Why would coral become extinct because of ocean acidification, when coral species have already survived other ocean chemistry changes over geological history?
The danger from ocean acidification is related to the current rate of change, the concentration of atmospheric CO2 expected, and the magnitude of change of atmospheric CO2 forecast if we keep emitting CO2 at the same rate. The present rise in atmospheric CO2 is ~2 ppm per year, and atmospheric CO2 has increased more than 100 ppm since the beginning of the Industrial Revolution. In the transition between the end of the last ice age to the current warm period, CO2 concentrations increased 80 ppm occurred over more than 10,000 years. Today’s rates of CO2 increase in the atmosphere are therefore approximately 100 times greater than most changes sustained over geologic time. Other than at times of the great mass extinctions, there is no evidence in the geologic record for sustained rates of change in atmospheric CO2 that have been as great or greater than today’s. Even during extreme ocean chemistry changes in geological history—- for example, during the Paleocene/Eocene thermal maximum 55
