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 

Title: Uncertainties and Misunderstood Natural Effects of the Pacific Decadal Oscillation and ENSO State: Out-of-Phase Dynamics and Their Implications for Local and Global Climate, Farming, and Fisheries

 Author: David I Birch 

Affiliation: Independent Oceanic Researcher Date: March 24, 2025

Abstract

The Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillation (ENSO) are dominant drivers of interannual to decadal climate variability, yet their interactions and natural effects remain poorly understood. This paper explores the uncertainties surrounding these phenomena, particularly when their phases are misaligned (e.g., negative PDO with El Niño or positive PDO with La Niña), which can dampen or obscure expected climatic outcomes. We assess the implications for local and global climate, weather patterns, temperature anomalies, and their cascading effects on agriculture and fisheries. Case studies from the North Pacific and adjacent regions, including data from 1977, 1998, and 2015–2016, illustrate these dynamics. Our analysis highlights the need for a critical re-examination of oversimplified climate narratives and improved predictive frameworks to address these complex interactions.

1• Introduction 

The Pacific Decadal Oscillation (PDO) and El Niño-Southern Oscillation (ENSO) are oceanic-atmospheric phenomena that exert profound influence on global climate systems. The PDO, characterized by decadal-scale sea surface temperature (SST) anomalies in the North Pacific (north of 20°N), oscillates between warm (positive) and cool (negative) phases, typically lasting 20–30 years (Mantua et al., 1997). In contrast, ENSO operates on shorter timescales (6–18 months), with El Niño (warm phase) and La Niña (cool phase) driving equatorial Pacific SST anomalies and atmospheric teleconnections (Trenberth, 1997). While their individual impacts are well-documented, the interplay between PDO and ENSO—especially when out of phase—introduces significant uncertainties that challenge predictive models and conventional interpretations.

Out-of-phase conditions, such as a negative PDO coinciding with El Niño or a positive PDO with La Niña, can dampen or mask the expected effects of ENSO, leading to misunderstood natural variability. This paper critically examines these dynamics, their influence on local and global climate, weather, and temperature, and their socioeconomic consequences for farming and fisheries. We incorporate case studies to ground our analysis in historical events, emphasizing the need to move beyond simplistic climate narratives.

2. Uncertainties in PDO and ENSO Interactions

The PDO is not a singular mode of variability but an aggregate of processes, including ENSO teleconnections, stochastic atmospheric forcing, and North Pacific gyre dynamics (Newman et al., 2016). This complexity introduces uncertainty in attributing causality to observed climate shifts. Similarly, ENSO’s influence extends beyond the tropics via atmospheric bridges (e.g., Rossby wave propagation), yet its interaction with the PDO remains inadequately resolved in models (Kumar et al., 2013). A key misunderstanding lies in assuming PDO amplifies ENSO linearly, when evidence suggests out-of-phase alignments can neutralize or reverse expected outcomes. For instance, a negative PDO features cooler SSTs along the North American coast and a weaker Aleutian Low, potentially counteracting the warm, wet conditions typically associated with El Niño. Conversely, a positive PDO, with warmer coastal SSTs and a stronger Aleutian Low, may offset La Niña’s cooling and drying tendencies. These interactions challenge the reliability of seasonal forecasts and highlight gaps in our understanding of natural variability versus anthropogenic signals.

3. Out-of-Phase Dynamics and Climatic Effects

3.1 Local Climate and Weather

Out-of-phase PDO and ENSO states can significantly alter local weather patterns. During a negative PDO, cooler North Pacific SSTs weaken the jet stream’s intensity, reducing storminess along the North American west coast. When paired with El Niño, this can suppress the expected increase in precipitation, as seen in California during the 1997–1998 El Niño event amid a transitioning PDO phase (Gershunov & Barnett, 1998). Conversely, a positive PDO enhances coastal warmth and moisture transport, potentially mitigating La Niña’s drought-inducing effects in the south-western United States.

3.2 Global Climate and Temperature

Globally, these misalignments influence atmospheric circulation patterns, such as the Pacific-North American (PNA) teleconnection, which modulates temperature anomalies across continents. A negative PDO with El Niño may weaken the PNA’s positive phase, reducing warming in north-western North America and cooling eastern regions less than anticipated. During a positive PDO with La Niña, the reverse occurs, potentially tempering global cooling signals. These effects complicate attribution of temperature trends to ENSO alone, as PDO’s decadal persistence introduces a low-frequency filter.

