Question

A group of scientists is analyzing ice core data to understand past climate patterns. They notice a repeating pattern of increased carbon dioxide levels every 100,000 years. Which reasoning best explains how this data supports the existence of long-term natural cyclic fluctuations in Earth's climate?
A.

The data shows random changes in carbon dioxide levels, indicating unpredictable climate changes.
B.

The repeating pattern of increased carbon dioxide levels suggests a natural cycle, such as glacial and interglacial periods, influencing Earth's climate over long timescales.
C.

The data only reflects recent human activities, not natural cycles. Data on natural cycles is necessary.
D.

The pattern is likely due to errors in data collection rather than actual climate cycles, due to errors in the data collection process being an often occurence.

Answer 1

B.

A consistent ~100,000‑year recurrence of higher CO2 levels is strong evidence of a natural long-term cycle (glacial–interglacial cycles). Ice cores record CO2 and temperature over many hundreds of thousands of years, and the periodicity matches known orbital (Milankovitch) forcing and associated feedbacks that drive these long climate cycles. Options A, C and D contradict the periodic, long‑term nature and provenance of the ice‑core record.