A new assessment of how quickly we have to act to keep global temperature rise below 2°C, the threshold scientists have identified as being critical for averting dangerous climate change, shows (again) we have to act now -- and should have acted a while ago.
Without a firm commitment to put in place the mechanisms to enable an early global emissions peak followed by steep reductions thereafter, there are significant risks that the 2C target, endorsed by so many nation [in the Copenhagen Accord], is already slipping out of reach.
The report says that emissions must peak by 2020 and be reduced "well below" 1990 levels by 2050, if we are to have a "likely" (greater than 66%) chance of keeping temperature rise below 2°C by 2100.
If emissions peak at 2030, we may be able to hold temperature rise to 3°C.
Should emissions continue on a business-as-usual trajectory, sometime between 2040-2060 we will cross the 2°C threshold.