The Lower Bound Changed From 1.5 to 4.5 Degrees Centigrade

In 1990, IPCC enshrines this range as its likely range for climate sensitivity. This key variable that links concentrations to temperatures, what we ultimately should care about, we don't know much more. In 2007 the lower bound changed from 1.5 to 2.5 degrees centigrade. Fast forward to October 2013 and apparently we are back to where we started in 1979.