William (Billy) D’Andrea is a Lamont-Doherty Earth Observatory paleoclimatologist and a Center for Climate and Life Fellow; he studies how environments have changed over time by reconstructing climate history using the molecules preserved in lake sediment cores. Fat molecules from plants and algae are preserved in the sediments that accumulate each year on the bottom of lakes and the ocean. D’Andrea analyzes these to learn how temperature, precipitation, and evaporation have changed through time.