PLEA Network

7 June 2019, The Conversation, Why there’s more greenhouse gas in the atmosphere than you may have realised. This week brought news that atmospheric carbon dioxide (CO₂) levels at the Mauna Loa atmospheric observatory in Hawaii have risen steeply for the seventh year in a row, reaching a May 2019 average of 414.7 parts per million (ppm). It was the highest monthly average in 61 years of measurements at that observatory, and comes five years after CO₂ concentrations first breached the 400ppm milestone. But in truth, the amount of greenhouse gas in our atmosphere is higher still. If we factor in the presence of other greenhouse gases besides carbon dioxide, we find that the world has already ticked past yet another milestone: 500ppm of what we call “CO₂-equivalent”, or CO₂-e. In July 2018, the combination of long-lived greenhouse gases measured in the “cleanest air in the world” at Cape Grim Baseline Atmospheric Pollution Station surpassed 500ppm CO₂-e. As the atmosphere of the Southern Hemisphere contains less pollution than the north, this means the global average atmospheric concentration of greenhouse gases is now well above this level. Read more here