Atmospheric concentrations of carbon dioxide (CO2) recently surpassed a notable milestone, reaching above 400 parts per million (ppm) for the first time in human history. The new measurement came from analyzers atop Mauna Loa, the volcano on the big island of Hawaii that has long been ground zero for monitoring the worldwide trend on CO2. Carbon dioxide pumped into the atmosphere by fossil fuel burning and other human activities is the most significant greenhouse gas contributing to climate change. Its concentration has increased every year since scientists started making measurements on the slopes of the Mauna Loa volcano more than five decades ago. The rate of increase has accelerated since the measurements started, from about 0.7 ppm per year in the late 1950s to 2.1 ppm per year during the last 10 years. Read more »
