On May 10 the planet marked a milestone of sorts. Scientists recorded that for every million molecules of air, 400 were of carbon dioxide – the key gas that accumulates over decades in the air and leads to global warming. The figure sent alarm bells ringing. A large section of scientists has long predicted that if the accumulated CO ² rose above 350 parts per million (about 200 years ago the concentration was 280ppm) it’d trigger catastrophic, perhaps irreversible changes. When the 400ppm mark was reached, global media went into a spin. Scientists and civil society called for swift action to reduce global greenhouse gas (GHG) emissions.