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 research, led by Isabel H. Smith of the University of Reading, together with Paul D. Williams and Reinhard Schiemann, quantifies changes in moderate-or-greater mountain wave turbulence by 2050 under a high-end warming scenario. The team used a multi-model approach built on the high-resolution tier of the Coupled Model Intercomparison Project, known as HighResMIP, which was designed to close the gap between climate models and numerical weather prediction. After testing seven horizontal grid spacings across three global climate models, the authors settled on three of the finest: HadGEM3-GC3.1-HM at 25 kilometres, EC-Earth-3P-HR at 36 kilometres and MPI-ESM1.2-XR at 34 kilometres. The choice mattered. In their comparison of the 1950s with the 2040s, coarser models with grid spacings of 60 kilometres or more failed to resolve many known turbulence zones altogether, a consequence of smoothed topography and terrain gradient thresholds that erase the steep slopes where mountain waves are born.

Diagnosing turbulence in climate model output is an art of proxies. Because the models cannot simulate turbulent eddies directly at these scales, the researchers applied six established clear-air turbulence indices, including horizontal temperature gradient, frontogenesis function, wind divergence, wind speed, flow deformation and a combined flow deformation and wind speed measure. Each index was then multiplied by a terrain-dependent factor requiring surface heights above 200 metres, terrain gradients steeper than 0.5 kilometres per metre and sufficient low-level wind speed below one kilometre. This construction, validated in earlier work against pilot reports, effectively isolates turbulence generated by mountains. The team defined moderate-or-greater turbulence as the 98th percentile of each index at the 200 hectopascal pressure level, roughly the cruising altitude of jet aircraft, and only accepted trends that passed a 95 percent confidence test in a linear regression over the 101-year period from 1950 to 2050.

The headline result is a world divided. The largest increase in mountain wave turbulence is projected over the Antarctic, where the average trend reaches 0.52 percent per year, equivalent to roughly 52 percent more turbulence over the century, with the strongest seasonal rise of 0.31 percent per year in the Southern Hemisphere summer. Greenland follows closely, a finding with direct consequences for the busy transatlantic corridors that cross its southern slopes. Regions covering Georgia, Azerbaijan and eastern Turkey, along with parts of Chile and Argentina in the southern Andes, also show significant increases. In contrast, the Alps, the Atlas Mountains and the northern and central Andes are projected to become calmer, as are broad swaths of Africa. The study’s sub-continental analysis across 28 regions reveals that even within a single continent the picture can reverse: North America as a whole gains turbulence, yet the zone covering the Rocky Mountains loses it in every season, with a decline of more than 50 percent in spring, the greatest decrease found anywhere in the study.

Seasonality emerges as a critical dimension of the projections. Over North America, winter and autumn carry the strongest increases, consistent with the known climatology in which lowered tropopause heights and peak westerly winds crossing mountain ranges perpendicularly favour wave generation. The region encompassing Greenland, Iceland and northeastern Canada shows increases of 18.2 percent in summer, 16.2 percent in autumn, 11.1 percent in spring and 7.4 percent in winter by 2050. Over Asia, home to the Himalayas and the Tibetan Plateau, the models project more turbulence in winter but less in summer, with trends of 0.023 and minus 0.014 percent per year respectively. Australia displays a particularly sharp seasonal split, with significant declines in the southern summer and autumn but unanimous increases across all models and indices in winter and spring. The Antarctic is most turbulent in Southern Hemisphere winter and least so in summer, yet both seasons show rising trends.

The mechanism behind these shifts appears to lie substantially in the winds near the surface. Mountain waves draw their energy from low-level airflow, so any change in wind speed over terrain directly modulates wave amplitude and the likelihood of breaking. The study found a positive correlation between projected changes in turbulence and changes in 10-metre wind speed, examining both average and maximum winds to capture the general trend and the occurrence of extreme gusts. In the Antarctic, increases in turbulence in both summer and winter were linked to strengthening average and maximum low-level winds, a finding that echoes observational work by the British Antarctic Survey showing surface winds there have strengthened by about 15 percent since 1980. Over Canada and Alaska, rising turbulence tracked increasing winds, while the decline over the Rockies in autumn was associated with weakening maximum wind speeds, and the drop over India and Sri Lanka followed a decrease in average low-level winds.

