There is no longer any reasonable doubt about global warming and man's influence. To become assured about this matter, please see the paper by Pingzhong Zhang and 16 coauthors mostly from China, with American contributions from Minneapolis (MN) and Irvine (CA). They describe "A Test of Climate, Sun, and Culture Relationships from an 1810-Year Chinese Cave Record" (Science, 7 November 2008, pp 940-942, which is accompanied by a useful news focus on Archaeology in China). Their own data came from just one stalagmite in Wanxiang Cave at 33.32°N, 105.0°E, altitude 1200 m:

Supplementary data from the Science paper, with thanks to Science and the authors

Rather like the study of tree rings, the authors studied isotopes of water deposited on their stalagmite by drops of water dripping from the roof of the cave. The data told them about monsoon rain amounts. I published a paper on tree rings myself, generously helped by Phil Jones of the Climate Research Unit. (Phil Jones has been maligned by people who don't realize when and when not to take his words seriously - as has happened to me quite often.) The notorious hockey stick graph by Michael Mann and Phil Jones is shown in the context of other such graphs within the Science paper. It looks a bit wild among the other graphs. At a relatively early date, the truth of the matter was made clear without reference to any controversy.

The authors of the Science paper pointed out close correspondences between rain epochs and Chinese dynasties. Their abstract ends by saying that the sign of the correlation between the Asian Monsoon and temperature (related to the ratio delta(18)O among oxygen isotopes) switches around 1960, suggesting that anthropogenic forcing superseded natural forcing as the major driver of Asian Monsoon changes in the late 20th century. [Ratios delta(18)O have now been related to Moisture Residence Times (water content/precipitation rate) by Aggarwal et al., GRL, doi:10.1029/2012GL051937].