D'Arrigo, R., Wilson R., and Jacoby G. (2006) On the Long - Term Context for Late Twentieth Century Warming, Journal of Geophysical Research, 111, D03103, DOI: 10.1029 / 2005JD006352. (mpra.ub.uni-muenchen.de)
Late twentieth century warming was primarily due to the increased greenhouse effect. (legalinsurrection.com)
If you look at the temperature record posted by NOAA or at HadCRUT3 from CRU you will notice a «late twentieth century warming» shown as starting in the late seventies and continuing through the eighties and nineties. (deepclimate.org)