Final answer:
The Last Glacial Maximum is considered to be more global in extent than other climatic time periods. The Little Ice Age, which was a period of global cooling, was mainly caused by volcanic eruptions and changes in the earth's orbit.
Step-by-step explanation:
The climatic time period that is thought to be more global in extent, either in terms of warming or cooling, is a. Last Glacial Maximum. The Last Glacial Maximum occurred around 20,000 years ago and had a significant effect on the entire planet, creating large ice sheets that covered much of the Northern Hemisphere. This contrasts with the Medieval Warm Period and the Little Ice Age, which were significant but less extensive in their global impact. The Holocene Optimum was a period of warming that followed the Last Glacial Maximum, but it was not as profound in its global reach as the Last Glacial Maximum.
Regarding the cause of the Little Ice Age, the correct answer is c. volcanic eruptions and changes in the earth's orbit. These factors led to significantly cooler temperatures across most of the Northern Hemisphere and had profound effects on agriculture, society, and the climate system.