…despite what the Guardian says. Update: …as the Guardian now agrees.
[Update: 9 Oct 2013 13.01 pm: The headline and first paragraph of the article have now been changed following email correspondence between Fiona Harvey and me. Credit to Fiona and the Guardian for this response. The links now lead to the updated version which can be compared with the screenshot below. Further update: See also http://www.newssniffer.co.uk/articles/690315/diff/0/1 for a side-by-side comparison.]
Fiona Harvey’s article in the Guardian on 3 October 2013 Ocean acidification due to carbon emissions is at highest for 300m years misrepresents the scientific literature. This error has propagated across the Twittersphere.
(H/T Latimer Alder for the tweet that alerted me to this article)
Harvey wrote (my emphasis)
‘The oceans are more acidic now than they have been for at least 300m years, due to carbon dioxide emissions from burning fossil fuels, and a mass extinction of key species may already be almost inevitable as a result, leading marine scientists warned on Thursday.
In the starkest warning yet of the threat to ocean health, the International Programme on the State of the Ocean (IPSO) said: “This [acidification] is unprecedented in the Earth’s known history. We are entering an unknown territory of marine ecosystem change, and exposing organisms to intolerable evolutionary pressure. The next mass extinction may have already begun.” It published its findings in the State of the Oceans report, collated every two years from global monitoring and other research studies.’
Harvey’s phrase ‘oceans are more acidic now than they have been for at least 300m [million] years’ was tweeted (paraphrased) by a number of accounts including
Update: see corrected Newshour article.
BBC World Service (@bbcworldservice) October 03, 2013
Oceans are more acidic now than in 300 million years, due to CO2. A mass extinction of key species may be inevitable theguardian.com/environment/20…—
Steve Easterbrook (@SMEasterbrook) October 03, 2013
and questioned by a few
Guardain claims 'ocean acidification' is highest for 300 million years. Has anybody seen any data to confirm?—
Latimer Alder (@latimeralder) October 03, 2013
Justin Templer (@justintempler) October 03, 2013
[Update (9.10.2013): and by Paul_K and others in the comments in the Guardian article, see my comment below]
What does the State of the Oceans Report actually say?
Harvey’s article does not give an exact source for her assertion, and there does not seem to be a single ‘State of the Ocean Report‘ but a series of papers in a special issue of Marine Pollution Bulletin (open access).
In one of the linked articles, (Bijma et al. 2013, Climate change and the oceans – What does the future hold? (Marine Pollution Bulletin 2013, in press)) the authors say
‘the present day carbon perturbation and the concurrent ocean acidification is unprecedented in the Earth’s history and occurring much faster than at any time in the past 55 million years (Kump et al., 2009) or even 300 million years (Hönisch et al., 2012; Fig. 5).
The term ‘acidification’ as used here is ambiguous, but from their cited references it appears that Bijma et al. mean the rate of acidification rather than the extent of acidification (level of acidity) of the oceans. In fact the references make clear that the oceans are currently more alkaline than in almost all of the past 300 million years.
Bijma et al. cite Hönisch et al. 2012, The geological record of ocean acidification. Science 335, 1058 (paywalled). Figure 4D of Hönisch et al. shows the pH of the ocean over the past 300 million years (low pH = high acidity).
The whole of Figure 4 is shown here.
Bijma et al. 2013 also cite Kump, L., Bralower, T., Ridgwell, A., 2009. Ocean acidification in deep time. Oceanography 22, 94–107 which shows a similar graph in Figure 1B, which is not surprising since Ridgwell was the author of reference 73 in Hönisch et al. 2012, and so appears to be the ultimate source of both graphs.
Pearson and Palmer 2000 (Atmospheric carbon dioxide concentrations over the past
60 million years Nature 406: 695-699 – open access) was not cited by Bijma et al. 2013, but also showed that ocean pH has been much lower (more acidic) than today during the past 60 million years as shown below.
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
a number of climate scientists 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?
I will email a link to this post to Fiona Harvey. The Guardian could of course respond by quietly changing the text of the first paragraph to say ‘The oceans are acidifying faster now than …’ but that will not recall the egregious tweets that have publicised a false picture of ocean pH by many who should know better. [Update: which is exactly what they did]
Update 7 Oct 2013: Kudos to Nature Geoscience for the following response
Nature Geoscience (@NatureGeosci) October 07, 2013