Measurements of carbon dioxide, the chief greenhouse gas, averaged 417.1 parts per million at Mauna Loa, Hawaii, for the month of May, when carbon levels in the air peak, the National Oceanic and Atmospheric Administration said. That's 2.4 parts per million higher than a year ago.
Even though emissions of carbon dioxide from the burning of fossil fuels dropped by as much 17% in April, it was a brief decline. Carbon dioxide can stay in the air for centuries, so the short-term reductions of new carbon pollution for a few months didn't have much of a big picture effect, said NOAA senior scientist Pieter Tans.
“It illustrates how difficult it is — what a huge job it is — to bring emissions down,” Tans said. “We are really committing the Earth to an enormous amount of warming for a very large time."
Records with direct measurements go back to 1958. And carbon dioxide levels are now nearly 100 parts per million higher than then. That's a 31% increase in 62 years.
Carbon levels in the air were higher in the distant past before humans, Tans said.
Carbon dioxide levels peak in May because starting in late May, because growing plants suck up more of heat-trapping gas, causing carbon amounts in the air to drop, Tans said.
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