3.3 Data Insights

Historical PDO indices (e.g., from JISAO) and ENSO records (e.g., Niño 3.4 index) reveal frequent out-of-phase periods. From 1947–1976 (negative PDO), El Niño events were less frequent and intense, while the 1977–1998 positive PDO coincided with stronger El Niños (e.g., 1982–1983, 1997–1998). Since 1998, a predominantly negative PDO has overlapped with variable ENSO states, including the muted 2015–2016 El Niño, underscoring the dampening effect.

4. Impacts on Farming and Fisheries

4.1 Farming

Out-of-phase PDO-ENSO dynamics disrupt precipitation and temperature patterns critical to agriculture. In the U.S. Midwest, a positive PDO with La Niña may reduce expected drought severity, sustaining corn and soybean yields, as observed in 2011–2012. Conversely, a negative PDO with El Niño can diminish rainfall in California’s Central Valley, impacting almond and grape production, as seen in 1997–1998 when yields dropped by ~10% due to below-average precipitation (USDA data).

4.2 Fisheries

The North Pacific’s fisheries, notably salmon, are highly sensitive to PDO-ENSO interactions. A positive PDO enhances coastal upwelling and nutrient availability, boosting salmon returns during La Niña years (e.g., 1977–1989 Alaskan salmon boom; Hare & Mantua, 2000). However, a negative PDO with El Niño reduces upwelling, depressing stocks, as evidenced by the 1997–1998 decline in Oregon coho salmon landings (~20% below average, NOAA Fisheries).

5. Case Studies

5.1 Case Study 1: 1977 PDO Shift and El Niño (Negative PDO Transition)

In 1977, the PDO shifted from negative to positive amid a weak El Niño. Despite El Niño’s warming tendency, western North America experienced cooler-than-expected temperatures and reduced rainfall, attributed to lingering negative PDO effects. California wheat yields fell by 15% due to drought, while British Columbia salmon catches remained stable, highlighting localized dampening.

5.2 Case Study 2: 1998 Negative PDO and Strong El Niño

The 1997–1998 El Niño, one of the strongest on record, coincided with a PDO shift to negative. California anticipated heavy rains, but precipitation was 30% below forecasts, linked to PDO-driven jet stream suppression. Fisheries off Oregon saw a 25% drop in chinook salmon, reflecting reduced ocean productivity.

5.3 Case Study 3: 2015–2016 El Niño with Negative PDO

The 2015–2016 El Niño, during a sustained negative PDO, failed to deliver expected rainfall to the U.S. Southwest, exacerbating drought conditions. Arizona cotton yields declined by 12%, while Gulf of Alaska cod stocks plummeted due to warmer SSTs unmitigated by PDO cooling, disrupting regional fisheries.

6. Discussion

The interplay of PDO and ENSO, particularly when out of phase, reveals significant gaps in climate science. Models often overestimate ENSO’s dominance, underrepresenting PDO’s modulating role (Seager et al., 2019). This mischaracterization affects farming and fishery management, where reliance on ENSO forecasts alone proves inadequate. The case studies underscore how natural variability can confound expectations, urging a re-evaluation of predictive tools and a deeper exploration of oceanic-atmospheric feedbacks.

7. Conclusion

The uncertainties and misunderstood effects of PDO-ENSO interactions, especially in out-of-phase states, have profound implications for climate, weather, and socioeconomic systems. Negative PDO with El Niño or positive PDO with La Niña can dampen ENSO’s signature, altering local and global patterns in unpredictable ways. Enhanced monitoring and modelling, integrating decadal and interannual scales, are critical to refining our understanding and supporting adaptive strategies in agriculture and fisheries. This analysis challenges the establishment’s tendency to oversimplify these phenomena, advocating for a more nuanced approach.

References

Gershunov, A., & Barnett, T. P. (1998). Interdecadal modulation of ENSO teleconnections. Bulletin of the American Meteorological Society, 79(12), 2715–2725.

Hare, S. R., & Mantua, N. J. (2000). Empirical evidence for North Pacific regime shifts in 1977 and 1989. Progress in Oceanography, 47(2–4), 103–145.

Kumar, A., et al. (2013). Does knowing the oceanic PDO phase help predict atmospheric anomalies? Journal of Climate, 26(4), 1268–1285.

Mantua, N. J., et al. (1997). A Pacific interdecadal climate oscillation with impacts on salmon production. Bulletin of the American Meteorological Society, 78(6), 1069–1079.

Newman, M., et al. (2016). The Pacific Decadal Oscillation, revisited. Journal of Climate, 29(12), 4399–4427.

Seager, R., et al. (2019). Persistent discrepancies between observed and modelled trends in the tropical Pacific Ocean. Journal of Climate, 35(14), 4571–4589.

