Why 507?

The short answer (TL;DR)

507 parts per million (ppm) is the atmospheric concentration of CO₂ that the world is heading for. Forget about anyone’s future if that happens. Everything we do is working towards changing that future and bringing the level back to the safe zone: 350 ppm.

The long answer

Full disclosure: when we first named 507climate we used models from an earlier generation of science and policy work that tried to describe “safe futures” under a 1.5 °C warming scenario. Back then, the forecasts indicated that an atmospheric concentration of CO₂ of 507 ppm broadly equated to 1.5 °C of warming since the pre-industrial era — the goal of the Paris Agreementi and Net Zero pledges around the world.

Since then, both the IPCC and climatic models have evolved their analysis. It is now likely that 507 ppm would bring about 3 °C of warming — a future that would bring system-wide ecological and economic collapse and truly lock in the next mass extinction event. It has become clear that truly protecting people and ecosystems requires going well beyond the 1.5–2 °C targets and bringing CO₂ back down towards 350 ppm or below: the “safe zone.”

Our name now reflects the uncomfortable truth that human activity is still steering the planet towards a 507 ppm reality. If that materialises, we will have failed all future generations, of every species. At the time of writing, we sit at 420 ppm CO₂. From policies and fossil-fuel use to governmental, corporate and personal actions — we must all play our part in taking us off the road to ruin, to 507 ppm, and back on the path to a vibrant, healthy and prosperous world.