Chapter 1 of the IPCC Fourth Assessment Report: Climate Change 2007 (AR4) will provide with a long list of citations. In the summary for policy makers
The understanding of anthropogenic warming and cooling influences on climate has improved since the TAR, leading to very high confidence[7] that the global average net effect of human activities since 1750 has been one of warming, with a radiative forcing of +1.6 [+0.6 to +2.4] W m–2 (see Figure SPM.2). {2.3, 6.5, 2.9}
The combined radiative forcing due to increases in carbon dioxide, methane, and nitrous oxide is +2.30 [+2.07 to +2.53] W m–2, and its rate of increase during the industrial era is very likely to have been unprecedented in more than 10,000 years (see Figures SPM.1 and SPM.2). The carbon dioxide radiative forcing increased by 20% from 1995 to 2005, the largest change for any decade in at least the last 200 years. {2.3, 6.4}