These results complicate a simpler narrative from earlier research. Previous studies of clear-air turbulence, which is driven largely by shifting and strengthening jet streams, have consistently projected global increases under warming, and a 2023 analysis of mountain wave turbulence using coarser models found increases over roughly two-thirds of the globe, concentrated in the mid-to-high latitudes. The new high-resolution work partially confirms that latitudinal pattern but adds important exceptions, notably the declines over the Rockies and the northern and central Andes, which sit outside the tropical band where weakening was expected. The authors attribute some of the divergence to terrestrial stilling, the observed and projected slowing of surface winds across many Northern Hemisphere mid-latitude regions, which suppresses the raw energy available to generate mountain waves even as upper-level dynamics change.

The study is candid about its limitations. Climate model topography remains smoother than reality, so some known turbulence hotspots in the western United States are not fully captured, and mountain wave turbulence often develops downstream of ranges in ways that fixed terrain-gradient thresholds may miss. All projections assume the high-end SSP8.5 emissions scenario with little mitigation, so the changes described represent an upper bound rather than a central expectation. Index choice also matters: over South America, one index placed turbulence changes in a range of 0 to 50 percent while another suggested 180 to 250 percent, a spread the authors view as complementary rather than contradictory, since different diagnostics capture different generation mechanisms. Averaging across models and indices can also mask disagreement, as occurred over the Himalayas, where one model’s significant increase outweighed two smaller declines.

For the aviation industry, the practical message is one of targeted vigilance rather than uniform worsening. Turbulence already costs airlines millions of dollars a year in delays, injuries and structural damage, and pilot reports, the traditional observational record, carry median position uncertainties of around 50 kilometres. The new projections suggest airlines serving polar and subpolar routes, particularly those crossing Greenland or the few routes over the Antarctic, should anticipate a measurably rougher atmosphere by mid-century, while carriers over the Alps, the Atlas and the northern Andes may face somewhat reduced exposure. As high-resolution climate models continue to close the gap with weather forecasting systems, studies of this kind are turning an invisible, radar-proof hazard into something that can at least be mapped in advance, giving flight planners and meteorologists a decades-long head start on the turbulence of tomorrow.

Subject of Research: Projected global changes in mountain wave aviation turbulence under climate warming

Article Title: Global shifts in mountain wave turbulence within high resolution climate models

Article References: Smith, I. H., Williams, P. D., & Schiemann, R. (2026). Global shifts in mountain wave turbulence within high resolution climate models. Weather and Climate Dynamics, 7(3), 1733-1758. https://doi.org/10.5194/wcd-7-1733-2026

Image Credits: AI Generated

DOI: 10.5194/wcd-7-1733-2026

Keywords: mountain wave turbulence, aviation safety, climate change, HighResMIP, CMIP6, clear-air turbulence, gravity waves, Greenland, Antarctic, Rocky Mountains, terrestrial stilling, climate models

The observational record is striking. Drawing on measurements from 150 meteorological stations operated by the National Meteorological Information Center of the China Meteorological Administration, the team found that annual mean near-surface wind speed over the Tibetan Plateau declined at a rate of 0.159 meters per second per decade between 1979 and 2014. The decline was not spread evenly through the year. Spring showed the steepest weakening, with wind speeds falling by 0.235 meters per second per decade, a seasonal signal that matters because spring winds play a central role in the plateau’s exchange of heat and moisture with the surrounding atmosphere and in shaping the Asian monsoon system downstream.

To test whether climate models could reproduce this stilling, the researchers turned to the Coupled Model Intercomparison Project Phase 6, specifically its High-Resolution Model Intercomparison Project, known as HighResMIP. This experiment was designed in part to answer a long-standing question in climate science: would simply cranking up the horizontal resolution of global models improve their simulations? The team assembled 22 historical simulations from 11 model pairs, each pair consisting of a higher-resolution and a lower-resolution version of the same model, and compared them against the station observations over the 1979 to 2014 period.

The verdict on resolution was sobering. Both the higher-resolution and lower-resolution ensemble means captured the broad spatial pattern of wind speed across the plateau, but both badly underestimated the magnitude of the decline. The higher-resolution ensemble produced an annual trend of only 0.024 meters per second per decade, while the lower-resolution ensemble managed just 0.020 meters per second per decade. In other words, the models reproduced only about one-seventh of the observed stilling. Perhaps more telling, the difference between the two resolution tiers was small, suggesting that increasing horizontal resolution alone offers limited improvement in capturing the historical wind decline over this complex, high-altitude terrain.

