Comparing the climate of 2026 to 1976

 Should we really make comparisons 

Comparing the climate of 2026 to 1976 is an incredibly compelling exercise, but because of that ~90 ppm gap in atmospheric carbon dioxide ~{CO}_2), we have to change how we make the comparison.

​In 1976, global ~{CO}_2 levels were hovering around 332 ppm; today in 2026, we are sitting near 422 ppm. Because of this massive shift in the global baseline, a direct "apples-to-apples" comparison of absolute temperatures or specific weather anomalies can be misleading. Instead, we look at 1976 through two distinct lenses: forced climate trends versus internal climate variability.

​Here is how to approach the comparison effectively:

​1. Establishing the New Baseline (Forced Trend)

​The 90 ppm difference represents a massive increase in radiative forcing. The primary consequence is that the "normal" background temperature has shifted dramatically.

• ​The Temperature Floor has Risen: A severe heatwave or drought in 1976 occurred on a cooler planet. If you took the exact same atmospheric pressure patterns from 1976 and superimposed them onto 2026's atmosphere, the resulting heatwave would be significantly more intense today purely because the baseline tropospheric temperature is higher.
• ​Ocean Heat Content: The oceans have absorbed over 90% of the excess heat trapped by that extra 90 ppm of {CO}_2. Comparing current Sea Surface Temperatures (SSTs) to 1976 requires accounting for this global marine warming, which alters everything from hurricane potential intensity to marine heatwaves.

2. Comparing Synoptic Dynamics (Internal Variability):

Where a comparison to 1976 remains highly valuable is in analyzing atmospheric circulation patterns. The extra ~{CO}_2 changes the energy balance, but it doesn't completely rewrite the laws of fluid dynamics or erase natural cycles like El Niño Southern Oscillation (ENSO), the North Atlantic Oscillation (NAO), or jet stream behavior.

You can effectively compare 1976 to 2026 by looking at:

• ​Jet Stream Behavior: 1976 was famous for a prolonged, deeply blocked jet stream that led to the historic UK/European drought. Comparing the wavelength and persistence of 2026’s jet stream to 1976 helps scientists understand if climate change is making these stagnant atmospheric blocks more frequent or persistent.
• ​Relative Anomalies: Instead of comparing absolute temperatures, compare how far 1976 departed from its local 30-year climatological norm against how far 2026 departs from its current norm. This isolates the structural efficiency of the weather patterns themselves.

3. The "Non-Linear" Complication:

We also cannot assume the climate responds in a perfectly linear fashion to that 90 ppm increase. The climate system has feedback loops and thresholds. For instance, the loss of Arctic sea ice over the last 50 years has altered the latitudinal temperature gradient between the equator and the pole. This potentially impacts jet stream waviness in ways that wouldn't have been captured in the 1976 data.

Summary:

Don't directly compare absolute temperatures or SSTs without adjusting for the modern warming trend.

Do compare the synoptic setups—like pressure anomalies, omega blocks, and planetary wave setups—to see how effectively the atmosphere is transporting heat and moisture under two very different thermodynamic regimes.

Written on the 9th July 2026

Author David I Birch 

Is a reversal of AMO imminent

 

Whether the Atlantic Multidecadal Oscillation (AMO)—also referred to as Atlantic Multidecadal Variability (AMV)—is due to flip from its current warm phase to a cool phase is one of the most heavily debated topics in modern climatology.

Because the AMO operates on long timescales, a shift is statistically "due" soon, but an increase in Global temperaturea is making predicting the exact timing highly complex.

​Historical Timing Between Phases:

​Based on historical instrumental records, a full AMO cycle spans roughly 60 to 80 years, meaning each individual warm or cool phase typically lasts between 30 and 40 years. 

Historical phases of the AMO - warm/cool

As shown in the historical data above, the shifts follow a distinct multidecadal rhythm:

1880–1900: Warm Phase (~20 years                           recorded)

1900–1930: Cool Phase (~30 years)  

1930–1965: Warm Phase (~35 years)  

1965–1995: Cool Phase (~30 years)  

1995–Present: Warm Phase (Currently at              31 years)

Because the current warm phase has been active since roughly 1995, the North Atlantic has spent over three decades in a warm state. Statistically, this puts the climate system near the typical window for a reversal.

Likelihood of a Reversal:

​Predicting the likelihood of an imminent flip involves tracking two competing forces: internal ocean dynamics and external atmospheric forcing.

1. Signs of Potential Cooling (The Case for a Flip)

​Oceanographers closely monitor the Atlantic Meridional Overturning Circulation (AMOC)—the deep ocean conveyor belt that pumps warm water north. Subsurface observations in the North Atlantic subpolar gyre have periodically shown cooling trends and a weakening AMOC. When the AMOC slows down, it delivers less heat northward, which is historically the primary trigger for a negative (cool) AMO phase. Some decadal forecasting models suggest a transition toward a cooler North Atlantic state could materialize within the coming decade.

