I’ve noticed several queries for record atmospheric CO2 concentrations lately and I hadn’t posted anything on the subject since March. Since March 2010, two more all-time records were set – one in April and one in May.
As has been the case for years, the yearly maximum value of atmospheric CO2 concentration was reached in May: 392.94ppm.
June’s value edged down from this, but is still the 3rd highest monthly value ever observed: 392.04ppm.
July’s value fell further, but still managed to stay above 390ppm: 390.09ppm.
You can expect these values to fall for another three months or so, then climb back up over the Northern Hemispheric winter and spring next year.
The average monthly value so far for 2010 is 390.99ppm. This will likely be the last year that the full yearly mean value of atmospheric CO2 is below 390ppm. The reason is the yearly number has been moving up at just under 2ppm per year in recent years. 2009 saw a mean value of 387.35ppm. 2010 should therefore register somewhere near 389ppm and 2011 should likewise register a value near 391ppm. Of course, this means that by the middle of this decade, mean yearly CO2 concentrations should pass 400ppm without much hope of coming back below that level for decades.
Remember that leading climatologists have identified 350ppm as a likely target for humanity to aim for if we want to keep Earth’s climate in a state near to what it was during our evolutionary development over the past 100,000+ years.