far more homogeneous than land, inter-dataset biases between IASI, ERA5, and the ESA CCI/C3S analysis generally stayed below 1 kelvin, with root-mean-square errors near 1 kelvin over the open ocean. The largest discrepancies clustered at high latitudes, where cloud detection, sea-ice contamination, and weak thermal contrast degrade infrared retrievals, and where the very definition of skin temperature diverges across products. One subtle caveat the authors highlight concerns clear-sky sampling itself: during the 2020 to 2022 La Niña, increased tropical cloudiness reduced the availability of clear-sky IASI retrievals, pulling the IASI global mean cooler in a way that reflects sampling changes rather than genuine surface cooling. It is a reminder that even carefully constructed satellite climate records can be modulated by where and when clouds happen to allow a glimpse of the surface.

The heart of the study lies in its trend analysis. Using the robust Theil-Sen estimator on yearly deseasonalised averages, with significance assessed by the Mann-Kendall test, the team mapped warming and cooling across the globe for morning and evening overpasses separately. The dominant signal is unambiguous: skin temperatures have risen since 2008, more strongly over land than over the ocean, and most intensely at high northern latitudes. Alaska and Siberia light up in every dataset, a spatial fingerprint of Arctic amplification, the well-documented phenomenon by which the Arctic warms nearly four times faster than the global average. Daytime land trends ranged from +0.04 to +0.12 kelvin per year depending on the dataset, while nighttime land trends spanned +0.05 to +0.11 kelvin per year, with the all-sky ESA CCI/C3S product showing a modest oceanic warming of about +0.03 kelvin per year consistent with the clear-sky records.

But the most eye-catching findings are the exceptions, places where the planet’s skin is cooling even as the globe warms. India shows significant daytime cooling across all six datasets, a signal the authors link to rising aerosol emissions, which scatter sunlight and offset part of the greenhouse gas warming, compounded by cloud effects that vary seasonally and by time of day, and by land-use change and greening. Parts of central and eastern Africa cool as well, plausibly because increased cloud cover and latent heat release from more intense rainfall suppress surface temperatures. And in the southeastern Pacific off South America, a coherent zone of cooling sits squarely over the Humboldt Current upwelling system, where strengthening alongshore winds drive Ekman divergence and draw cold subsurface water to the surface, a wind-driven mechanism that can produce local cooling even amid global ocean warming, further modulated by Pacific decadal variability on these short timescales.

The study also showcases the growing sophistication of retrieval science. The new IASI neural-network product uses 87 carefully selected window-region channels, discards those sensitive to carbon dioxide to improve long-term stability, and incorporates monthly, time-varying emissivities from the CAMEL database, an important refinement given that neglecting emissivity trends can overestimate global skin temperature trends. The EUMETSAT Climate Data Record, retrained on more than 120 million IASI observations, produces smoother time series that pass significance tests more often, while the neural-network product offers greater independence from ERA5. With the IASI constellation guaranteed through at least 2030 and the IASI-New Generation series extending coverage toward 2045, Earth’s skin temperature is poised to become a cornerstone of climate monitoring, offering a direct, diurnally resolved view of how our planet’s surface responds to a changing atmosphere, one morning and one evening at a time.

Subject of Research: Multi-satellite intercomparison of land, sea, and ice skin temperature trends from 2008 to 2022

Article Title: Assessing Earth's skin temperature trends: consistent signals from IASI, MODIS, ESA CCI and ERA5

Article References: Safieddine, S., Sinnathamby, S., Hadji-Lazaro, J., Doutriaux-Boucher, M., Ghent, D., Whitburn, S., Clarisse, L., & Clerbaux, C. (2026). Assessing Earth's skin temperature trends: consistent signals from IASI, MODIS, ESA CCI and ERA5. Earth Observation, 1(1), 59-75. https://doi.org/10.5194/eo-1-59-2026

Image Credits: AI Generated

DOI: 10.5194/eo-1-59-2026

Keywords: skin temperature, land surface temperature, sea surface temperature, IASI, MODIS, ESA CCI, ERA5, climate change, Arctic amplification, aerosol cooling, upwelling, satellite remote sensing

