The 21st century CCSM4 simulations are integrated following the protocol from
the Climate Model Intercomparison Project CMIP5 (1) with prescribed
atmospheric CO2 from a high emissions scenario (RCP8.5). RCP stands for
Representative Concentration Pathways, which are based on specified global
radiative forcing levels (in this case +8.5 W/m 2 by 2100); socio-economic and
emissions scenarios have been constructed to match each RCP (2).

(1) K.E. Taylor, R.J. Stouffer, G.A. Meehl. A summary of the CMIP5 experimental design.
http://cmip-pcmdi.llnl.gov/cmip5/experiment_design.html (2009).

(2) R.H. Moss, et al. The next generation of scenarios for climate change research and
assessment. Nature 463, 747-756 (2010)