Atmospheric carbon levels have likely passed 400 ppm threshold permanently

Climate Central : Throughout the month of September, atmospheric carbon dioxide levels failed to drop below 400 ppm, a significant milestone for Earth’s climate. Although CO₂ levels normally fluctuate throughout the year, September is usually the month when they’re at their lowest. Therefore, it is unlikely that CO₂ levels will ever drop below 400 ppm again, according to Gavin Schmidt, NASA’s chief climate scientist. Atmospheric greenhouse gas concentrations have been rapidly increasing since the Industrial Revolution, and it was only a matter of time before the 400 ppm threshold would be reached. And as carbon levels have risen, so have global temperatures. In fact, 2016 may turn out to be the hottest year on record. Although world leaders are working to reduce carbon emissions following last year’s Paris climate agreement, it may already be too late for some parts of the world that are prone to heat waves, droughts, and flooding.