Trenberth, K. E. (1997). The definition of El Niño. Bulletin of the American Meteorological Society, 78(12), 2771–2777.

Uncertainties surrounding CO2 and Global temperatures.

Implications of a Hypothetical Cooling Trend

Authors: David I Birch- Gareth P Nugent-                             William A Marsh.

Date: March 29, 2025

Affiliation: Independent Oceanic and Atmospheric research studies.

Abstract

This paper examines the complexities and uncertainties inherent in the relationship between atmospheric carbon dioxide (CO2) and global temperature. While the greenhouse gas theory posits a direct correlation between increased CO2 and warming, historical climate records and the influence of other climate forcings reveal a more nuanced picture, particularly over shorter timescales. In this paper we analyses a hypothetical scenario where the Earth experiences a cooling trend over the next 30 years despite a continued increase in CO2 levels. This scenario, while seemingly contradictory to the established theory, is explored in the context of natural climate variability, including solar activity, volcanic eruptions, and ocean oscillations, as well as the role of aerosols and limitations in current climate modelling for short-term projections. The implications of such a cooling trend for the greenhouse gas theory are discussed, concluding that it would likely lead to a refinement rather than a rejection of the fundamental understanding of CO2's role in the climate system. The paper also explores alternative scientific explanations for such a decoupling of CO2 and temperature trends, emphasizing the multifaceted nature of Earth's climate system.

1. Introduction

The Earth's climate system is a complex interplay of various factors, with the greenhouse effect playing a pivotal role in maintaining a habitable temperature. This natural phenomenon involves certain atmospheric gases trapping heat radiated from the Earth's surface, preventing it from escaping into space. Key greenhouse gases responsible for this effect include water vapour, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3). Among these, carbon dioxide is recognized as a crucial component in regulating Earth's temperature; its removal would lead to a significant drop in the planet's average surface temperature. 

Since the onset of the Industrial Revolution in the mid-18th century, human activities, primarily the combustion of fossil fuels for energy, have led to a substantial increase in the concentration of atmospheric CO2.This anthropogenic increase in CO2 has enhanced the natural greenhouse effect, resulting in a discernible warming trend across the globe. Current data indicates that atmospheric CO2 levels have reached unprecedented heights, exceeding 430 parts per million (ppm) in recent years, with the rate of increase being significantly faster than natural fluctuations observed in the past. Concurrently, global average surface temperatures have shown a marked rise since the late 19th century, with the decade spanning 2011 to 2024 being the warmest on record. While long-term trends suggest a correlation between rising CO2 and temperature, the relationship is not always linear on shorter timescales due to the influence of other factors. This paper aims to investigate the inherent uncertainties in the relationship between atmospheric CO2 and global temperature. Specifically, it will analyse the implications of a hypothetical scenario where the Earth experiences a cooling trend over the next 30 years despite a continued increase in CO2 levels for the qestablished greenhouse gas theory.

2. The Foundational Understanding of the Greenhouse Gas theory.

The greenhouse effect is initiated by solar radiation entering the Earth's atmosphere, with a portion being absorbed by the planet's surface. The Earth then radiates energy back into the atmosphere in the form of infrared radiation, also known as heat. Greenhouse gases present in the atmosphere possess the property of absorbing and re-emitting this infrared radiation in all directions, effectively trapping some of the heat within the atmosphere. Different greenhouse gases exhibit varying capacities to absorb energy, referred to as radiative efficiency, and have different durations they persist in the atmosphere, known as atmospheric lifetimes. To facilitate comparisons of the warming impacts of different gases, the concept of Global Warming Potential (GWP) is utilized, which measures how much energy the emission of one ton of a gas will absorb over a given period relative to the emission of one ton of carbon dioxide.While CO2 serves as the reference gas for GWP with a value of 1, other greenhouse gases like methane and nitrous oxide possess significantly higher warming potentials per molecule, although their atmospheric concentrations are considerably lower than that of CO2. Water vapour, the most abundant greenhouse gas, plays a crucial role as a feedback mechanism, amplifying the warming initiated by other greenhouse gases. The amount of heat these gases can absorb and re-radiate determines their contribution to the greenhouse effect. Carbon dioxide specifically absorbs infrared energy at particular wavelengths, and an increase in its atmospheric concentration leads to greater absorption of outgoing infrared radiation, resulting in a net warming effect. Furthermore, CO2 plays a regulatory role in the amount of water vapour in the atmosphere, which in turn influences the planet's temperature. Even in a scenario where the absorption of radiation in the lower atmosphere reaches saturation, the addition of more CO2 in the upper atmospheric layers would still alter the planet's energy balance. This highlights that the influence of CO2 extends beyond direct heat trapping, impacting other critical components of the climate system and establishing it as a key driver of long-term temperature changes.The understanding of the greenhouse gas theory has evolved over centuries, with initial recognition of the effect dating back to the 19th century through the work of scientists like Joseph Fourier, John Tyndall, and Svante Arrhenius. Tyndall's experiments demonstrated that gases such as CO2 and water vapour absorb and radiate heat, laying the physical basis for the greenhouse effect. Arrhenius was among the pioneers who calculated the potential for human-induced emissions to cause a rise in global temperatures. Early on, some scientists held skeptical views, suggesting that the oceans would readily absorb any excess CO2 released into the atmosphere. However, in 1938, Guy Stewart Calendar presented arguments linking the observed warming to the increasing concentrations of CO2. The 1960s saw a significant advancement with Charles David Keeling's precise measurements confirming the rapid increase in atmospheric CO2 levels. Since then, the Intergovernmental Panel on Climate Change (IPCC) has provided comprehensive and periodic assessments of the scientific understanding of climate change, including the role of greenhouse gases . This historical progression underscores that the greenhouse gas theory is not a nascent concept but has been developed and refined over a considerable period, supported by a growing body of evidence and rigorous scientific inquiry .

