 Temperature proxies include accounts of the tar used on the deck melting or fresh water on the ship freezing.Ummenhofer and Walker must cross check around 650 log books from similar areas to come up with a 8-9 points of data, which they put into the University's database.Whaling vessels are especially important to Ummenhofer work in the Indian Ocean because these ships sailed outside of established trade routes, and into more remote areas such as the Indian Ocean and Arctic Ocean.