Just as scientists have been predicting, the world just passed another major climate milestone. The Mauna Loa Observatory, located in Hilo, HI, recorded its first-ever carbon dioxide reading in excess of 410 parts per million. In science and engineering, the parts-per notation is a set of pseudo-units to describe small values of miscellaneous dimensionless quantities. Since these fractions are quantity-per-quantity measures, they are pure numbers with no associated units of measurement. Carbon dioxide hasn’t reached that level in millions of years. This is the new atmosphere that humanity will have to contend with. Currently, our atmosphere is one trapping more heat and causing the climate to change at a quickening rate.
Carbon dioxide has set a record high each year since measurements began. It stood at 280 ppm when record keeping began at Mauna Loa in 1958. In 2013, it passed 400 ppm. Earlier this year, the U.K. Met Office scientists issued their first-ever carbon dioxide forecast. They projected carbon dioxide could reach 410 ppm in March and almost certainly would by April. Carbon dioxide concentrations have skyrocketed over the past two years due to in part to natural factors like El Niño causing more of it to end up in the atmosphere. But it’s mostly driven by the record amounts of carbon dioxide humans are creating by burning fossil fuels.
Even when concentrations of carbon dioxide level off, the impacts of climate change will extend centuries into the future. The planet has already warmed 1.8°F (1°C), including a run of 627 months in a row of above-normal heat. Sea levels have risen about a foot and oceans have acidified. Extreme heat has become more common. All of these impacts will last longer and intensify into the future even if we cut carbon emissions. But we face a choice of just how intense they become based on when we stop polluting the atmosphere.