3. Complexities and Uncertainties in the CO2-Temperature Nexus

The relationship between atmospheric CO2 and global temperature is not a simple linear one, but rather a complex interaction influenced by various factors, including climate feedback mechanisms and natural climate variability. Climate feedbacks are natural processes that respond to an initial warming or cooling by either amplifying (positive feedback) or diminishing (negative feedback) the change in the climate system Positive feedback mechanisms tend to enhance the initial temperature change. For instance, the water vapour feedback is a significant positive feedback, where warmer temperatures lead to increased evaporation, resulting in a higher concentration of water vapour in the atmosphere. Since water vapour is a potent greenhouse gas, this increase further warms the planet. Another crucial positive feedback is the ice-albedo feedback. As global temperatures rise, ice and snow melt, reducing the Earth's reflectivity (albedo). The darker surfaces of land and water then absorb more solar radiation, leading to further warming and more ice melt. The thawing of permafrost in polar regions also represents a positive feedback, as it releases significant amounts of methane and CO2, both potent greenhouse gases, into the atmosphere, thereby enhancing warming. Cloud feedback is a more complex area, as changes in cloud cover can have both positive and negative effects on temperature depending on the type, altitude, and reflectivity of the clouds.Conversely, negative feedback mechanisms tend to counteract the initial temperature change. The Planck response is a fundamental negative feedback where, as the Earth warms, it emits more infrared radiation into space, acting as a natural thermostat. The lapse rate feedback, which involves changes in the rate of temperature decrease with height in the atmosphere, is generally a negative feedback that weakens the greenhouse effect, although it can be positive in polar regions . Increased atmospheric CO2 can also lead to a limited negative feedback through enhanced photosynthesis by plants, which absorb CO2 from the atmosphere. The interplay of these positive and negative feedbacks ultimately determines the climate sensitivity, which is the estimated temperature increase resulting from a doubling of atmospheric CO2 concentrations. The wide range of estimates for climate sensitivity reflects the uncertainties associated with these complex feedback mechanisms, particularly cloud feedback, which remains a significant challenge for accurate climate modelling.

 While CO2 is a primary focus in discussions about climate change, other greenhouse gases also significantly influence the global energy balance. Methane (CH4) and nitrous oxide (N2O) are also potent greenhouse gases, exhibiting higher GWPs than CO2 over shorter timeframes. Methane, although having a shorter atmospheric lifetime compared to CO2, absorbs considerably more energy . Nitrous oxide is a long-lived greenhouse gas with a high GWP. Fluorinated gases (F-gases), while present in much smaller quantities, possess exceptionally high GWPs . Increases in the atmospheric concentrations of these gases also contribute to global warming. In 2021, carbon dioxide constituted the largest proportion of greenhouse gas emissions in the European Union, followed by methane. Therefore, a comprehensive understanding of global warming necessitates considering the contributions of these other greenhouse gases alongside CO2 in climate models and mitigation strategies.