The instrumental weather stations that dot this remote region simply have not been operating long enough to say whether the hydroclimatic changes of recent decades are unusual or just another turn of natural variability. That is precisely the gap the new reconstruction fills. By extending the precipitation record back to the mid-eighteenth century, the team led by Junhui Guo and Feng Chen of Yunnan University, working with colleagues in Russia, the United Kingdom and Tajikistan, has provided the long-term context that short observational records cannot supply. The result is one of the most complete pictures yet of how rainfall has behaved in central Siberia over nearly three hundred years.

The technical foundation of the reconstruction rests on a well-established principle of dendrochronology: trees growing in moisture-limited environments record the water available to them in the width of their annual growth rings. In cold, high-latitude regions, however, the relationship between tree growth and climate can be complicated by permafrost, snow cover and short growing seasons. The researchers therefore began by testing which seasonal window of precipitation best explained ring-width variability in their spruce cores. The answer was an unusually long one: total precipitation from May of the previous growing year to April of the current year, a period designated P5–C4. During the calibration period from 1968 to 2018, this cumulative precipitation measure correlated with tree growth at r = 0.649, a highly significant relationship with a p-value below 0.001.

Using this strong statistical link, the team built a regression model that explained 42.1 percent of the observed variance in precipitation over the calibration period. That may sound modest, but in paleoclimate reconstruction it represents a robust signal, particularly for a variable as noisy as precipitation. The model was then applied backward in time to generate annual precipitation estimates from 1735 to 2024. To correct for the tendency of regression models to underestimate the true range of past variability, the researchers applied variance scaling, a standard technique that adjusts the amplitude of the reconstruction to match the variance observed in the instrumental record. The final product captures both sharp year-to-year swings and slower, low-frequency oscillations in the region’s water supply.

What does three centuries of Siberian rainfall look like? The reconstruction shows that the past was anything but stable. Several persistent dry intervals and equally persistent wet episodes punctuated the record across the eighteenth, nineteenth and twentieth centuries, demonstrating that central Siberia has long experienced multi-year to multi-decadal hydroclimatic swings. Yet the most recent decades are distinctive. The record shows a marked shift toward wetter conditions in recent years, a feature that stands out against the full 290-year backdrop and suggests that the current wetting is not simply another natural fluctuation but part of a genuine, ongoing hydroclimatic transition.

To understand what might be driving this shift, the researchers turned to the large-scale ocean–atmosphere machinery that governs northern Eurasian climate. The reconstructed precipitation shows significant associations with several major modes of climate variability. North Atlantic sea-surface temperature anomalies emerged as closely related to precipitation variability at Turukhansk, consistent with growing evidence that Atlantic multidecadal variability exerts a remote influence on Siberian rainfall. Wavelet coherence analysis, a technique that reveals how the correlation between two time series changes across both time and frequency, showed that the relationships between precipitation and the Atlantic Multidecadal Oscillation, the Arctic Oscillation, and the Scandinavian pattern all vary through time and across timescales. In other words, the teleconnections that deliver moisture to central Siberia are not fixed; they strengthen, weaken and reorganize over the decades.

The most provocative finding, however, concerns the Arctic itself. The recent wetting coincides with rapid Arctic warming and with declining sea-ice concentration, and the strongest statistical relationship with sea ice occurs over the Barents–Kara Seas, the sector of the Arctic Ocean immediately north and west of the study region. This matters because sea-ice loss is a cornerstone of Arctic amplification, the phenomenon by which the Arctic warms two to four times faster than the globe as a whole. Open water releases heat and moisture to the atmosphere, alters the temperature contrast between the pole and mid-latitudes, and reshapes the jet stream and storm tracks. The study’s atmospheric circulation and moisture-transport analyses provide the mechanistic link: wetter conditions in central Siberia are accompanied by circulation anomalies that favor enhanced moisture transport toward the region and its convergence over central Siberia. Together, these lines of evidence support a close linkage between regional wetting and Arctic amplification.

