Re: Global warming; fossil fuels; and the global Carbon Cycle

Additionally, Dr. Fred Singer, a major climate expert, as reported in an article in Forbes online;

(http://www.forbes.com/sites/larrybell/2013/09/24/alarmists-are-in-way-over-their-heads-on-rising-ocean-claims/)

asserts that the warming we find today, indicated by measurably rising sea levels, is not caused by the burning of fossil fuels, but is a continuing effect of the natural event that ended the last Ice age, when sea levels rose over 400 feet.

What was, and is, considered to be the scientific "cause" of that event, and its continuing contemporary effect?