June 30, 2016, by Tim Radford
The cliffs of Amsterdam Island are a haven for sea birds such as the yellow-nosed albatross.
Image: StormPetrel1 via Flickr
French scientists find that carbon dioxide levels in the atmosphere have now topped 400 parts per million even on a remote, unpolluted island in the Indian Ocean.
LONDON, 30 June, 2016 – Human emissions of the greenhouse gas carbon dioxide have reached another landmark. They have surpassed atmospheric levels of 400 parts per million even in one of the most distant, most unpolluted measuring stations on the planet.
In May, according to scientists working for France’s National Centre for Scientific Research (CNRS), atmospheric concentrations of CO2 reached 400 ppm at a meteorological station on Amsterdam Island in the southern Indian Ocean.
The island is little more than a mountain sticking out of the sea, and is populated only by albatross, skua gulls, terns, rockhopper penguins and researchers at a small French observatory, where records have been maintained for 35 years.
Through most of human history, carbon dioxide concentrations in the atmosphere have oscillated about an average of 285 ppm. The symbolic 400ppm level was first surpassed in the northern hemisphere during the winter of 2012/2013, although it fell again.
The gas is an important one – it provides the fertility of all plant life and maintains the planet at a habitable temperature. But since the start of the Industrial Revolution, and the global investment in coal, oil and then natural gas, concentrations have been rising. And so have global temperatures.
“Crossing the 400ppm threshold at Amsterdam Island means that this value has been reached practically all over the planet”
Last month, researchers announced that global average levels had crept above 400ppm and were likely to stay above that figure for a lifetime.
Global average temperatures have already risen by 1°C since the start of the 20th century, and last month the extent of Arctic sea ice was measured at its lowest since records first began, with polar winter temperatures as much as 10°C above historic levels.
Here to stay
So even in the southern hemisphere, at the end of a southern summer, where seasonal variations are in any case tiny, and in a place far from any roads, cities, factory chimneys, power stations and cement works, and where measured levels have always been lower than anywhere else in the world, the news that concentrations of CO2 have reached 400ppm means that the increase is here to stay.
Levels of CO2have been rising by 1.75 ppm a year for decades, and since 2012 have accelerated to 2ppm a year. “Crossing the 400ppm threshold at Amsterdam Island therefore means that this value has been reached practically all over the planet,” say the CNRS scientists. – Climate News Network
Tim Radford, a founding editor of Climate News Network, worked for The Guardian for 32 years, for most of that time as science editor. He has been covering climate change since 1988.