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1091001 VA CHAPEL HILL: OPINION MARCH 28,201711:45 AM Climate change drives mass extinctions I News & Observer Climate change drives mass extinctions; are we next? BY THE ORANGE COUNTY COMMISSION FOR THE ENVIRONMENT This is the 2nd of 2 parts, Read the first part here: www.newsobserver.com / news /local/ community /chapel -hill- news /chn- opinion /article 13 96042 8 8.html Paleoclimate Climate change in the distant past informs us about climate change today. Evidence demonstrates that carbon dioxide drove climate change then just as is occurring now. In fact, there is a strong link between atmospheric CO2 and temperature throughout, the past 550 million years of earth history. During warm periods CO2 was high and when CO2 was low, long - lived and widespread continental glaciation prevailed. Scientists infer ancient climates or paleoclimates from climate imprints called proxies, sources of climate information from natural archives. Proxies represent any bit of evidence that can be used to infer climate, e.g., ice cores, tree pollen, stable oxygen isotopes, sediment cores, coral reefs, and calcareous shells. Oxygen isotope ratios may be the most important proxy and can be used to infer past water temperatures. Ultimately, past climates are reconstructed using a combination of different proxies. Perhaps the best ancient analog of modern climate change is the Paleocene- Eocene Thermal Maximum (PETM), a 200,000 -year period of natural global warming that took place 56 million years ago. During the PETM the earth warmed approximately 11 degrees Fahrenheit over 20,000 years. Today the globe is warming at least 10 times faster than during the PETM. Because the PETM involved rapid warming caused by an onslaught of greenhouse gases, the event can be used to predict potential effects of modern climate change. Among these effects are: ocean acidification and circulation reversal, higher ocean temperatures and sea levels, dissolution of calcifiers' shells, coral die -off, and extinction events. The geologic record demonstrates that when CO2 changes were big and rapid (like today) the consequences were catastrophic, in some cases leading to mass extinction. At least eight major mass extinctions have been recognized. During these events a significant proportion of the world's flora and fauna ( >50 prcent) were eliminated in geologically short amounts of time (tens of thousands to less than 1 million years). Conversely, it can take millions of years for biodiversity to recover from a mass extinction event. Gi THE GEOLOGIC RECORD DEMONSTRATES THAT WHEN CO2 CHANGES WERE BIG AND RAPID (LIKE TODAY) THE CONSEQUENCES WERE CATASTROPHIC, IN SOME CASES LEADING TO MASS EXTINCTION. Extinctions occurred during times of regional volcanism releasing huge volumes of CO2 accompanied by anoxia (oxygen deficiency), euxinia (sulfidic conditions), and ocean acidification. Reef building stopped, resulting in gaps in the geologic record that mark climate change and mass extinction. Two catastrophic mass extinctions are known to have occurred: the end of the Permian (252 million years ago) and the end of the Cretaceous (66 million years ago) periods. The Permian extinction was the worst in history wiping out an estimated 90 percent of all life in approximately 200,000 years. What emerges from the geologic record is that mass extinction has occurred multiple times and is likely to occur again. In fact, extinction is underway now and has been termed the Anthropocene extinction, beginning when human activity started to impact global earth systems. Only the starting point of the latest extinction event is in question. Many point to the start of the industrial revolution, while others would start the clock earlier during the Pleistocene (Ice Age). Evidence suggests humans caused the extinction of the Ice Age megafauna and Neanderthals in a geologic instant but at a rate that was too gradual to be perceived by the human perpetrators. Additional evidence suggests that right now human activities are causing further extinction. The contemporary extinction rate greatly exceeds the naturally occurring background rate. Whether humankind continues on a path to a potentially catastrophic mass extinction event or one similar to the many lesser extinction events that punctuated the last 550 million years remains to be seen. Homo sapiens, as the agent of extinction, risk being one of the�ctims of the pending extinction event. http: / /Www.newsobserver.com /news /local /com m unity /chapel -hi I I- news /chn -opi nionlarti cl el 41000668. htm I 1/3