What does this 350 number even mean?

350 is the number that leading scientists say is the safe upper limit for carbon dioxide—measured in “Parts Per Million” in our atmosphere. 350 PPM—it’s the number humanity needs to get back to as soon as possible to avoid runaway climate change.

From the beginning of human history until the Industrial Revolution, global atmospheric carbon dioxide did not exceed about 280ppm.

Now, after three centuries of burning coal, oil, and gas, we’re at 400ppm – that’s above any levels we’ve seen in recorded history.

Accelerating arctic warming and other early climate impacts (such as extreme weather) have led scientists to conclude that this is above the safe zone. And, unless we are able to rapidly return to below 350 ppm this century, we risk reaching tipping points and irreversible impacts such as the melting of the Greenland ice sheet and major methane releases from increased permafrost melt, just to name a couple.

Read Bill McKibben’s Rolling Stone article about the terrifying new maths here.

Read about basics of climate change and science behind it here.

So, what is global warming and what’s the problem anyway?

The science is clear: global warming is happening faster than ever and humans are responsible. Global warming is caused by releasing what are called greenhouse gases into the atmosphere. The most common greenhouse gas is carbon dioxide. Many of the activities we do every day like turn the lights on, cook food, or heat or cool our homes rely on the combustion of fossil fuels like coal and oil, which emit carbon dioxide and other heat-trapping gases when burned. This is a major problem because global warming destabilizes the delicate balance that makes life on this planet possible. A change in just a few degrees in temperature can completely alter the world as we know it, and threaten the lives of millions of people around the world. But don’t give up hope! You can help stop global warming by taking action with us here at 350.

If we’re already past 350, are we all doomed?

No. We’re like the patient who goes to the doctor and learns he’s overweight, or his cholesterol is too high. He doesn’t die immediately—but until he changes his lifestyle and gets back down to the safe zone, he’s at a higher risk for heart attack or stroke. The planet is in its danger zone because we’ve poured too much carbon into the atmosphere, and we’re starting to see signs of real trouble: melting ice caps, rapidly spreading drought, and more. We need to scramble back to safety as quickly as we can.

The 350 campaign focuses on making the connections between our actions and climate change easier to understand so we can turn this around.