The amount of carbon dioxide in the world's atmosphere has reached its highest point since humans came into existence, and there's little chance of reversing the damage.
In March 2015, the US National Atmosphere Administration (Noaa) measured the global concentration of the gas as 400 parts per million (ppm), adding that the last time it was this high was between three and five million years ago.
It had already reached this level at individual locations on the planet – in 2012 the Arctic passed the 400ppm level, followed by Mauna Loa in Hawaii in 2013, but never in recent history has the whole world's average been so high.
The graph below shows how steadily the level has been rising since 2010, with seasonal fluctuations reflecting the presence and absence of plants to absorb the carbon dioxide from their surroundings.
"It was only a matter of time that we would average 400 parts per million globally," said Mr Tans, lead scientist at Noaa's Global Greenhouse Gas Reference Network. Nooa collects the data using air samples from 40 sites around the world.
But it seems to have become more of an issue recently, with the increase accelerating – the average growth rate of carbon dioxide concentration in the atmosphere from 2012 to 2014 was 2.25 ppm per year, the highest ever recorded over three consecutive years.
“This marks the fact that humans burning fossil fuels have caused global carbon dioxide concentrations to rise more than 120 parts per million since pre-industrial times,” added Tans. “Half of that rise has occurred since 1980.”
James Butler, another senior figure at Noaa, warned that once the damage is done, it's done – you can't easily take the carbon dioxide back out of the atmosphere.
“Elimination of about 80 percent of fossil fuel emissions would essentially stop the rise in carbon dioxide in the atmosphere, but concentrations of carbon dioxide would not start decreasing until even further reductions are made and then it would only do so slowly,” he said. "It was only a matter of time that we would average 400 parts per million globally," said Mr Tans, lead scientist at Noaa's Global Greenhouse Gas Reference Network. Nooa collects the data using air samples from 40 sites around the world.