By John Parnell
Global atmospheric CO2 concentration is edging towards the 400 parts per million (ppm) mark for the first time in millions of years.
That’s the expectation ofÂ scientistsÂ at the Mauna Loa recording station in Hawaii, widely regarded as the most reliable record of atmospheric CO2.
The landmark approaches as talks at the UNFCCC on a universal deal to reduce emissions reach a critical juncture.
The Scripps Institution of Oceanography started the CO2 record at Mauna Loa in 1958. The data shows a sawtooth pattern of CO2 concentrations that rise and fall with the seasons. The annual peak is in May just before summer plant growth sucks more CO2 out of the atmosphere. Levels have risen every year since recording began.
Scripps estimates that the 400ppm mark could be breached this year and if not, it will definitely be broken in 2014. These levels were last sustained 3.2-5 million years ago when temperatures were 2-3Â°C warmer.
âI wish it werenât true, but it looks like the world is going to blow through the 400ppm level without losing a beat,â said Scripps geophysicist Ralph Keeling, whose father Dave established the network of remote CO2 monitoring. âAt this pace weâll hit 450ppm within a few decades,â said Ralph Keeling.
In order to monitor its rise, a Twitter feed (@Keeling_curve) with updates from the so-called Keeling Curve, will publish the latest recordings.
398.36 parts per million CO2 in airApril 22, 2013
â Keeling_Curve (@Keeling_curve) April 23, 2013
Some stations measured 400pm momentarily last year but a sustained recording of 400ppm at Mauna Loa would have added significance.
âThe 400ppm threshold is a sobering milestone, and should serve as a wake-up call for all of us to support clean energy technology and reduce emissions of greenhouse gases, before it’s too late for our children and grandchildren,â said Tim Lueker, oceanographer and carbon cycle researcher with the Scripps CO2 Group.
A limit of 350ppm has been identified by climate scientists as the threshold to avoid dangerous levels of climate change. Some believe a concentration of 450ppm would pass a number of tipping points, pushing the earth into an ice free state.
This recommendation of 350ppm has given its name to Bill McKibbenâs campaign group, 350.
CO2 concentrations show the sum total of rising greenhouse gas emissions once the effects of vegetation changes and ocean absorption and the rest of the natural carbon cycle are factored in.
Global greenhouse gas emissions continue to rise despite a raft of new policy initiatives to tackle climate change. UNEP estimates thatÂ emissionsÂ must be reduced to 44 Gigatonnes of CO2 a year from the 2010 total of 50.1 GtCO2. The current projections for 2020 emissions is 58 GtCO2.