I went on to watch a debate between Denning and Roy Spencer. I found Spencer's talk to be intriguing, but too optimistic:
1) He says that by his calculations, climate sensitivity is about 1.3 degrees Celsius, and could be lower. But he doesn't mention is could be higher, also.
2) He says that there has been no warming in the past decade or so, but doesn't address recent sea level rise and ice melt that does indicate warming.
3) He says he believes carbon dioxide in the atmosphere will not triple and may not even double, but offers no reasoning to support his beliefs.
The truth is that no one knows exactly what will happen, and Dr. Spencer could turn out to be right. But he gives no reason to be so optimistic. He just is. What if he's wrong? I remain skeptical of his beliefs.