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Atmospheric CO₂ (Mauna Loa) vs US Rural Population

Atmospheric CO₂ (Mauna Loa) and US Rural Population correlate at r = -0.93 over 66 years (1960–2025), p < 0.0001. With the time trend removed, r = +0.44. Direction flips without the trend.

Verdict: Direction flips without the trend. The raw correlation is -0.93, but once each series' time trend is removed it becomes 0.44. The year-to-year movements run the opposite way to the long-run trends, so the headline number is misleading.

Pearson r
-0.93
p-value
< 0.0001
Years compared (n)
66 (1960–2025)
95% confidence interval
-0.96 to -0.89
Correlation with the time trend removed
+0.44

Sources

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Correlation does not imply causation. How the verdict is worked out.