Natural climate variability also plays a crucial role in modulating global temperatures, sometimes masking or amplifying the long-term warming trend driven by greenhouse gases. These natural factors include solar activity cycles, volcanic eruptions (and their aerosol effects), and oscillations in ocean currents. The Sun's energy output fluctuates over an approximately 11-year cycle and potentially on longer timescales . While variations in solar activity can lead to some climate variability, they are not considered the primary driver of the significant warming observed in recent decades . Mechanisms through which solar activity might influence climate include changes in total solar irradiance, variations in ultraviolet radiation, and potentially effects on cosmic rays that could influence cloud formation. Volcanic eruptions, particularly large explosive ones, can inject substantial amounts of aerosols, such as sulfur dioxide, into the stratosphere. These sulfur dioxide molecules convert to sulfuric acid aerosols, forming a haze that reflects incoming sunlight back into space, leading to a temporary global cooling that can last for a few years. While volcanoes also release greenhouse gases like carbon dioxide, the quantities emitted in contemporary eruptions are considerably smaller than those from human activities, this is however debatable.

Ocean currents play a vital role in redistributing heat across the globe, thereby influencing both regional and global climate patterns . Significant changes in ocean circulation, such as a slowdown of the Atlantic Meridional Overturning Circulation (AMOC), could potentially lead to regional cooling in areas like Western Europe despite overall global warming. Ocean-atmosphere oscillations, such as the El Niño-Southern Oscillation (ENSO), contribute to interannual variability in global temperatures. Furthermore, the ocean's immense capacity to absorb heat results in a delay in the full manifestation of greenhouse gas warming at the Earth's surface . Understanding these natural cycles and their impacts is essential for accurately interpreting temperature data,especially over shorter timeframes.

4. Limitations of Current Climate Modelling in Short-Term Projections.

Climate models serve as essential tools for understanding and projecting future climate change. These models are sophisticated computer simulations of the Earth's climate system, incorporating our knowledge of the physical, chemical, and biological processes that govern the climate. Despite their complexity, these models have inherent challenges and limitations, particularly when it comes to accurately predicting temperature trends over shorter time scales, such as 30 years. 

One significant limitation stems from computational power. The finite resolution of climate models can prevent the accurate representation of small-scale but important phenomena like clouds. While downscaling techniques are used to achieve higher resolution in specific regions, these can introduce boundary interactions that may contaminate the modelling area and propagate errors . Furthermore, our understanding of certain climate processes remains incomplete, leading to uncertainties in how these processes are represented within the models. Examples include the formation and behavior of clouds, the complex interactions involving aerosols, and the dynamics of deep ocean circulation. The chaotic nature of the climate system also makes it difficult to perfectlypredict the timing and magnitude of natural climate variability events, such as solar cycles, volcanic eruptions, and ocean oscillations, over short timescales. Accurately modelling the interactions and strengths of the various climate feedback mechanisms, both positive and negative, continues to be a challenge. In addition to these inherent complexities, climate models can also have biases, and measurement errors in input data contribute to the overall uncertainty in their projections. Short-term predictions are also more sensitive to the initial state of the climate system, which may not be known with perfect accuracy. It is important to note that the confidence in climate model predictions is generally higher for long-term climate change projections, which are driven by sustained forcings like increasing greenhouse gas concentrations, compared to short-term weather-like forecasts.Factors such as model resolution significantly impact the ability to simulate climate processes. Low-resolution models often fail to capture regional climate details and important phenomena such as clouds . Clouds themselves present a major challenge for climate models due to their multifaceted role in the climate system. They can reflect incoming sunlight, leading to a cooling effect, but they can also trap outgoing heat, contributing to warming. The net effect of clouds is sensitive to their type, altitude, and optical properties, which are difficult to model precisely. Deep ocean circulation is another critical component of the climate system, playing a significant role in the distribution of heat globally However, the slow and complex nature of these deep currents makes them challenging to represent accurately in climate models.

Unpredictable natural events, such as volcanic eruptions, can inject cooling aerosols into the stratosphere, temporarily offsetting the warming trend caused by greenhouse gases. Similarly, variations in solar activity, which can influence the amount of solar radiation reaching Earth, are also difficult to predict with high precision over the next 30 years . The inherent unpredictability of these natural climate drivers, coupled with the ongoing limitations in accurately representing complex processes within climate models, implies a higher degree of uncertainty in shortterm temperature projections.

