The rise of carbon dioxide (CO 2 ) in Earth's atmosphere is detectable and measurable in the blood of its human inhabitants, a new study suggests. In 20 years' worth of health data from a US population database, scientists have found shifts in blood chemistry that, they say, are consistent with higher exposure to CO 2 . It's not dangerous yet, but if the trend continues , some blood chemistry values could approach the limit of today's accepted healthy range by around 2076, according to the