Ask them what the cost would be for a several thousand feet thick ice sheet over parts of North America, Europe and Asia?
Why? Do you think that a real possibility in the next century or two?
It's not as probable as long as we keep increasing CO2 emissions like we have been, right?
But we don't fully understand the trigger mechanisms so who is to say it isn't possible given the existing background conditions which are favorable for northern hemisphere glaciation. When it comes to climate we are dealing with probabilities and not certainties. That works both ways. A point that seems to have been lost in the insanity. The reality though is that the earth is uniquely configured for cooling and not warming. And the consequences of a drastic cooling - which is exactly what the data shows would happen - versus a gradual warming are much more severe. Which is another point that seems to have been lost in all of the insanity.