You should first break out the relationship between CO2 and time, and the relationship between temperature data and time. You effectively normalize both for tim

You should first break out the relationship between CO2 and time, and the relationship between temperature data and time. You effectively normalize both for time. So, in effect, you model the correlation between CO2/time vs. temperature/time. The interesting correlation would be if every time CO2/time deviates you can find a correlation with a temperature/time deviation.