My problem with the whole argument for man-made global warming is the narrowness of the time frame of observations being used. My reservations are based on my personal experience. I grew up in Missoula, Montana. It was a prehistoric lake. I was painfully aware of this as a kid, because anytime anybody tried to dig a hole to plant something there was about an inch of topsoil, an inch of gravel and then a seemingly infinite layer of big smooth boulders, most much bigger than the original size of the hole, that had to be removed. It turns out that Lake Missoula got filled repeatedly as the result of ice dams on the Clark's Fork River 15,000 to 13,000 years ago. Periodically the dams would break up suddenly and flood everything downstream with the contents of the Lake Missoula.