Final answer:
Scientists determine Earth's temperature from millions of years ago by analyzing indirect measures of climate such as ice cores, tree rings, and ocean sediments.
Step-by-step explanation:
Scientists can determine Earth's temperature from millions of years ago by analyzing indirect measures of climate such as ice cores, tree rings, glacier size, pollen counts, and ocean sediments. These sources provide evidence of past climate conditions, including temperature. For example, ice cores and tree rings can reveal information about temperature variations over time.
In addition to these sources, scientists also study changes in Earth's orbit around the sun and the activity of the sun itself, which can impact global temperatures. By examining these various indicators, scientists can reconstruct Earth's temperature from millions of years ago.