Based on historical data from the last 160,000 years, what is the correlation between CO2 levels and temperature?

• A. They are inversely related; when CO2 increases, temperature decreases.
• B. They have a direct relationship; when CO2 increases, temperature generally increases.
• C. There is no clear relationship between CO2 and temperature.
• D. Temperature drives CO2 with no feedback.

Answer: (B)

A key concept is that historical climate data show a strong positive relationship between CO2 and temperature. Ice core records from the last 160,000 years reveal that when the climate warmed during transitions from glacial to interglacial periods, CO2 levels rose, and when the climate cooled, CO2 fell. The changes in CO2 and temperature generally track together, and this coupling helps explain why higher CO2 concentrations are associated with warmer periods. It’s also important to note that CO2 changes lag behind initial temperature changes by a few hundred to around a thousand years, which tells us that orbital or other forcings started the warming and the resulting CO2 increase amplified it through the greenhouse effect. This combination shows a direct, positive relationship: as CO2 goes up, temperatures tend to go up, and as CO2 goes down, temperatures tend to fall. The idea that the two move in opposite directions, that there’s no clear link, or that temperature drives CO2 with no feedback does not fit what the long-term record shows about their intertwined evolution.