The Reference Frame: Eichler et al.: Half of recent warming was solar

Note that if 0.3 °C or 0.4 °C of warming in the 20th century was due to the increasing CO2 levels, the climate sensitivity is decisively smaller than 1 °C. At any rate, the expected 21st century warming due to CO2 would be another 0.3-0.4 °C, and this time, if the solar activity contributes with the opposite sign, these two effects could cancel. Even if you try to stretch these numbers a little bit - but not unrealistically - you have to become sure that the participants of the Poznań conference are lunatics.