Scientists do not analyze pollen in ice cores. They look at dust, samples of ancient air trapped in tiny bubbles, isotopes of oxygen in the water that makes up the ice, etc. My sense is that you didn't really do the background reading. Otherwise, you should have done better with these facts. Pollen grains have a distinct shape which enables scientists to determine the type of plant they came from.
Tree rings differ in pattern, width, and density depending on the cllimate conditions of the time.
Trees can grow for hundreds or thousands of years, and the rings preserve a record of these conditions. The issue of global warming is one of the most important reasons to study climate change. But in order to be adequately prepared for coming changes, we need to learn how much the earth is warming, how long it has been warming, and the reasons for the change. Ice core research can help answer these questions , Cravens said. Quoting websites is far inferior to quoting real sources.