We start at Cape Grim in Australia - where an atmospheric measuring station is picking up atmospheric CO2 levels that are on the verge of breaking 400 parts per million for the first time in human history.

And unlike other measuring stations where concentrations fluctuate seasonally - the station at Cape Grim is in a region with stable CO2 concentrations - meaning CO2 levels in that area won't dip below 400 parts per million once it crosses that milestone.

On May 6th - scientists picked up a CO2 reading at Cape Grim of 399.9 parts per million - meaning that within weeks the reading will be permanently above 400 parts per million.

This isn't the first station to cross the 400 ppm threshold - the first station to detect CO2 levels above 400 parts per million was the Mauna Loa observatory back in 2013.

CO2 concentrations at the Mauna Loa observatory fluctuate throughout the year - but soon CO2 concentrations there will be so high that they'll never dip below 400 parts per million, either.

And last March - the global monthly average using all global readings crossed 400 parts per million - which guarantees that truly dangerous global warming is inevitable.

James Butler - director of the global monitoring division as the National Oceanographic and Atmospheric Administration - compared the situation to an electric blanket.

He told the Guardian that "It's like lying in bed with your electric blanket set to three. You jack it up to seven - you don't get hot right away but you do get hot. And that's what we're doing."

And that's the problem - it's difficult to know how much warming exactly we've guaranteed now that we're crossing the 400 parts per million threshold - especially considering that scientists said years ago that to avoid catastrophic warming we need to keep carbon concentrations below 350 parts per million.

What's clear is that yearly and monthly temperature averages have continued to break records regularly in the last couple of years - and with atmospheric CO2 concentrations at 400 parts per million - that trend will continue for years to come, even if we stopped emitting carbon completely today.

The fossil fuel industry has blocked and disputed the science on climate change for so long now that now we can guarantee that the oceans will continue to acidify - warm - and lose oxygen - and we can guarantee that storms will get stronger - droughts will get worse - and communities will be devastated.

We need to hold the fossil fuel industry accountable for misleading the public for so long and for guaranteeing that a child born today will never know a planet with CO2 concentrations below 400 parts per million - and we need to go 100% renewable immediately.