The implications extend beyond the reconstruction itself. The team examined bias- and variance-adjusted projections from the CMIP6 multi-model ensemble, the latest generation of global climate models, under three future emissions scenarios: SSP1-2.6, a low-emissions pathway; SSP2-4.5, an intermediate pathway; and SSP5-8.5, a high-emissions pathway. Across all three scenarios, the models indicate that wetting in central Siberia is likely to continue through the twenty-first century, with progressively larger precipitation increases under stronger forcing. The convergence between the tree-ring evidence, the observational analyses and the model projections strengthens the case that the recent wet shift is an early expression of a longer-term trend rather than a passing anomaly.

Why should anyone outside Siberia care about more rain in one of the planet’s most sparsely populated regions? The answer lies in the outsized role the Siberian boreal zone plays in the Earth system. These forests store vast quantities of carbon, and changes in water availability influence tree growth, permafrost stability, wildfire regimes and the flux of freshwater into the Arctic Ocean. Increasing river discharge to the Arctic has already been documented, and precipitation changes over central Siberia feed directly into that flow. Wetter conditions could boost forest productivity in some areas, but they also interact with thawing permafrost, changing fire dynamics and shifting vegetation zones in ways that scientists are only beginning to untangle. A reliable long-term precipitation baseline is essential for interpreting all of these changes.

The study also demonstrates the enduring power of tree rings as climate archives. Because the spruce trees sampled near Turukhansk integrate moisture conditions over an extended window spanning two growing seasons, they capture hydroclimatic information that single-season records can miss. The 290-year reconstruction now serves as a benchmark against which both natural variability and anthropogenic trends can be measured. As the authors conclude, the record provides long-term context for the recent hydroclimatic shift in central Siberia and suggests that wetter conditions will remain an important feature of the region’s climate as warming continues. In a century defined by drought headlines across much of the world, the message from the spruce trees of central Siberia is a reminder that climate change writes very different stories in different places, and that some of the most dramatic of those stories are unfolding at the top of the planet, where melting sea ice is quite literally raining down on the forests below.

Subject of Research: A 290-year tree-ring reconstruction of precipitation in central Siberia and its link to Arctic amplification

Article Title: A 290-year tree-ring reconstruction of precipitation in central Siberia shows recent intensified wetting linked to arctic amplification

Article References: Guo, J., Bakhtiyorov, Z., Chen, F., Agafonov, L., Gurskaya, M., & Chen, Y. (2026). A 290-year tree-ring reconstruction of precipitation in central Siberia shows recent intensified wetting linked to arctic amplification. Climate Dynamics, 64(11), Article 447. https://doi.org/10.1007/s00382-026-08406-7

Image Credits: AI Generated

DOI: 10.1007/s00382-026-08406-7

Keywords: Siberia, tree rings, precipitation reconstruction, dendrochronology, Arctic amplification, sea ice, Barents–Kara Seas, Atlantic Multidecadal Oscillation, Arctic Oscillation, CMIP6, climate dynamics, boreal forest

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 motivation for the work lies in one of the most persistent puzzles in climate science. Observations show that since 1979 the Arctic has warmed nearly four times faster than the global average, a rate so extreme that it has reshaped the temperature contrast between the pole and the equator. Because that temperature gradient is the engine that drives the midlatitude jet stream, the fast-moving river of air that steers storms and separates cold polar air from warmer subtropical air, many scientists have suspected that Arctic amplification must be altering the position, strength, and waviness of the jet. Yet the evidence linking the two has remained contested, with some studies pointing to connections with extreme cold outbreaks and prolonged droughts, and others finding the signals too weak or too model-dependent to be meaningful.

Part of the difficulty is that Arctic amplification is not driven by a single cause. Rising sea surface temperatures warm the planet broadly, while the loss of reflective sea ice exposes dark ocean water that absorbs sunlight and warms the Arctic locally. Previous work has shown that sea ice loss plays a central role in polar warming, but disentangling its effects from those of simultaneous ocean warming requires experiments in which each factor is varied in isolation. That is precisely what Saurral and Kucharski set out to do. Using an intermediate-complexity atmospheric model, a class of models that strips away some of the computational complexity of full climate models while retaining the essential physics of the atmosphere, they ran a suite of simulations in which sea surface temperatures and sea ice concentrations were modified separately and together, allowing them to isolate the fingerprint of each forcing.

