The United States’ National Oceanic and Atmospheric Administration this week reported that levels of carbon dioxide in the atmosphere have reached a new high. In April, mean levels of the greenhouse gas in the atmosphere over the Arctic exceeded 400 parts per million. Meteorological stations in Japan also reported similar levels in March and April.

The average reading for 2012 is expected to be 393 parts per million, as respiration led emissions of the gas to reach its peak in April. Though largely symbolic, the milestone serves as a grave reminder of the effect humanity is having on the environment.

Whilst it is not the most damaging, carbon dioxide is the most prevalent greenhouse gas. Although it is largely released by natural sources, carbon dioxide in the atmosphere has increased from 280ppm before the industrial revolution, a dramatic increase which scientists have attributed to human activity.

Polluting greenhouse gasses released by agricultural operations around the world are primarily nitrous oxide and methane, which are many times more potent than CO2. Figures from the UK, released in February, show that, although greenhouse gas emissions from agriculture account for 9 per cent of the UK total, 44 per cent of methane and 80 per cent of nitrous oxide emissions come from agriculture.

Researchers in the United States have suggested that elevated carbon dioxide levels may affect rice growing. Authors of a study published in scientific journal PLoS One suggested increased carbon dioxide in the atmosphere could affect the reliability of rice crops, one of the world’s staple grains.  

Overall, despite efforts to curb emissions, levels of carbon dioxide in the atmosphere appear to have reached record highs in 2011. There is little scope for CO2 levels to increase without causing extremely damaging effects for life on Earth.

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