Earth’s atmosphere is changing more quickly than ever before in human history … (because) Humans are releasing a flood of greenhouse gases, into the air by burning fossil fuels. CO2 lingers in the sky for centuries.

“This is the first time in human history our planet’s atmosphere has had more than 415ppm CO2,” says meteorologist Eric Holthaus “Not just in recorded history (or) since the invention of agriculture (but) before humans existed millions of years ago.”

For anyone who isn’t aware, CO2 traps solar heat on Earth. There’s a long historical link between CO2 and temperature (https://earthobservatory.nasa.gov/features/CarbonCycle/page4.php).

Extreme weather swings can lead to crop failures and famines and rising sea levels endanger about 200 million people who live along the planet’s coastlines.

While the Pliocene might be a useful guide, there is a key difference: The Pliocene climate developed slowly over time, and we’re reviving it at an unprecedented speed. Species can usually adapt to slow environmental changes … but even we are ill-equipped to keep pace with this upheaval.

“This milestone is a wake-up call that our actions in response to climate change need to match the persistent rise in CO2,” said Erika Podest, a carbon- and water-cycle scientist at NASA’s Jet Propulsion Laboratory … Climate change is a threat to life on Earth and we can no longer afford to be spectators.”

https://www.treehugger.com/the-pliocene-called-it-wants-its-co-levels-back-4868159