Atmospheric carbon dioxide levels measured at Hawai’i’s Mauna Loa Observatory breached 420 parts per million (ppm) in April for the first time in human history.
Considered the gold standard for accurate measurements of atmospheric CO2, the new measurements were released by the National Oceanic and Atmospheric Administration (NOAA), reports the Independent.
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The NOAA data release shows CO2 levels hitting 420.23 ppm in April, eight years after they breached 400 ppm (400.2 ppm) in May, 2013.
Last May, atmospheric CO2 concentrations at Mauna Loa stood at 419.13 ppm. In May 2002, they were 375.93 ppm, and in 1958, the first year scientists began to measure atmospheric CO2 at Mauna Loa, levels stood at 317.51 ppm.
May typically records the highest levels of atmospheric CO2, just before the northern hemisphere’s summer kicks in with an explosion of plant growth that pulls carbon out the atmosphere, causing levels to drop.
Emissions from fossil fuel burning, plus the loss of natural carbon sinks through the destruction of forest, wetlands, and mangroves, now mean that even the lowest seasonal CO2 levels—typically measured in September before the leaves fall—are far too high for climate health.
Last year, September readings at Mauna Loa stood at 413.30, well above the safe limit of 350 ppm long urged by climate scientists.
And CO2 is not the only thing to worry about, the Independent notes.
Atmospheric concentrations of the two other major greenhouse gases, methane and nitrous oxide, are also rising sharply. Methane is about 85 times more potent an atmospheric warming agent than CO2 over a 20-year span; nitrous oxide is 300 times more powerful.
Atmospheric methane levels now stand at 1980.9 parts per billion (ppb), up 340 ppb from the early 1980s, while nitrous oxide just reached 335.2 ppb, up from 316 ppb just 20 years ago.