The phrase
"reference temperature" refers to a standard or normal temperature used as a basis for comparison in scientific or technical measurements.
Full definition
Sap also refers to just one set of monthly external
reference temperatures for England and Wales, which has a very significant bearing on transmission and ventilation losses.
The Summary for Policy Makers at the beginning of AR5 defines «the past»
by referencing temperatures to the global mean surface temperature averaged over 1985 - 2005.
This provides a
stable reference temperature structure for the fast feedback processes to operate and maintain the amounts of atmospheric water vapor and clouds at their quasi-equilibrium concentrations.
Better still before KR kindly pointed to that graph, I had broken down and endeavoured to digitize the FAR graphs myself and
reference temperature trends over the period prior to 1985 from the FAR graphs.
The Central England set suggests the northern hemisphere reached
contemporary references temperatures in the 1940s (as shown by the NH HadCRUT2v track used by Jones and Mann) and likely did so in the 1830s and 1720s as well.
Mean reference temperatures are ~ 3.8 °C greater than preindustrial in 2100, in accord with projections for the higher end emissions pathways in recent simulations (Forster et al. 2013).
vp, «The Summary for Policy Makers at the beginning of AR5 defines «the past»
by referencing temperatures to the global mean surface temperature averaged over 1985 - 2005.
Preindustrial is
the reference temperature for all the pledges and the uncertainty in preindustrial is around + / -0.35 C degrees, maybe a little more with BEST, but what exactly what is «preindustrial» global mean surface temperature?
For # 6, the thermometer records are valid, but my impression that
the referenced temperature record referred to long - term proxies.