Final answer:
Fossils, ice cores, tree rings, and sediment cores are examples of widely used climate proxies in the study of past climates.
Step-by-step explanation:
The examples of widely used climate proxies in the study of past climates are fossils, ice cores, tree rings, and sediment cores. These proxies provide information about temperature and precipitation patterns in the Earth's past. Fossils can indicate the climate through the types of organisms found, while ice cores, tree rings, and sediment cores contain records of past climatic conditions.