The last post introduced the concept of Representative Concentration Pathways (RCPs), which are used by the Intergovernmental Panel on Climate Change (IPCC) to represent possible trajectories of atmospheric concentrations of green house gases (GHGs) over the next century. These Pathways were designed to model a set of conditions that would lead to various upper limits of climate forcing by 2100 – climate forcing being the heating effect caused by GHGs in the atmosphere. Heating effects are calculated in watts per square meter. The RCPs are named after their targeted heating effects. For instance, RCP8.5 represents a trajectory that could result in atmospheric heating of 8.5 watts per meter squared by 2100. RCP8.5 is the most extreme of the four RCPs considered by the IPCC.  It projects a mean temperature rise of 3.7°C and a likely increase range of 2.6 to 4.8°C by 2100, wreaking all sorts of havoc along the way.

Starting with a target heating effect by 2100, the RCPs work backwards to create a plausible"story line" that would result in the target effect. The story line of RCP8.5 has been described as "conservative business as usual".  Here are some its key plot points:

  • Delayed development of renewable energy technologies
  • Rebound of human population to 12 billion by 2100
  • Wide and increasing international disparities in productivity, energy efficiency, and GDP
  • Delayed improvements in agricultural land use
  • 10-fold increase in the use of coal as a power source
  • Move away from natural gas as an energy source
  • Little change in environmental and economic policies across the world

In brief, RCP8.5 paints a picture of “… low income, high population and high energy demand due to only modest improvements in energy intensitythroughout the 21st century. Is this truly a “business as usual” scenario?