Jon is widely admired and respected by the best scientists. His models and analyses are innovative and credible. He is tackling some of the toughest issues of climate change.

The bottom line is that the scientific evidence from 2005 and early 2006 is powerful and conclusive. If society wishes to avoid catastrophic disruption of our lives, the time for action is now. Individual citizens are powerful agents of change, but communities, businesses, the state and the federal government will need to do their part.

The evidence is overwhelming that even simple changes can be a big help and have a huge cumulative impact. If every American switched just three light bulbs to compact fluorescent bulbs, it would be the equivalent of taking 3.5 million cars off the road. If everyone switched to a car with five miles-per-gallon better mileage, that would be equal to the taking another 150 million automobiles off the roads. Individual actions add up to big changes.

What has become clear is that if society wants to avoid future disasters, it should do two things ? prevent even greater disruption to the climate system and prepare for the climate changes already set in motion. There is urgency on both fronts, reducing emissions and preparing to adapt.

The dialogue is now shifting gears from climate science to climate action. There's still a lot we need to learn about the science, but the events of the past year have ended much of the lingering debate and controversy. The most important question now is what can individuals, communities, states and nations do to reduce and prepare for climate change.

I am not a scientist. I am, rather, an impresario of scientists.