5.16—Evidence for climate change

Evidence for climate change can come from instrumental temperature and carbon-dioxide records, biological indicators such as pollen, and natural archives such as tree rings. Each proxy measures a different variable and has its own uncertainty.

Agreement among independent records strengthens a conclusion; disagreement may reveal dating, calibration or spatial limits rather than immediately falsifying the trend. Evidence for change is distinct from evidence for a particular cause.

A rising instrumental temperature record alongside higher atmospheric CO2 and a dated shift in pollen composition supports a changing climate, but each record must be aligned in time and location.

A proxy is not a direct thermometer. Do not treat correlation alone as proof of causation, and do not extend a local record beyond its sampled range without justification.