The results reveal a striking division of labor between the two drivers. Warming sea surface temperatures dominate the temperature response at low and midlatitudes, spreading warmth across the subtropics and temperate zones, while the loss of sea ice is the primary control on how much the Arctic itself warms. In other words, the global ocean sets the background of the warming world, and the cryosphere determines how extreme the polar amplification becomes on top of it. Neither factor alone can reproduce the observed magnitude of polar amplification: when the researchers imposed sea ice loss on its own, the model overestimated Arctic warming, and when they imposed sea surface temperature changes on their own, the model underestimated it. Only when both forcings were applied together did the simulation produce a realistic picture of the amplified Arctic that observations describe.

Perhaps the most consequential finding concerns the jet stream. The two forcings produced circulation responses that push in opposite directions. Changes in sea surface temperatures drove a poleward shift of the atmospheric jet, consistent with the widening of the tropical circulation and the expansion of the Hadley cell that many studies have documented under global warming. Sea ice loss, by contrast, induced changes in the jet that ran counter to that shift. When the two forcings were combined in a single experiment, their interaction produced a reduced and less robust atmospheric response than either forcing alone, suggesting that the competing influences partially cancel each other out. This cancellation helps explain why different modeling studies, which may weight these forcings differently, have reached such different conclusions about how the midlatitude circulation responds to Arctic change.

The physical logic behind the opposing responses is rooted in how each forcing alters the temperature gradient that sustains the jet. Broad ocean warming raises temperatures most strongly in the tropics and subtropics, steepening the equator-to-pole contrast in the upper troposphere and encouraging the storm tracks and the jet to migrate poleward. Sea ice loss does the opposite at the polar end of the gradient: by warming the lower Arctic atmosphere, it weakens the contrast between the pole and the midlatitudes near the surface, a change that tends to pull the circulation in the other direction. The new experiments show that in a medium-complexity model these two effects do not simply add up, and that their interference is a genuine feature of the coupled response rather than noise.

These findings arrive in the middle of a long-running scientific controversy. An influential hypothesis proposed in 2012 suggested that Arctic amplification would make the jet stream wavier, producing more persistent weather patterns and more frequent extremes such as cold winters and heat waves in the midlatitudes. Subsequent research, including large coordinated model intercomparisons under the Polar Amplification Model Intercomparison Project, has generally found the circulation response to sea ice loss to be robust but weak, and several studies have concluded that Arctic amplification has little influence on midlatitude climate variability. The new work does not settle that debate, but it offers a physical framework for interpreting it: the midlatitude response to climate change reflects the combined effect of global processes, carried by ocean warming, and regional processes, carried by sea ice loss, and the two can work against each other.

The study also carries a methodological message. In an era when climate science increasingly relies on enormous high-resolution simulations, Saurral and Kucharski demonstrate the continuing value of medium-complexity models. Because such models are computationally inexpensive, researchers can run large ensembles of targeted experiments, varying one boundary condition at a time, and thereby isolate mechanisms that would be difficult to separate in comprehensive coupled models where ocean, ice, and atmosphere evolve together. The authors argue that this experimental clarity is exactly what is needed to interpret polar amplification as the joint product of global and regional processes, and to understand why the atmospheric response to Arctic change has proven so elusive in more complex systems.

The implications extend to how scientists project the future. If sea surface temperature changes and sea ice loss produce opposing circulation fingerprints, then the net response of the jet stream and the storm tracks will depend on the balance between them, and that balance may shift as the climate continues to warm. Observations have already documented trends in the jet streams that some researchers have linked to tropical warming, and the new results suggest that any such trend represents the residual of competing influences rather than the effect of a single driver. For regions such as the Mediterranean, where earlier work by some of the same authors has connected sea ice loss to drought conditions, understanding this balance could sharpen assessments of regional climate risk.

