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