I have to admit I am a bit of a skeptic on global warming. I do not deny greenhouse gases have been rising because of human activity and greenhouse gas levels are the highest in a very long time. Also temperatures since 1850 have risen by around on average 0.8-0.9C.
However when I look back at climatic history, even in the very stable Holocene period there are been periods when temperatures globally were 1C warmer on average during Holocene Climate Optimum around 6000-3000 BC, as evidenced in the Vostok Ice Core in Antarctica. Also going back further to previous interglacial periods which have seen temperatures up to 2C warmer globally on average than now.
There were also the Medieval Warm Period and Little Ice Age which were global rather then regional events, in the little ice age temperatures globally were around 1C cooler than today, however the medieval warm period was as warm or even warmer than today evidenced by analysis across the world (including tree rings) and the fact that the Norse were farming in Southwestern Greenland where the permafrost still exists today.
This was back when human contribution to greenhouse emissions was tiny. There are factors other than CO2 emissions contributing to Earth's climate, solar cycles, water vapor, Milankovitch cycles (which could be why the earth has gone into glacial and interglacial periods rather than changes in CO2 levels, which some believe occurs after the temperature change).
I am trending on the side of caution on this issue. While I support efforts to get the world off it's dependence on fossil fuels, I believe that the uncertainties and facts, do not justify the potential cost of denying economic development in the third world or decreasing living standards even in the developed world.
