How to answer climate change denial

It's claimed there are two groups of 'denialists': to which group does Professor Richard Lindzen belong? 'Lobbyist'  or 'Ignorant'?

Richard Lindzen: 'Emeritus professor of meteorology at MIT, where he was the Alfred P. Sloan Professor, beginning in 1983. Prior to that he was the Robert P. Burden Professor of Dynamic Meteorology at Harvard University'.

"The UNFCCC was established twenty five years ago to find scientific support for dangers from increasing carbon dioxide. While this has led to generous and rapidly increased support for the field, the purported dangers remain hypothetical, model-based projections. By contrast, the benefits of increasing CO2 and modest warming are clearer than ever, and they are supported by dramatic satellite images of a greening Earth."

https://wattsupwiththat.com/2017/03/09/lindzen-responds-to-t...

I think a counterpoint that often gets overlooked is that, since denialists express doubt in current predictions, can we afford to take that risk? Can we afford to keep increasing CO2 levels, until we know it won't lead to unwanted and/or irreversible changes?

I.e. prove that more CO2 is safe, not that it's dangerous, before emitting more.