Rising carbon dioxide in the atmosphere may be leaving a measurable imprint inside the human body. Researchers analyzing more than two decades of U.S. health data found that blood bicarbonate levels have climbed about 7% since 1999, while calcium and phosphorus have declined—changes that closely track increasing atmospheric CO2.
geez. 7% since 99 so more than a quarter percent per year but I bet its going up faster more recently than at the turn of the millenia.