Which of the following is an example of a climate proxy used to reconstruct past climates?

• A. Ice cores trap ancient air and dendrochronology reveals growth conditions.
• B. Tree rings only reflect rainfall and are not proxies.
• C. Satellite data are direct measurements, not proxies.
• D. Direct modern temperatures are proxies.

Answer: (A)

Proxies are indirect records that stand in for past climate when we don’t have direct measurements. Ice cores are a prime example because they trap ancient air in layered ice, preserving information about past temperatures and atmospheric composition. Tree rings, studied through dendrochronology, reveal how growing conditions vary from year to year; the ring width and density respond to temperature and moisture, providing a record of past climate. Together, these natural archives are used to reconstruct climate history long before modern instrumentation.

The other statements miss or mischaracterize proxies: tree rings do carry climate information and are indeed proxies, not mere reflections of rainfall. Satellite data are measurements of current conditions, not direct records of ancient climates. Direct modern temperatures are actual readings, not proxies.