According to early estimates by the International Energy Agency (IEA), global CO2 emissions from fossil fuel combustion reached a record high of 31.6 gigatons in 2011, a 3.2 percent increase over 2010.
The rates of carbon entering the atmosphere in the lead-up to these extinctions are estimated to have been 2.2 and 1 to 2 gigatons of carbon per year respectively, over several thousand years.
Stabilizing greenhouse gas concentrations at 550 ppm -- which would invoke a rise in temperature of about three degrees Celsius -- would require energy emissions to rise no higher than 33 gigatons and would need to fall in the longer term.