Researchers in the United States and Europe are seeking funding so that the ice cores used to study Earth's past climate can have the same luxuriously chilly storage facilities currently enjoyed by prize tuna. The cylindrical cores, drilled at multi-million-dollar expense from polar and glacial ice, can be kilometres long. They contain tiny bubbles of trapped air, allowing scientists to measure the concentration of carbon dioxide in the atmosphere from hundreds of thousands of years ago. The relative ratios of oxygen and nitrogen, and their isotopes, can also reveal temperature variations and help to date the trapped gas.