THE ECONOMIC CASE
Cutting emissions will not be enough to keep global warming in check.
Greenhouse gases must be scrubbed from the air.No one in power is listening to the climate skeptics anymore.
One discovery after another suggests the world is warming faster, and climate damages are appearing sooner, than anyone had expected. Much of the policy discussion so far has been aimed at keeping the atmospheric concentration of CO2 below 450 parts per million (ppm) — which was until recently thought to be low enough to prevent dangerous levels of warming. But paleoclimatic evidence shows 450 ppm is the threshold for transition to an ice-free earth. This would imply a catastrophic rise in sea levels, eventually flooding all coastal cities and regions.
To avoid reaching such a crisis stage, climate scientists now call for stabilizing CO2 concentrations at 350 ppm. The world is now around 390 ppm and rising.
Some scientists and activists believe that a concentration of over 350 parts-per-million of carbon dioxide in the atmosphere could lead to feedback loops (the release of methane from Arctic permafrost, for example) that could make warming almost impossible to stop.
A British team demonstrated that coral reefs won’t survive acidified waters unless we get CO2 concentrations back down below 360 ppm.