An atmospheric measuring station at Cape Grim in Australia is poised on the verge of 400ppm CO2 for the first time in May 2016. Graphic: CSIRO

By Michael Slezak
11 May 2016

(The Guardian) – The world is hurtling towards an era when global concentrations of carbon dioxide never again dip below the 400 parts per million (ppm) milestone, as two important measuring stations sit on the point of no return.

The news comes as one important atmospheric measuring station at Cape Grim in Australia is poised on the verge of 400ppm for the first time. Sitting in a region with stable CO2 concentrations, once that happens, it will never get a reading below 400ppm.

Meanwhile another station in the northern hemisphere may have gone above the 400ppm line for the last time, never to dip below it again.

“We’re going into very new territory,” James Butler, director of the global monitoring division at the US National Oceanographic and Atmospheric Administration, told the Guardian.

When enough CO2 is pumped into the atmosphere from burning fossil fuels, the seasonal cycles that drive the concentrations up and down throughout the year will eventually stop dipping the concentration below the 400ppm mark. The 400ppm figure is just symbolic, but it’s psychologically powerful, says Butler.

In Hawaii in May 2016, the Mauna Loa station measurement of atmospheric carbon dioxide is sitting above 400 ppm and might never dip below it again. Graphic: National Oceanic and Atmospheric Administration

The first 400ppm milestone was reached in 2013 when a station on the Hawaiian volcano of Mauna Loa first registered a monthly average of 400ppm. But the northern hemisphere has a large seasonal cycle, where CO2 concentrations decrease in summer but increase in winter. So each year since it has dipped back below 400ppm.

Then, combining all the global readings, the global monthly average was found to pass 400ppm in March 2015.

In the southern hemisphere, the seasonal cycle is less pronounced and atmospheric levels of CO2 hardly drop, usually just slowing in the southern hemisphere summer months. This week scientists revealed to Fairfax Media that Cape Grim had a reading of 399.9ppm on 6 May. Within weeks it would pop above 400ppm and never return.

“We wouldn’t have expected to reach the 400ppm mark so early,” said David Etheridge, an atmospheric scientist from the CSIRO, which runs the Cape Grim station. “With El Nino, the ocean essentially caps off it’s ability to take up heat so the concentrations are growing fast as warmer land areas release carbon. So we would have otherwise expected it to happen later in the year.

“No matter what the world’s emissions are now, we can decrease growth but we can’t decrease the concentration.

“Even if we stopped emitting now, we’re committed to a lot of warming.” [more]

World's carbon dioxide concentration teetering on the point of no return


  1. Anonymous said...

    Love how they mislead with the "teetering on the point of no return" claim.

    C02 will never be lower then it was yesterday, or today, or tomorrow (as far as humans are concerned). C02 will always be going up - until it kills us all (starvation comes first).

    The widely spread lies that we are going to lower C02 levels - a very long lived gas on the order of 1000 years or so - have become so commonplace that everybody seems to have forgotten that this gas isn't going anywhere but up.

    The "point of no return" began hundreds of years ago as concentrations began to rise from human contributions, worsening with each new technological revolution (increasing human growth and activity).

    C02 has never gone back down. It will never go back down until LONG after we have all gone extinct. So the "point of no return" is extremely misleading and disingenuous.  

  2. Kjell Arne Rekaa said...

    I'm not all agree with you there ...

    If we happened to stop all emissions and allow nature to start working on the" imbalance of CO2" you said yourself "the order of 1000 years".
    To be more more precise I will explain what David Archer has found about known physics and earlier periods in earth with high CO2:
    - The ocean will accumulate far more than 50% of the extra CO2 on a timescale of several 100 years (typically 300 years)
    - The next phase for chemical building of CaCO3 in the ocean will take thousands of years (5000)
    - The last phase of going back to statuses as before the CO2 release started actually takes several of 100 000 of years (400 000 years)

    So we talking in the scale of half million years or a timescale which is more than double of the time since Homo Sapient evolved!

    I have a figure of this in my blog post about actual future sea level rise, referenced from the book "The Long Thaw" by David Archer:
    (I'm sorry it's in Norwegian - but let your browser translate it to your favorite language;)  


Blog Template by Adam Every . Sponsored by Business Web Hosting Reviews