Which of the following is NOT a common data source used to study past climates?

• A. Satellite measurements
• B. Ice cores
• C. Fossil records
• D. Signs of past glaciers

Answer: (A)

Understanding past climates relies on proxy data that preserve climate information from times before modern instruments existed. These proxies extend far back in time and include ice cores, which trap ancient atmospheric gases and climate signals; fossil records, which reflect long-term ecological responses to climate; and signs of past glaciers, such as moraines and glacial formations, that mark prior cold periods.

Satellite measurements, while incredibly valuable for monitoring current and recent climate change, do not form long, continuous records of the deep past. They only cover the span since satellites began, which is a relatively short window for reconstructing long-term climate history. Therefore, they are not commonly used as primary data sources for studying past climates. They can help calibrate or complement proxy records, but the primary sources for paleoclimate reconstruction are ice cores, fossil records, and glacial geomorphology.