Ocean acidity levels are increasing at an unprecedented rate that can only be explained by human activity. As excess human-produced CO2 in the atmosphere is absorbed by the oceans, the acidity level of the water increases. Acidity levels in the oceans are 25-30% higher than prior to human fossil fuel use. [107] According to a 2014 US Government Accountability Office (GAO) report, oceans have absorbed about 30% of the CO2 emitted by humans over the past 200 years, and ocean acidity could rise approximately 100-200 percent above preindustrial levels by 2100. [36] According to a 2013 report from the World Meteorological Organization, the current acceleration in the rate of ocean acidification "appears unprecedented" over the last 300 million years. [37] High ocean acidity levels threaten marine species, [16] and slows the growth of coral reefs. [38] According to a 2014 report by the Convention on Biological Diversity, "it is now nearly inevitable" that within 50-100 years continued human produced CO2 emissions will increase ocean acidity to levels that "will have widespread impacts, mostly deleterious, on marine organisms and ecosystems.