Greenhouse gases numbers

Nicholas Stern apunta algunas posibles tendencias, consecuencias y recomendaciones sobre el efecto de los gases de efecto invernadero:

1. Concentrations of carbon dioxide and other greenhouse gases in the atmosphere have reached 435 parts per million (ppm) of CO2-equivalent, compared with about 280 ppm before industrialization in the nineteenth century.

2. [C]oncentrations could reach 750 ppm by the end of the century. Should that happen, the probable rise in global average temperature relative to pre-industrial times will be 5˚C or more.

3. It has been more than 30 million years since the earth’s temperature was that high [5˚C]. The human species, which has been around for no more than 200,000 years, would have to deal with a more hostile physical environment than it has ever experienced.

4. To avoid the severe risks that would result from a rise in global average temperature of more than 2˚C, we must get atmospheric concentrations below 450 ppm. This will require a cut in annual global emissions from about 50 gigatonnes of CO2-equivalent today to below 35 gigatonnes in 2030, and less than 20 gigatonnes by 2050.

5. Today, per-capita annual emissions in the European Union are 12 tonnes, and 23.6 tonnes in the United States, compared to six tons for China and 1.7 tons for India. As the projections for 2050 suggest that the world’s population will be about nine billion, annual per-capita emissions must be reduced to approximately two tons of CO2-equivalent, on average, if the global annual total is to be less than 20 gigatonnes.