5. Historical Insights: Decoupling of CO2 and Temperature Records.

Analysing historical climate records reveals periods where the correlation between CO2 concentrations and global temperatures has not been direct or immediate . Over very long geological timescales, such as during the ice age cycles of the past million years, CO2 and temperature have generally exhibited similar patterns, with both increasing and decreasing in tandem. However, during the transitions into and out of glacial periods, evidence suggests that temperature changes sometimes preceded changes in CO2 concentrations.On shorter timescales, within the last century and a half, there have also been instances where temperature trends did not perfectly align with the continuous rise in CO2 levels . For example, a period of cooling was observed globally from approximately 1942 to 1975, despite a concurrent increase in atmospheric CO2 concentrations. Similarly, the early part of the 20th century experienced a warming trend with a relatively slow increase in CO2 emissions, while the post-World War II era saw a rapid acceleration of CO2 emissions coinciding with a period of cooling. The eruption of Mount Pinatubo in 1991 led to a temporary global cooling that lasted for a few years, despite the ongoing increase in CO2 levels . Furthermore, the rates of increase in both CO2 and global temperature were slower during the late 19th and early 20th centuries compared to the latter half of the 20th century and the beginning of the 21st century . These historical observations indicate that while CO2 is a significant long-term driver of Earth's climate, other factors can exert a dominant influence on temperature trends over shorter periods, leading to a temporary decoupling of the otherwise expected direct correlation .

Several scientific explanations account for these historical discrepancies. The high heat capacity of the Earth's oceans plays a crucial role, causing a delay in the full impact of increased CO2 on surface temperatures as the oceans absorb a significant portion of the excess heat . Natural climate variability, particularly in the form of ocean oscillations like the El Niño-Southern Oscillation (ENSO), can cause substantial interannual fluctuations in global temperatures that can temporarily mask or amplify the underlying warming trend driven by CO2. Major volcanic eruptions that inject cooling aerosols into the stratosphere can also temporarily offset the warming effect of increasing greenhouse gases. Changes in solar activity, although not the primary cause of recent warming, can also contribute to short-term temperature variations . Additionally, anthropogenic aerosols, such as sulfate particles released from industrial pollution, have a net cooling effect on the climate by reflecting sunlight. Changes in the emissions of these aerosols, for instance due to air quality regulations, can therefore influence temperature trends. It is also important to note that the relationship between CO2 and temperature is not always unidirectional; over very long geological timescales, changes in temperature can drive changes in CO2 concentrations, such as through the outgassing of CO2 from warming oceans. These historical instances of decoupled CO2 and temperature records underscore the complexity of the climate system and highlight that the effect of increasing CO2 can be modulated or temporarily overshadowed by other significant climate forcings and natural variability.

6. Analysing the Hypothetical Cooling Scenario (Next 30 Years)

The hypothetical scenario of Earth experiencing a cooling trend over the next three decades despite a continued increase in atmospheric CO2 levels presents an apparent contradiction to the established understanding that rising CO2 leads to global warming . Such a phenomenon would likely be met with increased skepticism regarding the role of CO2 in driving climate change, despite the overwhelming scientific consensus supporting this link . Therefore, any observed cooling trend under conditions of rising CO2 would necessitate careful and thorough scientific analysis to ascertain the underlying causes . A 30-year cooling trend would indeed be a significant climatic event that would demand intensive investigation and would likely spark considerable discussion within both the scientific community and the broader public and political spheres. Such a scenario would not necessarily invalidate the fundamental principle of the greenhouse gas theory, which posits that CO2 is a greenhouse gas capable of trapping heat in the Earth's atmosphere. However, it would strongly suggest that other factors are exerting a dominant influence on global temperatures during this specific 30-year period, potentially masking or even offsetting the expected warming effect of the increasing CO2 . Furthermore, it might indicate that the climate system's sensitivity to CO2 over shorter timescales is more complex and nuanced than currently understood, or that the timing of the warming response is being significantly modulated by other processes, such as the uptake of heat by the deep ocean, Therefore, this hypothetical cooling trend would likely prompt a re-evaluation of the relative importance of different climate forcings and the role of internal climate variability when considering temperature changes over decadal timescales.

7. Implications for the Greenhouse Gas Theory: Invalidation or Refinement?

A 30-year cooling trend occurring alongside increasing atmospheric CO2 levels would not be of sufficient duration to invalidate the fundamental principles of the greenhouse gas theory. Climate trends are typically evaluated over longer periods, such as three decades, to effectively account for the inherent natural variability within the climate system. The greenhouse gas theory is underpinned by a robust foundation of evidence derived from laboratory experiments demonstrating the heattrapping properties of CO2, extensive atmospheric measurements confirming the increasing concentrations of greenhouse gases, and paleoclimate studies that reveal the long-term relationship between greenhouse gas levels and global temperatures. A temporary cooling trend of three decades would more likely signify the influence of other powerful climate forcings or modes of natural variability that are operating on shorter timescales. The core understanding of the greenhouse effect and the capacity of CO2 to absorb and re-emit infrared radiation, thus trapping heat, would likely remain valid.However, such a scenario would necessitate a careful consideration of whether other climate forcings or internal variability could indeed be strong enough to temporarily mask or counteract the warming effect expected from rising CO2. For instance, a prolonged period of unusually low solar activity could potentially contribute to a temporary cooling trend. Some research suggests that a future extended solar minimum could lead to a slight reduction in global average temperatures. Similarly, a series of major volcanic eruptions occurring within a relatively short period could inject substantial amounts of cooling aerosols into the stratosphere, potentially offsetting global warming for a decade or two. A significant and persistent shift in major ocean current systems, such as a substantial slowdown or even a temporary reversal of the Atlantic Meridional Overturning Circulation (AMOC), could also redistribute heat in a manner that leads to a global cooling trend over three decades, even if the overall heat content of the Earth system continues to increase. Furthermore, changes in anthropogenic aerosol emissions could play a role. While current trends are towards cleaner air and reduced aerosol emissions, a hypothetical scenario involving a large and sustained increase in sulfate aerosol emissions (although less likely given current environmental regulations) could enhance global cooling.