This widespread stilling bias is not merely an academic curiosity. Near-surface wind speed governs a host of processes with real-world consequences: the evaporation of water from land surfaces, the dispersal of air pollutants, the mixing of the atmospheric boundary layer, and the output of wind turbines. The Tibetan Plateau is also the source region of major Asian rivers and a critical driver of monsoon circulation, so systematic errors in simulating its winds can propagate into broader failures in regional climate prediction. Previous studies have linked wind declines across China to factors ranging from urbanization and increased surface roughness to weakening pressure gradients and changes in large-scale circulation, but representing these processes faithfully in global models has remained elusive.

To dig into why the models fall short, the team applied a random forest machine learning analysis, a technique that can rank the relative importance of many candidate variables in explaining an outcome. The analysis pointed to biases in key dynamical and thermodynamical processes, with snow variability and surface sensible heat flux emerging as particularly influential factors. This makes physical sense. Snow cover on the plateau alters surface albedo and the partitioning of energy between sensible and latent heat, which in turn modulates the temperature contrasts that drive near-surface winds. If a model misrepresents how snow accumulates and melts across the plateau’s rugged topography, the resulting errors in surface heating can distort the very circulation features that generate wind.

Having identified which simulations performed best against observations using multiple statistical metrics, the researchers selected seven optimal models and constructed an optimal ensemble mean for future projections. Under the high-emission Shared Socioeconomic Pathway 5-8.5, the projections indicate that the stilling of the Tibetan Plateau will continue through the coming decades. Between 2015 and 2049, the ensemble projects an annual wind speed decline of approximately 0.02 meters per second per decade, unfolding alongside continued regional warming. While the projected rate is gentler than the historical observed trend, the direction of change is consistent, lending robustness to the conclusion that winds over the plateau will keep weakening in a warming world.

The juxtaposition of a robust future decline with a poorly simulated past decline creates something of a paradox for climate scientists. If models underestimate how much wind has already slowed, should we trust their projections of future slowing? The authors argue that the consistency of the projected decline across the selected optimal models, combined with the physical plausibility of continued warming-driven circulation changes, supports confidence in the sign of the projection even if the magnitude remains uncertain. At the same time, the study makes clear that closing the gap between simulated and observed trends requires more than computational horsepower.

That message may be the study’s most consequential takeaway for the modeling community. HighResMIP was conceived on the premise that finer grids would better resolve steep orography, coastlines, and mesoscale processes, and for some variables that promise has held. But for near-surface wind over the Tibetan Plateau, the near-identical performance of high- and low-resolution model pairs indicates that the bottleneck lies elsewhere, in the representation of physical processes such as snow-atmosphere interactions, surface energy budgets, and boundary-layer dynamics. Improving these process representations, the study suggests, may matter more than simply increasing spatial resolution for reducing persistent model biases in wind simulation.

For the people and ecosystems of the plateau, the implications extend well beyond model evaluation. Weakening winds influence glacier mass balance through altered turbulent heat exchange, affect the timing and intensity of the monsoon onset that billions of people depend on, and reshape the viability of wind energy development in one of the world’s most promising but fragile high-altitude environments. As the Third Pole continues to warm faster than the global average, the slow, steady quieting of its winds serves as another reminder that climate change reshapes even the most fundamental features of the atmosphere, and that our models, for all their sophistication, are still learning to listen.

Subject of Research: Evaluation and projection of near-surface wind speed trends over the Tibetan Plateau using CMIP6 HighResMIP simulations and station observations

Article Title: Near-surface wind speed over the Tibetan Plateau: evaluation, trend and projection

Article References: You, Q., Wu, F., Wu, T., Cai, Z., Sun, G., Jin, Z., Jiang, Z., Ullah, S., & Li, M. (2026). Near-surface wind speed over the Tibetan Plateau: evaluation, trend and projection. Climate Dynamics, 64(10), Article 411. https://doi.org/10.1007/s00382-026-08342-6

Image Credits: AI Generated

DOI: 10.1007/s00382-026-08342-6

Keywords: Tibetan Plateau, near-surface wind speed, global stilling, CMIP6, HighResMIP, climate modeling, Climate Dynamics, SSP5-8.5, random forest, snow cover, sensible heat flux, monsoon