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The global circulation models are getting more powerful and increasingly being applied to past geological periods. They are generally doing a reasonable job describing conditions on earth that match the low-resolution available.
In this study one such model is being applied to explore possible causes for the large extinction event 250 million years ago called the Permian-Triassic boundary.
Key Points from the article:
- Modeled Permian-Triassic boundary ocean shows no widespread anoxia
- Model shows very low surface ocean pH during Permian-Triassic boundary
- Modeled compared well with paleoproxies
Co2 levels were roughly 3000ppm (about 11 times pre-industrial levels) and drive the modeled Ph as low as 7.1. At that level most of today's shellfish cannot produce their shells and can not survive. The suggestion being that the high Co2 levels of the past might have precipitated the great extinction by ocean acidification.
Does this have application to our current Co2 levels? Well most predictions of Co2 level get us to 750-1000ppm by the end of the century. Full exploitation of tar-sands and coal would push us well over 1000ppm. Our current Ocean is about 8.1 PH already a 30% increase in acidity compared to pre-industrial levels.
I've said many times on this forum that comparisons to geologic past conditions are full of uncertainty because of different solar insolation, different continental configurations, and unknown orbital parameters--essentially a different planet in many ways. On the other hand shell chemistry and ocean acidity isn't that complex an issue and this study could be one more reason to pay close attention to what Co2 levels are doing to our oceans.
Here's a copy of the abstract.
Climate simulations of the Permian-Triassic boundary: Ocean acidification and the extinction event
