Scientists estimate that surface ocean acidity increased by about 100 percent during the Paleocene-Eocene Thermal Maximum in a few thousand years or more, and stayed that way for the next 70,000 years. Scientists have long suspected that ocean acidification caused the crisis -- similar to today, as humanmade CO2 combines with seawater to change its chemistry. Now, for the first time, scientists have quantified the extent of surface acidification from those ancient days, and the news is not good: the oceans are on track to acidify at least as much as they did then, only at a much faster rate....