This figure shows another possible energy-consumption scenario in which a global commitment has been made to stabilize long-term atmospheric CO2 concentration at 550 ppmv (about double the preindustrial level of 280 ppmv); the current level is around 380 ppmv.* Placing limits on CO2 emissions provides an incentive for developing noncarbon-emitting energy technologies and reducing energy consumption through conservation and improvements in energy efficiency. Over the century, increased biofuel consumption combined with reductions in energy use would displace hundreds of exajoules of fossil-fuel energy, and by 2100 biofuels would equal roughly all fossil-fuel usage today (coal + oil + natural gas). By decreasing fossil-fuel use in the stabilization case, hundreds of gigatons of CO2 emissions would be avoided. *The case of 550 ppmv was chosen to illustrate the types of changes that might occur; currently, no scientific basis exists for preferring any particular CO2 concentration.
Credit or Source: Office of Biological and Environmental Research of the U.S. Department of Energy Office of Science. science.energy.gov/ber/
US DOE. 2005. Genomics:GTL Roadmap, DOE/SC-0090, U.S. Department of Energy Office of Science. (p. 202) (website)