Even if the internal ocean circulation shifts to a cooling mode, it may manifest as a "pause" or a deceleration in rapid warming rather than a dramatic drop into historical cold anomalies.

Summary: While a shift toward the cooler ocean mechanisms of a negative AMO is moderately likely to build momentum over the next decade due to natural internal cycles, background global SST's warming may blunt or mask the actual cooling effects traditionally associated with past negative phases.

Written on the 2nd July 2026

Author - David I Birch 

Reference - Wikipedia - NCAR climate data -                        guide, NOAA GFDL.

Physics behind why El Niño suppresses the Asian monsoon

The suppression of the Asian monsoon during an El Niño event is a direct consequence of a fundamental reconfiguration in the Walker Circulation—a massive east-west atmospheric overturning cell driven by sea surface temperature (SST) gradients across the Pacific.

The walker circulation pivot: Shifting Trade winds.

1. The Normal State: Strong Zonal            Gradient:

In a non-El Niño year, the tropical Pacific maintains a strong zonal pressure gradient.

Thermal Engine: Intense solar radiation keeps the Western Pacific (the "Warm Pool" near Indonesia) significantly warmer than the Eastern Pacific.

Convection: This temperature contrast drives deep convection. Air rises over the warm Maritime Continent, travels eastward in the upper troposphere, sinks over the cool Eastern Pacific, and returns westward at the surface as the Trade Winds.

Monsoon Coupling: The rising limb of this circulation over the Maritime Continent creates a vast low-pressure area that anchors the Asian monsoon, pulling moisture-laden air into the Asian landmass.

2. The El Niño Pivot: Convective              Dislocation:

​During El Niño, the Pacific undergoes a positive SST anomaly in the central and eastern basin.

​The Eastward Shift: As the warm pool spreads eastward, the center of deep convection follows. The primary rising limb of the Walker Circulation is no longer anchored over Indonesia/Southeast Asia but pivots toward the Central or Eastern Pacific.

​Physics of Suppression (Subsidence):The atmosphere must conserve mass. Because the primary convective engine has "moved" east, the air that was previously rising over Southeast Asia is replaced by anomalous subsidence (sinking air).

​Pressure Inversion: Subsiding air creates a local high-pressure anomaly. In fluid dynamics, this effectively "caps" the region. It inhibits cloud formation and suppresses the low-level cyclonic moisture transport that the Asian monsoon relies on.

3. The Thermal Inertia Problem:

The Asian monsoon is essentially a giant thermal engine driven by the land-sea temperature contrast: 

T_{land} - T_{ocean} > 0.

By disrupting the Walker Circulation, El Niño alters the large-scale moisture convergence. When the convective branch shifts away:

Reduced Latent Heat Release: The massive release of latent heat (which usually fuels the upper-level monsoon flow) is reduced over the Maritime Continent.

Weakened Jet Stream: The weakening of this tropical heating source leads to a downstream perturbation of the jet stream, often altering the timing and intensity of the monsoon's "burst" phases.

In short, the monsoon mechanism is starved of its primary convective "pump," and the local high-pressure anomalies created by the shift in the Walker Circulation act as a physical barrier to the typical moisture flux needed for heavy rains.

Written on the 1st July 2026

Author - David I Birch 

Interbasin connections of ENSO and Hurricane season

There is a substantial inverse correlation between tropical Pacific Sea Surface Temperatures (SSTs) and tropical Atlantic activity, which directly modulates conditions in the Atlantic Main Development Region (MDR). This interbasin connection is primarily driven by the El Niño-Southern Oscillation (ENSO) cycle via atmospheric teleconnections.

1. The ENSO Teleconnection Mechanism:

The relationship is not driven by a direct mixing of water, but rather by changes in the global atmospheric circulation (specifically the Walker Circulation) triggered by Pacific SST anomalies.  

When Pacific SSTs are Warm (El Niño):

When the central and eastern equatorial Pacific experiences anomalously warm SSTs (+ENSO), it triggers intense atmospheric convection over the Pacific.

Increased vertical wind sheer:

This shifts the upper-level wind patterns, sending strong westerly winds across the Caribbean and into the tropical Atlantic MDR. These strong winds clash with the low-level easterly trade winds, creating high vertical wind shear. High shear literally rips developing tropical disturbances apart.

Atmospheric Stability:

El Niño induces broad anomalous sinking motion (subsidence) and warmer upper-tropospheric temperatures over the Atlantic basin, which stabilizes the atmosphere and suppresses deep convection. 

MDR Response:

Even if local Atlantic MDR waters are warm, an active El Niño act as a powerful "brake" on hurricane development.

