What can the study of fossil pollen tell us about global climate change during the past 100,000 years?

The chemical structure of sporopollenin that covers most spores makes them stable and strong. Therefore, spores are well preserved even in sediments for those that settle and do not sprout. Thes spores vary (in size and shapes) by plants hence paleontologists use this uniqueness to determine the types of plants that grew in the past. By comparing those ancient plant with today's, they are able to extrapolate the changes in climate that resulted in the extinction of evolution of particular plants.