It may help to clarify some of the facts related to the lively exchange between Bob Ward and Lord Ridley about the Transient Climate Response (TCR). The TCR is defined by the IPCC as “the change in the global mean surface temperature, averaged over a 20-year period, centred at the time of atmospheric carbon dioxide doubling, in a climate model simulation in which CO2 increases at 1% yr – 1.”
Lord Ridley is right that the IPCC in its recently published AR5 Working Group I report gave an estimated likely (66–100% probability) range for TCR of 1 – 2.5°C.