Answers to Analyzing Data 25.1 Questions

1. There is around a 0.05 drop in pH over the two-decade period of observation. Thus, between 2000 (pH = 8.10) and 2100, the pH should drop about 0.25 units (10 decades ? 0.025 pH units/decade), for an estimated ocean pH of 7.85. The IPCC estimate is lower, due in part to the assumption of a continued increase in the rate of anthropogenic CO₂ emissions from fossil fuels.

2. Both the IPCC and empirically derived estimates for ocean pH in 2050 and 2100 are around 7.9 and 7.75, respectively. The results in Figure B indicate around a 90% decrease in abundance and a 75% decrease in species richness by 2050, and extinction of foraminiferans by 2100.