6.2.3—Ice core, tree ring, sediment data
- Syllabus
- First assessment 2026
- Objective
- 6.2.3
- Level
- SL
Read the Proxy before the Trend
A proxy is an indirect record of past climate; interpret its measured variable before claiming a temperature trend.
Ice cores preserve past gas concentrations and isotopic evidence; tree rings record growth conditions; deposited sediments preserve layered biological or chemical signals. Together, records spanning the past 800,000 years show glacial-cycle co-variation between atmospheric CO2 and global temperature.
A narrow tree ring may reflect drought, cold or another stress, so calibrate each proxy and compare independent records before attributing a temperature change.
Check dating, calibration, local representativeness and missing intervals. Positive CO2-temperature correlation supports a relationship but does not by itself identify the full causal mechanism.
A positive correlation is evidence of co-variation, not proof that one proxy caused the other.