From Fred White, Nottingham, UK
We are at more than 424 parts per million (ppm) of carbon dioxide in the atmosphere and rising. With no reference to temperatures, the chemist James Lovelock – who proposed the Gaia hypothesis – considered approaching 450 ppm to be reckless; by then, damaging, irreversible positive feedbacks would start locking into place.
Unlike speculating about temperatures, CO2 levels have the politically inconvenient property of clearly quantifying the carbon quota remaining for nations over the next 10 years before reaching Lovelock’s point of no return.