A 30-year cooling trend amidst rising CO2 would likely prompt scientists to re-examine and potentially refine the quantitative aspects of the greenhouse gas theory. This could include a closer look at climate sensitivity estimates and the relative strengths of different feedback mechanisms, particularly those that operate on shorter timescales. Such an event might also spur improvements in climate models to better represent the complex interactions between long-term forcings like greenhouse gas increases and shorter-term natural variability. 

Additionally, it could highlight areas where our understanding of specific climate processes, such as cloud feedback mechanisms or the rate of ocean heat uptake, requires further refinement and investigation. Thus, while not invalidating the core theoretical framework, a cooling trend under these conditions would likely stimulate further research and potentially lead to a more nuanced and precise quantitative understanding of the climate system's dynamics.

8. Exploring Alternative Explanations for a Cooling Trend with Rising CO2.

Several potential scientific explanations could account for a global cooling trend occurring over the next 30 years despite a continued increase in atmospheric CO2 concentrations . One possibility involves a prolonged period of exceptionally low solar activity . While the long-term warming effect of increased CO2 is substantial, a deep and extended solar minimum could potentially exert a cooling influence that partially offsets this warming, possibly leading to a net cooling trend over three decades. Historical records suggest that periods of reduced solar activity have, in some instances, coincided with cooler global temperatures.

Another plausible explanation could be a series of major volcanic eruptions occurring within a relatively short timeframe. If several large, explosive volcanic eruptions were to happen in succession, the cumulative effect of the sulfur dioxide injected into the stratosphere could lead to a sustained increase in the reflection of solar radiation back into space, causing a global cooling effect that might last for a couple of decades. A substantial and persistent shift in major ocean current systems represents another potential mechanism for a cooling trend . A significant weakening or a change in the path of key ocean currents, such as the Gulf Stream or other components of the Global Conveyor Belt, could lead to a redistribution of heat across the globe. This could result in a cooling trend in some regions and potentially a net global cooling over a 30-year period, even if the overall heat content of the Earth system continues to rise due to greenhouse gas forcing .

While current global trends are towards reducing air pollution, it is worth considering the role of anthropogenic aerosols. Sulfate aerosols, released primarily from the burning of fossil fuels, have a cooling effect on the planet by reflecting sunlight. A hypothetical scenario involving a large and sustained increase in sulfate aerosol emissions, perhaps due to a resurgence in the use of coal without stringent pollution controls, could potentially lead to an enhanced global cooling effect that might temporarily overwhelm the warming from rising CO2. However, this scenario is less probable given the increasing global awareness of air quality issues and the push for cleaner energy sources.

Anthropogenic aerosols, particularly sulfate aerosols originating from industrial pollution and the burning of fossil fuels, are known to reflect incoming solar radiation, thereby exerting a cooling influence on the Earth's climate. This cooling effect has been estimated to have partially offset the warming caused by the increase in greenhouse gases over the industrial era. Consequently, changes in the emissions of these aerosols can have a significant impact on global temperature trends. For example, reductions in aerosol emissions, driven by efforts to improve air quality, could lead to a decrease in this cooling effect, potentially resulting in a period of accelerated warming as the masking effect of aerosols diminishes.Conversely, a substantial and sustained increase in sulfate aerosol emissions, while less likely under current global trends, could theoretically contribute to a cooling trend. However, achieving a 30-year global cooling trend solely due to changes in aerosols while CO2 continues its upward trajectory appears improbable, given the magnitude of the warming forcing associated with increasing greenhouse gas concentrations.

9. Discussion

The hypothetical scenario of a 30-year global cooling trend despite increasing atmospheric CO2 concentrations presents a complex challenge to our understanding of the climate system. While the fundamental physics of the greenhouse effect, where CO2 traps outgoing infrared radiation, is well-established , the climate system's response to this forcing is modulated by a multitude of interacting factors. A sustained cooling over three decades would strongly suggest that other powerful natural or anthropogenic forcings are temporarily overriding the expected warming signal from rising CO2.

