Atmospheric CO2 at Mauna Loa

As atmospheric CO2 has risen at Mauna Loa—the world's most reliable barometer of humanity's combustion habits—swimming pool drownings in the US have declined, a correlation that suggests either that carbon dioxide makes pools safer or that we are solving the wrong problem with considerable efficiency. The coefficient is -0.913 across seventeen years, during which the atmosphere got worse and the pools got safer, and the chart connecting them became the kind of thing you show to someone who does not yet understand what "spurious" means.

Atmospheric CO2 at Mauna Loa grew from about 380 ppm in 2005 to over 420 ppm by 2021, on the relentless upward trajectory that has defined industrial civilization since we started burning fossil fuels at scale. Pool drownings declined as safety regulations improved, fencing became standard, and water safety education programs expanded. Both metrics are monotonic trends—one always going up, one always going down—which guarantees a strong negative correlation regardless of any causal link. The atmosphere does not know about the pools, and the pools do not know about the atmosphere. Both are simply doing what they have been doing for decades.

Seventeen years of CO2 rising and drownings declining is a correlation that captures the absurdity of the statistical condition: two entirely independent phenomena, moving in opposite directions, producing a number that looks meaningful and is not. The air gets worse, the water gets safer, and the chart sits between them like a mirror reflecting nothing. The planet warms. The pool fence holds.