The most pessimistic predictions of sea level rises as ice sheets are melted by global warming may have to be scaled back as a result of an extraordinary discovery that ice persisted when the Earth was much hotter than today.
Scientists have discovered that glaciers survived for hundreds of thousands of years during an extraordinary era when crocodiles roamed the Arctic and the tropical Atlantic Ocean was as warm as human blood.
They had thought that Earth was ice free during the so called Turonian period, a “super greenhouse world” between 93.5 million and 89.3 million years ago. But now evidence has been found of hothouse glaciers that persisted by studies of tiny plankton and other marine organisms.
Read the rest of the Telegraph article here.
I was hoping to link to a BBC website article, but they don’t seem to find it newsworthy.
Read the article in Science magazine, if you have a subscription, or the abstract if you don’t:
Isotopic Evidence for Glaciation During the Cretaceous Supergreenhouse
André Bornemann,1,2* Richard D. Norris,1 Oliver Friedrich,1,3 Britta Beckmann,4 Stefan Schouten,5 Jaap S. Sinninghe Damsté,5 Jennifer Vogel,1 Peter Hofmann,4 Thomas Wagner6
The Turonian (93.5 to 89.3 million years ago) was one of the warmest periods of the Phanerozoic eon, with tropical sea surface temperatures over 35°C. High-amplitude sea-level changes and positive 18O excursions in marine limestones suggest that glaciation events may have punctuated this episode of extreme warmth. New 18O data from the tropical Atlantic show synchronous shifts 91.2 million years ago for both the surface and deep ocean that are consistent with an approximately 200,000-year period of glaciation, with ice sheets of about half the size of the modern Antarctic ice cap. Even the prevailing supergreenhouse climate was not a barrier to the formation of large ice sheets, calling into question the common assumption that the poles were always ice-free during past periods of intense global warming.
1 Scripps Institution of Oceanography, University of California, San Diego, Geosciences Research Division, 9500 Gilman Drive, La Jolla, CA 92093–0244, USA.
2 Institut für Geophysik und Geologie, Universität Leipzig, Talstraße 35, D-04103 Leipzig, Germany.
3 School of Ocean and Earth Science, National Oceanography Centre, European Way, Southampton SO14 3ZH, UK.
4 Institut für Geologie und Mineralogie, Universität Köln, Zülpicher Straße 49a, D-50674 Köln, Germany.
5 Department of Marine Biogeochemistry and Toxicology, Royal Netherlands Institute for Sea Research, Post Office Box 59, 1790 AB Den Burg, Texel, Netherlands.
6 School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.

Jennifer Marohasy BSc PhD has worked in industry and government. She is currently researching a novel technique for long-range weather forecasting funded by the B. Macfie Family Foundation.