Ocean acidification on track to be among the worst of the last 300 million years

Scott K. Johnson in Ars Technica: Some like to point to cycles when dismissing climate change, brushing off warming as simply being the thing that happens right before cooling. In this view, concern about climate change is akin to the naïve worry that half of schools are performing below average. This is why we need context. We need to know whether an observed change is more like a world premiere or a familiar re-run.

A new paper in Science examines the geologic record for context relating to ocean acidification, a lowering of the pH driven by the increased concentration of carbon dioxide in the atmosphere. The research group (twenty-one scientists from nearly as many different universities) reviewed the evidence from past known or suspected intervals of ocean acidification. The work provides perspective on the current trend as well as the potential consequences. They find that the current rate of ocean acidification puts us on a track that, if continued, would likely be unprecedented in last 300 million years.

...While the authors frequently point out the difficulty in teasing apart the effects of ocean acidification and climate change, they argue that this is really an academic exercise. It’s more useful to consider the witches’ brew with all the ingredients—acidification, temperature change, and changes in dissolved oxygen—since, historically, those have come together. That combination produces unequivocally bad news.

The authors conclude, “[T]he current rate of (mainly fossil fuel) CO2 release stands out as capable of driving a combination and magnitude of ocean geochemical changes potentially unparalleled in at least the last ~300 [million years] of Earth history, raising the possibility that we are entering an unknown territory of marine ecosystem change.”

From 2007: Estimated change in sea surface pH from the pre-industrial period (1700s) to the present day (1990s). Δ pH here is in standard pH units. This change is caused by the invasion of anthropogenic CO2 (see Ocean acidification). Image by Plumbago, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license