As surely as the rains fall and flowers blossom, the Northern Hemisphere awakens every June to another, less inspiring rite of spring—a new peak level for global atmospheric carbon dioxide. This year, that number is 419 CO₂ molecules for every million molecules of air, a.k.a. parts per million.
Based on geological evidence collected over the six decades scientists have been tracking atmospheric CO₂, this year’s peak appears to be the highest in as long as 4.5 million years. This continued accumulation of greenhouse gas is driving dangerous global heating around the world.