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Atmospheric CO₂ (Mauna Loa) vs US Homicide Rate

Atmospheric CO₂ (Mauna Loa) and US Homicide Rate correlate at r = -0.66 over 31 years (1990–2023), p < 0.0001. With the time trend removed, r = +0.84. Direction flips without the trend.

Verdict: Direction flips without the trend. The raw correlation is -0.66, but once each series' time trend is removed it becomes 0.84. The year-to-year movements run the opposite way to the long-run trends, so the headline number is misleading.

Pearson r
-0.66
p-value
< 0.0001
Years compared (n)
31 (1990–2023)
95% confidence interval
-0.82 to -0.40
Correlation with the time trend removed
+0.84

Sources

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