When Pacific SSTs are cool: 

Cool (La Niña) Conversely, when Pacific SSTs are below average (-ENSO), the opposite occurs.

Reduced Vertical Wind Shear: 

Convection shifts to the far western Pacific, causing the upper-level westerlies over the Atlantic to weaken. Increased Instability: The atmosphere over the MDR becomes much more unstable, with enhanced rising motion and deep tropical moisture pushed into the region. MDR Response: This creates an environment highly conducive to tropical genesis and intensification.

2. The "Relative SST" Concept

​In modern climate science, researchers look closely at Relative SSTs—the temperature of the Atlantic MDR relative to the rest of the global tropical oceans.

​If the tropical Pacific warms faster or is warmer than the Atlantic, the global tropical troposphere warms, raising the thermodynamic threshold required for convection in the Atlantic. Therefore, even if the MDR is technically warmer than its historical average, it may underperform if the Pacific is significantly warmer. Conversely, if the Pacific cools (La Niña) while the Atlantic MDR remains exceptionally warm, the two factors work in tandem to create hyper-conducive conditions for extreme development.

               Current conditions.

Right now, we are seeing a fascinating, textbook setup of this exact interbasin relationship playing out in real time. The ocean-atmosphere setup has changed dramatically over the last few months, shifting the outlook for the hurricane season.

Here is exactly how the anomalies look across both basins as of June 2026:

1. The Tropical Pacific: A Rapidly Intensifying El Niño

The tropical Pacific is undergoing a confident warming trend. NOAA and the Met Office officially declared the start of an El Niño event, and it is ramping up incredibly fast, we spotted this back in April when subsurface temperatures were romping eastward. The Core Anomalies: In the central equatorial Pacific (the critical Niño 3.4 region), weekly SST anomalies have surged to +1.7^\circ\text{C}.  

Subsurface Heat:

Beneath the surface (at depths of 50–150 meters), a massive reservoir of warm water is packed into the central-eastern Pacific, with localized anomalies hitting up to +6^\circ\text{C}. This acts as a massive engine room, guaranteeing that this El Niño will continue to intensify through the summer and autumn.  

Atmospheric Response: 

The atmosphere has fully coupled with the ocean. The Southern Oscillation Index (SOI) is strongly negative (sitting at -21.9), and the easterly trade winds have severely weakened or even flipped to westerlies.

Current climate models are highly aligned, predicting this will peak as a strong to very strong El Niño later this year, potentially ranking among the most intense events observed since 1950.  

2. The Atlantic MDR: Robust Anomalous Cooling

While global sea surface temperatures as a whole remain exceptionally warm, the tropical Atlantic Main Development Region (MDR) is presenting a very stark contrast to the record-breaking warmth seen over the last couple of years.

The Local Anomalies:

The eastern and central tropical Atlantic MDR have actually experienced significant anomalous cooling, dropping below average for this time of year. Only the far western tropical Atlantic (near the Caribbean) is holding onto near-average temperatures.  

The "Relative SST" Trap: Because the Pacific is warming at a near-historic pace while the central/eastern Atlantic MDR has cooled below climatological norms, the Relative SST values for the Atlantic are deeply negative.

3. The Real-World Impact on the Seasonal Outlook

Because the anomalies have lined up this way, major meteorological institutions (like Colorado State University) have notably reduced their 2026 seasonal hurricane forecasts to below-normal levels.  

Normally, a warm global ocean provides plenty of background thermal energy, but the combination of a potent, rapidly growing Pacific El Niño and cooler-than-normal local MDR waters is expected to unleash exceptionally high vertical wind shear straight across the Caribbean and tropical Atlantic. This atmospheric "shear wall" is anticipated to act as a major suppressor, keeping a lid on deep tropical organization and storm track development through the peak of the season.

Written by David I Birch 

28th June 2026

Rapid equatorial Pacific SST's amidst a negative PDO

 Rapid intensification of equatorial SST's, amidst a negative PDO.

The Pacific Decadal Oscillation (PDO) is currently negative. As of March 2026, the PDO index was recorded at -1.25°C, maintaining a persistent negative (or "cool") phase that has largely dominated the North Pacific basin over the last several years.  

Even though a negative PDO usually runs counter to El Niño, its interaction with the rapidly developing 2026 El Niño is creating a fascinating and highly unusual climate scenario.

How a Negative PDO Changes the El Niño Dynamics.

The PDO is essentially a long-term, decadal cousin of ENSO that is centered in the North Pacific (poleward of 20°N). When it is in a negative phase, it features a massive horseshoe-shaped footprint of cooler-than-average waters along the west coast of North America and into the subtropics, wrapping around a warmer core in the central North Pacific.  

