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