Climate Change AGU News

How Did We Get Here?

With a discovery made from fossils in the seabed, paleoceanographers and paleoclimatologists began tracing the delicate path between ancient eras and our future.


The shells of tiny ancient sea organisms hold the evidence that underpins one of the newest fields in the Earth sciences. In the 1950s, Cesare Emiliani at the University of Chicago was learning how to measure stable isotopes in invertebrates and use those data as a proxy to make conclusions about environmental factors. One day he turned that study to ancient foraminifera taken from sediments in the ocean floor. The oxygen isotopes he found in their shells told him that the ocean was once much warmer—that, in fact, the ocean changed over time. Paleoceanography was born.

In April, as AGU continues its Centennial celebrations, we’re looking at this nascent but critical field, which has already proved so prolific it’s expanded into two major components. AGU launched its Paleoceanography journal in 1986 and, as it embraced the growth and evolution in the field, changed its name to Paleoceanography and Paleoclimatology last year. “We now use, in addition to fossils, a broad and growing range of stable isotope compositions, trace element concentrations and organic biomarkers in fossils and sediments as quantitative proxies for a growing number of environmental properties,” wrote journal editor in chief Ellen Thomas when she announced the change in Eos. “In our present time of environmental change, it is, more than ever, important to use proxy data on Earth’s past in order to evaluate Earth’s future, thus making our past a key guide to our future.”

Paleoclimatologists know better than anybody that understanding Earth’s past is necessary for understanding what’s happening to the climate today—and why the recent warming can’t simply be explained by natural cycles. As a result, this young field has been uniquely shaped by the challenge and urgency in communicating its findings to the public. It’s no surprise that a recent workshop for scientists to learn lessons in persuasive communication from lawyers was funded by the National Science Foundation (NSF) Paleoclimate Program.

We know that however our society reacts to that information in the coming decades, the consequences will be reflected in our environment for a very long time. For this reason, one important topic of study right now is determining how much heat is stored in the oceans. A recent study used data collected by the HMS Challenger expedition that launched in 1872, beginning the modern era of the study of oceanography. Comparing the temperature observations with those taken today shows that the Pacific Ocean is still cooling in response to the Little Ice Age during the 14th to 19th centuries. This direct evidence of the ocean’s “long memory” means that modern climate models—most of which only use data from the beginning of the Industrial Revolution—need to incorporate ancient signals and that the effects from modern warming will be seen throughout the planet for a long, long time.

Cesare Emiliani’s revolutionary work continues today through programs such as the core drilling conducted aboard the JOIDES Resolution vessel and that of NSF’s Paleo Perspectives on Climate Change, which is currently soliciting proposals that will provide data on Earth’s past climate sensitivity to specific variables.

At AGU and Eos, we continue to support the work of and listen carefully to the information learned by paleoceanographers and paleoclimatologists because every time we learn more about our past, we learn a little bit more about our future.

—Heather Goss (@heathermg), Editor in Chief, Eos

Citation: Goss, H. (2019), How did we get here?, Eos, 100, Published on 01 April 2019.
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