Over the past 70 million years, what has been the overall trend in global temperatures?

The overall trend in global temperatures over the past 70 million years has generally been characterized by a cooling phase. During this time period, the Earth transitioned from the warm conditions of the Late Cretaceous, which featured high global temperatures and sea levels, towards the cooler conditions seen in the present day. This long-term cooling is associated with various geological and climatic shifts, including continental drift, changes in ocean currents, and the development of polar ice sheets.

While there have been fluctuations between warm and cool periods, the overarching trend has been a gradual decrease in temperature, especially during the last few million years, when the planet has experienced glacial and interglacial cycles. Modern evidence from ocean floor sediments and ice cores supports this cooling trend, as they provide vital records of past temperatures and environmental conditions. Therefore, the correct answer underscores the significant climatic shifts that have occurred, emphasizing the long-term cooling of the Earth's climate system.