State of the Climate in 2015

This is the 26th edition of the annual assessment now known as State of the Climate. The year 2015 saw the toppling of several symbolic mileposts: notably, it was 1.0°C warmer than preindustrial times, and the Mauna Loa observatory recorded its first annual mean carbon dioxide concentration greater than 400 ppm. Beyond these more recognizable markers, trends seen in recent decades continued.