Even if the onslaught paled next to great winter outbreaks of the past, it was impressively persistent across some influential areas, including southeast England and the U.S. mid-Atlantic.

Years before Congress began debating greenhouse-gas reduction, more than 500 U.S. cities had pledged to reduce their carbon footprints in line with the goals of the Kyoto Protocol. Now American cities are leading the way on adapting to climate change.

A growing body of research now confirms that the Montreal agreement averted at least one catastrophic form of climate change, even if others still loom. "The Montreal Protocol is a major success story," says William Randel.

Clearly, the end of the Copenhagen conference isn’t the end of work on climate change—though, with regards to Winston Churchill, it might be the end of the beginning.

In eastern Tennessee a portrait of Earth's progression from ice age to present is taking shape. Each day, up to 100 years of climatic history unfolds. By early this year, the story will be complete, thanks to some five million processing hours on supercomputers at the Oak Ridge National Laboratory.