Daniel Schrag is Professor of Earth and Planetary Sciences at Harvard University. Schrag studies climate and climate change over the broadest range of Earth history. He has examined changes in ocean circulation over the last several decades, with particular attention to El Niño and the tropical Pacific. He has worked on theories for Pleistocene ice-age cycles including a better determination of ocean temperatures during the Last Glacial Maximum, 20,000 years ago. Schrag has also developed the Snowball Earth hypothesis, proposing that a series of global glaciations occurred between 750 and 580 million years ago that may have led to the evolution of multicellular animals.

Schrag is currently working on creating integrated models of climate change and economic stability for developing countries. Schrag came to Harvard in 1997 after teaching at Princeton, and studying at Berkeley and Yale.

He was named a MacArthur Foundation Fellow in 2000.