The problem with the below link is they cite Mann's data, which the Sargasso Sea data contradicts as well as does the Little Ice Age. This is basically circular reasoning since it is the Mann's data that is disputed by almost all of the opponents. http://www.ncdc.noaa.gov/paleo/globalwarming/medieval.html In "Near-Term Climate Prediction Using Ice-Core Data from Greenland", Sergey R. Kotov, Institute of Precambrian Geology and Geochronology, Saint Petersburg, Russia shows that current global temperatures are not unusual over the past 10,000 years. I could cite numerous other papers. The main points to be made are: 1. Have we had past episodes of warm climate that are comparable to today? I think there are compelling reasons to answer yes to this question. Before the current need to "get rid" of the Medieval Warming Period, I saw a PBS special on Erik-the-Red and Leif Erickson settling Greenland in which it was clearly accepted that the earth was warmer then. They had to leave Greenland several decades later as the earth cooled and we went into the Little Ice Age. Both of these periods are well documented historically. 2. Are the CO2 levels in the atmosphere much higher than in the past? Antarctic ice core data indicates that they are but they are not direct measurements of CO2. If the recent article in Energy and Environment by German researcher Ernst-Georg Beck is correct than more than 90,000 direct measurements of CO2 in the atmosphere during the last 100 years contradict the ice core assumptions. His data shows that CO2 levels have fluctuated greatly over the past 100 years and are not currently at higher than "normal" levels. 3. Why is there such an amazing correlation between solar activity and earth temperatures. The book "The Role of the Sun in Climate Change" (my email doesn't do italics) by NASA scientist Keith Schatten and Douglas Hoyt shows page after page of charts showing correlations between solar activity and global temperatures. As I said before, get out your Norton Star Atlas and look at the difference in sunspot activity for the 1800's versus the 1900's. I tend to weigh heavily historical information and books (such as Schatten's) written before global warming became such a political football because proponents on both sides of the issue now have so much to lose.