What the study ultimately provides is a cleaner conceptual map of a tangled problem. Arctic amplification emerges only when global ocean warming and regional sea ice loss act together, the two leave distinct and partly opposing marks on the midlatitude circulation, and their interaction dampens the overall atmospheric response. As the Arctic continues to transform, experiments of this kind, run in deliberately simplified models where every forcing can be switched on and off at will, may prove to be among the most powerful tools for reading the fingerprints that a changing pole is leaving on the weather of the middle latitudes.

Subject of Research: The separate and combined effects of sea surface temperature warming and Arctic sea ice loss on midlatitude atmospheric circulation in an intermediate-complexity global atmospheric model

Article Title: Arctic amplification fingerprints on the midlatitude circulation in a medium-complexity global atmospheric model

Article References: Saurral, R. I., & Kucharski, F. (2026). Arctic amplification fingerprints on the midlatitude circulation in a medium-complexity global atmospheric model. Climate Dynamics, 64(10), Article 415. https://doi.org/10.1007/s00382-026-08373-z

Image Credits: AI Generated

DOI: 10.1007/s00382-026-08373-z

Keywords: Arctic amplification, sea ice loss, sea surface temperatures, jet stream, midlatitude circulation, climate dynamics, medium-complexity model, polar warming, Hadley cell, storm tracks, climate modeling, atmospheric circulation

The jet stream is a narrow, meandering current of air near the tropopause, the boundary between the troposphere and the stratosphere, typically located several kilometres above the surface and flowing from west to east at speeds that can exceed 50 metres per second in winter. Over the Atlantic–European sector, this current is maintained by the temperature contrast between the warm subtropical ocean and the cold polar region, a contrast that generates pressure gradients at upper levels of the atmosphere. Because the jet acts as a kind of atmospheric conveyor belt, guiding storm systems from the ocean toward the continent, even modest shifts in its strength or position can reshape winter weather across Britain, Scandinavia, central Europe and the Mediterranean.

Understanding how the jet responds to greenhouse warming has been one of the more contested questions in climate dynamics. One influential line of argument holds that rapid Arctic amplification—the fact that the high northern latitudes are warming several times faster than the globe as a whole—reduces the equator-to-pole temperature gradient near the surface. A weaker gradient, in this view, should sap the energy available to the jet, producing weaker winds, larger meanders and a greater tendency toward persistent blocking patterns that lock cold air over Europe for weeks at a time. Another line of argument emphasizes that the upper troposphere warms more strongly than the surface in the tropics and mid-latitudes, which increases the vertical shear of the winds and can actually strengthen the jet aloft while shifting it poleward.

The new analysis addresses this debate by looking not only at the average behaviour of the Atlantic–European jet in winter but at the full distribution of its variability, including the extreme tail. Using observational and reanalysis datasets—long records of atmospheric conditions reconstructed from weather observations and satellite data—the researchers tracked jet strength over recent decades and examined how frequently the jet reached its most intense values. The central result is a nuanced one: the typical winter jet has become stronger, consistent with the expectation that upper-level warming and changes in the temperature gradient enhance the mean flow, but the extremes of jet strength have not kept pace. In relative terms, the jet is becoming a steadier current rather than a more violent one.

This distinction between the mean and the extremes matters for how scientists and society interpret jet stream change. A stronger mean jet is generally associated with a more vigorous storm track, which can bring more frequent passages of Atlantic low-pressure systems and the mild, wet, windy weather they deliver to northwestern Europe. Extreme jet episodes, by contrast, are often linked to exceptional weather: an unusually intense jet can coincide with explosive cyclogenesis, in which storms deepen rapidly and cause damaging windstorms, while an unusually weak or displaced jet can coincide with prolonged cold spells or drought. If the mean strengthens while the extremes moderate, the net effect on hazardous winter weather may be less dramatic than either a simple strengthening or a simple weakening story would suggest.

