Global Warming 101

The accelerating pace of global warming is provoking anxiety that the Earth is reaching an ominous threshold, a point of no return. Within a decade or two, various feedbacks may take greenhouse warming past any human ability to contain or reverse it. Carbon-dioxide levels in the atmosphere are rising rapidly, fed by increasing fossil-fuel use world-wide, melting permafrost, slash-and-burn agriculture in Indonesia and Brazil, increasing wildfires, as well as rapid industrialization using dir...