LiveScience: Scientists have started to see some of the expected effects of Earth’s increasing carbon dioxide burden: The shells of microscopic animals in the ocean are becoming thinner thanks to the ocean’s absorption of some of that excess carbon dioxide, a new study shows. The shells of those creatures studies are about one-third lighter. As carbon dioxide from the burning of fossil fuels has accumulated in the atmosphere, some of it has been absorbed by the ocean. As the gas dissolves …