Remember this number for the rest of your life.
On this day twenty years ago, when Dr. James Hansen of NASA’s Goddard Institute of Space Studies warned the US Congress of global warming forced by greenhouse gases emitted through human activities, CO2 stood at 350 ppm.
That was then. Today it is up to 385 ppm. Sixteen years after the UN Convention on Climate Change was agreed upon to stabilize greenhouse gases at a level preventing dangerous human interference with the climate system, global carbon emissions are still increasing – more rapidly than ever. We are well on our way to 450 ppm and beyond.
What does the best science tell us?
Until recently, scientific consensus set the safe zone to avoid the worst effects of climate change at 450 ppm. But today the latest science tells us the danger zone may already begin at 350 ppm. Catastrophic effects cannot be ruled out if levels above 350 ppm are maintained for a long time.
What does this mean?
We’ve gone too far. In a dangerous direction. We know enough now. To act now. To foresee and forestall any risk of massive and irreversible damage to the earth and all its inhabitants for generations to come, we must reduce atmospheric CO2 to levels below 350 ppm. Scientific insights bring political responsibilities. We need leadership that respects the planetary boundaries of life.
We, the signatories of this message from all continents, call upon all nations in the ongoing climate negotiations to adopt 350 as the target to be reached peacefully and deliberately, with all possible speed.
350 is one of our planet’s boundary conditions. It should not have been transgressed. We must go back for a future:
<350
The Vision
The Signatories
The Science