For the first time in human history, carbon dioxide in the atmosphere has exceeded 415 parts per million -- a dangerous level confirming the untrammeled rise in levels of planet-warming greenhouse gases or GhGs.
According to data from the Mauna Loa Observatory in Hawaii, the concentration of CO2 in the atmosphere stood at 415.26 parts per million (ppm), far higher than at any point in the last 800,000 years, or since before the evolution of homo sapiens.
The Mauna Loa Observatory is a research outpost of the National Oceanic and Atmospheric Agency (NOAA).
Its peculiar heat-absorbing properties mean CO2 adds to the greenhouse effect in a way other emissions don't. The notoriety of CO2 as a leading GHG is due to its ability to absorb wavelengths of thermal energy that things like water vapor can't do.
This means the ongoing increase in atmospheric CO2 is responsible for two-thirds of the total energy imbalance causing Earth's temperature to rise, according to NOAA.
"This is the first time in human history our planet's atmosphere has had more than 415 ppm CO2," tweeted meteorologist Eric Holthausin in a widely shared post.
"Not just in recorded history, not just since the invention of agriculture 10,000 years ago. Since before modern humans existed millions of years ago. We don't know a planet like this."
Climate and water scientist Peter Gleick tweeted, "Atmospheric CO2 levels have now reached 415 ppm. The last time humans experienced levels this high was... never. A human didn't exist.#climatecrisis #climatechange."
Experts said that during the Pliocene Epoch some three million years ago, global temperatures were estimated to be 2°C to 3°C warmer than today. At this time, CO2 levels are believed to have peaked between 310 ppm to 400 ppm.
During this epoch, the Arctic was covered in lush forests, while summer temperatures in the far north were only some 15°C (60°F). Global sea levels during the Pliocene were thought to be an astounding 25 meters (82 feet) higher than today.
High levels of CO2 in the atmosphere, which are mainly caused by people burning fossil fuels and destroying forests, prevent the Earth's natural cooling cycle from working. In addition, CO2 traps heat near the surface and causes global temperatures to rise and rise with devastating effects planetwide.
Scientists have confirmed the release of CO2 and other GhGs has already led to a 1°C rise in global temperatures. A further rise is all but inevitable if more immediate action isn't taken by world governments. The CO2 level spike to 415 ppm is indication governments are failing to do so.
In a world 2°C warmer, there will be 25 percent more hot days and heat waves, according to 70 peer-reviewed climate studies. This climate catastrophe will bring with it major health risks and risks of wildfires while slowing down economic growth worldwide and boosting poverty.
The studies also show 37 percent of the world's population will be exposed to at least one severe heat waves every five years. The average length of droughts will increase by four months, exposing some 388 million people to water scarcity, and 194.5 million to severe droughts.