One prominent factor to consider is natural climate variability. The Sun's activity follows an approximately 11-year cycle, and prolonged periods of lower solar output have been linked to cooler temperatures in the past . While current scientific consensus indicates that solar variations are not the primary driver of the long-term warming trend , an exceptionally deep and extended solar minimum could potentially exert a significant cooling influence over a 30-year period.

Volcanic eruptions represent another significant source of natural climate variability. Major explosive eruptions inject sulfur dioxide into the stratosphere, (most recently Hunga Tunga) which converts to sulfate aerosols that reflect sunlight back into space, causing a temporary global cooling. A cluster of large eruptions occurring within a few decades could potentially lead to a sustained cooling trend that lasts for the better part of 30 years.

Ocean currents play a crucial role in redistributing heat around the globe. Shifts in major ocean circulation patterns, such as a significant weakening of the Atlantic Meridional Overturning Circulation (AMOC), could lead to regional cooling in some areas and potentially contribute to a global cooling trend over several decades. The slow timescales associated with deep ocean processes mean that their impact on surface temperatures can unfold over extended periods.

Anthropogenic aerosols, particularly sulfate aerosols from the burning of fossil fuels, have a net cooling effect on the climate by reflecting sunlight. While efforts to improve air quality are leading to reductions in these aerosols in many parts of the world, a hypothetical scenario involving a substantial and sustained increase in their emissions could enhance global cooling, potentially masking the warming effect of rising CO2 for a few decades.

It is important to note that a 30-year cooling trend would not necessarily invalidate the greenhouse gas theory. Climate scientists emphasize that long-term trends, typically assessed over periods of 30 years or more, are needed to discern the impact of sustained forcings like greenhouse gas increases from shorter-term natural variability. A temporary cooling period would more likely highlight the complex interplay of various factors that influence Earth's climate and the potential for other forcings to dominate on decadal timescales.

Such a scenario would undoubtedly spur further scientific investigation into the relative contributions of different climate forcings and the mechanisms through which they interact. It might also lead to refinements in climate models to better capture the nuances of shortterm climate variability and improve their predictive capabilities over decadal timescales. Ultimately, while a 30-year cooling trend alongside rising CO2 would be an intriguing phenomenon, it would likely serve as a catalyst for deeper understanding rather than a refutation of the fundamental role of CO2 in Earth's long-term climate.

I hope you have enjoyed reading this paper.

David-Gareth and Bill.

Heatwaves. How they happen.

            Example of an omega block.

1. A Stubborn, Blocked "Heat Dome"

​The core engine of this heatwave is a massive, highly stable area of high pressure that has settled directly over continental Europe and expanded into the UK. 

​The jet stream—which normally brings cooler Atlantic air and rain showers across the UK—has drastically weakened and buckled far to the north. This disruption created an atmospheric block, essentially locking the high-pressure system in place. As the air within this dome sinks, it compresses and heats up rapidly, completely suppressing cloud formation and letting the high mid-summer sun bake the ground all day long.

2. The Saharan Plume (Warm Advection)

​The rotation of this stalled high-pressure system has acted like a giant atmospheric conveyor belt. It is actively pulling a plume of exceptionally hot, dry air straight out of the Sahara Desert and dragging it northward across Spain, France, and into the UK.

3. Pre-Dried Soils (Feedback Loop Failure)

​The foundation for this heat was laid months ago. Spring brought significantly below-average rainfall to much of England and western Europe, leaving the soil unusually dry as summer began.

​Normally, the ground uses the sun's energy to evaporate moisture, which acts as a natural air conditioner for the region. Because the soil is already parched, that cooling mechanism is broken. Virtually 100% of the intense June solar radiation is going straight into heating the dry ground and the air directly above it, supercharging daytime temperatures.

​4. High Humidity and "Tropical Nights"

​Unlike some dry summer heatwaves, this event is carrying an oppressive amount of moisture alongside the heat, creating intense heat stress. Because the air is so muggy, nighttime cooling has been severely limited. This has triggered widespread, record-breaking "Tropical Nights"—where overnight temperatures are failing to drop below 20°C (and even staying as high as 23.5°C in places like Cardiff). Without night-time relief, the heat simply accumulates day after day.

Conclusion

Many factors combined create heatwaves, when conditions are right there is an air of inevitability that we will see soaring temperatures, Thunderstorms and localised flash flooding.

 

Written on 26^th June 2026

David I Birch.