The carbon in proven conventional oil and gas reserves was estimated to be much less than the cumulative carbon emissions associated with atmospheric stabilization of CO2 concentrations at levels of 450 ppmv or higher. The "Third Assessment Report" suggested that the future makeup of the world's energy mix would determine whether or not greenhouse gas concentrations were stabilized in the 21st century. The future energy mix might be based more on the exploitation of unconventional oil and gas (e.g., oil sands, shale oil, tight oil, shale gas), or more on the use of non-fossil energy sources, like renewable energy. Total primary energy production from fossil fuels in the SRES outlooks range from a mere 50% increase from year 2010 in the B1 family to over 400% in the A1 family.