The annual peak of global heat-trapping carbon dioxide in the air has reached another dangerous milestone: 50% higher than when the industrial age began.

And the average rate of increase is faster than ever, scientists reported Monday.

The National Oceanic and Atmospheric Administration said the average carbon dioxide level for May was 419.13 parts per million. That's 1.82 parts per million higher than May 2020 and 50% higher than the stable pre-industrial levels of 280 parts per million, said NOAA climate scientist Pieter Tans.

Carbon dioxide levels peak every May just before plant life in th...