Typically, a negative PDO acts as a "brake" on El Niño development by reinforcing stronger trade winds and keeping the eastern Pacific cool. However, the 2026 El Niño is behaving quite differently due to its overwhelming thermodynamic strength:

Tug-of-War with the Trade Winds:

Normally, a negative PDO tries to push back against El Niño by strengthening the easterly trade winds. Right now, however, the atmosphere over the equatorial Pacific has completely decoupled—the trade winds have already collapsed or reversed into westerly wind bursts, rendering the PDO's usual dampening effect ineffective.

The Subsurface "Fuel Tank": The sheer volume of subsurface heat content currently sitting in the equatorial Pacific is nearly twice what was observed at this exact same point during the development of the major 2023 El Niño. This massive reservoir of warm water is overpowering the mid-latitude cooling signals of the PDO.

Suppressed Extratropical Warmth: While the equatorial regions (like Niño 1+2 and 3.4) are experiencing extreme, borderline "Super El Niño" warming, the negative PDO is keeping the waters immediately off the coast of North America much cooler than they would be during a classic, fully constructive positive PDO/El Niño pairing.

What This Means for the 2026 Peak and Beyond.

Because the equatorial forcing is so incredibly dominant, the negative PDO will not prevent this El Niño from peaking as a strong, potentially historic event later this winter.

Instead, the main impact of this clash will likely be seen in the global weather teleconnections (the atmospheric bridge that alters weather patterns worldwide). The combination of a strong tropical El Niño and a negative mid-latitude PDO can distort the jet stream in unusual ways. For instance, it can warp the typical winter storm tracks over North America and Europe, making downstream weather impacts—such as winter rainfall patterns—harder to predict using historical El Niño analog years alone.

Written 27th June 2026

David I Birch 

Advancing features of El Niño 2016

 

The equatorial Pacific is undergoing a rapid, significant warming phase. NOAA officially issued an El Niño Advisory earlier this month, confirming that El Niño conditions have developed and are strengthening quickly, as we discussed back in April as we continued to monitor the transition of sub- equatorial temperatures.

​The current sea surface temperature (SST) anomalies across the specific ENSO regions reflect this transition:

​Niño 3.4 (East-Central Pacific): This critical monitoring region has crossed firmly into El Niño territory. As of mid-June 2026, the weekly SST anomaly here has climbed to +0.7°C to +1.7°C (with the mid-June weekly index spiking sharply to +1.7°C, a value last seen in January 2024. This indicates a rapid transition toward a moderate, and potentially very strong, El Niño event.

​Niño 1+2 (Far Eastern Pacific / Coast of South America): The warming is even more pronounced in this eastern boundary zone. The latest official weekly anomaly in the Niño 1+2 region stands at an exceptional +3°c a value last seen in late June 2023.

This intense coastal warming in the east, combined with a substantial reservoir of subsurface heat and weakened trade winds, suggests that this El Niño is highly likely to continue intensifying as we head into the autumn and winter months.

The question is when will it peak? We suggest between NDJ with a peak value of around 2.75°c and a peak weekly value of 3°c in Dec.

Written on 27th June 2026

David I Birch 

El Niño and Hurricane formation

 A strong El Niño acts like a massive atmospheric spoiler for the tropical Atlantic, particularly across the Main Development Region (MDR)—the stretch of ocean between West Africa and the Caribbean where most major hurricanes form.

The primary mechanism driving this is a dramatic increase in vertical wind shear (the change in wind speed and direction at different altitudes). Here is exactly how it unfolds:

The Atmospheric Pipeline

When a strong El Niño develops, the waters of the central and eastern tropical Pacific become exceptionally warm. This intense oceanic heat triggers massive, persistent thunderstorms over the Pacific.

As these storms pump warm air high into the upper troposphere (around 30,000 to 40,000 feet), it alters global air currents via teleconnections (atmospheric domino effects). This creates a powerful stream of upper-level westerly winds that race eastward across the Caribbean and directly into the Atlantic MDR.

     Wind sheer anomalies during El Niño 

Why This Tears Hurricanes Apart

To understand why this suppresses tropical activity, look at the conflict between the upper and lower atmosphere in the MDR during an El Niño: At the Surface: The prevailing winds are the low-level easterly trade winds, blowing from east to west (Africa toward the Americas). In the Upper Atmosphere: El Niño introduces powerful, anomalous westerly winds blowing from west to east.

Because the bottom layer of the atmosphere is moving west while the top layer is rushing east, any developing tropical disturbance gets caught in a violent tug-of-war. Hurricanes require a calm, vertically aligned column to chimney warm air upward and intensify. High vertical wind shear tilts this core, separating the low-level circulation from the upper-level heat source, effectively tearing the storms apart before they can organize. Even if ocean temperatures in the Atlantic MDR are warm enough to fuel a storm, the sheer mechanical force of these conflicting winds usually keeps a lid on the hurricane season.

We should not expect an above average season in 2026 due to these factors.

Written 26th June 2026

Author -David I Birch