One of the unique features of the Eocene's climate as mentioned before was the equable and homogeneous climate that existed in the early parts of the Eocene. A multitude of proxies support the presence of a warmer equable climate being present during this period of time. A few of these proxies include the presence of fossils native to warm climates, such as crocodiles, located in the higher latitudes, the presence in the high latitudes of frost-intolerant flora such as palm trees which cannot survive during sustained freezes, and fossils of snakes found in the tropics that would require much higher average temperatures to sustain them. Using isotope proxies to determine ocean temperatures indicates sea surface temperatures in the tropics as high as and, relative to present-day values, bottom water temperatures that are higher. With these bottom water temperatures, temperatures in areas where deep water forms near the poles are unable to be much cooler than the bottom water temperatures.