Scientists from around the world are gathering in Wellington today for a conference looking at how evidence of historic climate change events can help our understanding of the warming the world is currently facing.
A highlight of the conference is the Greenhouse Earth Symposium, a one-day symposium (14 January) in which leading researchers explain how their studies of ancient greenhouse climates have advanced understanding of modern climate change. Presentations are aimed at a non-specialist audience with an interest in the science behind climate change and, specifically, greenhouse-gas induced global warming.
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Visiting scientist James Zachos, Professor of Earth & Planetary Sciences, Paloeoceanography, Paleoclimatology, Marine Stratigraphy at UC Santa Cruz provides comment below on what we can learn from climactic shifts of millions ago.
SMC: Does your research show evidence of sudden climactic shifts in the past? Can you give examples of changes that occurred on the scale of a human lifespan or within several generations?
There are changes in past climate that occurred on human time scales, for example during the glacial periods. As for greenhouse warming, at least one extreme event occurred over a few thousand years or faster, possibly centuries some 55 million year ago at the boundary between the Paleocene and Eocene epochs. its the event we call the Paleocene-Eocene Thermal Maximum
SMC: How does your evidence from Earth’s climate millions of years ago offer perspective on future changes coming our way? Where does it fit in the context of predictions coming out of the IPCC reports?
The predictions in the IPCC report are based on very sophisticated models. There is some disagreement among the various models as to how much warming will occur in the future, how precipitation patterns will shift, particularly at much higher greenhouse gas levels. To assess the models, climatologists have turned to simulating aspects of past climates, for example, the extreme polar warmth of greenhouse intervals. The challenge for geologists is to reconstruct the details of those climates. This is why the most recent IPCC included a chapter on paleoclimates (see pages 442-444 of the report).