The physical reasoning behind such a divergence can be traced to how different components of the climate system respond to warming. The mean jet strength is governed largely by broad-scale temperature gradients and by the vertical structure of tropospheric warming, both of which evolve smoothly and predictably with rising greenhouse gas concentrations. Extreme jet episodes, however, often depend on transient processes: the phasing of planetary-scale Rossby waves, the life cycles of individual baroclinic storms, and episodic coupling with the stratospheric polar vortex. Some of these transient drivers may weaken or become less variable under warming, damping the upper tail of the jet distribution even as the background flow intensifies. The study’s results are consistent with such a mechanism, in which variability about the mean contracts even as the mean itself rises.

The findings also speak to a long-running scientific controversy about Arctic influence on mid-latitude weather. Over the past decade, a vigorous debate has played out in the journals over whether sea-ice loss and Arctic warming make European winters more prone to blocking and severe cold. Proponents of this view point to episodes such as the cold winters of recent decades and to modelling experiments in which reduced sea ice favours a wavier jet. Critics counter that the observational record is short, that internal variability is large, and that model projections more often show a strengthened, poleward-shifted jet with reduced waviness in winter. By documenting a strengthening yet less extreme jet, the new work lends weight to the second camp, while underscoring that the answer may differ by season, by region and by which aspect of the jet is measured.

Methodologically, the study illustrates the value of going beyond simple averages when assessing climate change signals. Jet stream behaviour is notoriously noisy: individual winters can differ enormously, and the Atlantic–European sector in particular is influenced by modes of variability such as the North Atlantic Oscillation, which swings between phases that strengthen or weaken the westerlies on timescales from weeks to decades. Separating a forced climate signal from this internal noise requires careful statistical treatment, long datasets and, in many cases, large ensembles of climate model simulations in which many parallel realizations of the same warming scenario are run to isolate the common response. The researchers’ focus on the distribution of jet strength, rather than a single metric of average speed, allows a more complete picture of how the flow is evolving and reduces the risk of drawing conclusions from a few memorable extreme winters.

The implications extend to practical forecasting and adaptation. Winter storm risk assessment for Europe depends on assumptions about how often severe windstorms strike, and those assumptions are typically based on historical statistics. If the character of the jet is changing—stronger on average but with moderated extremes—then the historical record may be an imperfect guide to the coming decades. Insurers, infrastructure planners and emergency services all have an interest in knowing whether the tail risks of winter weather are growing or shrinking. The new results suggest that for jet-driven wind extremes, at least, the most catastrophic outcomes may not intensify as rapidly as the mean conditions do, although the researchers caution that other hazards, such as precipitation extremes associated with a moister, warmer atmosphere, continue to worsen independently of the wind field.

There remain open questions. The observational record of the upper atmosphere is only a few decades long, and reanalysis products carry uncertainties, particularly in the earlier satellite era and in the data-sparse regions of the North Atlantic. Disentangling the roles of tropical upper-tropospheric warming, Arctic amplification, stratospheric variability and ocean circulation in shaping the jet will require further modelling work. Nevertheless, the study offers a clear and somewhat reassuring refinement of the picture: the Atlantic–European winter jet is not collapsing into weakness and chaos, nor is it becoming uniformly more ferocious. Instead, it is strengthening as a background current while its wildest excursions become relatively less extreme—a reminder that climate change rarely moves every aspect of a system in the same direction, and that the most useful science is often found in the details between the averages and the extremes.

Subject of Research: Winter strengthening and reduced extremity of the Atlantic–European jet stream

Article Title: A strengthening yet less extreme Atlantic–European jet during winter

Article References: Brönnimann, S., Brugnara, Y., & Kallabis, P. (2026). A strengthening yet less extreme Atlantic–European jet during winter. Nature Geoscience. https://doi.org/10.1038/s41561-026-02069-z

Image Credits: AI Generated

DOI: 10.1038/s41561-026-02069-z

Keywords: jet stream, Atlantic–European jet, winter climate, North Atlantic Oscillation, Arctic amplification, storm track, climate variability, reanalysis, stratosphere, extreme weather, climate change, geoscience