WMO Secretary-General Michel Jarraud said this means that we will "soon" be living with globally averaged CO2 levels above the dangerous milestone of 400 ppm "as a permanent reality."
"We can’t see CO2. It is an invisible threat, but a very real one," Jarraud said. "It means hotter global temperatures, more extreme weather events like heatwaves and floods, melting ice, rising sea levels, and increased acidity of the oceans. This is happening now and we are moving into uncharted territory at a frightening speed."
Already we're seeing the deadly effects of climate change in the form of rising seas, monster storms, wildfires, and extreme weather of all kinds. Passing 400 ppm is an ominous sign of what might come next -- and it sends a clear signal that the world must act ahead of the UN climate talks in Paris this December.
The safe level of carbon dioxide in the atmosphere is 350 parts per million. The only way to get there is to immediately transition the global economy away from fossil fuels and into into renewable energy, energy efficiency, and sustainable farming practices.
The last time CO2 levels were this high, humans did not exist. Our dependence on fossil fuels is fundamentally changing the nature of the planet -- and it's time to act.
The annual report also notes that the Earth's rising surface temperature is driving another vicious cycle, where increased concentrations of water vapor, a short-lived greenhouse gas, further adds to the warming effect by trapping even more heat. "The laws of physics are non-negotiable," Jarraud added.