Seasonality

The graph below compares the seasonality of CO2 and surface temperature (average 1991-2020)

There are two causal explanations: (i) CO2 rise precedes temperature rise – i.e. rising CO2 causes warming or (ii) temperature rise precedes CO2 rise – i.e. rising temperatures cause CO2 to rise.

That explanation (i: CO2 causes warming) is correct is difficult to argue. The Greenhouse effect is instantaneous to human observers, a 2.5-month delay in causation cannot be the explanation.

The explanation (ii: Warming causes CO2 to rise): must be the causal explanation. There is a perfectly good causal explanation in the photosynthesis cycle which is dominated by the Northern hemisphere and gives rise to a 9.5 month delay.

Googe AI gives the following: • monthly changes in global temperature often precede seasonal fluctuations in CO2 by approximately 4 to 12 months. • 9 months: Lag between CO2 and lower troposphere temperature. • 10 months: Lag behind global surface air temperature. • 11–12 months: Lag behind global sea surface temperature.