Latest data shows steep rises in CO2 for seventh year

(The Guardian, 4 Jun 2019) Readings from Hawaii observatory bring threshold of 450ppm closer sooner than had been anticipated.

The concentration of carbon dioxide in the atmosphere has increased by the second highest annual rise in the past six decades, according to new data.

Atmospheric concentrations of the greenhouse gas were 414.8 parts per million in May, which was 3.5ppm higher than the same time last year, according to readings from the Mauna Loa observatory in Hawaii, where carbon dioxide has been monitored continuously since 1958.

Scientists have warned for more than a decade that concentrations of more than 450ppm risk triggering extreme weather events and temperature rises as high as 2C, beyond which the effects of global heating are likely to become catastrophic and irreversible.

May is the most significant month for global carbon dioxide concentrations because it is the peak value for the year, before the growth of vegetation in the northern hemisphere starts to absorb the gas from the air. The seasonal peak and fall can be seen in the Keeling curve, named after Charles Keeling, who started the observations on Mauna Loa because of its isolation in the Pacific Ocean.

This is the seventh consecutive year in which steep increases in ppm have been recorded, well above the previous average, and the fifth year since the 400ppm threshold was breached in 2014. In 2016, the highest annual jump in the series so far was recorded, from 404.1 in 2015 to 407.66 in 2016.

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The Guardian, 4 Jun 2019: Latest data shows steep rises in CO2 for seventh year