Mollie seemed more sensitive to acid waters than her friendsRuth Dixon has an interesting blog post on ocean acidification and in particular Fiona Harvey's claim that oceans are "more acidic now than they have been for at least 300m years". Following the claim to its source reveals that the truth has been lost in translation.
Hönisch et al. 2012, cited by the State of the Oceans report, showed in Figure 4D that
the ocean has been more acidic for most of the past 300 million years than it is now. The rate of acidfication may be faster now, but Hönisch’s graph has a resolution of 20 million years, so cannot address that question.
It is unfortunate that an environmental journalist should confuse the rate of acidification with levels of acidity, but appalling that this story was tweeted uncritically by Nature Geoscience and other influential accounts. This is not some esoteric area of climate science. It is well known that CO2 was much higher during parts of the past 300 million years than it is today and therefore ocean surface pH would be expected to be lower. Why was Harvey’s assertion that “[the] oceans are more acidic now than they have been for at least 300m years” not challenged (as far as I can see) by anyone from the scientific establishment?