There was a great stir a couple of years back when atmospheric CO2 levels first spiked through the 400 ppm mark, a harbinger for ever more global warming to come. It was an on/off thing affected by seasonal change. It was - back then.
It's no longer an on/off thing. We've passed 400 ppm and we're going to stay past it for the rest of your natural life and then a bit more.
In the centuries to come, history books will likely look back on September 2016 as a major milestone for the world’s climate. At a time when atmospheric carbon dioxide is usually at its minimum, the monthly value failed to drop below 400 parts per million (ppm).
That all but ensures that 2016 will be the year that carbon dioxide officially passed the symbolic 400 ppm mark, never to return below it in our lifetimes, according to scientists.
September is usually the month when carbon dioxide is at its lowest after a summer of plants growing and sucking it up in the northern hemisphere. As fall wears on, those plants lose their leaves, which in turn decompose, releasing the stored carbon dioxide back into the atmosphere. At Mauna Loa Observatory, the world’s marquee site for monitoring carbon dioxide, there are signs that the process has begun but levels have remained above 400 ppm.
Now keep this to yourself. We don't want you telling Justin, not after he's just tossed a giant carbon bomb in British Columbia. And we wouldn't want to rattle him when he's about to rubber stamp our corrupt National Energy Board's approval of the Kinder Morgan bitumen pipeline. That would never do.