It has been estimated, for example, that the globe's seawater has been acidified (actually made less basic) by about 0.1 pH unit relative to what it was in pre-industrial times; and model calculations imply an additional 0.7-unit drop by the year 2300 (Caldeira and Wickett, 2003), which decline is hypothesized to cause great harm to calcifying marine life such as corals.