13.There is no empirical evidence supporting an temperature amplification from 1.2°C to 4°C
http://www.skepticalscience.com/climate ... ediate.htmClimate sensitivity from empirical observations There have been a number of studies that calculate climate sensitivity directly from empirical observations, independent of models.
Lorius 1990 examined Vostok ice core data and calculates a range of 3 to 4°C.
Hoffert 1992 reconstructs two paleoclimate records (one colder, one warmer) to yield a range 1.4 to 3.2°C.
Hansen 1993 looks at the last 20,000 years when the last ice age ended and empirically calculates a climate sensitivity of 3 ± 1°C.
Gregory 2002 used observations of ocean heat uptake to calculate a minimum climate sensitivity of 1.5.
Chylek 2007 examines the period from the Last Glacial Maximum to Holocene transition. They calculate a climate sensitivy range of 1.3°C and 2.3°C.
Tung 2007 performs statistical analysis on 20th century temperature response to the solar cycle to calculate a range 2.3 to 4.1°C.
Bender 2010 looks at the climate response to the 1991 Mount Pinatubo eruption to constrain climate sensitivity to 1.7 to 4.1°C.