The most strident voices in the global warming debate base their (pessimistic) arguments on models that purport to forecast what will happen. In my work (which has nothing to do with climate) I also try to forecast the future and would note that such models are wrong more than 90% of the time. If you don't believe me, try to forecast the results of the next batch of soccer matches, the oil price and the stock-market.
The models turn out to be wrong either because input data was incorrect (the known unknowns); or something that should have been included was not (the unknown unknowns). That doesn't mean we shouldn't try to forecast the future, only that we need to show some humility on our ability to do so.
I suspect that global warming will go the way of fear of US-Russia nuclear obliteration (the 1960's), global cooling (the 1970's) and Y2K problems (remember them?). However, it might not. So let us keep the debate rational and think with our minds not our emotions.
Lord Lawson has several advantages over most of the Greens who disagree with him. He is older than they are, seen more, done more and made mistakes. I suspect when they reach his age, they will have made many more mistakes. I hope they will also have learned from them.