As The Economist reports:
As a rule of thumb, CO2 concentrations will have to be restricted to about 450ppm if global warming is to be kept below 2°C (a level that might possibly be safe). Because CO2 stays in the atmosphere for decades, artificial emissions of the gas would have to be cut immediately, and then fall to zero by 2075, in order to achieve 450ppm. There seems no chance of that. Emissions are still going up. At current rates, the Mauna Loa reading will rise above 450ppm in 2037.Or sooner.
Let it be noted that the 400ppm milestone (gravestone?) was passed a year earlier than originally predicted.
Will this moment - the highest concentrations of atmospheric CO2 in 3-5 million years - pass away with the days news, and will the graph be allowed - and make no mistake, it is a choice - to continue its grim, inexorable, and rapid upward climb?