Many people don't have the thinnest understanding of redox chemistry. Yes, carbon dioxide lowers water pH, because it pulls oxygen out of the water by requiring an OH- ion to dissolve. Temperature is critical to the behaviour of carbonic acid, it is somewhat unusual amongst acids because it is a gas, and no reaction occurs EVER, anywhere, without dissolution, such other types of reactions can only be caused by radioactivity or quantum effects, they don't affect ionic bonding directly. Hot liquids dissolve less gases. Solid and liquid acids increase solubility with temperature, gaseous ones the opposite.
Further, nitrous, sulphurous and phosphorous based acids are liquid/solid at typical temperatures, and solubility of these acids is limited in ocean brine because of competition for those counterions that heat favours solid/liquid acids and cold favours gaseous (mainly carbonic), this means also that if temperature rises pH will go down because carbonic acid acts like a base compared to nitric, sulphuric and phosphoric acids, if temperature goes down those acids are less soluble and pH will rise towards carbonic acid's intrinsic pH level, which is still acid compared to sodium chloride's 6.3.
Lastly, the solubility of oxygen in water, reduced also by higher temperatures, affected by salinity, is also reduced in low pH solutions which is why vinegar stops decomposition of food stored in it, hence the use of both salt and acid, often both, as food preservation techniques. So, a lower relative proportion of oxygen in the atmosphere, and increase in acid, is obviously going to reduce oxygen and reduce the population and most unfavourably affect those with the lowest oxygen efficiency in their metabolism.
It's not really new science but lo and behold archaeology is agreeing with ionic chemistry!