"the risk of climate change does exist"...I would say this is an understatement. If you look back over the long history I would say the risk of climate change is assured. 100% chance of change. The climate has always changed and it will continue to change. Sometimes it changed in quite dramatic fashion and relatively quickly. The last "little ice age" was 10K years ago where at the time there was a sheet of ice over, what is now New York, that was a mile thick. In geologic time, 10K years is a blip.

"the consequences could be serious enough that action should be taken"...again, an understatement. It is almost assured that at some time, another ice age will occur. This will be serious enough that action should be taken. What action is the option he left wide open. I would suggest if we have another ice age, minor or major, RUN...SOUTH would be the appropriate action that should be taken. Anything less might well find you entombed in ice much in the fashion of the Woolly Mammoths they sometimes find in Alaska.

“The type of action seem to be where the largest areas of debate exist in the public discourse."...Yea, they can have a public discourse if they want to...me...South baby, South. I'll come back after it thaws and see if they're still debating.

“The increase in the greenhouse gas concentrations in the atmosphere are having an effect,” Tillerson said. “Our ability to predict that effect is very limited.”...what I would have asked him after this statement is...if our ability to predict the effect of, so called, greenhouse gas concentrations is very limited...how then do we know whether there is any effect at all?

"Tillerson told lawmakers he thought a carbon tax would better address greenhouse gas emissions than cap-and-trade."...Maybe a carbon tax would better address, so called, greenhouse gas emissions than cap and trade. Maybe. Maybe not but maybe but maybe not. That's all he said.

I suspect he artfully skirted the issue because it's stupid and he wanted to get passed the idiots on the hill.